<?page no="0"?> Electrostatic Encyclopedia WOLFGANG SCHUBERT GÜNTER LÜTTGENS Think in fieldlines <?page no="1"?> Wolfgang Warmbier is located in the south of Germany near the Swiss border. The privately owned company has been producing and distributing ESD control products on its 23.000 sqm facility since 1982. Besides production and distribution, our activities include EPA consulting and planning, ESD training and workshops, ESD audits, and materials qualification according to the current ESD standards. • ESD trainings and workshops • Own registered ESD packaging, own developed measuring and test equipment, own ESD oor systems • Fast delivery due to very large storage capacity • Measurements and analyses in in-house ESD laboratory • Calibration of the ESD measuring instruments in our own calibration laboratory (see picture above) • Walk-in climatic chamber www.warmbier.com Wolfgang Warmbier GmbH & Co. KG · Untere Gießwiesen 21 · 78247 Hilzingen Tel. +49 7731 / 8688-0 · info@warmbier.com Expertise in all topics of ESD control products <?page no="2"?> Electrostatic Encyclopedia <?page no="4"?> Wolfgang Schubert / Günter Lüttgens Electrostatic Encyclopedia <?page no="5"?> Bibliographic information of the Deutsche Nationalbibliothek The Deutsche Nationalbibliothek lists this publication in the Deutsche Nationalbibliothek; detailed bibliographic data can be found on the Internet at http: / / dnb.dnb.de. DOI: https: / / doi.org/ 10.24053/ 9783381117024 © 2025 · expert verlag - A company of Narr Francke Attempto Verlag GmbH + Co. KG Dischingerweg 5 · D-72070 Tübingen The work, including all its parts, is protected by copyright. Any use outside the narrow limits of copyright law without the consent of the publisher is prohibited and punishable by law. This applies in particular to reproductions, translations, microfilming and storage and processing in electronic systems. All information in this book has been compiled with great care. Nevertheless, errors cannot be completely ruled out. Neither the publisher nor the authors or editors therefore accept any liability for the correctness of the content and are not liable for incorrect information and its consequences. This publication may contain links to external third-party content over which neither the publisher, authors nor editors have any influence. The respective providers or operators of the sites are always responsible for the content of the linked sites. Internet: www.narr.de eMail: info@narr.de Printing: Elanders Waiblingen GmbH ISBN 978-3-381-11701-7 (Print) ISBN 978-3-381-11702-4 (ePDF) ISBN 978-3-381-11703-1 (ePub) <?page no="6"?> Contents Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Preliminary remark and thanks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 User notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 A - Z . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 M Mathematic toolbox . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 405 M.1 Field constants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 407 M.1.1 Permittivity ε . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 407 M.1.2 Permittivity number of a material ε r . . . . . . . . . . . . . . . . . . . . . . . . . . 408 M.1.3 Electric susceptibility χ e . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 408 M.1.4 Permeability μ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 408 M.2 Force F, ~ F . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 408 M.3 Charge Q . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 409 M.3.1 Coulomb ’ s law . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 409 M.3.1.1 Attraction of two point-charges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 409 M.3.1.2 Field of point charge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 410 M.3.1.3 Specific charge Q spec . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 410 M.3.1.4 Volume charge density ρ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 410 M.3.2 Surface charge density σ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 410 M.3.3 Breakdown field strength E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 411 M.4 Voltage U . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 411 M.5 Homogeneous field between planar plates . . . . . . . . . . . . . . . . . . . . . . . . . . . . 411 M.6 Capacitance C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 411 M.6.1 Energy W stored in capacitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412 M.6.1.1 Minimum ignition energy W MIE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412 M.6.1.2 Correlation energy - power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412 M.6.1.3 Electric power P . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412 M.6.2 Charging voltage U c (t) and discharging voltage U d (t) at the capacitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 413 M.6.3 Time constant τ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 413 M.6.3.1 Time constant τ (in RC combination) . . . . . . . . . . . . . . . . . . . . . . . 413 M.6.4 Configuration of some capacities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 414 M.6.4.1 Plate - plate (same size) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 414 M.6.4.2 Sphere across a conductive area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 414 M.6.4.3 Conductive sphere in space . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 415 M.6.4.4 Cylinder (wire) over surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 415 M.6.4.5 Coaxial cable / cylinder capacitance . . . . . . . . . . . . . . . . . . . . . . . . . 415 <?page no="7"?> M.6.4.6 Circuits of capacitances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 415 M.6.4.6.1 Parallel connection (shunt) of single capacitors . . . . . . . . . . . . 415 M.6.4.6.2 Series connection of single capacitors . . . . . . . . . . . . . . . . . . . . . 416 M.6.4.6.3 Series connection of two single capacitors . . . . . . . . . . . . . . . . 416 M.6.4.7 Impedance of a capacitance R C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 416 M.7 Resistance - conductivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 416 M.7.1 Resistances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 416 M.7.1.1 Resistance R of a material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 416 M.7.1.2 Leakage resistance R L (object or material) . . . . . . . . . . . . . . . . . . . 417 M.7.1.3 Surface resistance R S (object or material) . . . . . . . . . . . . . . . . . . . . 417 M.7.1.4 Volume resistivity ρ v (object or material) . . . . . . . . . . . . . . . . . . . . 417 M.7.1.5 Circuits of resistors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 418 M.7.1.5.1 Parallel connection (shunt) of single resistors . . . . . . . . . . . . . 418 M.7.1.5.2 Parallel connection (shunt) of two single resistors . . . . . . . . . 418 M.7.1.5.3 Series connection of single resistors . . . . . . . . . . . . . . . . . . . . . . . 418 M.7.1.5.4 Series connection of impedances . . . . . . . . . . . . . . . . . . . . . . . . . . 418 M.7.1.5.5 Parallel connection (shunt) of impedances . . . . . . . . . . . . . . . . . 419 M.7.2 Conductivity κ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 419 M.7.2.1 Conductivity unit cu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 419 M.7.2.2 Conductance G (applied electrical engineering) . . . . . . . . . . . . . . 419 Appendix A - D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 420 Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 429 Laws and Regulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 435 Rules and Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 436 Standards (Status 2024) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 438 Contents 6 <?page no="8"?> Foreword “ I can ’ t believe you ’ re reading a real book! Everything ’ s on the internet these days and it ’ s far more up to date. Yet here you are with an encyclopaedic dictionary in your hand! Why not just go online? It ’ s far more practical. ” As you haven ’ t stopped reading by now, I assume you have your reasons. If you ’ ve ever found yourself heading somewhere in an unfamiliar town without the aid of a GPS, you ’ ll understand the value of reliable resources. If we get lost, we usually seek guidance from a local. If they point us in the right direction, we should reach our destination. If not, the search continues, sometimes leading us further astray. Since you ’ re continuing to read this book, I assume you ’ re interested in electrostatics. And whether by luck or judgement, you ’ ve certainly hit upon very capable authors, Günter and Sylvia Lüttgens, the founders of this encyclopaedic dictionary. They dedicated their careers to exploring electrostatic phenomena, not only to fully understand those themselves, but also with a view to helping others understand their complexity. The current author, Wolfgang Schubert, was so fascinated by electrostatics during his early days in the printing industry that he ’ s been keenly solving electrostatic problems ever since. His involvement in this dictionary was truly fortuitous for the Lüttgens - and now for you as well. When revising and enlarging this encyclopedia, Wolfgang Schubert meticulously reviewed and updated the content of each and every entry to keep the wording precise and succinct. Moreover, he also made every effort to show how different terms are interlinked. How do I know this? I, too, was directly involved - through countless emails and phone conversations - as he combed through original literature, studied definitions and standards in textbooks and reference works, and honed the entries to ensure they were accessible to lay readers, yet remained accurate. Look up any term, and you ’ ll quickly perceive Wolfgang Schubert ’ s passion for electrostatics as you follow references to other entries. You ’ ll soon find yourself captivated by the contents, despite merely holding a reference book. Whether you ’ re seeking specific knowledge or are just inquisitive, congratulations - you ’ ve come to the right place! Dr. Oswald Losert <?page no="10"?> Preliminary remark and thanks My dear companion and advisor, Dipl.-Ing. Günter Lüttgens, with whom his wife Sylvia and I had written two books together, asked me at the end of 2019 whether I could imagine revising his encyclopedia “ Static Electricity ” , which had already been published in several editions. At that time, I had no idea of the great challenges I was facing. Electrostatics has become a hobby I ’ ve loved for over 27 years. In the spring of 2020, we started to revise the first terms together and realized that the structure of the lexicon also needed to be redesigned. Future users should get a tool that can be used in practice. For example, if you are looking for measuring electrodes, you can now find a large number of them in one place. Due to the geographical distance, we spent many hours on the phone, exchanged numerous emails and struggled to describe the terms as perfectly as possible. Nothing was invented, but found, researched, checked, sorted, and translated into hopefully understandable language. Unfortunately, our collaboration came to an abrupt end in March 2021 with the sudden death of the 87-year-old. The vast knowledge of Günter was no longer available to me. In order to complete the work on electrostatics, I looked for experts whom I knew from my previous work and whom I found while researching on the Internet. Other people interested in the book and consultants from related fields also helped me in many ways with their knowledge. I would like to thank all of them, although I can only name a few here: Dr. Ulrich von Pidoll, Dr. Oswald Losert, Dr. Maciej Noras, Hermann Künzig, Christian Vogel, Christian Hinz, Dr. Florian Baumann. Without the intensive support of my wife Beate, the lexicon would not have come into being. With great patience, precision, and untiring persistence, she accompanied me on my way and created the space for it. This encyclopedia is also intended as a memorial to Günter Lüttgens, who, together with his wife Sylvia, has held seminars and lectures on the subject in Germany and abroad for many years, has written expert reports, and has worked in many standards committees. Years ago, the couple founded the “↑ Elstatik-Stiftung ” , a foundation, which promotes young scientists for services in the field of electrostatics and energy efficiency. Wolfgang Schubert Taucha in December 2024 <?page no="12"?> User notes This lexicon is an extensively revised and supplemented translation of the German edition of 2022, attempting to follow international standards. The terms have been translated in accordance with the terminology of the IEC - International Electrotechnical Commission (www.iec.ch or electropedia.org). However, important German regulations have been retained so that foreign users of the dictionary can also refer to them when working with this book. Some international regulations have been researched and added, but without any claim to completeness. The lexicon contains not only static electricity terms, but also terms that contribute to a deeper understanding of the subject. To ensure that the lexicon can be used fully and without disappointment, here are some tips on how to use it. An essential term in electrostatics is ‘ influence ’ , which in English is translated as ‘ induction ’ . In German, the term influencing as electrostatic influence has become established as a more precise term due to the Latin origin of the word. For this reason, the dictionary ’ s translation retains the term influence. The term ‘ earth ’ is used internationally with the noun earth and refers to ‘ the planet earth with all its physical matter ’ . [IEC 60050] Only in American usage is the term ‘ ground ’ used. We have therefore decided to use only the noun earth and the verb earth. Cross-references are intended to help open up the content of the encyclopedia in all directions. The reference arrow ↑ suggests that you look up the term behind it to find more information or cross-references. Among many others, two references are fundamental to electrostatics: ● DGUV-Information: TRGS 727, Avoidance of Ignition Hazards due to Electrostatic Charges, (free download: https: / / www.baua.de/ DE/ Angebote/ Regelwerk/ TRGS/ TRGS-727) This is cited in the text, along with the relevant chapter, where applicable. (Example [TRGS 727 Section 4]) TRGS 727 is the German version of [IEC/ TS 60079-32-1]. ● Textbook: Lüttgens, G., Schubert, W., Lüttgens, S., Pidoll, U. v., Emde, S., (2020) Statische Elektrizität, Durchschauen - Überwachen - Anwenden. Unfortunately, this is not available as an English translation. Nevertheless, the reference to this source is retained in the text so that those interested can use it. It is mentioned in the text in connection with the respective chapter. (Example [SE Section 2]) <?page no="14"?> A Absolute error. Difference between the “ true ” value and the measured value. If the true value is not known, it is replaced by the average of a larger number of measurements. ( ↑ measurement accuracy, ↑ measurement error) Absolute humidity, ↑ humidity Absolute temperature, ↑ temperature, ↑ Kelvin [K] Absorption (Latin: absorbere, “ absorb ” ). Absorption of gases (vapors) in solids or liquids and subsequent uniform distribution within the absorber. Absorption increases as the temperature of the absorber decreases and the pressure of the gas increases. Conversely, gas or liquid can be released from the absorber ( ↑ desorption). This leads to ↑ hysteresis, i. e. the absorber “ remembers ” its initial state. For ↑ hygroscopic materials, the absorption of water steam from the atmosphere has a major influence on their electrostatic properties, e. g. surface resistance ( ↑ humidity, ↑ water activity). ● Dielectric absorption. Describes the relaxation effect of a dielectric in a strong electric field. In capacitors, it manifests itself as a reappearing voltage (recharging effect) after a discharge (short-circuit) and a slowly decreasing leakage current at a newly applied constant voltage. This effect is particularly common in electrolytic capacitors and is usually electrochemical in origin. The recharging effect can cause considerable hazards in power capacitors, which is why they must always be stored and transported in a short-circuited condition. ● Absorption of radiation. Attenuation of the power of ↑ electromagnetic radiation as it passes through a material ( ↑ shielding) and thereby conversion to heat. In the case of absorption, there is generally an exponential decrease in irradiated power with increasing layer thickness. ● Absorption attenuation. Material thickness is a significant factor in the absorption of radiation. However, since high-frequency currents propagate primarily at the surface due to the ↑ skin effect, the influence of the total material profile on the absorption of electromagnetic radiation decreases with increasing frequency compared to the area near the surface. ● Absorption method for determining absolute humidity. The air to be tested is passed over calcium chloride (CaCl 2 ). The water contained in the air is absorbed. The amount of air is measured with a flowmeter and the amount of water absorbed is measured with a balance (increase in weight of calcium chloride), giving the absolute humidity in [g/ m 3 ]. AC, short for ↑ alternating current AC discharge, ↑ ionizer <?page no="15"?> Accelerator. Devices for accelerating electrically charged particles to high kinetic energies ( ↑ electronvolt). Accelerators include: ↑ Van de Graaff generator, ↑ betatron, ↑ linear accelerator, ↑ synchrotron, ↑ synchrocyclotron, ↑ cyclotron. Acceptor. ↑ Foreign atom in the semiconductor that causes a mobile ↑ defect electron in the ↑ valence band. Acceptors are also materials that have a high ↑ electron emission energy and therefore accept electrons on contact from materials that have a lower emission energy ( ↑ donor, ↑ charging, ↑ Brønsted-Lowry definition). The interaction of acceptor and donor in the range of ≤ 10 -9 m is essential for understanding the generation of electrostatic charges ( ↑ charging). However, it must be assumed that the interaction conditions can constantly change extremely depending on the contact points, since there are no pure surfaces in this range. ( ↑ permittivity, ↑ permeability, ↑ contamination, ↑ pollution) Accumulator. Storage devices for electrical energy, with ↑ lithium-ion accumulators currently dominating the market. While charging with direct current, an electrochemical transformation takes place that is reversible during discharging. The discharge current flows in the opposite direction to the charge current. The charge voltage is higher than the discharge voltage. The ampere-hours absorbed by a lead-acid battery during charging, for example, can be recovered up to 90 %, whereas the efficiency in terms of the number of Watt-hours is < 75 %. The discharge voltage of a cell is currently between 1 and 4.2 V. By connecting many cells in series, accumulators with voltages of over 100 V can be obtained ( ↑ capacitance, ↑ capacitor). Active discharge bar, ↑ ionizer Active ionizer, ↑ ionizer Active part. Term for any conductor or conductive part intended to be live during normal operation, including the neutral conductor, but not, by common agreement, the ↑ PEN conductor. Active resistance, ↑ alternating current quantity Adaptation. Operating condition for an electrical system to make optimum use of a ↑ voltage source (circuit diagram). A distinction is made between current, voltage, and power adaptation with the following constraints: Maximum current: R e < R i , maximum voltage: R e > R i , maximum power: R e = R i In high-frequency systems, adaptation refers to a constant impedance ( ↑ alternating current quantity) from the source to the sink of a signal system. Each point on the signal curve can be considered according to its impedance change. In practice, however, this occurs only at technically conditioned transitions from component to component (e. g. cable to connector) in the signal path. The most common impedance in high-frequency systems is 50 Ω . Impedance describes the ratio of the magnitudes of the electrical and magnetic components of the continuous signal wave. Accelerator 14 <?page no="16"?> Only if the signal always encounters this impedance along its path will the entire electrical component always be transformed into the magnetic component and back again, with the corresponding phase shift, and thus continue along its signal path. If the purely ohmic losses of the line are ignored, the same level of the RF signal is measured at each point of the signal path ( ↑ charge transfer - measurement). If the adaptation is not ideal at a certain point, it is not possible for one of the two components of the signal to be fully converted into the other component since the changed impedance suddenly forces a change in the ratio of the electric to the magnetic component. However, the non-convertible component of the affected component is not simply destroyed, but is reflected in the direction of its source, creating a wave component that is superimposed on the main wave traveling toward it. Since the outgoing and returning waves travel at the same speed on the same line in opposite directions, a pattern of both waves in the form of a standing wave is created between the source and the mismatched location. To the extent that the adaptation at the point in question is not ideal, i. e. to the extent that the changed impedance deviates from the source impedance, there will be a difference between the wave maxima and minima of the standing wave on the line. In the case of a short-circuit or an open end of the line, there is a total reflection of the signal at that point and a standing wave with minima of magnitude zero (standing wave ratio). When the voltage amplitude across the line is used as a quantity, it is called the voltage standing wave ratio, or VSWR. This value is most often specified in the data sheet for RF components to indicate the accuracy of the component in maintaining the nominal impedance, i. e. its adaptation, over the operating frequency range. Addition (of powder/ dust). ↑ Bulk material in the form of ↑ powder or ↑ dust must not be added from open plastic containers to ↑ receiving vessels containing flammable solvents, so appropriate protective measures must be provided: ↑ inerting, ↑ PTS, ↑ personal protective equipment, ↑ earthing, ↑ exhaust system. [TRGS 727 Section 6.3] Additional insulation, ↑ insulation Additive. Many materials contain additives that can lead to the generation of an ↑ electret if their ↑ permittivity is in the higher range (e. g. titanium dioxide with ε = 111). {Appendix A}, [SE Section 2.15] Adherence effect. Utilization of the ↑ Coulomb force for the adherence of opposite polarity charged materials to each other. When using a ↑ charging electrode, these must be positioned between its tip row and a counter-potential ( ↑ counter electrode), which has the other polarity or an earth potential. The surfaces are charged and have different charge signs. Several flat structures can also be electrostatically charged with each other in such a way that they are locked together (adherence) and achieve high stability with a correspondingly long relaxation time. This adherence effect can, for example, replace an adhesive, a stiffener or even mechanical fixation ( ↑ electro adhesion, ↑ useful application, ↑ Van der Waals forces). [SE Section 8.3] Adhesion. The adhesion of particles can be achieved by material bridges (adhesive, sintering, liquid) or, if the distance is adequate, by one of the following three mechanisms: - Van der Waals forces ( ↑ molecular forces, ↑ adsorption) Adhesion 15 <?page no="17"?> - Form-fit adhesion due to the tackiness of materials with appropriate surface structures - ↑ Coulomb forces between oppositely charged particles that attract each other. Only these are responsible for electrostatic adhesion. ( ↑ useful application, ↑ electro adhesion) A charged object in the vicinity of a ↑ conductor can influence a charge of opposite polarity, which attracts and holds it ( ↑ contamination, ↑ soiling, ↑ image charge). These adhesive forces can be used, for example, to temporarily fix insulating objects to conductive surfaces. ● Adhesion of an insert (printing industry), a melt flag (film production), a label in the injection mold: ↑ in-mold labeling Adjustment (Latin: iustus, “ just ” ). Setting or ↑ calibration of a measuring device in order to eliminate any deviations detected. In contrast to calibration, adjustment is always an intervention in the measuring device that causes a permanent change. Admittance, ↑ alternating current quantity ADR, short for French: Accord relatif au transport international des marchandises dangereuses par route (Agreement concerning the International Carriage of Dangerous Goods by Road), ↑ dangerous goods Adsorption. In contrast to ↑ absorption, represents the binding of gases/ vapors (atoms and molecules) only at the surface of a solid, under otherwise comparable interactions to absorption. ● Physisorption: Bonding of molecules by ↑ Van der Waals forces without altering them. ● Chemisorption: Bonding by chemical forces (reaction) that can modify the molecules. Adsorption depends on: - Chemical nature of the adsorbent - Chemical nature of the adsorptive (e. g. selective adsorption can adsorb only parts of it) - Structure of the surface (surface-specific adsorption) - Ambient pressure and temperature - Presence of other adsorptive substances [Wedler, G., Freund, H.-J. (2018)] Aerosil ® . Very finely divided silicon dioxide (SiO 2 ), commonly known as silica, with particle sizes in the nm-range, used primarily as a filler. Because of its large specific surface area, Aerosil ® is extremely effective at dissipating electrostatic charges. For example, even a few parts per thousand Aerosil ® in insulating liquids can result in an order of magnitude higher charge due to interface enlargement. On the other hand, Aerosil ® deposited on solid surfaces can reduce charging effects by keeping surfaces in contact with large areas at a distance ( ↑ charging). Aerosol (Latin: solutus, “ dissolved ” ). Term for a gas (especially air) containing suspended solid or liquid matter (diameter 10 -9 to 10 -4 m), e. g. smoke, mist, fog, carbonic dioxide snow ( ↑ electro aerosol). Aerosols play an important role in weather patterns as condensation nuclei. The deliberate artificial generation of aerosols (e. g. oil mist for combustion Adjustment 16 <?page no="18"?> processes) can also be achieved by electrostatic ↑ atomization ( ↑ useful application). Aerosols are used for inhalation and pest control, for example. Electrostatically charged aerosols can simulate gas charging ( ↑ gas). ● Aerosol separator, ↑ separation of substances Aerosol-air mixture. The manner in which the ↑ aerosol is generated has a significant influence on the formation of an explosive aerosol-air mixture. The results are highly dependent on the droplet sizes and their distribution (local concentration). For aerosols with droplet diameters < 20 μ m, it can be assumed that they have properties corresponding to the associated gases/ vapors. ( ↑ explosion hazard), [Hesener, U., Kampe, B. et al. (2017)] Agglomeration (Latin: agglomerare, “ to press together ” ). Loose ↑ adhesion of solid particles ( ↑ primary particles) to each other, often caused by electrostatic forces of attraction (seeking minimum surface energy states). Aggregate (Latin: aggregare, “ to pile up ” ). A mass of loosely packed particles. The surface area of these particles is less than the sum of the surfaces of the ↑ primary particles. Aggregation. Loose, low-energy assembly of ↑ ions or ↑ molecules. Agitator. The stirring devices in boilers and reactors can cause a ↑ charge of the liquid due to the flow processes they initiate if the conductivity of the liquid is less than 10 nS/ m. In general, stirring pure liquids does not generate high charges, but as soon as ↑ dispersions (liquid/ liquid, liquid/ solid) are involved, correspondingly high charges can occur due to the much larger contact surfaces. The conductivity of the ↑ continuous phase determines the level of these charges. In the case of internal glass-lined agitators, the charging can lead to electric ↑ breakdowns (punctures) in the glass layer ( ↑ gas discharge mark). [TRGS 727 Section 4] Air boundary layer (laminar). Depending on the surface structure, an air boundary layer is created in material webs moving at a sufficient speed, which impedes heat or mass transfer in process engineering processes (especially drying). This layer can be swirled by an ↑ ion current and thus influenced (e. g. exhausted). Heat/ substance transport is improved (see figure next page). [SE Section 8.2.9] Air boundary layer (laminar) 17 <?page no="19"?> Air breakdown arc. Marking a test method in which the electrode of the ↑ ESD test generator is brought so close to the device under test that the discharge occurs by a flashover directly toward the device under test. Air capacitor. Is a ↑ capacitor whose ↑ dielectric consists of air. Air conductivity. As air conductivity is based on the ion content of the air, dry air is - contrary to general belief - more conductive than air with high humidity. The conductivity of pure dry air under normal conditions is given as 30 fS/ m (femto-siemens/ meter), while it is 1 fS/ m for air at dew point temperature. The reason for this behavior is that the ↑ aerosols contributing to the ionic conductivity near the dew point temperature act as ↑ condensation nuclei and are separated with the mist droplets. Air ionization, ↑ ionization Air jet mill (micronizer). Grinds particles using the energy introduced by the grinding gas. The air jet mill often has a hard or elastic plastic lining to prevent product adhesion, especially in the area of the inlet nozzle. If electrically insulating materials are used, there is a risk of ignition due to the ↑ propagating brush discharge. The latter can be prevented or reduced to a safe level by perforating the lining in a grid of approximately 10 mm. Airbag. Protective device in vehicles in the form of an extremely rapidly inflating airbag, which is inflated by an electrically triggered gas generator. In several cases, electrostatic charging ( ↑ personnel charging), e. g. when getting out of a ↑ car, has caused airbags to deploy incorrectly. The cause was usually inadequate or missing earthing of metal parts of the airbag housing (especially in the steering wheel), which led to false triggering of the ignition elements due to ↑ influence or ↑ ESD. Alpha radiation. Particle radiation produced during radioactive decay (e. g. of polonium Po 210 ), which is identical to 2 times positively charged helium nuclei. Because alpha radiation has the highest ionization density of all nuclear radiation, it has often been used as an ↑ ion source to eliminate unwanted electrostatic charges or to measure electrostatic fields with radium Ra 226 (no longer acceptable today from a radiation protection standpoint). Under atmospheric conditions, a radiation energy of 1 MeV ( ↑ electronvolt) produces 6000 ion pairs/ mm from alpha radiation, 800 from ↑ beta radiation, and 40 from ↑ gamma radiation. Alpha radiation is easily shielded, e. g. with paper. Air breakdown arc 18 <?page no="20"?> Alternating current (AC). A current driven by an ↑ alternating voltage that periodically changes its direction and magnitude (amplitude), with its average value always being zero. The nominal value of an alternating current is the ↑ RMS value. ( ↑ alternating current quantity) Alternating current quantity (also sinusoidal size). It is used to describe the complex ↑ resistance and current components generated by the alternating current (e. g. sinusoidal). They result physically from the approximation of ↑ Maxwell ’ s equations for slowly varying magnetic and electric fields and their application to electrical circuits including their loads. It is common to use the terms “ apparent ” for complex quantities, “ active ” for the real part, and “ reactive ” for the imaginary part of the quantities (U = effective voltage, I = effective current, P = active power, Q = reactive power, R = resistance). ● Active voltage U w is the component of the alternating voltage U as a function of the operating phase shift φ between current and voltage at a resistive load: U w = P / I ● Active current I w defines the electrical work if the current and voltage are in phase: I w = P / U ● Reactive current I b defines the part of the current that is not available for electrical work. In the case of capacitive reactive current, the current leads the voltage by 90°; in the case of inductive reactive current, the current lags the voltage by 90°: I b = Q / U ● Reactive voltage U b = Q / I ● Impedance Z (also called complex alternating or apparent resistance), which is the sum of all resistances that oppose a time-varying energy transport and is composed of the resistance and the reactance. The resistance consumes active power, although it is not converted, because the energy supplied by the generator to the load is returned to the generator. This reactive power loads the lines. Impedance is the ratio of the effective value of the voltage U to the effective value of the current I eff in a network: Z = U / I ● Resistance R (also called active resistance), is the real part of the complex impedance, has the same effect as in a DC circuit and heats up the lines. Current and voltage are in phase. Unlike ohmic resistance, it is frequency dependent. It is calculated from the ↑ RMS values of the alternating voltage and current according to ↑ Ohm ’ s law: R = P / I 2 ( ↑ electric flux density). ● Reactance X (also reactive or apparent resistance), is generally composed of inductance and condensance and is the imaginary part of its impedance as a real value, which can also take negative values: X = Q / I 2 ● Inductance X L , inductive reactance where lags the voltage by 90° and whose value increases with frequency (X L = Ψ / I). It does not generate heat ( ↑ Joule ’ s law). ● Condensance X C , capacitive reactance where the current leads the voltage by 90° and whose value decreases with increasing frequency. In contrast to the DC circuit, where a capacitor “ breaks ” the circuit, in the AC circuit it is charged and discharged according to the frequency. (X C = 1 / 2 π fC) ● Admittance Y (also called complex apparent conductance), the reciprocal of impedance, which is made up of conductance and susceptance: Y = I / U. ● Conductance G (also called active conductance) is the reciprocal of the resistance: G = Re(Y). ● Susceptance B (also called reactive conductance), imaginary part B = Im(Y) of the conductance. Alternating current quantity 19 <?page no="21"?> Alternating voltage. Voltage U that changes periodically in magnitude and sign. With a sinusoidal time characteristic (symbol: ~), the instantaneous value is calculated from U = U 0 × sin ω t (where U 0 is the peak value and ω is the angular frequency 2 π f). The frequency f is expressed in ↑ Hertz [Hz]. The nominal value of the alternating voltage is the ↑ RMS value. Aluminothermic reaction (thermite reaction). Highly exothermic ↑ reaction (temperatures > 2000°C): 2Al + Fe 2 O 3 → 2Fe + Al 2 O 3 . Any type of aluminum on a rusty iron surface is a potential ↑ ignition source. [SE Section 4.8.6] Aluminum powder (particles < 500 µm). Aluminum powder produced in manufacturing processes reacts very quickly with atmospheric oxygen to form a thin insulating oxide layer ( ↑ ceramic). As a result, it can become dangerously charged in insulating or insulating-coated equipment, as well as in earthed conductive equipment. Reaction with atmospheric oxygen is an exothermic process that may result in spontaneous combustion (pyrophoric). Aluminum powder in combination with rust (Thermit ® ) can form a highly explosive dust cloud with a low ↑ MIE. It reacts with a strong chemical reaction on impact ( ↑ light metal). [NFPA 651], [DGUV Regel 109-001] Amber. Fossil resin of Eocene conifers, whose “ miraculous attraction ” to light particles when rubbed was reported by Plato around 360 BC. W. ↑ Gilbert studied and confirmed these curious effects of amber around 1600 and named the phenomenon “ electrica ” , derived from the Greek “ elektron ” for amber. The term “ electricity ” was later coined from this. Ambient temperature. Temperature of the surrounding medium (e. g. air) in which an operating resource (component, device, system) is used as intended. It is part of the physical ambient and operating conditions. [IEC 60204-1] Ammeter (current meter). Since the ↑ electrostatic is a current system, measuring the current is of greater importance, but only in the dimensions < 1 μ A. Thus, ↑ pico-ammeters are often the basic instruments for measuring high-resistances and electric charges ( ↑ influence electrostatic field meter as pico-ammeter). Amorphous. Describes solids without structure, contrast: ↑ crystalline. Ampere. ↑ SI unit [A] of electric current I, named after A. M. ↑ Ampère. The definition of the Ampere by the Lorentz force, valid since 1948, was replaced in 2019. It is now defined by setting the numerical value 1.602176634 × 10 -19 for the elementary charge e, expressed in the unit ↑ Coulomb [C], which is equivalent to the ampere-second [As]. Ampère, André Marie (1775 − 1836). French physicist whose investigations into the relationship between electrical and magnetic phenomena ( ↑ Ampère ’ s law) had a major impact on 19th century physics. Ampère ’ s law. Laws empirically found by A. M. ↑ Ampère on the relationship between electric current and magnetic field. Ampere-second. Unit [As] of ↑ charge Q. ( ↑ Coulomb [C]) Alternating voltage 20 <?page no="22"?> Amplitude (Latin: amplitude, “ size, width ” ). The largest oscillation width that the magnitude of a periodically varying process can reach, e. g. the maximum voltage of the mains voltage ( ↑ peak value). Analyze (Greek: analysis, “ dissolution ” ). Dissection of a whole into its parts. Chemical analysis is often the only way to clarify the interactions of ↑ antistatic agents with the material and its environment. Anion. Negatively charged atomic or molecular particle ( ↑ ion) that experiences a force effect toward the positive electrode in an electric field. Opposite: ↑ cation Anode. Positive electrode (e. g. in gas discharge tubes) on which the negative carrier ( ↑ anion) is absorbed. Anode fall. Strong voltage decay at the anode during ↑ gas discharge. Its magnitude is usually > 10 V and thus the magnitude of the ionization voltage, which depends on the type of gas in which the ↑ plasma is formed. The anode fall is caused by the negative space charge just before the anode and the spatial expansion is practically independent of pressure. ( ↑ cathode fall), [Dzur, B. (2011)] Anodized layer. A surface treatment of aluminum based on electrolytic oxidation with layer thicknesses up to 25 μ m. Anodized coatings are often transparent and give the appearance of bare metal. They typically have very high surface and volume resistivity in their thin film. When using materials with this type of surface coating in equipment and system construction, care must be taken to ensure safe earthing. If not earthed, they can become charged and cause ignition sparks ( ↑ insulation). [SE Section 7.5.18] Antenna. A device in electrical engineering with which ↑ electromagnetic radiation can be received or emitted. The design of antennas determines how sensitive and effective an antenna is in a particular direction (antenna gain) or position (polarization) ( ↑ spark detection device, ↑ gas discharge). Anti-coincidence circuit. A circuit that provides an output pulse only if a signal occurs only at a defined input. If signals also occur at other inputs at the same time, no output pulse is passed through. Antimisting. A form of ↑ useful application in which particle droplets are selectively charged and deposited on an oppositely charged surface. ( ↑ coating), [SE Section 8.2.11] Antimisting agent. Chemical additive to coating materials to prevent the formation of detached, unwanted particles at high web and roll circumferential speeds. Anti-neck-in, ↑ edge zone fixation, ↑ chill roll Antistatic. This property is not defined but is used colloquially. It is used to describe the property of reducing or preventing electrostatic charges. Due to the wide variety of products, a universal definition (e. g. by electrical resistance) is not possible. Since the term antistatic is not linked to a limit value, it should not be used in safety related questions ( ↑ astatic, ↑ antistatic agents). [TRGS 727 Section 2.13] Antistatic 21 <?page no="23"?> Antistatic agents. Are designed to prevent or reduce the electrostatic charge of insulating materials ( ↑ antistatic). Antistatic agents are mainly based on the principle of ↑ ionic conduction. Based on the knowledge that even a layer of water consisting of a few molecular layers on the surface of an object is sufficient to prevent unwanted or dangerous charges, ↑ hydrophilic and/ or surface-active substances (wetting agents) are used as antistatic agents. Antistatic agents are expected, on the one hand, to adhere to the surface of the insulating material and, on the other hand, to form a water-attracting new surface there. The quality of an antistatic agents is determined by how permanently they adhere to the insulating material and to what extent they succeed in binding so many water molecules even at low humidity that the surface resistivity does not exceed a value of about 1 T Ω . Antistatic agents can be divided into those that are applied to the surface after the insulating part is finished, e. g. by spraying or dipping, and others that are mixed into the polymer before processing. The latter migrate to the surface after completion of the plastic part and only after an appropriate storage time. The effectiveness of admixed antistatic agents is generally more durable than that of subsequently applied ones. While all antistatic coatings will lose their effect over time due to cleaning, diffusion, etc., mixed antistatic agents can diffuse from the inside of the material to the surface. The long-term effect depends mainly on the antistatic agent supply and thus on the surface-to-volume ratio: long effectiveness with thick-walled molded parts, but only short effectiveness with thin films. In addition to changes in the mechanical properties, admixed antistatic agents can also affect optical qualities (transparency). In principle, all surface-active substances (surfactants), including polyglycol ethers, alkyl sulphates, quaternary ammonium compounds, etc., are suitable as antistatic agents. In the case of synthetic fibers, the antistatic agents should have the highest possible washing resistance; they are therefore often added during the manufacture of the man-made fiber. The effectiveness of antistatic agents should always be verified and monitored by measurements. The occasional practice of achieving the promised dissipation capability of a material simply by adding a certain percentage of an antistatic agent has seriously contributed to doubts about the reliability of antistatic agents. The side effects of antistatic agents, such as making lamination and printing difficult, can be eliminated by ↑ corona pretreatment and ↑ glossing. ● Antistatic agents in liquids. Antistatic agents in liquids. Liquids with low or moderate ↑ conductivity (< 10 000 pS/ m) can become charged during flow in piping, Antistatic agents 22 <?page no="24"?> stirring, pumping, filtering, or other manipulation. Sufficient conductivity for safe handling can be achieved by adding antistatic agents in the ppm-range. Antistatic agents provide ions for conductivity ( ↑ charging). Antistatic brush, ↑ discharge brush Apparent impedance, ↑ alternating current quantity Application. Partial or planar application of particles or coating materials, is applied using electric field forces with increasing tendency, e. g. in ↑ copying processes, application of ↑ pesticide, etc. ( ↑ coating, ↑ useful application) Apron, ↑ personal protective equipment Arc. A spark transforms into an arc when a continuous current is applied (e. g. in the electrical grid). A glow appears between two ↑ electrodes as a result of impact ↑ ionization. The ionized gas path is conductive. The distance of the arc can be increased within limits without collapsing ( ↑ plasma). An arc against an insulating surface usually causes a burn mark, which can be conductive and thus destroy the insulation. Area limitation. Applies to surfaces of insulating objects or equipment for use in ↑ Exzones ( ↑ chargeability). An area limit of 100 cm 2 was first mentioned in 1967 in the German Directive 4 of BG Chemie. In 2004, the German ↑ Physikalisch-Technische Bundesanstalt (Federal Institute of Physics and Technology) published studies on this subject, which show the relationship between area and transferable charge. According to this, the area limitation has also been scientifically proven. For example, for ↑ RIBC it was found that an area surrounded by a metal frame can be increased by a factor of 4. The area limitation is summarized in [TRGS 727 Section 3.2] in the currently valid table. It should be noted that for curved surfaces their projection is used. Zone Surface area [cm 2 ] in explosion groups IIA IIB IIC 0 50 25 4 1 100 100 20 2 Action required is only if experience has shown that ignitable discharges occur. Zone Width or diameter [cm] in explosion groups IIA IIB IIC 0 0.3 0.3 0.1 1 3.0 3.0 2.0 2 Action required is only if experience has shown that incentive discharges occur. [IEC 60079-0], [Pidoll, U. v. et al. (2004)], {Appendix D} Area limitation 23 <?page no="25"?> Armature (also fitting), (Latin: armare, “ to equip ” ). Component used to change and direct the flow of material ( ↑ valve). If it is lined up on the inside with insulating materials (e. g. PTFE), it can be dangerously charged by the media flowing through it. In a closed system, it can be used without danger, but incendive discharges to the outside are possible ( ↑ spark discharge, ↑ gas discharge). Other conductive fittings must not be installed insulated in ↑ Ex-areas ( ↑ Ex-zone) because the liquid flowing through them can charge a non-earthed component and lead to spark discharge. The connection or end pieces of ↑ hose lines are also referred to as fittings. Arrester. Devices consisting essentially of voltage-dependent resistors ( ↑ varistors and/ or spark gaps, ↑ lightning arrester and/ or voltage-limiting semiconductors, ↑ Zener diodes, ↑ TVS diodes). They are used to protect electrical operating resources and installations against impermissibly high overvoltage, that are discharged to earth. The arresters are characterized by their response voltage and response time. Based on their surge current arresting capacity, they are divided into lightning arresters (thunderstorm lightning effects due to near strikes) and surge arresters (far strikes), switching overvoltage and electrostatic discharges. Artificial silk. Former name for synthetic fibers obtained from cellulose ( ↑ rayon fiber). Aspiration condenser, ↑ Ebert tube Aspiration psychrometer, ↑ humidity meter Assessment data. Compilation of ↑ assessment values and operating conditions. Assessment value. The value of a quantity applicable to a given operating condition, generally specified by the manufacturer for an element of a group, device or operating resources. For explosion prevention purposes, classification is made into ↑ equipment categories. Association for Electrical, Electronic & Information Technologies, ↑ VDE Association of German Engineers of all disciplines (German: Verein Deutscher Ingenieure (VDI)). Founded in 1856, based in Düsseldorf. Its committees develop the VDI guidelines, which are recognized rules of technology and standards for proper technical behavior. ( ↑ state of the art) Astatic. Sometimes used to refer to substances used to prevent electrostatically induced interference due to ↑ adhesion. The astatic additive does not improve conductivity like an antistatic agent, but only increases the distance between the charged parts. This is achieved by extremely fine particles in the nm-range, such as highly dispersed silicon oxide ( ↑ Aerosil ® ) or organic powders made from corn starch, which adhere to the particle Armature 24 <?page no="26"?> surfaces. In this way, the contact areas are reduced (lower charge separation) and the distances between charged surfaces are increased (reduction of coulombic attraction forces). In this way, agglomeration in bulk solids can be avoided, flow behavior can be improved (lower ↑ bulk cone), and wall adhesion can be reduced. In the case of larger charged parts, such as film sheets and the like, adhesion can also be reduced, e. g. when individual sheets or glass plates are lifted from a stack. Asymmetric rubbing (friction). When two materials rub against each other, the surfaces rubbing against each other can be of different sizes. This results in an asymmetrical load on the friction partners, e. g. in the way a bow strokes a violin string ( ↑ violin bow effect). [SE Section 2.6] ATEX. Term comes from the French Atmosphères Explosibles. In EC law, the nature (ATEX 114) and use (ATEX 137) of work equipment are strictly separated. The reorganization of national law on plant and operational safety follows this separation. ● ATEX 114 (formerly ATEX 95). Directive 2014/ 34/ EU of the European Parliament and of the Council of 26.02.2014 on the harmonization of the laws of the Member States relating to equipment and protective systems intended for use in potentially explosive atmospheres (recast). Since 21.04.2016, all equipment and devices placed on the market in the EU must comply with this directive. According to the safety requirements to be met, they are divided into equipment groups and ↑ equipment categories. All equipment used in potentially explosive atmospheres must be marked with the symbol shown (color: yellow). The purpose of ATEX 114 is to protect people who work in potentially explosive atmospheres or who may be affected by explosions. It was transposed into national law by the 11th Ordinance to the ↑ ProdSG [11. ProdSV] of 06.01.2016. ● ATEX 137. Directive 1999/ 92/ EC of the European Parliament and of the Council of 16.12.1999 on minimum requirements for improving the safety and health protection of workers potentially at risk from explosive atmospheres (15th individual Directive within the meaning of Article 16(1) of Directive 89/ 391/ EECIt sets out minimum requirements for improving the health and safety protection of workers. These essential requirements include the - Primary ↑ explosion prevention (prevention or limitation of the formation of ↑ Ex-atmospheres), - Secondary explosion prevention (prevention of effective ignition sources), - Constructive (tertiary) explosion prevention (limiting the effects of a possible explosion to a harmless level). ATEX 137 was implemented into national law in Germany in 2002 with the ↑ BetrSichV. This also includes the obligation to apply the illustrated marking (color: yellow) to areas where explosive atmospheres may occur. ( ↑ Federal Institute for Occupational Safety and Health (German: BAuA)) ● ATEX borderline cases. Lists products for which it is initially unclear whether they fall within the scope of the ATEX 114 directive (current version November 2022). ATEX 25 <?page no="27"?> Example: ↑ earth clamp (ground clamp) for earthing. In this case, it must be assessed on a case-by-case basis whether the design of the equipment contains potential ignition sources (e. g. a steel spring). The list does not replace the risk assessment of each product. In addition, ignition sources and explosion hazards associated with the use of all products must always be considered. ● ATEX guidelines. Provide a manual to facilitate the application of ATEX 114. They have been prepared by the European Commission in cooperation with the Member States, the European Standards Bodies and the ↑ Notified Bodies and are currently in their 3rd edition (May 2020). Atmosphere. The gaseous envelope of the Earth consisting of 78.08 % nitrogen (N 2 ), 20.95 % oxygen (O 2 ), 0.93 % argon (Ar) and trace gases, including 0.04 % carbon dioxide (CO 2 ). A change in the oxygen content of the atmosphere results in an increase or decrease in a fire or ↑ explosion hazard ( ↑ explosion prevention, primary, ↑ limiting oxygen concentration). ( ↑ barometric pressure) Atmospheric condition ● Term used in test engineering to indicate that the test is performed under normal atmospheric pressure at sea level (1013 hPa ~ 1 bar) and normal composition of the ↑ atmosphere. A rough classification is 78 % nitrogen and 21 % oxygen. ● For explosion prevention ( ↑ ATEX), total pressures of 0.8 to 1.1 bar and mixture temperatures of - 20 to + 60 °C under atmospheric conditions apply. Atmospheric electric field, ↑ field Atmospheric electricity. A generic term for all natural electrical phenomena in the Earth ’ s atmosphere. Charge carriers ( ↑ ion) are constantly generated in the Earth ’ s atmosphere by the influence of radioactive radiation, short-wave solar radiation, and ↑ cosmic radiation. They cause a potential distribution that results in vertical electric currents. The ↑ ionization of the upper layers of the atmosphere ( ↑ ionosphere) causes a reflection of electromagnetic waves (short wave receiving). Atmospheric potential gradient (APG). Potential gradient of the atmosphere ( ↑ atmospheric electricity). Atom (Greek: atomos, “ indivisible, uncuttable ” ). Atoms cannot be further divided by chemical means, but they can be broken down into elementary particles ( ↑ electron) by physical means. According to the atomic model developed by N. ↑ Bohr (outdated, but illustrative), the atom consists of the nucleus surrounded by electrons circulating on socalled quantum orbits. The nucleus (radius ~ 10 fm (10 -15 m)) is composed of positively charged protons and electrically neutral neutrons and represents almost the entire mass of the atom. In the atomic shell (radius ~ 10 pm (10 -12 m)), as many negatively charged electrons orbit the nucleus as it contains ↑ protons (the atom is electrically neutral). The electrons can only move around the nucleus on very specific paths corresponding to the possible energy values of the atom without exchanging energy. During the transition to lower energies, radiation quanta can be released ( ↑ gas discharge light). Absorption or release of electrons results in a charge state of the atom, it becomes an ↑ ion. ( ↑ impulse excitation) Atmosphere 26 <?page no="28"?> Atomic number. Symbol Z is the number of positive elementary charges in an atomic nucleus. It is equal to the number of protons in the nucleus of the chemical element. Atomic weight (also atomic mass). The mass of a single atom can be given in the SI unit [g] like any other mass. It is based on the carbon atom, whose nucleus consists of six protons and six neutrons. It is assigned to an atomic weight of 12. Thus, the atomic weight unit is 1/ 12 of the mass of the C-12 atom, which is 1.7 × 10 -24 g. Atomization (electrical). This term, which is not correct for nuclear physics, refers to the bursting of liquid droplets under the influence of an electric field. For the process itself, it is irrelevant whether the charging occurs by ↑ influence or by ↑ frictional charging. The figure shows a droplet floating in an electrostatic field. The mutual repulsive force based on the like charge inside the droplet causes expansion, which eventually overcomes the cohesion due to surface tension; the droplet becomes unstable and bursts ( ↑ Rayleigh limit). The positively charged aerosols resulting from the bursting of the drop follow the field lines, in this case to the nearest earthed object. Applications of the principle: ↑ coating, ↑ remoistening, distribution of ↑ pesticides, hair dryer with ionization pin, etc. Aurora borealis / Aurora australis. Luminous phenomenon caused by solar protuberances, in which high-energy cosmic radiation ( ↑ corpuscular rays) ionizes the nitrogen and oxygen atoms of the Earth ’ s atmosphere. It occurs primarily in the polar regions of the Northern Hemisphere (aurora borealis) and Southern Hemisphere (aurora australis) because the corpuscular rays are deflected toward the poles by the geomagnetic field. Auxiliary circuit, ↑ electric circuit Avalanche effect. Describes the rapid increase in charge carriers ( ↑ ion) in the event of an impact ↑ ionization ( ↑ gas discharge) and in ↑ Zener diodes. Avivage (French: aviver, “ to enliven ” ). Mainly process-enhancing finishing of yarns and fabrics, e. g. after a washing process, in which avivage (they are sometimes also counted among the refinements) is added. In the case of yarns, the aim is to improve the spooling capability (smoothing substances). Avivage improves the handle and color brilliance of fabrics, and antistatic properties can also be achieved. Avivages can contain fatty acids, derivatives, silicone oils, quaternary ammonium compounds ( ↑ antistatic agents) and phyllosilicates. Avivage agents can also be applied as fabric softeners in a softening cycle following the washing process, or the avivage active ingredients can be added directly to the detergent. Avogadro ’ s number. Since 2019 defines the unit of measurement ↑” mole ” and indicates how many molecules of a chemical compound or atoms of an element are contained in one mole. The dimensionless value of the Avogadro ’ s number is N A = 6.02214076 × 10 -23 mol -1 ( ↑ Loschmidt ’ s number). Avogadro ’ s number 27 <?page no="29"?> B Back-spraying. Sets in under ↑ atmospheric conditions when the ↑ surface charge density exceeds the maximum value of 26 μ C/ m 2 ( ↑ St. Elmo ’ s fire, ↑ corona discharge). This causes, among other things: - Reduction in charging during separation processes - Deterioration of the separation effect during gas purification ( ↑ separation of substances) - “ Cratering ” during powder ↑ coating and flocking {Appendix M.3.2} Bag. Powdery substances must not be transferred from rechargeable bags into containers already containing flammable liquids. Transfer must be through a sluice into the inert container and personnel must be earthed. Double flap systems, screw conveyors and socalled ↑ PTS, which do not neutralize the ↑ inerting in the receiving container, have proven to be effective airlocks in practice. Rechargeable bags may only be used if the point of entry is assigned to Zone 2. [TRGS 727 Section 6.3] Bag filters. They are used to separate dust from air and usually consist of textile bags that are exposed to raw gas (dust-laden air) on the outside. Regular shaking or blowing transports the separated dust into a collection container ( ↑ filter). If combustible dust is to be separated, the bag filters must be designed with discharge capability and must be checked regularly. [TRGS 727 Section 6.5] Bakelite. Synthetic resin molding material, invention of the Belgian chemist Baekeland (1907), produced by polycondensation of phenol and formaldehyde. Bakelite is considered to have electrostatic dissipation capability ( ↑ surface resistance). Ball lightning. Often described as a ball at the end of a ↑ thunderstorm lightning that moves in undefined trajectories and disappears with or without a bang. A clear scientific explanation has not yet been found. Ballo electricity. Occurrence of negative electric charges when water droplets burst (waterfall electricity, ↑ Lenard effect, ↑ Rayleigh limit). Ballooning. Spiders are able to detect the Earth ’ s electrostatic ↑ field, which causes stimulation to produce sufficient quantities and long spider threads. It can thus use the potential difference in the Earth ’ s field to take off and travel by the field alone or in addition to air movement. [Morley, E. L., Robert, D. (2018)] BAM, short for German: Bundesanstalt für Materialforschung und Materialprüfung ( ↑ Federal Institute for Materials Research and Testing) Banana roller. A special form of spreader roll (guide roller) for the wrinkle-free transport of webs through a production line. The special geometric conditions cause different <?page no="30"?> charges on the surfaces of the web. ( ↑ web tension profile, ↑ Lewis ’ s acid-base concept), [SE Section 2.14.1.1] (Source: www.kickert.de) Band gap, ↑ forbidden band, ↑ band model Band model. According to the model of the ↑ atom proposed by N. ↑ Bohr, ↑ electrons move on fixed orbits around the nucleus. Each orbit can be assigned a discrete energy. In solids, atoms are so close together that each electron is affected not only by its own nucleus but also by other nuclei ( ↑ electron conduction). The discrete energy levels are replaced by many sublevels with very small distances. The set of sublevels appears in solids as a quasicontinuous energy band. In the band model, the energy values on the Y-axis (E) are plotted against a spatial coordinate on the X-axis (Cartesian coordinates). For ↑ semiconductors and nonmetals, the energy states are described by the ↑ conduction and ↑ valence bands separated by a ↑ forbidden band (energy band gap). According to classical physics, the probability that a charged particle can enter such a zone is zero. Exceptions occur due to the ↑ tunnel effect. Bandwidth ● Bandwidth of measuring systems. Frequency range in which input signals of measuring instruments are evaluated. In the case of electrostatic measurements (small signals in high-impedance measuring circuits), care must be taken to ensure that there is sufficient distance between the interference range and the input range of the measuring instrument. This is important, for example, when non-contact bulk quantities ( ↑ mass flow rate) of electrostatically charged particles are to be recorded with the aid of an influence measurement probe. ● Bandwidth of signal systems. Frequency range within which the technical arrangement fulfills its required function, e. g. the frequency range of a cable within which signals can be transmitted with a given maximum power loss or the frequency range of Bandwidth 29 <?page no="31"?> an amplifier within which it can generate signals with a given amplification ratio to the input signal or with a given output power. Bar electrode, ↑ measuring electrode for solids no. 17 Barium oxide. Base material for ceramic insulators. Barium oxide is added to ceramic bodies as barite, witherite, or chemically produced carbonate. Barium titanate. ↑ Dielectric for ↑ capacitors based on titanium dioxide mixed with barium oxide. Barium titanate is made by reacting barium carbonate with titanium dioxide. As a dielectric, barium titanate is particularly valued for its high permittivity of ε r ≈ 1200 - 3000 (depending on the ↑ field strength) and high dielectric strength of E d ≈ 50 kV/ mm. It is also used to make ↑ electrets. Barometric pressure. The pressure exerted by the Earth ’ s ↑ atmosphere. The mean atmospheric pressure at sea level is: 1013.25 ↑ Pascal = 1013 hPa = 1013 mbar - In compressed air technology, the unit [bar] is often used, although it is not an SI unit (1 bar = 100 kPa). - In vacuum technology the unit [mPa] is used. - The Anglo-American system of measurement uses the unit [PSI] (pounds per square inch). 1 PSI is equal to the pressure exerted by a force of one pound (1 lb ≈ 4.44822 N) on an area of one square inch (1 in 2 ≈ 6.4516 cm 2 ) so 1 PSI ≈ 6894.76 Pa. Other pressure units that can still be found in some cases, but are no longer allowed, are: - Torr: 1 Torr = 1 mmHg (mercury column) = approx. 133.3 Pa = 4/ 3 mbar 1 Torr is the pressure exerted by a column of mercury (diameter 1 cm 2 ) at a temperature of 0 °C and a height of 1 mm at the base of the column. - Technical atmosphere (at) = 1 kp/ cm 2 = approx. 98066.5 Pa - Physical atmosphere (atm) = 760 Torr = 101325 Pa = 1013.25 hPa Barrel. Cylindrical packaging made of metal, cardboard, plastic or plywood, used as a transport and storage container for solid ↑ bulk materials or liquids ( ↑ container filling, ↑ packaging means, ↑ reconditioning). Basic insulation, ↑ insulation Basic unit, ↑ SI unit Battery. Originally a military term used by B. ↑ Franklin for the serial connection of ↑ Leiden jars. In electrical engineering, a battery is the interconnection of several devices of the same type (e. g. ↑ accumulator, ↑ capacitor, ↑ primary cell). BAuA, short for German: Bundesanstalt für Arbeitsschutz und Arbeitsmedizin ( ↑ Federal Institute for Occupational Safety and Health) Becquerel, Henri (1852 - 1908). French physicist, in 1896, while studying the phosphorescence of uranium minerals, found a previously unknown radiation emanating from Bar electrode 30 <?page no="32"?> uranium. For this discovery of natural radioactivity, he was awarded the Nobel Prize for Physics in 1903, together with P. and M. ↑ Curie. Becquerel. Unit [Bq], named after H. ↑ Becquerel, replaces the former unit ↑ curie [C]. The activity of a radionuclide is 1 Bq if 1 atomic nucleus of the amount present decays per second. Belt, ↑ transmission belt Belt electricity. A widespread form of static electricity at the time of transmission drives ( ↑ transmission belt). Discharge phenomena such as ↑ brush, ↑ spark and ↑ propagating brush discharges have been observed in manufacturing facilities that were often poorly lit in the past and where power was transmitted from a drive machine to several work machines via drive belts. Explosion events in the chemical industry have often been attributed to belt electricity. [TRGS 727 Section 3.5] In GDR law [DDR-Gesetzblatt 148 (1952)] it was formulated: To reduce hazards, drive belts “ may only be sewn, glued or held together by non-sparking belt fasteners. Belts and pulleys must be free of belt electricity. Protective measures against the generation of belt electricity: a) Avoid drive belts with direct motor drive; b) Use non-sparking belts; c) Make non-conductive belts conductive (e. g., by weekly coating of leather belts with a glycerinewater or glycerine-alcohol solution in a 1: 1 composition). ” Bessel, Friedrich Wilhelm (1784 - 1846). German astronomer and mathematician laid the foundations for astrometry. Bessel ’ s function. A solution found by F. W. ↑ Bessel by series development in the integration of cylindrical functions. This can be used to solve some electrical engineering problems, such as current displacement in wires ( ↑ skin effect). Beta radiation. Particle radiation resulting from radioactive decay, releasing predominantly high-energy electrons, e. g. 18 keV ( ↑ electronvolt) for tritium with a half-life of 12.3 years. Beta radiation is already absorbed by thin layers (e. g. 2 mm of plastic or 1 mm of aluminum). Betatron. In a betatron, electrons are accelerated to high energies in a ring-shaped vacuum tube by electromagnetic induction (transformer principle). The circulating electrons are kept on the ring orbit by appropriate magnetic field arrangements. This high-energy electron radiation can be used to generate extremely high charge densities in insulating materials, up to the point of electric ↑ breakdown ( ↑ dendrites). BetrSichV, short for German: Betriebssicherheitsverordnung (Operational Safety Regulation). The German Industrial Safety Regulation is the implementation of ATEX 137 into German law. The regulations for the BetrSichV (last amendment 05.2019) are the Technical Rules for Industrial Safety (German: TRBS). These form the instructions for the measures specified in the BetrSichV. If the TRBS are complied with, the user can assume that he has done everything to avoid accidents. Various TRBS have been further developed into Technical Rules for Hazardous Substances (German: TRGS) and assigned to the ↑ GefStoffV (e. g. TRBS 2153 to [TRGS 727]). BetrSichV 31 <?page no="33"?> Beyling, Carl (1872 - 1938). German mining inspector developed the basis for firedamp and explosion prevention in 1912 with his experiments on the firedamp proofness of specially protected electric motors and apparatus in coal mining. Bifilar (Latin: bis, “ double ” , filum, “ wire ” ). Two-threaded, two-wire, e. g. in one winding ( ↑ bifilar coiling). Bifilar coiling. Type of coiling, e. g. of resistance wires, to reduce ↑ self-induction. For this purpose, the wire is bent in half and the two halves are wound as a parallel double wire, insulated from each other. Since the same current flows through the adjacent wires, but in opposite directions, the magnetic fields generated in the forward and return conductors cancel each other out. The inductances of the two conductors also cancel each other out, but the capacitance of the system increases. Big Bag. Slang term for flexible intermediate bulk container, ↑ FIBC. Biogas facility. Due to its composition, biogas contain a high proportion of methane and other gases (e. g. hydrogen) in addition to carbon dioxide. Therefore, safety measures to prevent electrostatic ignition hazards are required for ↑ explosion group IIA. [TRGS 727 Section 3.2.1] Biological effects of electric fields. They are to be assessed according to [EU 2013/ 35]. No health limits have yet been agreed for DC electric and magnetic fields, as no hazards have yet been identified (natural ↑ field, ↑ primeval code). Bipolar charge, ↑ bipolar charge layer, ↑ excess charge, ↑ charge double layer Bipolar charge layer, also known as double layer charge. A phenomenon in which opposite-pole electrostatic ↑ charges are present mainly on plastic films with very low conductivity ( ↑ charge double layer). By applying charges of opposite sign to both sides of a thin insulating film, e. g. by corona charging ( ↑ useful application), a bipolar charge layer can be formed. The strong electric field of the charged film surface acts only between the top and bottom of the film, i. e. the ↑ Coulomb force acts in the film thickness, so that no electric field is effective to the outside. Therefore, the potential of a charge with a ↑ EFM is usually not measurable, and ↑ ionizers have no effect. The amount of ↑ surface charge density is limited only by the ↑ breakdown voltage of the film. Thus, much higher amounts of charge can be stored than in a monopolar film ( ↑ excess charge). Depending on the conductivity of the film, this state lasts for a very long time. The thinner and more resistive the film is, the harder it is to discharge. Bipolar charge layers are a prerequisite for the development of ↑ propagating brush discharges. It cannot be compared to an ↑ electret. Beyling 32 <?page no="34"?> Bipolar charge layers lead to significant problems in film processing. Only the systematic use of ↑ charging electrodes can create the possibility of eliminating them with ionizers by strongly disturbing the bipolar charge layer from the outside ( ↑ coercive field strength). When unwinding and rewinding films with bipolar charge layer, additional conditions resulting from mechanical ↑ charge accumulation and maximum charge coverage (propagating brush discharge, ↑ super brush discharge) must be considered. [IEC/ TR 61340-1], [SE Sections 4.2.3.1 and 5.4.1.3] ● A bipolar charge layer can be visualized as an ↑ equivalent circuit from which the ↑ relaxation time can be calculated via the capacitance (plate/ plate) in combination with the permittivity ε of the material. Here, the top and bottom surfaces, each with full charge coverage, are to be considered as plates. {Appendix M.1, M.6.3.1 and M.6.4.1} ● Metrological verification of a symmetrical bipolar charge layer is possible by using two ↑ influence electrostatic field meters in combination with the voltage probe and the use of two identical contact plates. ● When a bipolar charge layer is shorted, a high-energy propagating brush discharge is generated. This generates sufficient high energy to ignite dust. This can be well illustrated in an experiment if the film has been previously dusted with ↑ lycopodium, for example. The shock wave generated during the discharge causes the dust to be disturbed and immediately ignited. ( ↑ excess charge), [SE Sections 5.4.1 and 6.9.7.2] Bipolar charge layer 33 <?page no="35"?> Blizzard (winter thunderstorm). Sometimes lightning discharges can also be observed during heavy snowstorms. Again, friction and separation processes are likely to be the cause of the charge. Blocking. ↑ Useful application for stabilizing and fixing multiple layers of paper, film or wood fiber board into a block that only needs to remain stable until, for example, automatic palletizing or packaging is complete: The electric charge is applied to the product stack by a ↑ charging electrode or a chargeable metal plate with or without contact pressure against an earth potential. As a result of the ↑ charge displacement, the products stick together ( ↑ Coulomb force), provided that the charge cannot dissipate over the required time ( ↑ dissipation capability). The use of high-voltage generators of opposite polarity may be useful to improve the holding forces. [SE Section 8.2] Blow air. The combination of blow air and ionizers is successfully used in many places in industry for discharging and cleaning surfaces. A cleaning system must perform two tasks: - Eliminate static from the surface - Elimination and removal of adherent particles Blow-out pipe. Pipe through which burning gases or dust released when an ↑ explosion pressure relief is triggered are safely vented. If large quantities of particles are whirled up (e. g. rust or deposited dust), electrostatic charges must be expected, which can lead to ignition, e. g. if the explosion pressure relief is triggered incorrectly ( ↑ quench tube). Body current. Electric current through living beings ( ↑ electric shock, ↑ danger of electric shock). A “ dangerous body current ” usually causes a pathophysiological effect. In the case of electrostatic discharges, the potential for direct harm is generally low because these discharges are a one-time event. However, the secondary accidents and effects are often serious (startle reaction, strong muscle contraction up to bone fracture, etc.). [BS IEC 60479-2] Body of electrical equipment. Accessible, conductive part of electrical equipment that is normally not live but can become live in the event of a fault if the basic insulation fails. [IEC 60050] Blizzard 34 <?page no="36"?> Body short circuit. Conductive connection between living beings and active parts of electrical equipment caused by a fault. The body short circuit can cause an electric shock to the user. Bohr, Niels (1885 - 1962). Danish physicist, he established the atomic model named after him in 1913 by introducing his quantum conditions, following the ideas of Rutherford. Bohr ’ s atomic model, ↑ atom Borderline list, ↑ ATEX borderline cases Braking beams, ↑ X-rays Braun ’ s tube, ↑ electron-beam tube Breakdown (electric). Occurs spontaneously when the ↑ breakdown voltage is exceeded. Regardless of the medium, electrical energy is always converted to heat, causing damage. The mechanisms are as follows. ● Solid material: Individual conduction electrons, which are always present, are accelerated by a high electric ↑ field strength to such an extent that they release a large number of charge carriers by impact ionization in times < 1 μ s, heat the dielectric and finally cause a breakdown channel by partial stress cracks, melting or carbonization. ( ↑ dendrites) The result is perforation of the object (leakage). The test is performed according to [IEC 60243-1 and 60243-2]. ● Liquid: Hydrodynamic effects can deform the electric field between the electrodes, gas bubbles and/ or contaminants, as well as overheating due to turbulent ion movement (ion avalanche), which leads to fragmentation of the liquid molecules and ultimately causes a breakdown channel. This creates molecular clusters that lead to impurities (e. g. oil charring). The test is performed according to [IEC 60156]. ● Gas: ↑ gas discharge Breakdown field strength (dielectric field strength). A term generally used for gaseous, liquid, and solid insulators, preferably for solids. It is directly related to the ↑ surface charge density. The breakdown field strength can also be used to measure high voltages using a ↑ spherical spark gap. The breakdown field strength of air in a homogeneous field and under atmospheric conditions can be calculated: E = σ / ε 0 ≈ 3 MV/ m (surface charge density σ max = 26 μ C/ m 2 ; ↑ permittivity ε 0 = 1) The breakdown field strength depends on the gas pressure at which it occurs. ( ↑ Paschen ’ s law), {Appendix M.3.3} Breakdown resistance. Resistance at which the resistance can breakdown significantly (> 50 %) after continuously increasing measuring voltage and equally continuous measuring. In such measurements, the resistance to breakdown, the resistance after breakdown, and the voltage at the time of breakdown must be recorded. The breakdown resistance is used, among other things, to detect the ↑ shell effect ( ↑ tera-ohmmeter). [SE Section 3] Breakdown strength, ↑ electric strength Breakdown strength 35 <?page no="37"?> Breakdown voltage. Voltage value at which the number of newly created charge carriers in an insulating medium (solid, liquid, gas) on a discharge path has become so high that a significant current flow occurs. When the breakdown voltage is reached, the insulating material loses its insulating properties. The breakdown voltage is not a specific material property. It depends on the thickness of the sample, the shape of the test voltage curve, the rate of voltage rise, the duration of voltage exposure, ambient temperature, barometric pressure, relative humidity, and sample condition. The measurement result can also depend on the electrical and thermal properties of the medium surrounding the sample and on gas inclusions in the sample ( ↑ breakdown resistance, ↑ breakdown). ● Breakdown voltage in semiconductors or breakthrough. Characterizes a rapid increase in current, i. e. in this range a small change in voltage causes a large change in current ( ↑ Zener diode). In the field of electrostatics, the term breakthrough is mainly used for faults in electronic components caused by electrostatic charging. ( ↑ ESD) Bridge network (also bridge connection, bridge circuit). It is based in principle on the parallel connection of two voltage dividers consisting of the resistors R 1 and R 2 resp. R 3 and R 4 , whose partial voltages are compared via a zero instrument. If the bridge voltage U becomes zero (zero method), the following setting condition applies to the bridge circuit: R 1 / R 2 = R 3 / R 4 . When the bridge network is operated with an AC source, apparent impedances can also be measured. In the field of electrostatics, bridge networks are rarely used for ↑ resistance measurements, because measuring methods based on the voltage/ current principle using ↑ pico-ammeters are easier to implement for the range of about 1 k Ω to 1 P Ω to be measured. The lower accuracy compared to a bridge network is irrelevant for electrostatics. ( ↑ capacitance measurement) Common bridge networks are the ↑ Schering, ↑ Thomson, ↑ Wheatstone, and ↑ Wien bridges. Brønsted, Johannes Nicolaus (1879 - 1947). Danish physicist and chemist, best known for his acid-base theory, which he published at the same time in 1923, independently of T. M. ↑ Lowry. ( ↑ Lewis ’ s acid-base concept) Brønsted-Lowry definition. J. N. ↑ Brønsted and T. M. ↑ Lowry independently described an acid as a proton donor (a particle that can donate protons) and a base as a proton acceptor (a particle that can accept protons) in 1923. Any reaction of one partner as an acid necessarily requires the presence of a second partner as a base to which the acid can transfer its protons. The Brønsted-Lowry definition can possibly be used to explain the indeterminable charging of ↑ material webs, because the electrostatic ↑ charging takes place in the nm-range, where the impurities present on the material partners interact with environmental influences. ( ↑ Lewis ’ s acid-base concept) Brownian molecular motion. Irregular motion of tiny particles suspended in a liquid or gas, discovered 1828 by the British botanist R. Brown (1773 - 1858). It is based on the thermal motion of gas or liquid molecules (thermodynamics), in which the particles are Breakdown voltage 36 <?page no="38"?> constantly subjected to irregular collisions. Brownian molecular motion is responsible, among other things, for the ↑ charging of liquids. Brush discharge. ↑ Gas discharge to the nearest conductive earthed object or insulated conductive object of much higher capacitance, where the formation mechanism is similar to that of ↑ corona discharge. However, it originates from electrodes with larger radii (> 1 mm) and therefore requires a higher potential for its initiation. The charged insulating material has only a small amount of energy in the brush discharge region and, after initial plasma confinement, is used up for this purpose as a result of energy consumption during gas compression (Figure 1). Therefore, the brush discharge breaks off from the earthed electrode shortly after its start, leaving a plasma channel ( ↑ leader) for only a short distance (Figure 2, diagram). If the charge is replenished, e. g. by the passage of a charged material web, the process can be repeated and new brush discharges occur continuously, the discharge traces of which can be seen on a color film material (see photo). (visible ↑ charge distribution) Buckyballs (after R. Buckminster-Fuller), ↑ carbon Building lightning protection, ↑ lightning protection Bulk cone. Formed when fine-grained solids fall down (sedimentation), characterizes their flowability ( ↑ bulk cone height) and is characterized by its angle of repose. Bulk cone height. A measure of the flowability of finegrained bulk materials. The material to be tested is poured onto a vertical metal cylinder (diameter 50 mm) through a mesh mounted above it. Since the diameter of the bulk cone is constant, the bulk cone height is a direct measure of flowability. A cone height of < 20 mm is considered very good, while > 60 mm is considered unsatisfactory. Bulk cone height 37 <?page no="39"?> Bulk container. Must be earthed to prevent electrostatic hazards during ↑ container filling and emptying, but not during transport. Bulk containers include ↑ FIBCs or ↑ hobbocks made of conductive materials or containers with built-in conductive materials. Bulk material. A general term for particulate solids ranging in size from fine ↑ dust, semolina and ↑ granules to chips. Flammability ( ↑ MIE) increases as particle size decreases. Bulk materials are divided into three groups according to their ↑ resistivity: Low ρ B ≤ 10 6 Ω m Medium ρ B > 10 6 Ω m to ≤ 10 10 Ω m High ρ B > 10 10 Ω m When handling bulk material, electrostatic ↑ charging must always be expected ( ↑ explosion prevention, ↑ explosion-related parameters, ↑ measuring electrode, ↑ sieve analysis, ↑ resistance measurement). [TRGS 727] Bulk material charging, ↑ charging Bulk material discharge. Bulk materials generally have a high electrical resistance, which means that only a small amount of discharge is possible via intrinsic conductivity. Instead, the ↑ charge is transferred to a vessel wall via gas ions, for example ( ↑ charge transfer). Bulk solids with a resistivity < 10 6 Ω m, which can become charged during transport, e. g. in insulating pipes or hoses, are to be considered as insulated, unearthed conductive objects, since they can cause a ↑ spark discharge ( ↑ earthing). Therefore, their possible charge during filling must be dissipated by one or more earthed metal bars. The use of ↑ FIBC-C type as an earthing measure is not sufficient, since a breakdown voltage of ≤ 6 kV is allowed for this type, so that ignition-effective spark discharges can occur. ( ↑ cone discharge), [TRGS 727 Section 6.6], [Glor, M. et al. (1989)] Burst (old English: berstan). When a contact is opened in an inductive circuit, selfinduction can produce such high voltages that multiple ↑ arcs, called bursts, occur ( ↑ transient). Bursts are always expected in electrical power systems, so all electrical and electronic equipment must be designed to withstand them up to a certain voltage level. The burst generators used for testing deliver single pulses (rise time about 5 ns, duration about 50 ns) and are measured against a 50 Ω resistor. The burst can be adjusted in voltage level and repetition frequency of the pulses, as well as their duration and pauses. [IEC 61000-4-4] Bushing. An insulating device that guides one or more electrical conductors through an inner or outer wall of a housing. [IEC 60079-0] Bulk container 38 <?page no="40"?> C Cable (electrical). Electrical energy transport path. A “ fixed cable ” is attached to a base in such a way that its position does not change. A “ moving cable ” is connected at both ends but can move between its connection points. ( ↑ electrical disturbance), [IEC 60228] Cables usually consist of an insulating sheath and a metallic core (mainly copper), which should have as low a resistance as possible. For electrostatic applications, particularly in the field of ↑ coating (powder coating, wet painting, high-speed rotary atomization, etc.), cables with a conductive plastic core have proved to be an effective solution for supplying high voltage to the application equipment. The reason for this is the possibility of short circuits in such applications. If cables with a copper core are used, a short circuit can cause a current spike in the device (Figure 1). 2 m standard HV-cable (copper conductor), charging voltage: 20 kV, maximum current peak: 130 A, discharge time 6.4 µS (Source: www.schnier-elektrostatik.de) When so-called “ damped ” high voltage cables are used, the internal resistance (typically between 40 and 200 k Ω / m) reduces the current spike at the high voltage generator to less than 1 %. (Figure 2) 2 m damped HV-cable (plastic conductor), charging voltage: 20 kV, maximum current peak: 140 mA, discharge time: 300 µS (Source: www.schnier-elektrostatik.de) Cable charging. ↑ Electrical disturbance that must always be considered. Special cables should be used for electrostatic measurements (resistance < 10 12 Ω , current < 10 -12 A); if <?page no="41"?> these are placed on an earthed object, the result may be falsified ( ↑ measurement error). With an earthed base, additional capacitance, and possibly reduced insulation ↑ resistance to earth will falsify measurements (noise effect). Caution: Cable drums of shielded high-voltage cables that are not short-circuited may have stored residual charges due to their high-voltage test. Residual charge is also to be expected if the cable core was powdered with electrostatic support during manufacture ( ↑ useful application). Cable cross section. Particularly in the case of electrostatic earthing the appropriate cable cross-section must be selected if mechanical and corrosive stresses are to be expected. A permanent leakage resistance of R E < 10 6 Ω must be guaranteed. [TRGS 727 Sections 8.3 and 8.5] Cable designation. Contained in [DIN VDE 0292] as a system for type abbreviations for insulated cables and generally follows the following sequence: marking of the intended use / rated voltage / insulating material / structural elements / sheath material / special features in the structure / conductor type / number of cores / protective conductor / nominal conductor cross-section in [mm 2 ]. Cable system. The entirety of cables, conductors, and bus bars as well as their fastening elements and their mechanical protection. CAFE system. Describes a measurement method according to [ANSI/ ESD STM15.1]. CAFE stands for: - Charging: Can the material be charged by friction, motion or other ways? - Attenuation: How is the relaxation time? - Field: Measurement of the E-field at the sample. - Energy: How much charge can be released? Calender. Machine with mostly stacked sometimes individually driven rolls for processing textiles, paper, and plastic films (finishing process). The large area of contact between the rolls generates high charges, especially on webs with high resistance, which can lead to significant defects if not sufficiently dissipated during rewinding ( ↑ super brush discharge). Calibration (Greek: kalon, “ block of wood ” . This was drawn through clay tubes before firing to achieve their internal dimensional accuracy (caliber).). For accurate measurements, the ↑ measurement technology must be calibrated regularly, whereby the comparison is made with reference to the same unit, e. g. calibration of a ↑ voltmeter considering its tolerance with a voltage standard confirmed by ↑ verification. Calibration uncertainty. Always to be stated when specifying measurement results ( ↑ measurement accuracy). Calming section. Cross-sectional enlargement is installed in pipelines for chargeable liquids (e. g. mineral oil products), to reduce the flow velocity and thus also the charge of the liquids ( ↑ dwell time, ↑ charge density). [TRGS 727 Section 4] Cable cross section 40 <?page no="42"?> Calorie (Latin: calor, “ heat ” ). Obsolete unit [cal] of heat (energy), replaced by ↑ Joule [J] (one calorie equals 4.187 J). Originally, the water calories were used, defined as the energy required to heat 1 g of water from 14.5 °C to 15.5 °C. The thermochemical calorie was commonly used for the physiological calorific value of food. Now the unit [kJ] per 100 g is used. Canister (Greek: kanistron, “ basket woven from a tube ” ). Portable container for liquids. To prevent ignition hazards, canisters made of electrically insulating materials (e. g. plastic spare fuel canisters) must not exceed a volume of 5 l. [TRGS 727] Caoutchouc ● Natural caoutchouc, latex obtained from the sap of tropical trees (e. g. hevea brasiliensis), which is coagulated either by smoking or by precipitation. The caoutchouc obtained in this way can be mixed with fillers, factices (e. g. erasers), plasticizers, resins, etc. to produce various qualities of rubber. It can be highly elastic, waterproof, electrically insulating and abrasion resistant. Caoutchouc can be made conductive, for example by incorporating carbon black ( ↑ carbon). ● Silicone caoutchouc, organosilicon compound with high insulation values and good temperature resistance. Cables with this caoutchouc sheathing are well suited for electrostatic measurements ( ↑ measurement error). Its electrical resistance can be adjusted over a wide range by incorporating carbon black (down to 1 Ω m) without significantly affecting its mechanical properties. ● Synthetic caoutchouc, polymers produced by chemical synthesis ( ↑ polymerization) with rubber-elastic properties. Since they generally have a high electrical resistance, an interruption of electrostatic charge dissipation must always be expected when they are used, e. g. as elastic seals. For transport rollers in processing machines, nitrile butadiene rubber ( ↑ NBR) and polyurethane (PU) are used as polar materials, while ethylenepropylene-diene rubber ( ↑ EPDM) and silicone rubber are used as non-polar materials. [SE Section 2.14] Capacitance (Latin: capacitas, “ capacity ” ). Symbol C with the derived ↑ SI unit ↑ farad [F] or [As/ V], named after M. ↑ Faraday. It is the quotient of the charge on the surface of an electrical conductor and its potential (C = Q / U). There is a potential difference U between two electrically insulated metal plates separated by a certain distance, one carrying the charge +Q 0 and the other the charge -Q 0 . The capacitance of a ↑ capacitor is determined not only by its geometric dimensions, but also by the ↑ dielectric, the material that fills the space between its electrodes (plates). In electrostatics, capacitance is an important parameter because it quantifies the ability of a system to store charges {Appendix M.3} and thus energy {Appendix M.6}. Conventional wound capacitors are not suitable for ESD circuits because of their inductive resistance. Only plate or pulse capacitors consisting of interleaved tubular conductors in a liquid dielectric should be used for this purpose. In practice, all conductive objects insulated from earth form a capacitance ( ↑ stray capacitance), i. e. charges can be stored on them. Capacitance 41 <?page no="43"?> Reference values for some objects [pF] Single screw in plastic flange 2 Flange (e. g. in gas pipe) 10 Aluminum label (7 × 10 cm) as control impulse for web processing machines 12 Small metal objects (e. g. shovel, hose nozzle) 10 - 12 Bucket 10 Filter bag support element (insulated) 100 Small containers up to 50 l 50 - 100 Metal container from 200 - 500 l on insulated base 50 - 300 Person 100 - 200 Forklift with insulated tires 400 Motor vehicle with insulated tires 600 - 1000 Tank truck with insulated tires 1000 - 1500 Large plant components directly surrounded by an earthed structure 100 - 1000 The capacitance of the earth relative to space is about 0.7 mF. The earth behaves like a spherical capacitor {Appendix M.6.4.3}. Capacitance data for (e. g. very large) capacitors must not be equated with that of ↑ accumulators. For capacitors, the charge Q [C] is related to the voltage [As/ V] (farad). With accumulators, on the other hand, a largely constant voltage is assumed, so that the capacitance is only specified in charge values (e. g. [Ah]). In AC technology, the capacitance is characterized by the reactance ( ↑ alternating current quantity). ● Capacitance in Ex-areas: Unearthed capacitances (isolated conductor) in Ex-areas can be a source of danger. Conductive objects with a capacitance > 10 pF must be earthed. For smaller objects, the table according to [TRGS 727 Section 8.3.5] applies. Ex-atmosphere generated by hazardous substances in the Ex-groups Ex-area Ex-group I Ex-group IIA Ex-group IIB Ex-group IIC Ex-group III IIIA: combustible fluff/ flock IIIB: non-conductive dust IIIC: metal dust, conductive dust Mining (underground) 10 pF Zone 0 Note: flanges and bolts of glass apparatus must be earthed 3 pF 3 pF no insulated conductive objects or materials Zone 1 6 pF 3 pF 3 pF - Zone 2 - - - - Capacitance 42 <?page no="44"?> Ex-atmosphere generated by hazardous substances in the Ex-groups Ex-area Ex-group I Ex-group IIA Ex-group IIB Ex-group IIC Ex-group III Zone 20 or 21 MIE < 10 mJ - - - 6 pF Zone 20 or 21 MIE > 10 mJ - - - 10 pF Zone 22 - - - - Maximum allowable capacitance of ungrounded small objects, assuming no strong chargegenerating processes are occurring. {Appendix D} Capacitance measurement. In ↑ Ex-areas, only small insulated conductive objects with a low ↑ capacitance (1 - 10 pF) to earth are allowed [TRGS 727 Section 8], [IEC 60079-0]. The capacitance measurement is carried out with a ↑ capacitance measuring bridge or from the time required to charge or discharge the capacitance via a defined resistance (inverse ↑ Rothschild resistance measurement). ● Measurement setup [IEC 60079-32-2]: The measuring device should be a batteryoperated capacitance measuring bridge (maximum 9 V) with a measuring range of 0 - 100 pF and a resolution of at least 0.1 pF at a measuring frequency of 1 kHz, ideally switchable to 10 kHz (to detect ↑ earth leakage resistances). Measuring cables should be as short as possible ( ↑ measurement error). - A movable test object (small component) is placed on an insulated metal plate (much larger than the test object and with a resistance to earth > 10 T Ω ) in such a way that the distance between the conductor to be measured and the metal plate is so small that the two do not touch (a high-resistance, charge-free film can be used for this purpose). This arrangement gives the maximum possible capacitance in practice. Measurement 1: The positive pole of the meter is brought to within 3 - 5 mm of the conductor to be measured and the stray capacitance of this arrangement is measured. Measurement 2: The positive pole is brought into contact with the object to be measured. The measured value results from the difference between measurement 2 and measurement 1. Due to the high measurement uncertainty for small capacitances, values below 3 pF should not be specified as a measured value, but rather as “ < 3 pF ” . Capacitance measurement 43 <?page no="45"?> The measurement uncertainty to be aimed for should be about ± 0.5 pF for 10 pF and about ± 1 pF for 3 pF. Stray capacitances should be excluded as far as possible (measurement error). For large capacitances in the nF-range (e. g. ship), lower uncertainties in the region of ± 10 % result. If these are greater, the measurement should be discarded, and the cause sought. - For fixed installations, the negative pole of the meter is earthed. The measuring cable at the positive pole should be as far away from the negative pole as possible. Then perform the measurement as for moving objects. Capacitance measuring bridge. ↑ Wheatstone bridge operated with AC voltage for determining the capacitance of capacitors and objects. When measurements are made with a low-frequency bridge voltage, the results correspond to a first approximation of the values effective with direct current. Capacitive humidity sensor, ↑ humidity sensor Capacitive sensor. Sensor based on changes in the electrical capacitance through deformation of the plate distance (e. g. distance sensor, load cell), through changes in the ↑ dielectric or approach of an electrically conductive substance (e. g. touch screen), through changes in the effective plate area (e. g. variable capacitor) or by influencing the ↑ permittivity of the dielectric ( ↑ humidity sensor). Widely used capacitive sensors are probes for level measurement that form a ↑ capacitor in combination with the conductive container wall. The surfaces and their distances are known. As the liquid rises with a previously determined permittivity ε , the capacitance changes, from which the fill level can be derived. Capacitor (Latin: condensare, “ to condense ” ). Passive device for storing electric charges. The oldest type of capacitor is the ↑ Leiden jar. It consists of two conductive surfaces, insulated from each other, facing each other at a distance d, separated by a ↑ dielectric. The parameter for its storage capacity is the ↑ capacitance with the unit ↑ farad [F] or [As]. The charge and discharge times are given by the charge and discharge ↑ time constants. {Appendix M.6.3} Capacitors are divided into different types ( ↑ plate capacitor (Figure), coil capacitor, cylinder capacitor (Leiden jar)) and those with variable capacitance (variable capacitance capacitor, trimming capacitor, and ↑ variable-capacitance diodes (voltage-influenced ↑ junction capacitance)). Depending on the type of dielectric used, a distinction is made between air capacitors ( ↑ vacuum), paper capacitors, plastic film capacitors, ceramic capacitors, electrolytic capacitors, and double layer capacitors. In electrostatics, unwound low-inductance air (Source: www.endress.com) Capacitance measuring bridge 44 <?page no="46"?> capacitors are particularly important, as they are either present in practice as unwanted insulated conductors or are used to generate defined discharges. These capacitors can release their stored energy extremely quickly. - An ideal capacitor can release 100 % of its stored energy in a very short time. It has constant capacitance, no inductance, infinitely high insulation resistance, and the effect of the magnetic field caused by the current through the dielectric is zero. [Zastrow, D. (2004)] - Power capacitors (also known as high current capacitors) are used in high voltage and power electronics. They are usually coil capacitors, but also ceramic and vacuum capacitors. They can also be equipped with the inert gas SF 6 (sulfur hexafluoride) as a dielectric. These capacitors can also return to dangerous voltages after being completely discharged or after the short-circuit has been removed. This is due to changes in charge distribution (dielectric absorption) that occur in the dielectrics. Note: They must be stored and transported short-circuited. ● Double layer capacitor. Also known as power or SuperCap ® in reference to the term Helmholtz double layer ( ↑ charge double layer). They have electrodes made of thin metal foils, for example, coated with porous carbon, wetted with electrolyte liquid, stacked, or rolled into cylinders ( ↑ proton conduction). This structure corresponds to the conditions of a ↑ propagating brush discharge. When a voltage is applied, ions of opposite polarity accumulate at the electrodes and form a region of bound charge carriers with only a few molecular layers. These capacitors can store about a million times more than conventional capacitors of similar size. In contrast to rechargeable ↑ accumulators, which store energy chemically, here the charges are bound purely electrostatically ( ↑ charge bonding). As a result, they can deliver currents of several 100 A without delay. However, their specific energy is only about 5 - 10 Wh/ kg, which is significantly lower than that of lithium-ion accumulators, for example. On the other hand, these capacitors can store electricity efficiently and make it available again at short notice, e. g. for recovering broken energy in electrically powered vehicles. Compared to rechargeable accumulators, they have a lower self-discharge rate and achieve more than 500 000 charge and discharge cycles. With double layer capacitors, capacitances in the kF-range (up to 7 F/ cm 3 ) can currently be realized, so that capacitors can be used as an alternative to accumulators. Capacitor 45 <?page no="47"?> Property Double layer capacitor Accumulator Voltage 2.5 - 5 V 1.2 - 4.2 V Energy density 10 Wh/ l 200 Wh/ l Power density 10 kW/ l 0.5 kW/ l Charging time Seconds Minutes to hours Service life > 300 000 < 1000 Operating temperature - 40 to 70°C - 20 to 60°C In addition to its use in many industrial areas, an nBSC (Nano- Bio-SuperCap) with a volume of 1×10 -9 l was developed, which can provide a voltage of 1.6 V for a wide range of medical applications in combination with whole blood as an electrolyte. ● Rolled capacitor. Often used for small capacitors with high capacitance values, in which the metal layers are wound together with the ↑ dielectric (paper or film). These capacitors have high inductance, but this is not a concern for common low and high frequency applications. ● Metal paper capacitor. A widely used design in electrical engineering is characterized by the fact that after an overload ( ↑ breakdown), the resulting short-circuit is eliminated by a “ self-healing ” effect. They consist of a paper tape with a thin metal layer deposited in a vacuum. This layer is much thinner than the usual aluminum foil used in coil capacitors. When the capacitor fails, for example, due to a voltage spike, the thin metal coating evaporates in a large area around the failure. As a result, the area around the breakdown point is free of metal and the layers are insulated from each other again. ● Electrolytic capacitor. Capacitor whose dielectric consists of a thin oxide layer of light metal (aluminum oxide, tantalum oxide). This allows very small designs with high capacitance, especially in the low-voltage range. However, they have poor ↑ capacitor quality, making them poorly suited for electrostatic measurement purposes. They are generally designed for DC operation with superimposed AC voltages and may only be used with the specified polarity. ● Ceramic capacitor. Has a ceramic mass as the dielectric whose ↑ permittivity lies in a wide range. The conductive surfaces are vapor deposited (usually silver) or screen printed and sintered at high temperatures. Plate, pot, and bead-tube capacitors are common in high-voltage designs. Wires or tabs soldered to the pads form the connection. The influence of moisture is minimized by design, painting, and coating materials. Features are high insulation resistance, high dielectric strength, adequate (Source: [Bandari, V. K. et al. (2021)]) Capacitor 46 <?page no="48"?> capacitance constancy and low dissipation factor. The temperature coefficient can be influenced by the choice of base materials. ● Tuning capacitor. With air as the dielectric, changes their ↑ capacitance by changing the distance at a predetermined frequency (e. g. driven by ↑ piezo mechanics or tuning fork). When a charge is applied, an alternating voltage is produced whose amplitude is determined by the level of the charge. If the measurement voltage is amplified in an integrated circuit with a phase discriminator, a signal is generated whose magnitude and sign correspond to the applied charge ( ↑ coulometer, ↑ influence electrostatic field meter). The input resistance, and therefore the drift, is determined only by the insulation values of the capacitor. Capacitor circuit - Parallel connection. The total capacitance is equal to the sum of the individual capacitances. - Series connection. The total capacitance is always less than the smallest individual capacitance. The potential at the individual capacitors is determined by their capacitances only during the dynamic phase (charge - discharge). During the static phase, the potential distribution of capacitors connected in series depends largely on their insulation resistances ( ↑ capacitor quality), i. e. a capacitor with a low insulation resistance assumes only low potential and thus forces a higher potential on the capacitor with a high insulation resistance. {Appendix M.6.4.6} Capacitor quality. Because a ↑ dielectric is not an ideal insulator, a charged ↑ capacitor equipped with it will discharge due to its internal “ leakage current ” even without an external circuit. Capacitor quality is specified in terms of ↑ insulation resistance, or the resulting ↑ time constant (insulation quality) with which a capacitor charged to nominal voltage discharges itself. For electrolytic capacitors, capacitor quality is defined as the current still required from the DC source to maintain the charge after one minute of operation at nominal voltage. Car (automobile). All users of automobiles are familiar with the annoying ↑ electrostatic discharges that occur when getting out of the car and subsequently touching conductive parts (e. g. car body, garage door). Contrary to popular belief, they are not caused by the charging of the car, but by the ↑ charging of person, which occurs when clothing is removed from the car seat and cannot flow to earth quickly enough due to the high resistance of the footwear. The remaining countercharge on the vehicle is discharged to earth via the generally adequate dissipation capacity of the ↑ vehicle tires, so that further measures on the vehicle (e. g. earthing straps) are unnecessary. Incorrect deployment of ↑ airbags and ignition during ↑ refueling are other electrostatic problems in automobiles. The advantage of a car, besides the possibility of mobility, is that it acts as a ↑ Faraday cage when closed, providing reliable ↑ lightning protection. Carbon (Latin: carboneum). Occurs as the chemical element C with atomic number 6 in many modifications and, with its compounds, forms the basis of life on earth. Pure forms Carbon 47 <?page no="49"?> are the “ electrically insulating ” diamond, the electrically conductive graphite, and chaoite (mineral discovered in 1968). ( ↑ CAS number) - Graphite (Greek: gráphein, “ to carve, ” “ to write ” ), hexagonally crystallizing, stable form of pure carbon with good electrical ↑ conductivity. It can be used to improve the electrical conductivity of polymers ( ↑ polymer conductor). However, about 50 % is required for dissipation capability < 10 6 Ω . As a result, the mechanical properties are impaired and the price is currently not attractive, so that its use is generally limited to special applications (e. g. conductive paints for the internal coating of plastic housings for ↑ ESD protection). - Carbon black, microfine electrically conductive carbon that, when added to polymers, can reduce their electrical resistance over a wide range. It is usually produced in a closed reactor with oil and air during incomplete combustion. So-called high conductivity carbon blacks can be obtained by thermal cracking of acetylene. Depending on the type of carbon black, polymer, and processing technology, 20 - 45 % additives are required to achieve a significant reduction in resistivity. These concentrations significantly affect the properties of the polymer (e. g. increase in embrittlement and gas diffusion). Socalled conductive carbon blacks have therefore been developed, which percolate at additions of just a few percent, forming a conductive network and reducing resistance by more than 10 dimensions ( ↑ percolation, ↑ pearl string model, ↑ tempering). For all types of carbon black impurities, a slow increase in carbon black content leads to a sudden steep drop in resistance of many dimensions within a narrow concentration range. This is caused by the ↑ particle boundary contacts that build up in interaction with a ↑ tunnel effect that allows electron conductivity. The addition of carbon black can generally adversely affect the fire safety of polymers (e. g. PVC). ● Carbon microstructures are currently known to: - Nanotube (carbon nanotubes, CNT), microscopic tubular structures whose walls consist of carbon atoms. They have a honeycomb structure with hexagons and three bonding partners each. The diameter of the tubes is in the range of 0.5 - 50 nm, their length can be up to 100 mm. CNTs are not to be equated with carbon fibers. Due to their electrical conductivity and their elongated structure, they are ideally suited to make electrically conductive plastics and are thus far superior to the comparable concentration of conductive carbon blacks. Depending on the type of insulating plastic, resistance values in the k Ω -range can be achieved by adding 0.3 - 10 wt.% Carbon 48 <?page no="50"?> CNTs ( ↑ steel fiber addition). Note: In 2011, V. Castranova (www.cdc.gov) found that inhalation of CNTs, which resemble asbestos fibers in their needle-like structure, can also lead to malignant tumors in the lungs. - Fullerene (also known as buckyballs), an independent modification of plastic as a result of a closed, polyhedral molecular structure consisting of 60 - 90 atoms. C 60 fullerene consists of 12 pentagonal and 20 hexagonal carbon rings. The preparation of these structures is complicated. Useful applications include electrostatically conductive structures in insulating polymers. They owe their name to the architect Richard Buckminster-Fuller, whose domes have a similar design. (model of a football dome). - Graphene (also known as two-dimensional material), latticelike cross-linked layers consisting of only a single layer of carbon atoms. This makes it the thinnest material known. These layers are electrically and thermally conductive, yet nearly transparent, and about 100 times stronger than steel. Carbon black, ↑ carbon Carbon brushes. They are made of industrially produced carbon fibers. They are widely used for passive surface discharge. Carbon brushes are often brought into contact with the moving material to be discharged, resulting in contamination of the brushes. Contact with the materials causes discharge, but friction and separation create new charges. In the case of contamination, all ionization may stop because no individual bristles are protruding, which should cause a ↑ corona discharge. [SE Section 5.2.3.1] Carbon dioxide (CO 2 ), ↑ inerting, ↑ CO 2 fire extinguishing system, ↑ charging (in gases), ↑ explosion accident of Bitburg Carbon dioxide extinguisher, ↑ CO 2 fire extinguishing system Carbon fiber. In the field of electrostatics, carbon fibers refer to thin conductive fibers made of carbon black or graphite that are only a few millimeters long and are not the same as “↑ carbon - nanotubes ” . By adding conductive particles, the electrical resistance of insulating plastics can be reduced to the point where no disruptive electrostatic charges occur. The minimum amount of additive required is determined by the formation of conductive pathways in the polymer. This threshold, also known as ↑ percolation, depends not only on the size and distribution of the conductive particles, but possibly also on their ratio of diameter to length. The desired conductive network can be achieved with carbon fibers at significantly lower weight percentages than with round particles ( ↑ metal fibers). Carbon fiber brush, ↑ discharge brush Carnauba wax (also known as Brazilian wax or Ceara wax) (Latin: cera carnaubae). Is extracted from the leaves of the carnauba palm (Copernicia prunifera), which grows in Brazil. Carnauba wax has a melting point of 80 - 87 °C, depending on its purity, making it Carnauba wax 49 <?page no="51"?> relatively resistant to the effects of heat. Carnauba wax has a dipolar character, which makes it easy to polarize in the electrostatic ↑ field ( ↑ electret). Carrier. Charge mediator (preferably magnetizable metal beads with a diameter of 30 - 300 μ m), which in ↑ xerography ensures that the toner particles are charged with the aid of ↑ charge control agents and flow freely on the latent ↑ charge image. Cartesian coordinates. Rectangular coordinates, of which only the right-hand system is preferably used. The x-axis is horizontal, and the y-axis is vertical. In the case of spatial coordinates, the z-axis is added, which forms a right-handed system with the aforementioned axes when the positive direction leaves the drawing plane. CAS number, short for Chemical Abstracts Service. The international standard for uniquely identifying chemical substances. These numbers include the currently known ↑ explosion limits of flammable gases and vapors and the corresponding ↑ flash points of flammable liquids (GESTIS-Stoffenmanager ® , ↑ Chemsafe). Cascade connection. A series connection of similar stages is used for voltage division at high operating voltages, among other things. ( ↑ voltage divider) Cascade generator, ↑ high-voltage cascade Cast process. In the case of plastic films produced by the so-called cast process, the melt is fed directly from the slot die onto a cooling cylinder. During the cooling process, the film immediately begins to shrink. In order to minimize this shrinkage process, the melt is placed on the roll immediately after leaving the die and fixed either at the edge ( ↑ edge zone fixation) or over the entire width by means of a ↑ charging electrode opposite the earthed cooling cylinder. ( ↑ useful application, ↑ chill tack, ↑ chill roll). [SE Section 8.2.4] Cat fur. Occasionally it is still used to illustrate electrostatic charging, e. g. in experimental lectures. When “ rubbed ” with cat fur, almost all plastics become negatively charged according to the ↑ triboelectric series. (The trade in cat fur is prohibited in the EU for animal welfare reasons.) Carrier 50 <?page no="52"?> Catalyst. A substance that increases the rate of a chemical reaction without being consumed during the reaction or shifting the reaction equilibrium. Most reactions that produce high-molecular-weight substances from low-molecular-weight substances occur in the presence of catalysts. Cataphoresis. Migration of non-dissociated liquid particles and colloids as well as insulating solid particles in the direction of current. Among other things, it is the basis for electrocoating, in which paint particles dispersed in water are deposited on metal parts (priming of vehicle bodies). Category (Greek: kategoria, “ basic statement ” ). According to the German ↑ ProdSG, devices used in ↑ Ex-areas must not cause ignition ( ↑ ATEX, ↑ equipment category, ↑ equipment protection level). Cathode. An electrode at which the potential is zero or negative and from which negative charge carriers are emitted. Cathode fall. Strong ↑ voltage drop at the cathode during ↑ gas discharges. Its magnitude is usually > 10 V and thus the magnitude of the ionization voltage, which depends on the type of gas in which the ↑ plasma is generated. The cathode fall is caused by positive space charge shortly in front of the cathode and is current-independent. At high currents and small cathode areas, the cathode fall begins to become current-dependent (anomalous cathode fall). The spatial expansion of the cathode fall is strongly pressure dependent. [Dzur, B. (2011)] Cathode ray. Antiquated term for low energy ↑ electron beam. Cathode rays are emitted from a cold pin at high electric field strengths ( ↑ field emission, ↑ ionization pin). They are also generated by glow emissions or when positive ions collide with the cathode of a gas discharge tube. Cathode ray oscillograph, ↑ oscilloscope Cathode ray tube (CRT). ↑ Electron-beam tube used in a display device. Cathodic protection (CP or CCP). In contrast to passive corrosion protection, in which the surface of the object to be protected is provided with a ↑ coating, cathodic protection creates an electrical circuit ( ↑ galvanic element) in which the object to be protected is the consumer. Examples of external cathodic protection include steel pipelines, borehole piping, sheet piling, underground steel tanks, ships ( ↑ earthing) and internal cathodic protection includes domestic boilers and heat exchangers. It is also used for the reinforcement of reinforced concrete structures (bridge foundations, parking garages, etc.). [EN ISO 12696], [EN 12954], (see figures next page) Cathodic protection 51 <?page no="53"?> (Source: ARS Betriebsservice GmbH, Merseburg, Germany) (Source: Timm Technology GmbH, Reinbek, Germany) ● Cathodic protection without external current. Generally, it protects metals that are in contact with corrosive substances (e. g. water or soil). The metals to be protected from the cathode, the anode is made of a less noble metal. Both are conductively connected to each other so that a small current can flow as a result of the redox reaction. The protection of the more noble iron with a coating of the less noble zinc is also based on this principle. ● Cathodic protection with external current feeding. The part to be protected (cathode) becomes part of an electric circuit in which the current flows from the victim anode (e. g. iron-silicon, magnetite, or titanium) to the object to be protected via a conductive electrolyte (e. g. soil). When external current is fed in from the electrical supply network, currents of 1 μ A/ m 2 to 100 mA/ m 2 of protected area are required, which, depending on the size of the system, result in protective currents in the A-range that can cause ignition risks for ↑ Ex-atmospheres in the event of faults. ( ↑ ignition source) Cation. Positively charged atomic or molecular particle ( ↑ ion) that exerts a force toward the negative electrode in an electric field. Antagonist: ↑ anion Cation 52 <?page no="54"?> Cation-active substance. Substance that usually has a positively charged functional group and consists of a polar and a non-polar part. The polar moiety often consists of quaternary ammonium units, which are used, for example, to increase the ↑ conductivity of non-conductive or low-conductive liquids. The non-polar moiety is usually formed by alkyl groups. ( ↑ surfactants) Cavitation luminosity (also sonoluminescence) (Latin: cavitas, “ cavity ” ). Luminous phenomenon caused by negative pressure vapor bubbles due to extremely high flow velocities in charged liquids and in which ↑ gas discharges (at reduced pressure) can already be seen far below the atmospheric breakdown field strength. This type of ↑ selfdischarge can be observed, for example, in high-speed stirrers in insulating liquids. CCA, short for ↑ charge control agent CDM, short for charged device model. The CDM can be used to test the ESD sensitivity of electronic components (e. g. circuits) to electrostatic discharges. The ↑ ESD-Association (ESD-A) has classified the voltage sensitivities for the CDM into the following classes: CDM class Voltage sensitivity [V] 1 < 125 2 125 - 250 3 250 - 500 4 500 - 1000 5 1000 - 1500 6 1500 - 2000 7 > 2000 The CDM replicates the condition where a charged (electronic) component or object is brought close to an earthed surface, resulting in a discharge process. In the CDM test, the test part ( ↑ DUT) is slowly charged and then rapidly discharged for the actual test. The characteristics of the test parts are their small capacitance, inductance and resistance of the circuit, which are practically only determined by the “ scatter values ” . The discharge model is best by its curve, which is characterized by a very short and fast unidirectional discharge. [IEC/ TR 61340-1], [IEC 61340-5-1], [ANSI/ ESD S5.3.1], [IEC 60749-28] CE mark, short for French: Conformité Européenne (European Uniformity). Mark introduced products manufactured in 1995 in the EU. With the CE mark, the manufacturer, distributor or EU authorized representative declares, in accordance with EU Regulation 765/ 2008, “ that the product complies with the applicable requirements of the Community harmonizing legislation ” . It is affixed by the manufacturer and indicates to the supervising authorities (customs) that the relevant directives have been met. CE marking has been mandatory since 1/ 1/ 1996 under the EMC Directive and since 1/ 1/ 1997 under the Low Voltage Directive. Please note: The mark is also a guideline for ↑ Electromagnetic Compatibility (EMC), but not for ↑ Electromagnetic Compatibility of the Environment (EMCE). The CE mark is not a safety or quality feature in the true sense, such as the ↑ GS mark, TÜV mark, etc. Nor does it mean that a test has been carried out by a neutral, expert body. CE mark 53 <?page no="55"?> Since all manufacturers of certain products must affix the mark, it is also not a marketing tool. If the conformity of a product has been assessed and confirmed by a ↑ notified body, the complete marking includes not only the “ CE ” but also the four-digit identification number assigned by the notified body. Cell capacitance. Both the ↑ capacitance and the ↑ cell constant of an ↑ measuring electrode can be calculated from the geometry of the electrode size, shape, and arrangement. The capacitance measurement on the empty measuring cell can also be used to calculate the cell constant by dividing the capacitance value by the field constant ε 0 . {Appendix M.6} Cell constant. Measuring cells are used for ↑ resistance measurements on liquids ( ↑ measuring electrode). They are chambers in which the electrodes are highly insulated from each other and from earth. In analogy to the ↑ capacitance of a ↑ capacitor ( ↑ cell capacitance), the current-carrying area and the distance between the electrodes result in a numerical value that is multiplied by the measurement result as the cell constant to determine the ↑ volume resistivity [ Ω m]. Dipping electrodes in the form of plate electrodes usually have a cell constant of 1 ( ↑ capacitive sensor). Celluloid. The first large-scale industrially produced ↑ thermopolymer. It was first produced by A. Parkes (chemist in England) in 1855 by dissolving collodion wool (cellulose dinitrate, ↑ nitrocellulose). J. W. Hyatt improved the process in 1869 and coined the term celluloid. The brittle collodion wool is kneaded together with e. g. camphor as a plasticizer and mainly alcohol to form a mass which, after the alcohol has evaporated, becomes a malleable mass for further processing into a wide variety of products (billiard balls, spectacle frames, office supplies, watch glass, transparent film for film production, etc.). As celluloid dries, its ↑ chargeability increases and it takes on the character of an ↑ explosives, which is why it has been largely replaced by other substances. Celsius, Anders (1701 - 1744). Swedish astronomer introduced a temperature scale of 100 equal parts in 1742 ( ↑ Celsius). Celsius. Degree Celsius [°C], named after A. ↑ Celsius is a very common temperature unit worldwide with a scale divided into 100 equal parts. The reference point is the freezing point at about 0 °C and the boiling point at about 100 °C of water ( ↑ standard condition). Note that when converting ↑ Kelvin [K] to [°C], 273.15 is subtracted. ( ↑ Fahrenheit) CENELEC, short for French: ↑ Comité Européen de Normalisation Electrotechnique, the European Electrotechnical Standardization Organization. Central conductor. Term for an earthed rod or steel cable for the safe discharge of electrostatic charges, which must always be used before filling containers (originally also called earthing lance). In the case of liquids, a central conductor is also a ↑ filling pipe as defined in [TRGS 727 Section 4.4]. When handling bulk solids with a resistivity < 10 6 Ω m ( ↑ bulk material discharge), one or more earthed central conductors may serve as a possible device. [TRGS 727 Section 6.2.3.2] Centrifugal separator, ↑ cyclone Cell capacitance 54 <?page no="56"?> Ceramic. A general term for a non-metallic, inorganic, and predominantly polycrystalline product formed at room temperature and given its material properties by subsequent heating (firing/ sintering). Ceramics can also be applied as powder (e. g. aluminum oxide or chromium oxide) by plasma spraying onto e. g. metals ( ↑ coating). Special features include mechanical strength, high electrical and/ or thermal resistance, and high ↑ permittivity. Ceramic capacitor, ↑ capacitor Ceramic tile, ↑ floor Č erenkov radiation, ↑ Cherenkov radiation Certificate of conformity. Confirmation of compliance with a specified standard or regulation ( ↑ ProdSG). Chair. In ↑ ESD protected areas, chairs are also subject to charge prevention requirements: The backrest, seat, and armrests should have a surface resistance of < 10 G Ω , with a total leakage resistance across e. g. chair casters also < 10 G Ω . Channel discharge. Similar to a ↑ gas discharge, which (unlike the ↑ avalanche effect) is ignited by the formation of thin channels of highly ionized gas (called plasma tubes) between the electrodes. Channel rays. Emitted as positive ion radiation during a ↑ gas discharge at a perforated ↑ cathode. Charge ● Electric charge. Symbol Q, derived ↑ SI unit [C] ( ↑ Coulomb) or [As], named after C. A. ↑ Coulomb. It describes the amount of positive or negative electricity in or on a body, which characterizes the electrical state of a body. The charge is made up of ↑ elementary charges that cannot be divided. If there are equal amounts of ↑ electrons (negative charge) and ↑ defect electrons (positive charge), the total charge is zero. Since charge causes an electric ↑ field, which is noticeable by the force effects given by ↑ Coulomb ’ s law, an earthed conductive body is charged in this field by ↑ charge displacement. Despite the charge separation caused by the charge displacement, the total charge remains at “ zero ” until the first discharge occurs. Charge can therefore be measured in terms of magnitude and sign. Charges of the same name can accumulate on a body (additive behavior, ↑ charge accumulation). - Static charge is the source of the electrostatic field. - Moving charge generates an electric and magnetic field ( ↑ gas discharge, ↑ plasma). In a preferred direction, this represents an electric ↑ current. - Virtual charge is the ↑ image charge caused by ↑ influence. - Free charge can be transferred to bodies. ● Bound charge, ↑ charge bonding ● Specific charge describes the ratio of charge to mass of particles, especially in the evaluation of powdery bulk materials. ● Transferable charge, ↑ charge transfer [DIN 1324-1], {Appendix M.3} Charge 55 <?page no="57"?> Charge abduction. The process shown at ↑ charge displacement leads to charge transfer if the body (K) is mobile. This is illustrated by the example of a person wearing insulating footwear, walking past a charged plastic pipe or web of material and briefly touching the earthed handrail of a banister. The unbound induced charge is discharged to earth in the resulting ↑ electric shock. If the person continues walking and thus leaves the field emanating from (G), the previously bound induced charge is also released, the person is now charged with the opposite polarity and will feel a discharge again when touching an earthed object, which usually has enough energy to ignite a corresponding gas-air mixture. ( ↑ earthing, ↑ personnel charging), [SE Section 2.12.1] Charge accumulation. Occurs in two different ways: ● Accumulation is due to the electrostatic ↑ charging of non-earthed conductive objects and liquids as well as solid or liquid insulating materials. Ignition hazards can occur when the charge limit is exceeded or if earthed objects approach ( ↑ ignition hazard assessment). Active ↑ ionizers can neutralize charge accumulations depending on the arrangement and cleaning conditions. The addition of ↑ antistatic agents can increase the ↑ conductivity in liquids and insulating materials and thus prevent charge accumulation during ↑ earthing [TRGS 727 Sections 3 and 4]. ● Charging by accumulation of charged substances, in which the repulsive and attractive ↑ Coulomb forces of charged particles, substances or objects are overcome by external influences. Charge accumulation occurs when bulk material is filled into a ↑ silo and by charge compression due to ↑ gravity ( ↑ cone discharge) or stacking of objects. When winding up ↑ material webs, the charge is compacted by mechanical work ( ↑ super brush discharge). If the dissipation capability of the materials is not given, the charges cannot flow off to earth fast enough even when they come into contact. The individual charges add up, the space charge density and thus the electric field strength increase sharply until the breakdown field strength of the air is reached. Discharge occurs to the nearest earthed object (e. g. silo wall) or, in the case of mechanical charging, to a person ( ↑ personal hazard, ↑ electric shock). Charge amplifier. Charge-to-voltage converter that convert small charges to proportional voltage values, such as charge signals of a few femto-coulomb (10 -15 C) generated by piezoelectric sensors or certain electrostatic field meters. Conventional shielded cables cannot be used at the input because the slightest deformation due to triboelectric effects will falsify the measured value. Magnetic fields must be kept away. Charge abduction 56 <?page no="58"?> Charge bonding. Bound charges occur in electrically polarized matter ( ↑ permittivity), at molecular dipoles (e. g. at contact surfaces), associated with the orientation of the charge on a body to an approximate body of opposite sign ( ↑ influence, ↑ charge displacement, ↑ Coulomb force). The ↑ surface charge density can be greatly increased by surface contact between a chargeable film and an earthed metal plate (electret ↑ microphone). ( ↑ propagating brush discharge, ↑ capacitor) Charge carrier. Term for one or more particles carrying ↑ elementary charges ( ↑ charge, ↑ ion). Charge compression. Backing a positively or negatively charged insulating material with an earthed conductor can lead to charge compression, where the maximum possible ↑ surface charge density σ max of the insulating material in an air atmosphere can be greatly exceeded. The distance between the backside “ earth ” and the charged surface of the insulator determines the type of gas discharge possible. ( ↑ charge accumulation) For a ↑ corona discharge, the earth is “ infinitely far away ” . For a ↑ brush discharge, a “ distant earth ” is required. This is also true for the ↑ super brush discharge, where mechanical compression is added. If the earth is very close (< 9 mm from the contact), ↑ propagating brush discharges can occur in highly charge-generating processes or on highly charged insulating materials. Charge compression > σ max on one plane can also occur when one side of an insulating material is positively charged, and the other side is negatively charged ( ↑ bipolar charge layer). Charge control agent. Modern printing systems such as photocopiers and ↑ laser printers use triboelectrically charged ↑ toners whose electrostatic behavior (polarity and charge level) is influenced by charge control agents. From a process engineering point of view, these must be dispersible, thermostable, and compatible with the toner binder. ( ↑ carrier) Charge decay measurement, ↑ relaxation time Charge density. Amount of electricity per unit area ( ↑ surface charge density) or per unit volume ( ↑ volume charge) with homogeneous charge distribution. Estimating the charge density is particularly useful for liquids because they are always charged when flowing through pipes. For liquids with low ↑ conductivity, the charge density in an infinitely long pipe can be estimated using the formula ρ ∞ [ μ C/ m 3 ] = 5 × v [m/ s]. A pipe of length l [m] can be considered infinite if l ≥ 3 × v × ε r × ε 0 / κ (v [m/ s] - flow velocity, ε r - permittivity number of the liquid, ε 0 [As/ m] - electric field constant, κ [S/ m] - conductivity). [TRGS 727 Section A1], {Appendix M.3.1.4 and M.3.2} Charge detection ● Qualitative charge detection: The charge of particles can be detected by the ↑ Coulomb forces caused by them ( ↑ separation of substances, ↑ useful application). A charge state can be detected on charged objects by: - Hair standing up when approaching an earthed person, - A glow lamp that is earthed on one side lighting up, - Triggering ↑ gas discharges by approaching an electrode (e. g. knuckles), etc. Charge detection 57 <?page no="59"?> Charge states can also trigger weak gas discharges that are visible to the dark-adapted eye, e. g. a glowing seam at the separation point when an adhesive tape is removed. ● Quantitative charge detection: ↑ charge measurement, ↑ coulometer Charge displacement. Is either caused by unintentional ↑ influence or by intentional ( ↑ useful application): A: A ↑ Van de Graaff generator (G) serves as a charge source. (K) is a conductive, insulated body. Both are previously earthed. B: (G) is turned on for a short time and produces a negative charge on the sphere. The resulting ↑ Coulomb force causes a displacement of the conduction electrons on the previously electrically neutral surface of (K). C: To detect the charge displacement, the side of (K) facing away from the sphere is shortly earthed. D: The system appears electrically neutral due to ↑ charge bonding. E: When the sphere (G) is shortly earthed, its charge flows off; the electric ↑ field disappears. F: The positive charge spreads over the whole body (K). It now carries an ↑ excess charge, regardless of whether (G) remains earthed or not. This principle of charge displacement also applies to moving systems. ( ↑ charge abduction), [SE Section 2.12] Charge dissipation. Charged conductive objects safely dissipate their electric charge when discharged to earth. Charge dissipation from insulating materials cannot be achieved by earthing, but by ↑ corona discharge. ( ↑ ionizer), [TRGS 727] Charge distribution. Non-predeterminable charge in the nm-range on surfaces of insulating materials, usually caused by undefined distributed contaminations of various kinds ( ↑ charge double layer). ● Measurement of charge distribution. In some cases (e. g. ↑ xerography, investigation of ↑ electrets) it may be necessary to measure the charge distribution on charged Charge displacement 58 <?page no="60"?> surfaces. This is done with a ↑ EFM with a short response time and a very small measuring aperture ( ↑ field penetration), preferably in a homogenized field. The measuring head is moved in a grid pattern over the surface to be investigated at a distance corresponding to the measuring aperture, which makes it possible to generate a charge profile according to size and sign ( ↑ field strength measurement, ↑ field distortion). An indirect recording of the charge distribution is possible via ↑ scanning force microscopy. ● Visualization of charge distribution. The distribution of ↑ charges on charged insulating material surfaces (e. g. the mark after a ↑ propagating brush discharge) can be made qualitatively visible by dusting with fine powder. If the sign of the charge distribution is also to be recorded, a powder mixture of two differently colored components should be used, which is designed in such a way that one component becomes negatively charged and the other positively charged when shaken. When such a mixture is sprinkled on a charged surface, negatively charged particles are attracted to positively charged parts of the surface and vice versa. Recipe for such a paint powder mixture: For one component, 70 g of ↑ lycopodium is colored blue in 100 ml of a 2 % solution of methyl violet in ethanol and dried. The other component is sulfur bloom, 5 vol. % of which is ground with 1 vol. % of carmine red. Both powders must be mixed by shaking before use; an excess of sulfur may be useful. The sulfur becomes negatively charged and the lycopodium becomes positively charged. Accordingly, negatively charged areas will appear blue and positively charged areas will appear red. The check can be done by taking measurements in a ↑ Faraday cup. [Bürker, K. (1900)] Charge double layer. The terms Helmholtz double layer, double layer charge or ↑ bipolar charge layer (e. g. on films) are incorrectly used as synonyms for the phenomena of electrostatics on charge double layers. A distinction must be made: ● From an electrochemical point of view concentration shifts usually occur at the ↑ contact surfaces of two phases (e. g. bodies) compared to the conditions inside the phase. It does not matter which combination is involved: solid/ solid, solid/ liquid, liquid/ liquid, solid/ gas, liquid/ gas. At the molecular distance (10 -9 m and below) an ↑ adsorption layer is formed, which is generally associated with an electric potential difference, the surface potential χ . Depending on the combination of phases, neutral molecules can form a charge double layer, polar molecules can be aligned (polarized), or ions can be adsorbed. When ↑ excess charges of opposite polarity are present in two phases, they attract each other ( ↑ Coulomb force). The potential difference is called ↑ voltage Δ Ψ (external electric potential difference). [Wedler, G., Freund, H.-J. (2018), Section 2.7.7] The electric potential difference Δ Χ and the ↑ Voltaic potential Δ Ψ give the ↑ Galvani voltage Δ φ , also called the internal electric potential difference. H. v. ↑ Helmholtz first formulated the term “ double layer ” for the metal/ electrolyte combination as a “ rigid ” model in 1853. The surface of the solid is densely covered with ions, and the counterions want to get as close as possible to the surface. This combination can be roughly thought of as a ↑ capacitor, considering the factors of Charge double layer 59 <?page no="61"?> ↑ permittivity, electric ↑ field constant, and surface area. However, this system will not correspond to reality because the ↑ Brownian molecular motion and usually the thermal motion will lead to a diffuse double layer as described by M. Gouy (1910) and D. L. Chapman (1913). O. Stern in 1924 combined the models of Helmholtz and Gouy-Chapman, from which the processes of electrostatic charges can also be derived. Charge double layers play a role, for example, in dispersion processes ( ↑ dispersion), filtration and flotation, the stabilization of suspensions and emulsions; the characteristic quantity here is the ↑ zeta potential. ● From the electrostatic point of view, it is true that in the common boundary layers solid/ solid, solid/ liquid, liquid/ liquid there is an electron transfer ( ↑ tunnel effect) due to different ↑ electron emission energy ( ↑ acceptor, ↑ donor), by which the charge double layer is generated. To describe the energy states of electrons in conductors, semiconductors, and their conductivities, the so-called ↑ band model of physics with the central terms ↑ conduction band, ↑ forbidden band and ↑ valence band is used. The band model cannot be used to explain contact charging at contact surfaces of insulators, because crossing the forbidden band is not possible without significant energy input. However, for the combination of insulators, ↑ soiling by a wide variety of particles, atoms, and molecules must always be expected in the range of ↑ charge generation (10 -9 m and below), and thus the charge double layer is formed, consisting of two layers of opposite ↑ polarity and a potential difference Δ Χ in the mV-range near each surface. This is the prerequisite for the electrostatic charge generated by the separation of solids or liquids ( ↑ Brønsted-Lowry definition, ↑ Lewis ’ s acid-base concept). The ↑ Coehn ’ s rule ( ↑ triboelectric series) can no longer be applied to contact partners if one of the substances involved is nonpolar [Kanamura, K., Takada, T. (1939)]. As soon as any separating action, e. g. by mechanical energy, overcomes the electrostatic attraction (Coulomb force), the electric potential difference Δ Χ increases as an Charge double layer 60 <?page no="62"?> equivalent up to the kV-range. Several such contact and separation processes can lead to the addition of the electric potential (100 kV range). In phase combinations with “ gaseous ” , no electrostatic charge can be generated by contact and separation. Unlike solids and liquids, electrons in ↑ gases are not energetically in a low work function conduction band. Charge transfer would require high-energy ionization of gas. Extensive experiments have shown that liquids do not become charged when falling through air unless there is droplet separation ( ↑ Rayleigh instability) and there is no ionizing radiation. [SE Section 3.10], [Lüttgens, S. et al. (2015)], ( ↑ charging - falling drops) Charge equalization. Occurs when different objects are brought into contact with each other, and an existing potential difference is equalized by charge transport. The sum of the charges of the objects involved does not change. ( ↑ equipotential bonding, ↑ earthing) ● A conductive connection of two or more bodies causes charge equalization in order to bring them to approximately the same potential. ● When two substances are separated, there is - in addition to ↑ charging - a more or less large charge equalization between the last common contact points, regardless of whether they are phase boundaries on solids or liquids. ( ↑ tunnel effect, ↑ surface reverse current density) Charge equalization depends on the surface resistivity of the substances involved or the ↑ conductivity of ↑ liquids and the speed of the separation process or the flow velocity ( ↑ charging - of liquids). ( ↑ relaxation time), [SE Sections 2.5 and 4.2.3.3], [TRGS 727 Sections 3 and 4], {Appendix M.6.3.1} Charge equalization 61 <?page no="63"?> Charge image. Structure of an areic distribution of electric charges ( ↑ charge distribution). In the image recording chip (CCD) of a digital camera, for example, the incident light quanta ( ↑ photons) generate charges that represent a spatially resolved two-dimensional image of the incident light. The optically generated charge image is scanned line by line and converted into corresponding electronic signals. The goal is for the number of electrons generated to be proportional to the intensity of the incident light, resulting in a true-to-life brightness image on the image sensor in the form of a charge image. ● Latent charge image (Latin: latens, “ hidden, not immediately visible ” ). Image produced by exposure on a charged photographic semiconductor that has not yet been developed by ↑ toner and therefore shows no blackening ( ↑ copying process, ↑ xerography). Charge island, ↑ charge profile Charge measurement. In contrast to ↑ charge detection, it always records the value and polarity of a ↑ charge. - On conductive objects, the charge can be determined by measuring the voltage with a high-impedance voltmeter (R i > 10 14 Ω ). - On insulating objects, however, the charge can only be detected by indirect measurement via ↑ field strength or ↑ influence ( ↑ influence electrostatic field meter, ↑ influence field measurement probe, ↑ Faraday cup). [IEC/ TR 61340-1] The capacitances associated with the measurement setup (cable, clamp, etc.) must be considered for all measurements. Adequate ↑ shielding should be provided to prevent the measurement from being influenced by the “ moving ” capacitance of the measurer. The figures illustrate how an insulating granule particle is negatively charged as it slides through a steel tube, transfers its charge to a Faraday cup by influence, and its potential is measured via the voltage sensor “ S ” on the ↑ EFM (Figure). If the metal tube is replaced by a tube made of insulating material and the granule particle is replaced by a metal bead, the same process leads to a positive charge. [SE Section 6.5.1] Charge image 62 <?page no="64"?> ● Charge measurement by contact. A direct charge measurement of the total electrostatic charge, e. g. by connecting an electrically conductive contact to a measuring device, is only possible with suitable conductive objects. The potential is determined by its environment and the charge is calculated by multiplying it by its ↑ capacitance. ● Charge measurement by influence. As insulating and isolated materials are preferably charged in practice, which do not allow charge transport due to their high ↑ resistance, charge measurement via contact is ruled out for them. The ↑ charge transfer by influence from the object to the measuring device is used. A ↑ coulometer is approximated to a charged surface, where a charge is applied to the measuring electrode (usually a sphere), taking into account the measurement error due to the change in capacitance of the measuring setup. Depending on the amount of charge, a ↑ gas discharge may occur. This gas discharge only removes charge from a limited area, the rest remains on the object. Flat structures can be evaluated with an ↑ influence field measurement probe. ● Measurement setups - The ↑ Millikan experiment is suitable for the smallest particles. - Small, charged objects (e. g. powders, granules) can be collected in a ↑ Faraday cup and their potential measured. A specific ↑ charging can be determined from the ratio of the measured charge to the particle mass. In the charge measurement arrangement (Figure), three positively charged particles fall through the upper opening into the insulated Faraday cup and immediately bind the opposite polarity charge corresponding to their charge on the inside of the cup. The same amount of induced positive charge is then released on the outside of the measuring chamber and can be directed to a display device, thus achieving contactless detection of the particle charge. - For larger objects (e. g. packaging means), the charge state can be inferred by measuring the electric field with an ↑ EFM, considering the ↑ charge distribution. {Appendix M.3}, [SE Section 3.6.2] Charge neutralization, ↑ homogenization, ↑ field strength, ↑ earthing, ↑ ionizer Charge profile. The exchange of electrons that occurs during ↑ charging can produce charge profiles of different signs and amplitude in close proximity. This phenomenon is particularly common during the ↑ winding/ unwinding of film, paper or composite webs and can be detected by measurement. ( ↑ charging phenomenon, ↑ delta, ↑ charge distribution, ↑ gas discharge mark, ↑ Lewis ’ s acid-base concept, ↑ Lichtenberg figure, ↑ Brønsted- Lowry definition), [SE Sections 2.14 and 5.4.1] Charge relaxation, discharge ↑ time constant, ↑ relaxation time Charge replenishment. Does not usually occur with electrostatic ↑ gas discharges. With a ↑ Van de Graaff generator (e. g. also a roller processing machine), charge replenishment can be continuously generated with a sequence of gas discharges, which can be seen as a Charge replenishment 63 <?page no="65"?> ↑ sawtooth curve when recorded on an oscilloscope. A similar curve is produced when measurements are made with the 2 kV voltage measuring head of the ↑ influence electrostatic field meter and the breakdown strength of the sensor head is exceeded. Charge separation. There are two types: ● Separation due to the influence of electric fields on conductive bodies or objects. ( ↑ charging, ↑ influence, ↑ charge bonding, ↑ charge displacement) [SE Section 2.3] ● Separation by mechanical energy input ( ↑ charging). The mechanical separation of materials (solids and/ or liquids) that were previously in close contact leads to charging. High surface resistances and/ or high separation speeds lead to high charging ( ↑ surface reverse current). Friction alone does not lead to charging; it merely causes the surfaces to come into closer contact. Nevertheless, the terms ↑ frictional charging and - especially - ↑ triboelectricity are still commonly used. ( ↑ Coehn ’ s rule) Charge spoon. An electricity carrier for transporting charges from a charged conductive object to a conductive object insulated from the earth; in the Baroque era, it was a “ spoon with an amber handle ” (principle: conductive part with an insulating holder). It represents one half of a ↑ capacitor, the other half is formed by the floor, the walls of the room and the objects in the room. Depending on its ↑ capacitance, the charge spoon can absorb or release a certain charge and thus transport it ( ↑ influence, ↑ charging). Charge transfer. This can occur by ↑ charge transport or ↑ influence. ( ↑ charge separation) In the case of conductive materials, direct charge transport occurs. The electrical properties of the materials involved cause charge transfer in different ways. Charge separation 64 <?page no="66"?> - When bulk material is filled into a conductive, earthed container (Figure 1), charge transfer via air ions will occur if an insulating or low conductivity material has an adequate level of charging. In the case of contact, charge transfer may only be possible due to residual conductivity. For example, the positively charged bulk material is collected in the container, where gravity causes the repulsive ↑ Coulomb force to be overcome, resulting in an increase in the ↑ charge density. When the maximum ↑ surface charge density (26 μ C/ m 2 ) is reached, this leads to ionization of the air molecules surrounding the bulk material surface with a resulting ↑ ion current directed towards the container wall. This charge transfer, which can be seen as a faint glow in the dark ( ↑ surface reverse current), causes a partial discharge of the bulk material to earth and can result in a ↑ cone discharge or, in the case of liquids, a ↑ brush discharge. - When filling insulated containers (Figure 2), air ions inside the container transfer charge to the wall. This transferred charge cannot flow away, but results in a positive charge, for example. The electric field of this charge penetrates the container wall. The air ions endeavor to compensate for the charge so that an excess charge is generated on the outside. If the field is strong enough, this leads to ionization of the air molecules ( ↑ corona or brush discharge) on conductive and earthed objects outside the container (e. g. steel support). This can lead to such high field strengths in the container wall (e. g. of a ↑ FIBC) that ↑ propagating brush discharges are triggered there spontaneously or when a conductive object approaches. For liquids, this is transferable to ↑ RIBCs, where the earthed shell (e. g. grid) must be in close contact ( ↑ area limitation) and thus the charge can be discharged to earth. ● Charge transfer measurement. Possibility to determine the ignition potential of a brush discharge while observing certain parameters (e. g. electrode gap when measuring the ↑ MIE) ( ↑ MIQ). The usual measuring instrument is the ↑ coulometer. Brush discharges are very fast (nano-second) and only one event can be recorded at a time. This requires a fast storage oscilloscope (bandwidth ≥ 300 MHz, sample rate ≥ 1 gigasample/ s) 1 with an appropriate high-frequency shunt. This measurement setup was used to prove that there is a satisfactory correlation between the transferred charge and the ignition potential in the flammability range of gas-air mixtures for brush discharges. Since ignition potentials, defined in terms of MIE [mWs = mJ], cannot be equated with charge values [nAs = nC], the classification was made according to ↑ explosion groups (Table), as is already the case for the area limitation of chargeable surfaces. 1 gigasample/ s: 1 billion storable readings/ second Charge transfer 65 <?page no="67"?> Charge [nC] Allowed for Ex-group Examples of Ex-atmospheres Q < 60 II A Petrol, Cyclohexane Q < 30 II B Ethyl ether, Ethanol Q < 10 II C Acetylene, Hydrogen For example, if a capacitance of 10 nF is selected for measurement, the required range of 10 - 100 nC can be recorded with a voltage measurement of 1 - 10 V. The measurement is validated for assessing electrostatic ignition hazards (brush discharges from insulating surfaces and ↑ spark discharges from relatively small conductive parts (e. g. screws on insulating flanges ( ↑ capacitance)). Caution: To assess the risk, measurements must be taken at the highest expected charge! In the ↑ Ex-area, a ↑ work clearance permit must be available for this purpose. {Appendix M.3}, {Appendix D}, [SE Section 3.6.2], [TRGS 727], [IEC 60079-0] Charge transport. Movement of electric charges in a preferred direction. Charge transport in electrical ↑ conductors are called ↑ current ( ↑ electron conduction, ↑ ionic conduction). Charge transport can also occur when charged material is transported in conveying equipment (e. g. conveyor belt, bucket elevator, pneumatic conveying, flows in pipelines) and causes ↑ charge accumulation (e. g. bulk material in ↑ FIBC or liquids in ↑ RIBC) after leaving the conveying equipment. Chargeability ● Insulating materials, objects and equipment made of insulating materials can be charged. However, conductive or dissipation capable objects and equipment not connected to earth can also be charged ( ↑ charging). [TRGS 727 Section 2.16] This applies in particular to liquids and solid materials: - With a volume resistivity ρ v > 10 9 Ω m or - Surface resistivity ρ s > 10 12 Ω □ (Ohm square). The graph shows the relationship between surface resistivity and charge − expressed in field strength values − for the chargeability of materials. It has been determined through extensive testing in a test apparatus and converted to a separation speed of 1 m/ s ( ↑ charging: reproducible, instrument related). ● Not chargeable in the sense of electrostatics are: - Solid substances whose ↑ surface resistance R ≤ 10 9 Ω . The specific surface resistance ρ s is decisive for the assessment of chargeability. - Liquid substances whose ↑ conductivity κ > 10 000 pS/ m Charge transport 66 <?page no="68"?> - Conductive and dissipation capability objects if they are earthed [IEC 61340-2-3], [TRGS 727] Chargeability for the assessment of hazards and damage ● Chargeability of solid substances, [IEC 60079-10-1], [TRGS 727] ● Chargeability of liquid substances: - To be expected at low conductivity κ ≥ 50 pS/ m (2×10 10 Ω m) - Possible at medium conductivity 50 pS/ m < κ < 1 nS/ m ● Chargeability of gases. Pure gases do not charge when flowing. Charges observed in gas flows are always due to entrained aerosols ( ↑ wet vapor, oil mist in the case of compressed air, dust in the case of suction, compressed air or vacuum conveying of granules in the plastics industry). [TRGS 727 Section 5] ● Chargeability of bulk materials (solids). The charge level is mainly determined by the particle size and the processing method and extends over a range of eight dimensions of magnitude (Table: ↑ charging). ● Chargeability of textiles. In hazardous areas, it is of little importance for work clothing ( ↑ personal protective equipment), but it must be considered in ↑ ESD protected area because of possible damage to semiconductor devices. Here the standards of the group [EN 1149] are to be applied for measurement and evaluation. Charged device model, ↑ CDM Charged particle, ↑ ion, ↑ electron Charged plate monitor, ↑ CPM Charging (electrostatic). Occurs as an interfacial phenomenon between the phase boundaries of different materials and media (solids and/ or liquids), but not in combination with gases, because they do not form interfaces from an electrostatic point of view. Charging (electrostatic) 67 <?page no="69"?> ● Charging of two solids. The charging of two solids is shown schematically in figures 1 - 4. The process occurs correspondingly in the case of liquids, if these, such as oil in water, are not mixable with each other. When the two surfaces come into close contact, an electrical double layer is formed: according to the material properties ( ↑ electron emission energy), electron transfer occurs at the interfaces from substance A ( ↑ donor, low emission energy) to substance B ( ↑ acceptor, high emission energy). This electrical double layer, already described by H. v. ↑ Helmholtz in 1879, has a potential difference in the mV-range. Outwardly, however, the entire system of A and B is still neutral, since the opposite charges cancel each other out and, of course, no new charges are generated (Figure 2). The detectable charge - after the electron transfer - occurs when the materials, which were previously in close contact, are separated again ( ↑ charge separation). At least one of the materials involved must have such high electrical resistance that the charge does not equalize again during the separation process (Figure 3). Electrons are able to travel small distances (d < 10 nm) ( ↑ tunnel effect), but they can only travel larger distances in electrical conductors, not in insulators. It follows that: - High surface resistivities and/ or high separation speeds cause high charges, - Low surface resistances and/ or low separation speeds cause low charging. For separation, the electrostatic attraction ( ↑ Coulomb force) must be overcome. The equivalent of the mechanical energy to be expended for this purpose is found after the separation process in a correspondingly high electric potential (kV-range). At the two surfaces (Figure 4) there is a charge surplus of the same magnitude, but with opposite sign ( ↑ charge double layer, ↑ frictional charging). The amount of charge depends essentially on the surface structure (roughness) and the contact pressure as well as the separation speed. Reducing the contact area and contact pressure reduces the possible charge, while friction increases the intensity because it improves the contact between the surfaces by mechanically removing “ obstacles ” . This is why it is often referred to as frictional or triboelectric. The prediction of positively or negatively charged surfaces is only possible for manageable, but not for complex systems, because in the latter, surfaces with different charge signs often lie directly next to each other. Even the Charging (electrostatic) 68 <?page no="70"?> smallest impurities and/ or temperature differences lead to deviations from the triboelectric series ( ↑ violin bow effect), so that materials with the same properties can become charged with each other or even when cut. (mechano- ↑ luminescence), [SE Sections 2.3 and 2.4] ● Charging of fine solid particles (bulk material, granules, dust). Charging is much more complex here. It also follows the principle of charge separation, but because of the much larger surfaces with increasing fineness ( ↑ dust), the resulting charge per unit mass is also much higher. The decisive factor here is the process used. Process Specific charge [ μ C/ kg] Separation by sieving 10 -5 to 10 -3 Pouring form containers 10 -3 to 10 -1 Transport in screw conveyors 10 -2 to 1 Shredding in friction mills 10 -1 to 1 Shredding in jet mills 10 -1 to 10 2 Pneumatic transport through pipelines 10 -1 to 10 3 Triboelectric powder coating 10 3 to 10 4 ( ↑ pipe / pipeline, ↑ hose, ↑ filter, ↑ silos, ↑ packaging), [TRGS 727 Appendix A1 Table 12], [IEC/ TS 60079-32-1 Table A1] ● Charging of liquid during flowing, mixing, stirring, spraying. ( ↑ Lenard effect) In liquids, the charge is manifested only by ↑ ions, which also cause the conductivity as a function of temperature. The principle of charge separation described above is applicable to liquids only if the contact surfaces are not wet (e. g. water drops on PTFE, gasoline in water). Upon wetting, ions are fixed to the contact surface due to adhesion, resulting in the Helmholtz double layer (Figure 1). In quiescent liquids, a small charge arises, caused by ↑ Brownian molecular motion, in which individual ions diffuse into the liquid (Figure 2). With the onset of flow, the diffused charges are entrained, and charge transport occurs (Figure 3). In addition, liquids with high electrical conductivity have a low ↑ Debye length. The adhesion conditions on the tube wall lead to low velocities in the diffuse layer region and to low charge separation. Liquids with low electrical conductivity undergo charge separation (charge double layer) due to the larger Debye length. Charging (electrostatic) 69 <?page no="71"?> The actual charging results from overcoming the adhesive forces at the contact surfaces (charge separation). The level of charging increases with the speed of movement, turbulence (stirring, pumping) and the size of existing interfaces, e. g. on pipe walls, in filters, valves and the like. The principle shown in the figure therefore changes in many ways [TRGS 727 Section 4]. In the photo, the charging of a liquid (hydraulic oil in this case) is clearly visible: In the ↑ charge double layer, a thin layer of the liquid is “ held ” by strong ↑ charge bonding ( ↑ Coulomb force) and pushed upwards against gravity by subsequent liquid on the outside of the earthed pipe. Here the charge was so high that the ↑ gas discharge occurred. [SE Section 7.8] In the case of immiscible liquids, e. g. petrol/ water or toluene/ water, charging also occurs at the phase boundaries, which can be considerably higher than that at the walls (mechano- ↑ luminescence, ↑ flow velocity). ● Charging in gases. Gases can only be charged by ↑ ionization, but not by separation processes. They do not become charged when flowing past solids or liquids. Gases fill any offered volume and therefore cannot form their own boundaries. However, as soon as gases carry particles (dust or mists) (e. g. oil and water mists in compressed air, pneumatic conveying), charging can occur due to separation effects on the walls and between them. The figure shows a measurement setup for particle-laden air. Accordingly, solids and liquids are also not charged by passing gases, but only if no particles are removed by the gases. When compressed gases are expanded, strong cooling can occur at the nozzle due to the ↑ Joule-Thomson effect, causing ↑ condensation (fog) or even ↑ sublimation (snow). The resulting aerosols can become highly charged when separated from the nozzle wall (ignition hazard). This effect is often observed in ↑ CO 2 fire extinguishing systems ( ↑ explosion accident of Bitburg). ● For falling drops and particles, it has been experimentally determined that they are not charged even during free fall through the particle-free atmosphere, as long as they do not fractionate. ( ↑ Faraday cup), [Lüttgens, S. et al. (2015)] Charging (electrostatic) 70 <?page no="72"?> ● Freeze charging. It occurs when liquids freeze due to the difference in mobility of the ions. A drop of water, for example, starts to freeze from the outside to the inside. In the process, the concentration of the more mobile hydrogen ions H + increases in the outer shell and the negative OH ions remain in the interior. When the droplets are cooled further, e. g. in a thundercloud, they split as a result of the expansion differences in the droplet with a renewed charge due to separation ( ↑ cloud dipole). This results in the charge allocation in a thundercloud, etc. [Masuda, S. (1973)] ● Charging of persons. Has a specific position from the point of view of risk assessment, since the charge can be carried away by the person ( ↑ personnel charging, ↑ charge abduction). [IEC 61340-4-5], [TRGS 727 Section 7] Charging (equipment-related) ● Purposefully charging is a type of ↑ useful application in which an insulating material is exposed to a current flow between a ↑ charging electrode and a counter potential. The ↑ ions emitted by the corona pins are bound to field lines and can hardly be deflected by air flow. ( ↑ air boundary layer) ● Indirect charging is a type of useful application where, for example, a film is charged separately and then applied to an earthed surface ( ↑ in-mold labeling). ● Reproduceable charging is required to evaluate the chargeability of substances. The standard [IEC 60079-32-2] describes manual methods, all of which depend on the skill of the person performing the test and therefore have poor reproducibility. To obtain reproducible results, the mechanical friction apparatus shown in the figure was developed ([DIN 53486 (1975)] now withdrawn (2012)). For a detailed evaluation of the charging behavior of a material, it allows the determination of the following measured values: - Field strength after the 1st friction process - Field strength after the 10th friction cycle - Field strength at limit charge - Half-life after the end of friction charging - Field strengths after specified discharge times [SE Section 3.6.1], [Lüttgens, G. (1981)], [Lüttgens, G., Glor, M. (1989)] Charging (equipment-related) 71 <?page no="73"?> ● Triboelectric charging ( ↑ frictional charging) is a test method for textile production. It cannot be used for textiles whose dissipation capacity is located inside the fiber ( ↑ core fibers). For the latter, a test method with an ↑ influence field measurement probe is suitable. [SE Section 3.14.2] Charging current (also conduction current). Current, flowing through a charge storage device ( ↑ accumulator, ↑ capacitor) as the applied voltage is increased. When measuring the electrical resistance of insulating materials, the current through the ↑ specimen decreases asymptotically to a constant value after the measurement voltage is applied. The difference between the initial and final values represents the conduction current required to charge the electrode capacitance and to dielectrically polarize the sample. The charging current can be superimposed by an ion current, the strength of which also decreases as the ions are deposited on the electrodes and are no longer available for further charge transport. Since the steady state is usually reached after only one minute, the measured value should be read only after this ↑ waiting time ( ↑ resistance measurement). Charging electrodes. Are used in the ↑ useful application of electrostatic charges. They are used to apply a charge to a sufficiently high resistance material by means of emission pins. For ↑ touch protection, the emission pins are usually connected via protective resistors ( ↑ decoupling). Other charging electrodes are in the form of a corona wire ( ↑ separation of substances) or other geometric shapes. Charging hazard. To be determined as part of the ↑ risk assessment. A - Fixed clamping device, B - Field strength measuring device, C - Cylindrical rods, D - Test specimen, E - Guide rail, F - Tensioning device, G - Starting position of the carriage Charging current 72 <?page no="74"?> Charging phenomenon on fast moving material webs. The curves shown in the figure were published in 1977 by Letournel and Oberlin in a paper on charging on ↑ material webs. Type 1: The potential rises to a constant maximum. One explanation is that the material web runs at high speed (v > 1.5 m/ s) over a large number of rollers that have approximately the same circumferential speed as the web, i. e. the web is transported through the machine. Here, charging presumably occurs on both sides only by contact and separation. Type 2: The potential rises to a maximum, decreases, and changes the polarity to a new constant maximum. One explanation is, that the charged area of a film reaches the charge coverage σ max [C/ m 2 ], gas discharge into the environment occurs or, in the presence of earthed components, gas discharges ( ↑ brush or ↑ propagating brush discharge) and pole reversal at the material surface occur. Such gas discharge can be well detected with a suitable ↑ spark detection device. The friction necessary for generating the high charge coverage is mainly due to slippage. For material webs which are processed under negative pressure (e. g. ↑ vacuum metallization), this charging and discharging mechanism is influenced according to the “↑ Paschen ’ s law ” . [SE Section 5.6] Type 3: The potential increases, passes a maximum and decreases to a lower constant level without changing the polarity ( ↑ breakdown resistance). One explanation is, that a film reacts depending on the potential, meaning with higher potential, the leakage resistance becomes lower and stabilizes to an average value. The reason can be surfaces nearby of different polarity, which do not completely balance each other and lead to a remaining charge. Areas of different surface resistances and resulting ± charge profiles may have formed on the surface at a wide variety of distances due to contamination. Part of the charge flows off or is reduced by gas discharges until the breakdown field strength between the charge profiles is dropped below and the residual charge remains as islands of charge. An overcharged web is emitting charge into the environment, preferably at the edges. Charging phenomenon on fast moving material webs 73 <?page no="75"?> The diagram shows that unpredictable sign changes occur within tenths of a second. For example, a charge island of 50 × 50 mm 2 in a web moving at 10 m/ s will pass a sensor or ↑ ionizer in 5 ms. Obviously, it is not sufficient to attribute the charging mechanisms of high-speed material webs only to the principle of Helmholtz ’ s double layer, which in any case applies only to the solid/ electrolyte system ( ↑ charge double layer). Instead, if appropriate, the ↑ Lewis ’ s acid-base concept or the ↑ Brønsted-Lowry definition can be used to explain it. [SE Section 2.14.1], [Letournel, M., Oberlin, J.-C. (1977)], [Schubert, W. et al. (2021)], [Spice, J. E. (1971)] Charging process. Generally, for ↑ charging an ↑ accumulator or ↑ capacitor (charging and discharging ↑ time constant). Charging system ● Industrial: Electrode arrangement for the application of charge with the aim of achieving certain effects ( ↑ charging electrode, ↑ high-voltage generator, ↑ useful application, ↑ separation of substances). ● Medicine: For electrostatic charging for atomization of liquids ( ↑ atomization). In inhalation therapy, such substances are used to treat diseases of the respiratory organs. Charging tendency. This can be reduced by using additives to reduce the electrical resistance ( ↑ antistatic agents). [SE Section 2.10] Charging time constant, ↑ time constant Charpy strength. To evaluate the brittleness (toughness) of plastics, the impact bending test is performed on a notched specimen and the impact energy (relative to the specimen cross section at the notch) is determined. Specimen shapes, test procedure, test arrangement and evaluation are specified [EN ISO 179-1]. The notch toughness is generally reduced by the addition of carbon black ( ↑ carbon) to improve electrical conductivity. Chemical Abstracts Service (CAS), ↑ CAS number Chemical material. An antiquated and unenforceable term for ↑ plastic. There are the following group classifications: polymers, polycondensates, polyadducts. Charging process 74 <?page no="76"?> Chemical reaction as an ignition source. Chemical reactions involving the generation of heat ( ↑ exothermic reaction) can cause substances or systems of substances to heat up and thus become a source of ignition. ( ↑ aluminothermic reaction) Chemo galvanic metallization. Coating of an (insulating) plastic with a metal layer. Precious metal catalysts, e. g. palladium from an aqueous dispersion, are adsorptively bound to the surface of the initially roughened plastic parts ( ↑ adsorption). The catalytic effect of the precious metal enables the subsequent chemical nickel plating. This nickel layer, which is still very thin, makes the plastic part electrically conductive, so that the ↑ electroplating can then begin. Chemsafe. Database of the German: Bundesanstalt für Materialforschung und Materialprüfung (BAM) ( ↑ Federal Institute for Materials Research and Testing) and the German: ↑ Physikalisch-Technische Bundesanstalt (PTB) for ↑ explosion-related parameters in explosion prevention (www.chemsafe.ptb.de). Cherenkov radiation. A phenomenon discovered by P. A. Cherenkov in 1934 in which ↑ electromagnetic radiation is generated by energetic, charged particles when they move faster than the speed of light in an optically transparent medium. The maximum intensity of Cherenkov radiation is in the visible range between blue and ultraviolet. Chill roll. Electrostatic application/ adhesion of the edge zone to a cooling cylinder ( ↑ cast process, ↑ edge zone fixation, ↑ useful application). Chill tack. Electrostatic application/ adhesion of a plastic melt to the cooling cylinder by means of a ↑ charging electrode ( ↑ cast process, ↑ useful application). Chromatography. A method of analyzing and processing mixtures of substances. It uses the distribution processes that occur between a stationary phase and a mobile phase (e. g. as a result of ion exchange or adsorption). Depending on the type of stationary phase, a distinction is made between gas, liquid and thin-layer chromatography. CIP system, short for cleaning in place. Cleaning system within process plants. [SE Section 7.4.5] Cleaning. In general, ↑ charging must be expected during cleaning. Often combustible ↑ solvents are used, which generate flammable ↑ solvent vapors. If conductive, earthed parts are cleaned, hazardous charging is generally not to be expected. In the case of insulating parts (plastics), the surface dimensions must be observed ( ↑ chargeability). Persons and conductive objects must be earthed during cleaning ( ↑ earthing). [TRGS 727] Clearance ● Smallest distance in air between two conductive parts ( ↑ creepage distance). [IEC 61010-1] ● Electrode distance of a ↑ spark gap, measured in millimeters, at which a ↑ breakdown occurs. Clearance measurement. Determination of a possible concentration of hazardous substances with the aim of establishing that the atmosphere at the intended workplace Clearance measurement 75 <?page no="77"?> allows safe working ( ↑ work clearance permit). These are not measurements in the sense of the ↑ GefStoffV. [DGUV Regel 113-004 - Teil 1], [DGUV Grundsatz 313-002] Climate (Greek: klima, “ inclination ” ). The term comes from meteorology and is also used to describe test conditions for materials whose properties (e. g. ↑ surface resistance) are subject to the influence of climate. In engineering, the variables that characterize a climate are ↑ temperature and ↑ humidity. ● Climate influence. The electrostatic properties of materials are particularly affected by the climate, which is primarily based on the ↑ water activity of the materials. High humidity is deposited on surfaces, reducing the surface resistance. This effect is erroneously attributed to the conductivity of the air. Electrostatic measurements should therefore only be performed in a defined ↑ test climate (e. g. in climatic chambers) after sufficient acclimatization time. The temperature and humidity values must always be reported with the results. Experience has shown that the drier the climate, the more pronounced the electrostatic phenomena. Since many insulating materials are also influenced by ↑ temperature, the strongest charging phenomena can be observed in the cold season, i. e. in cool and dry rooms. ( ↑ antistatic agents) Cling effect. Consequence of ↑ adhesion or ↑ electro adhesion. The cling effect is particularly exploited in advertising and marketing with the targeted use of ↑ electret films. These can be quickly applied to a variety of substrates and removed without leaving a residue (e. g. guerilla marketing). When ↑ coating paper or film in ↑ gravure printing in combination with ↑ electrostatic print assist, the printing inks can form electrets depending on the pigments and resins used, resulting in a cling effect that can last for a very long time. Closed-loop system. Closed-loop control for active DC discharge bars ( ↑ ionizer), which detect electrostatic fields by means of internal or external E-field measurement ( ↑ EFM) or integrated current measurement and change the output of the discharge bar (voltage and/ or pulse width). Clothing. In industrial environments, people must wear appropriate and certified protective clothing. In flammable and hazardous areas, protective clothing must not be a source of ignition ( ↑ personnel charging) and must therefore have electrostatic dissipative properties ( ↑ dissipative capability). Note: When handling isopropanol (e. g. disinfection) and non-dissipative protective clothing, the solvent vapors may ignite. For testing, material, and design requirements, refer to the [EN 1149] series of standards, which also provides information on safe handling. Persons wearing electrostatic dissipative protective clothing must be securely and permanently earthed. ● Ignition hazards in hazardous areas. The application range of electrostatically dissipative protective clothing refers to flammable and explosive atmospheres with a ↑ MIE ≥ 0.016 mJ. Exceptions are oxygen-enriched atmospheres, presence ↑ Ex-zone 0 with simultaneous presence of gas-air mixtures of explosion group IIC and handling of primary ↑ explosives. Extended additional requirements may be necessary. [Köhler, J. et al. (2008)] Climate 76 <?page no="78"?> In flammable and hazardous areas, people must be safely and permanently earthed with an earth resistance ( ↑ earthing) of less than < 10 8 Ω . Without earthing, both the person and the protective clothing can become dangerously electrostatically charged. Electrostatic discharge protective clothing must be done and fully fastened before entering flammable and explosive atmospheres. Opening and removing static dissipative garments can result in a high level of charge on the garment and the wearer and is therefore prohibited in these areas. In general, safety risk and workplace analysis must be performed prior to use in flammable and explosive atmospheres. ● Working in ↑ ESD protected areas. Due to the potentially high electrostatic sensitivity of ↑ ESD, the wearing of conductive clothing is mandatory. [IEC 61340-4-9] applies in combination with [IEC 61340-5-1]. Although the clothing types according to [EN 1149] and [IEC 61340-4-9] are based on the same electrostatic dissipative functionality, they differ in terms of testing, construction, design and intended use. The dissipation capability is usually achieved by incorporating conductive fiber systems ( ↑ conductive fiber) into the outer material of protective clothing and work wear. The effectiveness of the electrostatic dissipation capability of clothing can be reduced by wear, soiling, or cleaning processes, among other things. Conductive (e. g. metal zippers) or non-dissipative (e. g. reflective strips) accessories attached to clothing can have a risky effect on the overall electrostatic behavior. Separate requirements apply. Carried equipment is not part of dissipative protective and work clothing. A separate assessment must be made of the potential hazards and risks. Separate standards also apply to gloves, safety shoes and safety helmets ( ↑ personal protective equipment). Cloud chamber (also called Wilson cloud chamber - C. T. R. Wilson (1869 - 1959). Used to detect ionizing particles. The cloud chamber is filled with supersaturated vapor (usually a mixture of ethanol and water) through which the webs of electrically charged particles ( ↑ ions) can be made visible in a fog trail. The incoming particles ionize individual atoms of the gas, which act as condensation nuclei (comparable to dust particles) to which water dipoles attach in a shell-like fashion, forming visible condensation trails. If a suitable electric or magnetic field is applied, the trajectories can be used to determine the type of particle. Cloud dipole. In large rain or ice clouds, corresponding temperature gradients (around 0 °C at the bottom and - 50 °C at the top) lead to strong upward currents that transport charged ↑ aerosols and thus generate vertically oriented ↑ dipoles, with the positive charge preferentially at the top and the negative charge at the bottom ( ↑ thunderstorm electricity). This effect can be enhanced by additional dust in ↑ tornadoes. A cloud dipole represents the large-volume charge storage for ↑ thunderstorm lightning. The process of charge separation in the cloud is not fully understood. The complex processes are based on the fact that fog particles agglomerate in the cloud to form droplets, or that water steam molecules on ↑ sublimation nuclei immediately turn into ice particles, which fall downward due to gravity and are carried upward again by updrafts. There they enter freezing zones, solidify Cloud dipole 77 <?page no="79"?> into hailstones, fall back down and melt into thick raindrops. The charge separation is attributed to ↑ solidification potential and/ or the ↑ Lenard effect. Occasionally, cloud dipoles occur during heavy snowstorms, causing lightning discharges (winter thunderstorms). Lightninglike discharges have also been observed in some cases during volcanic eruptions and the resulting large dust clouds (particles < 2 mm) with high turbulence of dust and ash particles, suggesting dust cloud dipoles. (Vesuvius (1767), Surtsey (1963 - 1966), Mount St. Helens (1980), Eyjafjallajökull (2010), Taal (2020, Philippines)) S. Masuda describes another experimentally proven mechanism of charge separation in a thundercloud: When a water droplet (diameter about 1 mm) is rapidly cooled, a thin ice shell forms on its surface, which immediately causes very fine water particles (diameter 1 - 20 μ m) to be ejected through pores in the outer shell. As the droplet freezes, the internal pressure increases to approximately 60 bar. As they escape, the small particles are carried upward by charging winds and the larger droplets fall downward as negative particles. The negative charge on the underside of the cloud causes a positive influence charge on the earth ’ s surface below. This can lead to thunderstorm lightning if the field strength is high enough. [Masuda, S. (1973)], ( ↑ atomization, ↑ Rayleigh limit) The microscopic image shows the ejection of positively charged daughter droplets when a water droplet freezes. [Cheng, R. J. (1970)] CLP Regulation. (EC) No 1272/ 2008 on Classification, Labeling and Packaging of substances and mixtures. The Regulation ’ s criteria are designed to identify hazardous chemicals and inform users of their hazards through standard symbols and phrases on labels and safety data sheets. It also sets out specific packaging requirements for certain hazardous substances and mixtures. The CLP Regulation aligns EU legislation with the ↑ Globally Harmonized System (GHS) for the classification and labeling of chemicals. [SE Section 7.5.18] Cluster. Physical term for coherent individual particles that can be regarded as a uniform whole. The ↑ dipole forces of the individual particles can also contribute to the formation of clusters. CO 2 fire extinguishing system. According to [DGUV Information 205-026, Section 5.7], the following must be observed to avoid electrostatic charging when using CO 2 fire extinguishing systems: - Pressurized CO 2 can become electrostatically charged when flowing through conductive, dissipative or insulating pipes and thus ignite an existing explosive atmosphere when extinguishing nozzles are discharged. - CO 2 fire extinguishing systems must therefore be automatically activated only until fire alarms are received from two independent fire detection elements. CLP Regulation 78 <?page no="80"?> - Functional tests of CO 2 fire extinguishing systems may only be carried out if the absence of an explosive atmosphere is ensured and documented. When using hand-held CO 2 fire extinguishers, be aware that persons wearing insulating shoes will become highly electrostatically charged in a few seconds and cause spark discharges when they come into contact with the earth. (This also applies to powder extinguishers.), ( ↑ explosion accident of Bitburg), [SE Section 7.3.8.2] Coating. Application of a permanently fixed layer of a formless substance for functionalization, quality improvement and information transfer on almost all surfaces. From an electrostatic point of view, the properties and ↑ layer thicknesses are particularly significant. The coating of metals with plastics, paints, etc. (e. g. for corrosion protection) can result in insulated conductive parts, which can lead to hazards due to charging, because a ↑ charge dissipation to earth is prevented (e. g. externally coated barrels and cans). Because safe charge transfer (charge dissipation) is not possible between insulated, coated metallic system parts (e. g. piping, flanges), additional earthing measures must be taken in ↑ Ex-areas. Dissipative ↑ floors (e. g. concrete or natural stone) may lose their dissipative capability due to coating (e. g. liquid sealing of roadway areas at ↑ filling stations). On metal surfaces with insulating coatings, charge densities can be so high that ↑ propagating brush discharges occur, e. g. in ↑ pneumatic conveying through pipes with insulating coatings on the inside. If the thickness of the insulating inner coating on conductive drums and tanks does not exceed certain limits, they can be filled and emptied in the same way as conductive containers. ( ↑ personal protective equipment), [TRGS 727 Sections 3.3 and 5.5], [IEC/ TS 60079-32-1], [DIN 8580], {Appendix D} ● Coating substrates. Usually solids, whose surfaces should be adapted to the coating material for good adhesion. The conditions at the contact surfaces of both substances have to be optimized, e. g. by ↑ corona pretreatment. For example, coating films with solvent-free inks that are cured under UV light requires a ↑ surface energy of 42 - 44 mN/ m. ● Coating process. In addition to mechanical (e. g. offset printing), chemical (e. g. galvanizing), thermal (e. g. whirl sintering) or thermomechanical (electroplating) applications, there are various electrostatic processes: ● 1) Powder coating, environmentally friendly, solvent-free, easy recovery and reuse of the powder coating surplus. After coating, the paint layer is formed by melting the ↑ powder paint in a sintering furnace at 150 - 200 °C. ( ↑ charge control agent) - By using high voltage. The fluidized powder (< 100 µm) is charged in the coating gun by a corona pin protruding from the open end of the gun ( ↑ corona charging) with maximum 100 kV and 10 - 800 µA. The particles follow the field lines oriented to the earthed workpiece ( ↑ wrap-around effect). Where paint particles are deposited on the workpiece, there is an increase in potential on the surfaces facing the spray nozzle and thus coated first, resulting in a field grip which leads to particle deposition on the reverse side. Depending on the polarity of the charge, different results can be expected. If the particles are negatively charged, there is a good wrap-around effect and the interior acts as a Faraday cage. Particle adhesion is achieved by influential charging ( ↑ image charge). Coating 79 <?page no="81"?> - By means of triboelectric charging. The powder is highly charged during ↑ pneumatic conveying as a result of frequent contact and separation effects with the wall material. In order to achieve a ↑ frictional charging comparable to the high voltage charging with as many powder coatings as possible, the tube wall must consist internally of a material that is strongly “ electronegative ” in the ↑ triboelectric series (e. g. PTFE). The powder coating is transported into the friction tube by the injector action of the compressed air nozzle, accelerated, and there are many wall contacts (e. g. by swirling) of the particles, which become positively charged. During the charge separation process, a negative reverse charge builds up on the inside of the tube. The more negative charge accumulated there, the lower the positive particle charge, which would eventually come to a stop if the negative charge were not dissipated by the tube. The dissipation takes place via an earthed corona pin near the compressed air nozzle ( ↑ corona discharge). On the discharge side of the gun, there is usually a diffuser that fans out the jet of positively charged particles so that they are deposited as uniformly as possible on the earthed workpiece. The advantage of this type of gun is that it eliminates the need for high-voltage equipment (hazards, cost). It should be noted that ↑ propagating brush discharges with resulting ignition hazards can occur in the friction tube. ● 2) Coating with liquid paint. Different variants in which the lacquer to be applied is electrostatically charged and transported to the part to be coated with the help of the electrostatic ↑ field. The charged droplets follow the field lines between the charged atomizer and the conductive, earthed parts to be coated. They are deposited there and cause an increase in potential at the paint surface, so that the field lines Coating 80 <?page no="82"?> are increasingly oriented toward the still paint-less sections and deflect subsequent droplets there. Due to this “ coating encompassing ” , the sections facing away from the coating applicator are also coated. Paint losses, especially on filigree objects, are thus extremely low. In principle, only conductive objects can be coated in this way. However, non-metallic materials and plastics can also be coated electrostatically if their undercoat resp. base is kept conductive and earthed during the process, e. g. by means of conductive foils, screen fabrics or the like. To prevent ↑ danger of electric shock, the required high voltage should be limited to non-hazardous current values. Since ↑ gas discharges are to be expected, which can lead to ignition of the liquid-air mixture, appropriate measures for ↑ explosion prevention are always required. [Tiedje, O. (2020)] - Electrostatic disc atomizers. Two rotating discs (up to 10 000 rpm) with sharp edges ( ↑ charging electrode) and high voltage (> 150 kV) feed the paint. Due to the narrow gap (< 1 mm), capillary forces prevent the paint from flowing out. When approaching an earthed object, a ↑ corona discharge occurs at the edges, charging the paint and transporting it to the object. - Electrostatically assisted highspeed rotating atomizer with internal charge. Due to the high rotational speed of the atomizer bell of > 50 000 rpm, the centrifugal forces displace the liquid film to the break-off edge of the bell, where it detaches in the form of droplets and is deposited in a field-directed manner on the earthed (oppositely charged) surfaces. Due to the contact charging, the detached droplets (aerosols) reach the maximum ↑ surface charge density σ because of their small size. As a result, the like-repellent forces are greater than the membrane tension of the droplets, which burst into smaller charged aerosols ( ↑ atomization). Since they are bound to the field lines, they cannot vagabond, and lossy overspray is prevented. Furthermore, the ↑ Rayleigh instability operates. This coating is suitable for non-conductive inks. - External electrostatic charge. To prevent internal charging of a conductive paint, which is associated with high insulation and safety requirements, a solution was found in which the high-speed rotating atomizer bell is at earth potential and the paint moves toward the object on the field lines of the external corona charge ( “ finger ” ). Coating 81 <?page no="83"?> ● 3) Coating with liquid media (e. g. water). The German engineer H. ↑ Künzig was the first to publish a technical solution in which water aerosols are moved along the field lines to the web in order to moisten it and thus discharge it ( ↑ material web, ↑ remoistening). A ↑ charging electrode (> 15 kV) intensifies the contact of the web with the earthed roll. The charge generated during separation (approx. 150 kV/ m) charges, e. g. water droplets, which, uninfluenced by laminar ↑ air boundary layers, move along the field lines to the web and wet it ( ↑ atomization). [Künzig, H. (1978)], [SE Section 8.2.8] ● 4) Flocking. A process of applying short fibers (free-flowing prepared flock fibers, length about 0.3 - 5 mm) to a substrate previously coated with adhesive using an electric field. Both the flock and the adhesive must be electrostatically dissipative. The substrate is coated with the adhesive and is earthed or rests on an earthed substrate. The applicator, usually pneumatically assisted in automatic systems, is connected to a high-voltage source so that a high field strength is generated in the direction of the substrate. The outgoing flock is charged and polarized by ↑ influence so that it is aligned parallel to the substrate in the electric field, accelerated, and “ shot ” vertically into the adhesive layer. Excess flock, i. e. flock not anchored in the adhesive, is recharged and flies back to the device, where it is recharged and sent back to the substrate. This results in a parallel oriented coating on the substrate, which is then fixed by drying. If the charge densities on the substrate are too high (the resistance of the flock is too high), back-spraying may occur, resulting in flocking defects such as cratering in the flock layer. In principle, all materials can be flocked, provided that the adhesive will adhere to them. Coating 82 <?page no="84"?> ● 5) Corundum coating. In the production of abrasive paper and the like, the property of Al 2 O 3 crystals ( ε r : 6 … 9) to orient themselves in an electric field is used. Currents in the higher Arange at voltages up to 100 kV are used for charging. ● 6) Ink jet. From about 1984, the first print heads for non-contact coating (non-impact printers) based on continuous droplet formation and electrostatic deflection became generally available. In principle, the continuous ink jet (CIJ) works like the cathode ray tube of an ↑ oscilloscope. A piezo oscillator (1) pushes the liquid jet out of the nozzle chamber (2), which breaks into reproducible droplets due to ↑ Rayleigh instability and pressure fluctuations. Since this breakup occurs within the charging electrode (3), a defined charge of these droplets can be achieved. In the deflection electrode pair (4), the droplets are deflected to the substrate (6) by the control voltage applied there. Droplets (5) not required for information formation are collected and returned to the circuit. In practice, two pairs of deflection electrodes are arranged in a series (as in the cathode ray tube) for deflection in the direction of the X and Y coordinates. This technique is commonly used for industrial applications. ● 7) Plasma coating - Plasma jet printing, atmospheric pressure process for applying nanomaterials on flexible substrates. This allows sensor and signal amplifier materials (e. g. ↑ carbon - nanotubes) to be applied to paper, for example, with high quality and density by using low temperatures (40°C). It can be used for the fabrication of e. g. bioand chemical sensors. [Gandhiraman, R. et al. (2016)] - Full face plasma coating, for functionalization of metal surfaces by application of metal powders (e. g. chromium and iron) or e. g. aluminum oxide and the like for ceramic coatings. - Partial plasma coating, e. g. for 3D printing or functionalization with defined structures. Coating 83 <?page no="85"?> (Source: www.hhft.de) ● 8) Copying and printing processes, ↑ xerography, ↑ laser printer, ↑ carrier, ↑ charge control agent, ↑ toner, latent ↑ charge image, ↑ magnetography, ↑ roller coating system ● 9) Pesticides and fertilizers can also be applied electrostatically. Plants, as objects that are always conductive, provide the best conditions for reaching the back of the leaves using the principles described. This targeted application can significantly reduce the amount of chemicals used [Patel, M. K. et al. (2016)]. Cockroft-Walton generator (cascade generator), ↑ high-voltage cascade Coehn, Alfred (1863 - 1938). German physicist who established ↑ Coehn ’ s rule in 1898 - 1909. Coehn ’ s rule. Defined by A. ↑ Coehn: for the ↑ charging to be expected because of the application of mechanical energy to separate the substances in contact, the following applies: - Of two bodies, the one with the larger ↑ permittivity (dielectric constant) is always positively charged, and the one with the smaller permittivity is always negatively charged. - The amount of charge depends on the difference in permittivity. The statements of Coehn ’ s rule have been verified many times ( ↑ triboelectric series). They are not always unambiguous. The strongest objection is that similar materials should not charge each other, but they do (e. g. unwinding a web from a roll, lifting identical sheets from a stack). Coehn ’ s rule does not apply if one of the two partners is a ↑ non-polar material [Kanamura, K., Takada, T. (1939)]. ( ↑ material web, ↑ separation of substances, ↑ violin bow effect) Coercive field strength (Latin: coercere “ to force ” ) ● Electric field strength that causes or cancels the dielectric displacement ( ↑ polarization) of a substance. The higher the coercivity, the better the polarization is maintained. Coercivity affects the piezoelectric properties. ● Magnetic field strength that causes magnetization or cancels residual polarization. The ability of a material to resist changes in its magnetic state. Cockroft-Walton generator 84 <?page no="86"?> Cohesion. Generally, the effect of attractive intermolecular cohesion forces between the atoms or molecules of the same substance. Cohesion occurs, for example, when a force must be applied to split a substance. Therefore, the magnitude of the cohesive forces can be inferred from the tensile strength of a solid or the interfacial energy of a liquid. ( ↑ adhesion, ↑ wettability, ↑ corona pretreatment, ↑ surfactants) Coincidence. Occurs when two or more events or signals occur within a time span defined by the temporal resolution of the detecting device. Coincidence circuit. A circuit that provides an output pulse only if an input pulse arrives at each of the inputs within a specified time ( ↑ anti-coincidence circuit). Cold impact toughness (also impact toughness at low temperature). Is the embrittlement of a plastic at low temperatures. Carbon black ( ↑ carbon), which is used to improve conductivity, can reduce cold impact toughness to such an extent that containers made from it fail the ↑ drop test ( ↑ glass transition temperature). Cold stretching. Some ↑ plastics exhibit the property of plastically deforming to a multiple of their original length under tensile stress in the solid state. When such stretching is carried out in the elastic region, fibers, and films, for example, gain significantly higher mechanical strength due to the highly oriented molecular structure. In polymers with conductive additives, the strong orientation of the conductor network due to cold stretching can lead to an increase in resistance due to tearing of the conductor paths ( ↑ pearl string model, ↑ tunnel effect). Collection container, ↑ container size / container material Colloid. Finely dispersed solid, liquid or gaseous substance that is in ↑ dispersion with other substances. Colloid is arbitrarily classified as a molecular aggregate or polymer with 10 3 to 10 9 atoms at a dimension between 10 -7 to 10 -5 cm. Combustible substances. Not to be confused with “ fuel ” , are classified for explosion prevention purposes as follows: - Flammable liquids: All liquids for which a ↑ flash point can be specified. - Flammable vapors: Liquid vapors that have an ↑ explosion range with air. - Flammable gases: Gases having a flammable range with air. - Combustible dust: Dust and finely divided granules that can form an explosive mixture with air. This includes primarily organic and metal dust. Combustion. Oxidation of combustible materials, which always occurs in the ↑ gas phase, i. e. when fuel and oxygen are in a molecular mixture. Metals are an exception, where oxidation occurs as a surface reaction. In the case of gaseous or vaporous fuels, combustion can occur immediately ( ↑ Ex-area, ↑ explosion limit, ↑ flash point, ↑ deflagration). Liquid or solid fuels must first be converted to the gas phase. Therefore, a significant portion of the ignition energy ( ↑ MIE) is required to convert the solid to gaseous hydrocarbons by vaporization, melting or cracking ( ↑ cracking process). This quantity of hydrocarbon must be large enough so that when the mixture is ignited in air, the amount of heat released is sufficient to ensure further thermal processing of the solid. Combustion 85 <?page no="87"?> Combustion process. Reaction between fuel and atmospheric oxygen and the resulting heat development with corresponding radiation emission. With regard to the combustible mixture, the combustion process and its speed are material-related variables that depend on pressure, temperature and turbulence [Steen, H. (2000)]. A fire is a quasi-stationary combustion process without pressure increase (flame speed below 0.1 m/ s). At optimum fuel/ oxygen mixing ratios ( ↑ explosion limit), an ↑ explosion occurs in a closed volume, with flame velocities up to about 10 m/ s (pressure rise up to about 10 times the initial pressure). If precompression occurs during an explosion, e. g. in pipelines, velocities of 1 km/ s and more can be reached, connected with corresponding pressure increases ( ↑ detonation, ↑ deflagration). Comitée Européen de Normalisation Electrotechnique (CENELEC) (European Committee for Electrotechnical Standardization). Prepares the European electrotechnical standards. Together with the Comitée Européen de Normalisation (CEN), they form the Joint European Standards Institution. The member states are obliged to adopt European standards. (www.cenelec.eu) Comparative tracking index (CTI) (also creep resistance or tracking resistance). This refers to the resistance of an insulating material to the formation of conductive creepage paths when conductive liquids drip onto a ↑ creepage distance and are given in volt. The tracking resistance of an insulating material is determined by, among other things, its ability to absorb water and is expressed as the proof tracking index (PTI). Voltages up to 1000 V with maximum currents up to 1 A are used. [IEC 60112] Component. An individual part of an electrical device that can be classified as an active component (e. g. electron tube, transistor) or a passive component (e. g. capacitor, coil, resistor). Composite. Material consisting of several different materials that are bonded to each other in various ways, usually over their entire surface (e. g. coated, laminated, vapordeposited), and is usually processed as a ↑ material web. Fully printed webs, e. g. of paper, should also be considered as composites, as they often have at least partially conductive layers on their surface (e. g. black, i. e. carbon black-filled printing ink). When processing composites with conductive layers (e. g. aluminum or ↑ ITO layer), high electrostatic charges may accumulate during the manufacturing process and be dissipated by ↑ spark discharges. Material webs that are also subjected to ↑ corona pretreatment can become ↑ electrets and cause electrostatic ↑ gas discharges. Note: Active ↑ ionizers are often used in composite processing. The ions emitted from their pins charge the conductive layers, which, depending on their size and thickness, have a very high electrical capacitance that can discharge during spark erosion ( ↑ electrical discharge machining) or ignition of an explosive atmosphere if the ↑ electric strength is exceeded. Therefore, active ionizers must not be used in manufacturing processes in combination with flammable liquids. The ionizers required in [TRGS 727 Section 3.3] must be installed as passive ionizers (e. g. ↑ earthing tongue). [SE Section 5.4.1.1] Combustion process 86 <?page no="88"?> It does not matter whether the conductive layer is on the outside or embedded in the composite. In the case of internal layers, spark discharges may occur at the exposed edges because the conductive metal layer is usually insulated by the encapsulating layers. [SE Section 7.5.18] A particular hazard exists if parts of the conductive layers (e. g. metal fragments) are electrically insulated or if only partial surfaces are metallized or coated with metal pigments. These store the charge and, with sufficient ↑ capacitance, also cause ignitable sparks, since they represent a ↑ capacitor that can be rapidly discharged by a high-energy spark discharge. Condensation. Transition of a substance from the gaseous to the liquid or solid ↑ state of matter when the pressure-dependent saturation density of a vapor is exceeded during its cooling ( ↑ dew point). During condensation, the heat of condensation required for evaporation is released again ( ↑ sublimation). Condensation occurs at the same temperature as evaporation, provided ↑ condensation nuclei are present. Condensation nucleus. Smallest particle (10 -4 to 10 -6 cm, e. g. fine dust, ↑ ion), which is necessary as a starting point for ↑ condensation at vapor saturation (e. g. 100 % relative ↑ humidity). Conditioning. Adaptation of materials for measurements and tests under a defined ↑ test climate. Temperature and relative ↑ humidity ( ↑ influencing factors) are important factors in electrostatic behavior. The choice of conditioning is based on the type and expected use. It should always be based on the most severe condition for the particular substance under which the product is to be used. In addition to the direct ↑ climate influence, the ↑ hysteresis in the moisture behavior of the sample must also be considered. Conductance, ↑ alternating current quantity Conduction band. According to the ↑ band model, the conduction electrons in the conduction band are not energetically bound to any atom in the ↑ crystal lattice but can be spatially moved by electric fields ( ↑ electron gas). At room temperature, valence electrons can move from the ↑ valence band to the conduction band. Conductive adhesive. Based on epoxy or polyimide resin to which conductive particles (metal, graphite, carbon black) are added ( ↑ percolation). If the conductive adhesive is to be a good electrical ↑ conductor, high levels of additives (up to 80 %) are required to achieve reliable ↑ particle boundary contact between the particles. Additions of only a few percent of conductive particles are generally sufficient to dissipate electrostatic charges because the ↑ tunnel effect is already at work. Conductive fiber. Four main types of conductive fiber are used to create the electrostatic ↑ dissipation capability of textiles: Conductive fiber 87 <?page no="89"?> - Core conductive fibers, in which a conductive core is surrounded by a polymer sheath in a variety of cross sections. - Surface conductive fibers, which can be coated with a variety of conductive materials (metal, e. g. silver) or carbon. - Combination fibers that are both core and surface conductive. - Metal fibers (e. g. silver, stainless steel) Conductive paint electrode, ↑ measuring electrode for solids no. 2 Conductive polymer, intrinsic ↑ conductivity Conductive rubber electrode, ↑ measuring electrode for solids no. 4 Conductive substance. In the sense of electrostatics, a solid or liquid substance whose specific electrical resistivity is not more than 10 k Ω m. [TRGS 727] Conductivity. Transport of ↑ charge in a system in which ↑ electrons or ↑ ions have sufficient mobility. A material or medium with a resistivity ρ v < 10 4 Ω m or a ↑ surface resistivity ρ s < 10 4 Ω □ is conductive. ( ↑ semiconductor, ↑ resistance measurement) ● Electrical conductivity. Symbol κ , unit Siemens/ meter [S/ m], is the reciprocal of electrical resistivity (also σ or γ , e. g. 10 000 pS/ m = 1 × 10 8 Ω m). It is preferably used for liquids (electrolytic conductivity). The electrical resistance of a liquid results from its ↑ ionic conduction. Conductivity can be increased by using ↑ antistatic agents. ● Conductivity unit (short cu). It is a special term in the petroleum industry instead of pico-siemens/ meter [pS/ m]. The ↑ Wiedemann-Franz-Lorenz law provides an approximate relationship between electrical and thermal conductivity. In the English-speaking world, the term “ mho ” is commonly used for conductivity (representing the backward spelling of Ohm [ Ω ] in place of [S]). 1/ Ohm = 1 Siemens = 1 mho 1/ kilo-ohm = 1 milli-siemens = 1 millimho 1/ mega-ohm = 1 micro-siemens = 1 micromho 1/ giga-ohm = 1 nano-siemens = 1 nanomho 1/ tera-ohm = 1 pico-siemens = 1 picomho {Appendix M.7.2} ● Intrinsic conductivity. Referring to the conductivity of insulating materials (polymers) that is “ intrinsic ” . For example, defects in the lattice structure of polymers are intentionally created by introducing an anion in an oxidation process to release conduction electrons. Such polymers, such as polyaniline (ORMECON ® ) or polyethylenedioxythiophene (PEDOT), are widely used in a variety of industries. ● Static conductivity. Measurements on liquids at a defined measuring temperature should only be carried out on resting, uncharged liquids. In the case of a charged (flowing) liquid, a discharge current would be superimposed on the measuring current for determining the resistance and falsify the result ( ↑ charging). [SE Section 3.7], [IEC 60079-32-2], [IEC/ TS 60079-32-1], [TRGS 727 Annex F] ● When mixing liquids. The conductivity of the main phase may decrease significantly due to the absorption of ions by the secondary phase. This can be counteracted by Conductive paint electrode 88 <?page no="90"?> adding antistatic agents. As a safety measure, the mixing process can be protected by ↑ inerting. [TRGS 727 Section 4] Conductivity carbon black, ↑ carbon Conductivity measurement, ↑ resistance measurement, ↑ measuring electrode Conductivity unit, short cu, ↑ conductivity Conductor (also used as a synonym for ↑ conductive substance) ● Electrical conductors. Materials, or objects that, unlike an ↑ insulator (non-conductor), conduct electric current well; their resistivity is ρ < 100 μΩ m. Materials with higher resistances up to about 1 M Ω m are called ↑ semiconductors; even higher resistances are generally called insulators ( ↑ electrostatic - system comparison, ↑ resistance of different materials). A general distinction is made between ↑ electron conduction (conductor 1st order in the ↑ conduction band) and ↑ ionic conduction (conductor 2nd order). ● Insulated conductors in electrostatics are any conductive objects that are insulated from ↑ earth and can therefore be charged by ↑ influence or ↑ charge transfer. They are a source of ↑ spark discharge hazards in ↑ Ex-areas. [SE Section 3.8]. ● The historical German term “ Conduktor ” is a special term for an insulated metal ball or cylinder used for capacitive storage of electric charges. ( ↑ Van de Graaff generator, ↑ cylinder electrification machine) Conductor short circuit. Parts or the entire resistance are bypassed in the event of a fault. ( ↑ earth fault, ↑ body short circuit, ↑ short-circuit) Conduit system. Installation technology for electrical systems with closed conduit systems in Exareas (especially in the USA). [IEC 61386-21] Cone discharge. ↑ Gas discharge generated during the filling of ↑ silos and large containers with charged bulk materials (e. g. pneumatic feeding of polymer granules). The mechanism is, to a first approximation, comparable to ↑ super brush discharges. A charge accumulation occurs at the bulk material cone ( ↑ charge). Due to the effect of ↑ gravity in large debris (e. g. high silos), the volume charge density (and thus the electric field) is significantly higher than in loose debris. The electric field emanating from this causes a repelling force on the subsequently falling product particles, which are charged in the same direction. If the particles are heavy enough, the repelling field forces can be Cone discharge 89 <?page no="91"?> overcome by gravity, resulting in ↑ charge accumulation ( ↑ Coulomb force). When the ↑ breakdown field strength of the surrounding atmosphere is reached, discharges occur that are conducted from the bulk cone to the earthed silo wall or to another earthed object (e. g. in the case of silos made of glass-fiber reinforced plastic (GRP)) or to an insulated conductive object with a significantly higher capacitance. [SE Section 7.5.11]. In a cone discharge, at least in part, the ↑ pinch effect occurs, i. e. the surrounding gas heats up, resulting in ↑ ignitability for flammable mixtures. The field strength E for a cone discharge in a silo can be approximately calculated ( ρ - ↑ space charge, R - radius of an approximately spherical fill, ε 0 - electric field constant): E ¼ R 3 " 0 {Appendix M.3.3}, [TRGS 727 Sections 6 and A3.6], [Steen, H. (2000)] Connector. Part of a device that allows connection to external electrical lines, also interface of a device with the external electromagnetic environment ( ↑ Electromagnetic Compatibility). ● Permanent connection of a cable. Direct connection to electrical operating resources by screwing, soldering, welding, pressing, etc. [IEC 60947-1] Constructive protective measures, ↑ protective measures Contact angle ϴ . Angle between a liquid and a solid surface, such as a drop on a surface. In the case of wetting, the contact angle is < 90°, in the case of non-wetting, it is > 90°. The different contact angles are caused by the molecular forces between the molecules of the liquid and those of the solid surface. Therefore, the contact angle can be influenced by electric charge states. ( ↑ surface tension) Contact charging (Latin: contingere, “ to touch ” ). Term for the study of ↑ contact electricity in the nm-range with contact probes < 1 μ m diameter (non-contacting ↑ scanning force microscopy). Contact discharge. Characterizes a test method for electrostatic discharges in which the electrode of the test generator is brought into contact with the device under test and the Connector 90 <?page no="92"?> discharge is triggered by a discharge switch located in the generator ( ↑ ESD test generator). The contact discharge should only be performed on those points and surfaces of the DUT that are accessible to persons during the intended use of the DUT. The electrode of the ESD generator must be held perpendicular to the surface, as this increases the reproducibility of the test result. [IEC 61000-4-2] Contact electricity. Older general term for electrical phenomena that occur at the contact surfaces of two substances in contact as a result of different ↑ electron emission energy or electron conduction. It is ultimately the cause of the ↑ static electricity released during the process of ↑ charging and subsequent separation. ( ↑ charge double layer) Contact electrode, ↑ measuring electrode for solids Contact potential. Electrical phenomenon at contact surfaces of different materials ( ↑ charge double layer). Contact potential describes a potential difference caused by different electron emission energies. This effect is called ↑ Voltaic potential (Voltaic effect) for the contact of two conducting or semiconducting materials (e. g. metals). H. v. ↑ Helmholtz first described the contact potential for the combination of liquid (electrolyte) and electrode for the double layer in 1879. For the combination of liquid (e. g. water) and gas (e. g. air), the contact potential is referred to as the ↑ Lenard effect. For the contact of two insulators, A. ↑ Coehn established his rule in 1898, according to which there is a ↑ triboelectric series for plastics based on their ↑ permittivity. However, the permittivity range for these materials is generally very broad, making it difficult to predict the magnitude of the charge balance. ( ↑ material web, ↑ Lewis ’ s acid-base concept, ↑ Brønsted- Lowry definition), [SE Section 2.4], [Coehn, A. (1928)] Contact pressure. Weight per unit area on a substrate. The contact pressure is a critical parameter for measuring surface and ↑ volume resistance ( ↑ measuring electrode). This also applies to the measurement of the dissipation capability of shoes ( ↑ personnel earthing tester). Contact protection, ↑ touch protection Contact resistance. Electrical resistance at the contact surface of two electrical conductors. It can be permanently influenced by oxide layers, adsorbed gas layers (removal by rubbing during ↑ charging), and by a decrease in the concentration of conductive particles in the boundary layers near the surface ( ↑ shell effect). Contact surface. Area between two substances of the same or different ↑ state of matter at which physical properties change strongly within a range of molecular dimensions, e. g. ↑ electron emission energy. Depending on the material, the contact area ranges from a few to several molecular diameters. In the field of electrostatic charge generation on solids, the layers are shown in the next figure. Contact surface 91 <?page no="93"?> Contact voltmeter. Device for measuring electrostatic charges on small components. The term is misleading because to measure electrostatic charge, the charge on the surface to be measured is converted into a voltage reading in the meter. ( ↑ EFM) Container cleaning. Sometimes containers to be cleaned still contain residues of flammable liquids or dust that can be ignited by electrostatic charges ( ↑ tank cleaning). This is even possible when cleaning with water. Protective measures in such cases are: - Containers made of conductive or dissipative materials must be earthed. - In the case of containers of insulating materials, the surface must be made wettable (e. g. by adding detergents ( ↑ surfactants)). Container filling. Chargeable liquids can become charged as they flow through piping and especially through ↑ filters. During filling, ↑ charge accumulation can occur in the container, resulting in an electrostatic ignition hazard ( ↑ charge transfer). Earthing metal containers (e. g. via conductive contact surfaces) is therefore a necessary but not always sufficient protective measure, because when the charged liquid surface approaches the filling pipe outlet, ↑ brush discharges can occur there ( ↑ filling pipe). Bottom filling avoids this danger. When filling in insulation containers (e. g. made of plastic), it should be noted that these may already have been electrostatically charged during manufacture, cleaning, or other handling. During filling, the charge can be discharged from the liquid, e. g. via an earthed dip tube. Metal containers with an insulating internal coating or lining (e. g. internally painted, plastic-coated, or fitted with a tight-fitting plastic liner) can be filled in the same way as uncoated metal containers (earthed! ), since ↑ charge bonding takes place via ↑ influence (coating thickness ≤ 2 mm for group IIA and IIB substances, ≤ 0.2 mm for group IIC substances). {Appendix D} The left half of the figure shows an insulated metal drum into which a chargeable liquid flows by gravity from an earthed storage vessel above. The right half shows the associated equivalent circuit: The charge generator G (storage container with contents), driven by gravity, supplies an electric current I (generated by the charged product) to the charge storage capacitor C Contact voltmeter 92 <?page no="94"?> (capacitance: between metal drum and earth). The resistor R, connected in parallel with the storage capacitor C, represents the insulation resistance between the barrel and the earth. From the specific ↑ charge of the product and the flow rate, a charging current I can be calculated, with which the capacitance C is charged, while at the same time the charge is dissipated via the insulation resistance R. The value of the ↑ potential to which the drum is charged is given by U = I × R ( ↑ Ohm ’ s law). The ↑ discharge time of the filled drum follows the relationship for the discharge ↑ time constant τ = R × C. The ↑ energy W of a possible ↑ spark discharge from the drum to the earth is calculated as W = 0.5 × C × U 2 . When filling containers with granules or powders, the statements made for liquids apply mutatis mutandis to electrostatics. [TRGS 727 Sections 4 and 6] Container size / container material. Must be considered when evaluating the electrostatic ignition hazard of liquid storage. For capacities up to 5 l, containers made of insulating and therefore chargeable materials can be used, taking into account the hazards caused by the substances and processes. For spill containment vessels larger than 5 l, they should be made of conductive substance and earthed. If ↑ funnels are used, they should have conductive tubes down to the bottom of the container (metal funnels must be earthed! ). [TRGS 727 Section 4.5.5] Contamination. Unlike mechanical contamination, electrostatically charged objects contaminate more than non-charged objects. It is of secondary importance whether the contaminating particles ( ↑ aerosol) are conductive or insulating and whether they carry charges or not. The electric field emanating from a charged object always shifts the positive and negative charges in each introduced particle against each other. In conductive particles, they are shifted to the surface due to ↑ influence, while in insulating particles - according to their ↑ permittivity ( ε r > 1) - they are shifted inward and strung together as ↑ dipoles ( ↑ polarization). Particles with such shifted charges always experience a force effect towards a region of higher field strength ( ↑ Coulomb force), i. e. towards the charged object, and are accumulated there ( ↑ dust figures). This can cause particular problems in health care facilities and in food production and distribution [IEC 61340-6-1]. Continuous phase (Latin: continuitas, “ uninterrupted continuation ” ). Term used to evaluate the electrostatic situation in the ↑ charging of liquids in ↑ dispersions. If, for example, a dispersion of gasoline and water is moved in a conductive container (agitator) and the continuous phase is insulating, i. e. the gasoline content predominates, a high charge and corresponding hazards are to be expected. On the other hand, if the water content is higher, the continuous phase is conductive, and the charge can be equalized via the container wall. ( ↑ spark discharge by charged water [SE Section 7.3.8.1]) Convener. Responsible organizer, e. g. for a standards project. (www.cenelec.eu) Conveying (pneumatic). Generally, it causes high electrostatic ↑ charging. In the case of combustible bulk materials, an ↑ Ex-atmosphere must be assumed inside the pipes used for transportation. This can also be present in the vicinity of the pipes and hoses. Accordingly, various requirements are placed on the wall structure of the pipes and hoses to prevent effective ignition sources. [TRGS 727 Section 6.4.2], [SE Section 7.4.5] Conveying (pneumatic) 93 <?page no="95"?> Conveyor belt. Endless traction and carrying elements running over rollers in belt conveyors. If such a belt is electrically insulating, dangerously high electrostatic charges can build up in the manner of a ↑ Van de Graaff generator. The level of charge to be expected is determined by the electrical properties of the belt, pulley and idler materials and increases with belt speed, belt tension and the width of the contact surface. For this reason, conveyor belts in hazardous areas must not exceed specified limits for electrical resistance and must run on conductive and earthed rollers. [TRGS 727] Copper beryllium (copper and 1.6 - 2.9 % beryllium). Low-sparking and chemically very resistant material. Tools made of copper beryllium are suitable for use in Ex-zones 1 and 21 ( ↑ ignition source). Copying process (electrostatically). Process based on photoconductivity, a property of certain semiconducting solids to reduce electrical resistance when exposed to electromagnetic radiation (e. g. light). In its original form, a paper coated with zinc oxide (ZnO) is used as the ↑ photo semiconductor (direct copying). After sufficient storage in the dark, ZnO has such a high electrical resistance that it retains this charge for a longer time (minutes) after being positively charged, e. g. by a ↑ corotron. Light reflected from the document to be copied is directed onto the charged ZnO layer and causes ↑ recombination of the charge at the exposed locations. This creates a latent ↑ charge image of the document, e. g. the black letters are imaged as charged surface elements. The ZnO paper is then placed in a developer (liquid toner), which consists of a highly insulated liquid (e. g. white spirit) in which dye particles ( ↑ toner) are dispersed. After the dye particles attach to the charge-carrying surface elements, the copy is removed and dried. In indirect copying, a drum is coated with the toner suspension, transferred to the paper, and dried. This process, still very much based on traditional photographic technology, was later replaced by a dry process called ↑ xerography. Core dummy charging. Probably the most common application in ↑ in-mold labeling is a core dummy, which forms the shape of the part and in which the decoration is usually fixed by suction. In the injection mold, this is applied to the earthed metal wall by the integrated charging tips ( ↑ charging electrode, ↑ useful application). [SE Section 8.2.6] (Source: Wittmann Robot Systeme GmbH, Nürnberg) Conveyor belt 94 <?page no="96"?> Core fiber. Synthetic fibers containing a core of electrically conductive substance, e. g. ↑ carbon fibers, to reduce their electrostatic charging tendency. Since the fiber core cannot be contacted, control by measuring ↑ surface resistance is not possible, but ↑ relaxation time measurement can be used to assess the effectiveness of core fibers. [SE Section 3.14.2] Core fibers are also called hollow fibers. Corona (Latin: “ wreath ” , “ crown ” ). Describes the luminous appearance of an electrical peak discharge, e. g. in air ( ↑ St. Elmo ’ s fire). Corona charging. Essential principle for experimental investigations, test purposes [IEC 60079-14] and industrial ↑ useful applications. The object to be charged is usually placed on a conductive base connected to one pole (earthed) of a high-voltage generator. The other pole is connected to a ↑ charging electrode placed at a distance, e. g. above. The gas ions generated at this electrode follow the electric field lines, reach the top of the object and charge it electrostatically. Charge densities up to electric breakdown ( ↑ propagating brush discharge) can be achieved on films. In principle, corona charging also works on freely suspended objects, but then only charge densities up to the maximum ↑ surface charge density can be achieved. In the case of negative corona, the corona current starts at a slightly lower voltage than in the case of positive corona. With a positive corona, however, the ↑ ozone development is much lower than with a negative corona. The ↑ ion wind that inevitably occurs with every corona charge can often be used to improve charge transport. For large-area charges, wires with a correspondingly small radius can be used instead of tips ( ↑ corotron). Corona discharge ● Electrostatic corona discharge. Weak, independent and nearly continuous ↑ oneelectrode discharge, which occurs at pointed earthed electrodes ( ↑ earthing tongue) or thin wires ( ↑ corotron) with a radius < 0.1 mm ( ↑ back-spraying). When these are brought into the electric field of a charged surface, their small radius of curvature results in a much higher field strength (field line density) than would be expected from the potential difference and the distance between the two. Once the ↑ electric strength of the surrounding gas is reached directly at the tip, electrons are emitted (minus) or absorbed (plus) from the surrounding atmosphere, depending on their polarity. The ↑ corona inception voltage is the lowest field strength value at which a corona discharge can be objectively detected by current measurement. The figure shows on the left a simplified representation of the field distribution without an electrode and in the middle the field distribution between a charged insulating material and a conductive earthed tip electrode. The μ A meter placed in the line to earth indicates a current as long as the charge on the insulating material at the tip causes a breakdown field strength. With a moving charged insulator (right), a fluctuating continuous current occurs at the meter. Depending on the ↑ influencing factors, a corona discharge always causes a much larger area to be discharged than a ↑ brush discharge. A corona discharge can be recognized with the dark-adapted eye as a faint blue-violet glow. [SE Section 4.2.2.1] Corona discharge 95 <?page no="97"?> ● Plasma corona discharge, also called DBD (dielectric barrier discharge), is a non-equilibrium plasma under ↑ atmospheric conditions. At least one ↑ dielectric is placed between a highvoltage electrode and an earth electrode. ( ↑ corona pretreatment, ↑ DC low-energy plasma), [Dzur, B. (2011)] Corona effect. In the case of ↑ corona discharge, the ↑ pinch effect does not occur and therefore no plasma channel is formed. Corona inception voltage (for discharge). Describes the onset of a measurable current between an electrostatically charged surface and an opposite earthed tip or series of tips ( ↑ Townsend discharge). The corona inception voltage depends on a number of factors: Tip or cut of the needle/ tip surface, distance between the needles ( ↑ field lines), distance to the charged surface, length of the needles, needle housing (are the earthed needles slightly above or below the housing), electrical capacity of the entire construction including the earth cable (the lower the better), polarity, humidity, support construction for the fibers or tips, air pressure. Of course, these factors also apply to the use of active discharge electrodes ( ↑ ionizer, ↑ earthing tongue). [SE Section 5.2.1] Corona pretreatment. It is used to achieve sufficient wetting ( ↑ wettability) of surfaces in many technical forms. Plastics (polymers) and other surfaces (e. g. textiles or material webs) must have a surface energy suitable for the coating partner. Corona effect 96 <?page no="98"?> (Source: Krüss GmbH) The surface energy is given in [mN/ m] or [N/ m] (1 N/ m ≙ 1 J/ m 2 surface energy/ area). The use of the term dyn/ cm or often just ↑ dyn to define a surface energy is not allowed. The calculation of the required dose for corona pretreatment is done according to the formula: Dose W min m 2 ¼ Power W ½ Electrode width m ½ Speed m min (To simplify the calculation, the term [min] for minute is used instead of second [s]). - Caution 1: Corona pretreatment often results in electrostatic charging of the treated material as an unwanted side effect due to unavoidable asymmetries of the AC voltage, which can manifest itself in adhesion problems. Therefore, corona pretreatment should always be followed by charge neutralization using ↑ ionizers. Corona pretreatment can “ freeze ” charges in the material ( ↑ electret, ↑ bipolar charge layer), which can lead to ignition hazards during further processing. - Caution 2: The use of corona pretreatment on ↑ composites with conductive layers is not without problems: Energy is also introduced through their usually open edges. A good electrical conductor, such as aluminum, stores the charge and cannot dissipate it through the insulation on both sides of the composite. This can lead to unwanted sudden discharges with consequences for people and machines. - Caution 3: Corona pretreatment cannot be performed in an ↑ Ex-area. An essential part of corona pretreatment is the treatment roller opposite the plasma electrodes on which the web is moved. In addition to bare metal rollers, these rollers are available with a variety of surface coatings, including silicone, ceramic, epoxy, Hypalon ® (chlorosulfonated polyethylene (CSM)), and glass. ● Corona pretreatment under ↑ atmospheric conditions. The most common is chemical oxidation in air. Oscillating gas discharges (plasmas) in the range of 15 - 40 kHz with an energy of about 10 to about 100 W × min/ m 2 are applied to the surface. The medium to be treated is placed on a conductive, earthed or insulating base (plate or roller). An electrode system (e. g. ceramic with internal metal bars, segmented Corona pretreatment 97 <?page no="99"?> metal electrodes, wires or tips) connected to a medium-frequency (typically 20 - 40 kHz) high-voltage is placed opposite the surface to be treated (typically 1 - 1.5 mm apart). The incident corona discharge causes chemical reactions on the surface to be treated, resulting in breaks in the polymer molecule chains, at the end of which oxidation can occur. Depending on the polymer, this results in different functional groups that improve wettability due to their polarity. Typical values for coating processes are 38 - 48 mN/ m, depending on the material combination. For wettability with highly water-based substances, values above 55 mN/ m can be useful. Since this modification of the plastic surface by corona treatment is usually only latent, a reduction of the effect occurs more or less quickly during storage, depending on the material. The corona pretreatment process is complex, so that the wetting properties can often only be optimized by experiment. Rough guide values (table) are available for some materials, which can be calculated using the above formula. The plasma burning between the electrode and e. g. a web during corona pretreatment heats the web by 10 - 30 °C (total temperature up to 60 - 70°C). To avoid excessive heating of the treatment roll, cooling cylinders are often used to dissipate the heat. If the web hits a very cold chill roller, condensation can form under unfavorable conditions, which can have negative effects on further processing steps (e. g. no adhesion of the coating material). If the treatment doses are too high, the surfaces will be destroyed. This can be seen, for example, when a haze on the film surface can be wiped away by hand (no adhesion). Required surface energy [mN/ m] Material (films) 38 - 40 43 - 45 50 - 60 60+ Polyethylene, high density PE-HD 13 16 22 27 Dose [W×min/ m 2 ] Polyethylene, low density PE LD (high slip) 22 27 33 43 PE-LD (low slip) 13 16 27 27 PE-LD (med slip) 16 19 32 32 PE-LD (without additives) 9 11 13 16 PE Linear LD 13 16 22 27 PE Metallized 16 19 27 32 Polyamide, PA Nylon 9 11 13 16 PA Nylon, high density 11 13 16 22 Polyethylene terephthalate, PET 11 13 16 22 Polypropylene, PP 16 22 27 32 Biaxially oriented, BOPP 27 32 40 46 Oriented PP, OPP 22 27 32 43 Polystyrene, ABS 9 11 13 16 Co-polymer PE/ PP/ PB-1 (sealing layer) 70 Polyvinyl chloride, PVC Soft 25 - 30 ● Other corona pretreatment systems allow the targeted functionalization of surfaces by replacing the atmospheric oxygen with process gases. This allows different variations. The figure shows examples: Corona pretreatment 98 <?page no="100"?> Corona roller separator, ↑ separation of substances Corona system, ↑ corona pretreatment Coronavirus. SARS-CoV-2, also known as Covid 19, has had a major impact on economic and social life since the pandemic year of 2020. Corotron. An arrangement based on the principle of corona charging can be used to improve the uniformity of charging of a surface, e. g. in photocopiers ( ↑ xerography). Usually there are several gold-plated corona spray wires (e. g. tungsten, diameter 80 μ m) inside an earthed counter-electrode. For homogenization and better control of the charging field, a grid is placed between the corotron and the ↑ photo semiconductor. Glass-clad corotrons can also be used to further improve the uniformity and speed of charging. [Goldmann, G. (2006)] Corpuscular rays (Latin: corpusculum, “ little body ” ). Consists of moving particles such as electrons, ions, neutrons, mesons, and alpha particles ( ↑ alpha radiation). They have a defined range and are deflected by electric and magnetic fields. Corrosion. Reaction of a metallic material with its environment causes a measurable change in the material and leads to an impairment of the function of the component or an Corrosion 99 <?page no="101"?> entire system. One cause of corrosion is an equalizing current due to the formation of a ↑ galvanic element ( ↑ cathodic protection). [ISO 8044] Cosmic radiation. Coming from sources outside the Earth, discovered by V. F. Hess in 1912 and confirmed by W. Kolhörster and W. Bothe in 1929. This high-energy particle and photon radiation ( ↑ muon) interacts with atoms in the Earth ’ s atmosphere ( ↑ ionizing radiation, ↑ aurora borealis), and the energy is ultimately consumed in breaking radiation effects in which ↑ electron/ ↑ positron pairs are produced. Cotton. As a material based on cellulose (seed hairs), as well as the ↑ paper made from it, has a relatively low resistance from an electrostatic point of view, but is classified as an insulating material from an electro-technical point of view. Its electrical resistance is strongly influenced by moisture (e. g. also body perspiration) ( ↑ water activity). Wearing cotton clothing is generally safe from electrostatic charges, but the antistatic properties of cotton can be impaired by treatments such as resins. Coulomb, Charles Augustin de (1736 - 1806). French physicist and inspector general of education in Paris. Fields of work: Electrostatics and magnetostatics, mechanical friction and torsion. Among other things, Coulomb invented the ↑ Coulomb ’ s balance, with which he established the ↑ Coulomb ’ s law on the effects of electrical forces, named after him. Coulomb. Derived ↑ SI unit [C] of the electric charge Q, named after C. A. ↑ Coulomb. It is defined in terms of ampere-seconds [As] with the ↑ elementary charge: e = 1.602176634 × 10 -19 C. Coulomb excitation. An experimentally known excitation of an atomic nucleus by the rapidly changing electric field of a passing charged particle. Coulomb force. The relationship between charge, force and distance in the electric field was first described by C. A. ↑ Coulomb. It is the force between two point-like electric charges or between the centers of gravity of two separate charge distributions. Its magnitude and direction are given by ↑ Coulomb ’ s law. When attractive or repulsive electrostatic forces are overcome, mechanical energy is converted into electrical energy: - Overcoming electrical attractive forces (as opposed to charges) causes an increase in potential ( ↑ charge). - Overcoming electrical repulsive forces (charges of the same name) causes an increase in ↑ surface charge density ( ↑ charge density, ↑ super brush discharge, ↑ cone discharge). Coulomb ’ s balance (also torsion balance). Developed by C. A. ↑ Coulomb for measuring small attractive or repulsive field forces. A beam-shaped, charged body attached to a suspension thread is twisted against an electrode charged in the same or opposite direction until the restoring torsional moment balances the torque of the acting force. Coulomb ’ s law (also called law of action of a force). Formulated in 1785 by C. A. ↑ Coulomb using the ↑ Coulomb ’ s balance, states that the force between two electrically charged bodies depends on the magnitude of their charges and the square of their distance (analogy to magnetism). Coulomb ’ s law is formally equivalent to Newton ’ s law of gravitation. The direction of the force is indicated by the tangents to the field lines of Cosmic radiation 100 <?page no="103"?> � SCHNIER Coulombmeter HMG 11/ 03 ' 1 / / 1 ' VISION Worldwide safe, efficient and reliable electrostatic applications @) MISSION We want to use our experience to support users in making electrostatic applications safe. We want to build the most reliable high-voltage power supplies in the world, to realize efficient and durable applications. www.schnier.de <?page no="104"?> the electric ↑ field between the bodies, i. e. the force acts in the direction of the line connecting the two charges. - Equal charges cause repulsion (Figure). - Inequal charges cause attraction. Coulomb ’ s law is not only important in physics, but also in chemistry, where it is used to calculate the Coulomb force of an ionic bond. Several industrial processes ( ↑ useful application) are based on Coulomb ’ s law: ↑ pesticide ↑ application, ↑ coating, ↑ separation of substances, ↑ xerography (office copying technology). However, many undesirable effects can also be attributed to Coulomb forces: ↑ adhesion, ↑ contamination, ↑ soiling. {Appendix M.3} Coulometer. Device for measuring the electric charge Q. It was formerly based on the principle of electrolytic deposition ( ↑ voltmeter), especially for determining large quantities of electricity. Coulometers measure the electric charge stored in a ↑ capacitance, e. g. when filling an insulated container ( ↑ container filling) or generated during charge generation (e. g. ↑ personnel charging when walking over a high-resistance plastic or carpet). The spurious influence of the ↑ input capacitance can usually be eliminated by a “ feedback circuit ” of the operational amplifier used in the input circuit. The coulometer is also used to measure possible transferable charge quantities. In this case, the sphere electrode of the device is brought close to the surface to be tested and the charge transferred during a ↑ brush discharge is recorded to assess possible ignition hazards ( ↑ charge transfer - measurement, ↑ EFM). {Appendix M.3} A coulometer can be checked with the ↑ influence electrostatic field meter (EFM) and a 40 kV voltage probe (HMK40: R i > 10 15 Ω , C i = 10 pF (Figure): The sphere on the voltage measuring head is briefly touched with an adjustable external high voltage source. The sphere of the coulometer is brought close to the charged sphere until a spark jumps over (both spheres must have the same diameter). Read the measured value Q = C × U = 100 nC (± 5 %) from the coulometer display. Counter discharge, ↑ thunderstorm lightning Counter electrode. A necessary component of systems for the ↑ useful application of electrostatic charging. A counter electrode can be earthed or carry the opposite charge to the ↑ charging electrode. Counter potential, ↑ counter electrode, ↑ useful application Counter potential 101 <?page no="105"?> Coupling. In the case of electrostatic measuring arrangements, interference due to coupling must be prevented. [SE Section 3.16.3] ● Inductive coupling can occur when the measuring circuit is in a magnetic field. It generates a low-frequency induction voltage in moving conductors. Mechanically fixed measuring setups with earthed shielding without moving connecting cables reduce this. ● Capacitive coupling is generated in the measuring circuit by alternating currents caused by electrically isolated external devices. The entire measuring circuit forms a capacitor electrode; the environment forms the ↑ dielectric (air) and the external device forms the counter electrode. This coupling can be largely prevented by using earthed, metallic shielding plates. Cover (electrical). Part of operating resources, providing protection against direct contact from all possible access directions [IEC 61010-1]. CPM, short for charged plate monitor. Used to determine the conductivity of insulating materials, but also to evaluate devices that generate ionized air (active discharge electrode, ↑ ionizer). The determining part is a chargeable plate ↑ capacitor with an ↑ EFM. One plate is earthed, and the second plate is high resistance insulated. The latter is charged with highvoltage and the EFM integrated in the earthed plate detects changes in the electric field in the gap. In the opinion of the authors, an automatic measurement with the CPM in the sense of [IEC 61340-4-7] is not successful, because if the discharging bars remain switched on, they will draw charge from the CPM already in the attempt to reach 1000 V and cause considerable measurement errors. [SE Section 3.14], [IEC 61340-2-1] Cracking process. Thermal splitting process used in petrochemicals to convert high-boiling crude oils or tar distillates into low-boiling gasoline, for example. It is based on the chemical cleavage of large molecules at high pressure and temperatures between about 300 - 600 °C. All solid organic substances must first be converted to a ↑ gas phase by cracking processes before they can be combusted ( ↑ MIE). [SE Section 1.1] Creepage distance. Shortest distance along the surface of an insulating material between two conductive parts at electric potential. ( ↑ clearance), [IEC 61010-1] Critical field strength, ↑ start field strength Cross-section. There is no requirement for cable cross-section to ensure ↑ earthing. The ↑ resistance of the cable must be ≤ 10 6 Ω to ensure the ↑ dissipation capability of the object Coupling 102 <?page no="106"?> to be earthed. The color of the cable is not specified, although the “ green/ yellow ” marking is common in Germany. The decisive factor is the mechanical strength of a cable for continuous earthing. Thin wires are therefore suitable. Crushing. Basic operation in process engineering to reduce the size of solids by mechanical stress. This generates new surfaces on which charge states manifest themselves in insulating materials. Since the cleavage planes during crushing are preferably located near defects, but the latter are the preferred location for ↑ trap electrons, charge transfer often occurs at the separation points. As a result, insulating materials are always charged after crushing, whereby experience shows that smaller particles are preferably negative and larger ones mostly positive (dust ↑ charging, ↑ cloud dipole). In the case of grinders, it must also be considered that intimate contact with the metal tool also leads to charging. Crystal (Greek: krystallos, “ ice ” ). Chemically uniformly composed solid whose building blocks (atoms, ions, molecules) are arranged in a spatial lattice and whose cohesion is based on various types of bonding. Ion crystals (e. g. halite) are held together by the electrostatic attraction of their oppositely charged components (Na + Cl - ). In the case of metal atoms, the strong bond is based on ↑ valence electrons. ↑ Van der Waals forces cause weaker bonds and result in correspondingly lower strengths, e. g. in mica. Crystal lattice. Describes the extremely complicated fine structure, preferably of metals. The crystal lattice contains free electrons, which can move through the lattice structure under the influence of an electric field, providing the good electrical conductivity of metals. Crystalline. Property of solids whose structures repeat spatially and/ or periodically in a lattice ( ↑ crystal lattice) (contrast: ↑ amorphous). Crystallization. Spontaneous formation, and growth of ↑ crystals in supersaturated vapors, liquids, and supercooled melts. In electrostatics, it is important to note that crystallization can lead to a drastic increase in the electrical resistance of substances (several orders of magnitude) and, in rare cases, to charge separation ( ↑ charging). CTI, short for ↑ comparative tracking index, ↑ creepage distance cu, short for conductivity unit, ↑ conductivity Curie. Unit [Ci] is named after M. and P. ↑ Curie for the activity of a radionuclide. It has been replaced by the unit ↑ becquerel [Bq]: 1 Ci = 3.7 × 10 10 Bq Curie, Marie (1867 - 1934). French chemist and physicist of Polish origin, known for fundamental work in the field of radiochemistry. Curie, Pierre (1859 - 1906). French physicist discovered ↑ piezoelectricity and the temperature dependence of diamagnetism. Curie point (also called Curie temperature). At which the transition from ferromagnetism to para-magnetism occurs, i. e. above this temperature ferromagnetic materials lose their magnetic force; below this temperature they become magnetic again ( ↑ ferroelectric). Curie point 103 <?page no="107"?> Current (also amperage). Symbol I with the ↑ SI base unit [A] ( ↑ ampere). Movement of electric charges in conductors in a preferred direction. If the charge movement occurs under the influence of a stationary electric ↑ field ( ↑ potential), it is a conduction current. Displacement currents (reactance) occur when the preferred direction changes over time ( ↑ alternating current quantity). Current carrying capacity. Maximum current that can be carried continuously by a conductor under specified conditions without its continuous temperature exceeding a specified limit. [IEC 60204-1] Current clamp. A special type of current transformer ( ↑ split core current transformer). Current density. For homogeneous current distribution, the quotient of the current and the area through which the current flows (e. g. A/ mm 2 ). The greater the current density in a conductor, the more it heats up. Current limiter (resistive or capacitive), ↑ ionizer Current mark. Generated by injury to a person as a result of the influence of a current with a pulse duration > 0.1 ms (electrical accident). In the case of electrostatic discharges, this should not be referred to as an electrical accident because, in contrast to conducted electricity, the charge is discharged with the influence. ( ↑ electric shock), [BS IEC 60479-2], [SE Section 4.2.4] Current source. Named after ↑ DIN and ↑ VDE. Misleading term for a device in which an electric current is generated. A current source is actually a ↑ voltage source, because it is ultimately a potential difference that causes electrons to move and thus causes an electric current ( ↑ open circuit voltage, ↑ short-circuit current). Current transformers. Special ↑ transformers that allow the measurement of alternating currents or current pulses without interrupting the current path. They can be loaded with very low impedance but must not be operated in no-load operation. Current-voltage measurement method (also I/ V measurement method). A method in which the current flowing through a measured object is determined as a function of the measured voltage and displayed directly on a meter as ↑ resistance according to the relationship R = U / I. Cut-off voltage. Refers to the potential applied to a ↑ diode in the reverse direction. Above the allowed cut-off voltage, the reverse current increases sharply ( ↑ Zener diode) and can destroy the diode. Cyclone (Greek: kyklos, “ circle ” ). Centrifugal separator for separating solid particles from liquids (hydro cyclone) or gases (dust cyclone). The latter is often used in ↑ pneumatic conveying to separate the conveyed material (granules, dust) from the conveying gas. The electrostatically charged particles are compressed in the conical cyclone outlet (overcoming the ↑ Coulomb force), which can result in such high volume ↑ charge densities that ↑ gas discharges occur spontaneously. This reduces the charging of the product during separation, resulting in a lower product charge in the ↑ silo. Current 104 <?page no="108"?> Cyclotron (Greek: kyklos, “ circle ” , electron). Particle accelerator in which charged particles repeatedly pass through an electric accelerating field, moving perpendicular to the magnetic field in a spiral from the source in the center outward. Cylinder capacitor, ↑ capacitor, ↑ Leiden jar Cylinder electrification machine. An electrification machine used in the 18th century with a glass cylinder and a bowl below it, in which leather was coated with the so-called Kienmayer amalgam (one part tin, one part zinc and two parts mercury). By rotating the cylinder, a charge was generated in which a row of tips ( ↑ conductor, ↑ ionizer test) was used to transfer the charge. This is connected to the so-called 1st conductor - a hollow cylinder. After half a revolution, a charge of approx. 30 kV can be measured on the sphere. [SE Section 5] (Source: Original in the Physical Cabinet in Görlitz, Germany) Cylinder electrode, ↑ measuring electrode for solids no. 14 Cylindrical electrode, ↑ measuring electrode for solids no. 6 Cylindrical electrode 105 <?page no="109"?> D Damage assessment. When evaluating suspected electrostatic discharge ignitions, proceed as follows: - Determine the possible of ↑ ignition source - Clarify of the ambient conditions (humidity, pressure, and temperature) - Check the applicable rules and regulations - Check the operations/ production processes - Inspection of the materials involved in the damage - Inspection of the condition of the machine/ plant Danger (also hazard, damage). Generally, a situation that is directly and very likely threatens the ↑ safety of people and property and can result in damage. The distinction difference between safety and danger is made by the term ↑ risk ( ↑ risk assessment, ↑ personal hazard, ↑ hazard). Danger of electric shock. Describes the dangers posed by the influence of electricity on the human or animal organism. The hazard is mainly determined by the strength of the electric current flowing through the organism, with low-frequency alternating currents being classified as more dangerous than direct current. The path of the current through the body is important in determining the risk to a person. The following list shows the effects of various current levels for 50 Hz alternating current. Current levels above this cause additional thermal tissue damage. [IEC/ TS 60479-1] up to 0.5 mA Not perceptible or slight prickling (threshold of perception) 0.5 … 5 mA Noticeable prickling to muscle spasms, cause can mostly be overcome by the patient (threshold of let go) 5 … 15 mA Painful spasms, the threshold of let go is exceeded (muscle irritation) 15 … 25 mA Obstruction of breathing and circulation noticeable 25 … 50 mA Difficulty breathing, cardiac arrhythmia, increasing blood pressure > 50 mA Ventricular fibrillation (VF), cardiac arrest with an exposure time of more than one cardiac cycle ( ≤ 1 s) In general, electrostatic charges and their discharge phenomena do not pose a physiological hazard, except from ↑ propagating brush or ↑ super brush discharges. <?page no="110"?> Dangerous goods (short HAZMAT for hazardous material). Are substances and objects which, due to their nature, properties, or condition in connection with their transportation, may pose a risk to public safety and order, in particular to the general public, to the life and health of human beings and animals, integrity of things and which are classified as dangerous goods by law. The transportation of dangerous goods is regulated by various laws ( ↑ GGBefG, ↑ ADR, ↑ hazmat officer). Dangerous Goods Transportation Act, German short [ ↑ GGBefG] Dark discharge. ↑ Gas discharge that produces ions and electrons in an appropriate electric field and does not emit visible light. (impact ↑ ionization, ↑ surface reverse current, ↑ Geiger-Müller tube) Davy, Sir Humphry (1778 - 1829). English chemist and physicist, developed, among other things, a safety miner ’ s lamp (1815, weather lamp) whose gasoline-fueled flame is surrounded by a close-meshed wire mesh. This cools the flame gases sufficiently to prevent them from igniting an explosive atmosphere outside the lamp ( ↑ MESG). In addition, the shape and color of the aureole above the flame indicate possible mine gas (methane) hazards. DBD actuator. An electrical component that can be used to influence flow. The standard DBD actuator consists of three elements: two metallic electrodes separated by an insulating material. The electrodes are arranged parallel to each other to provide a defined direction of actuation. When a high frequency (typically 0.5 to 30 kHz, sinusoidal AC voltage) is applied to the exposed electrode, the surrounding air is ionized, creating a plasma. The charged ions are accelerated by the applied electric field. The momentum is transferred by collision with neutral air molecules. This creates a volumetric force without changing the mass balance. This volumetric force can be used to control flows. The advantage of these actuators is their simple design, low weight and the possibility of real-time control. [Bruggeman, P.-J. et al. (2017)], [Duchmann, A., Reeh, R. et al. (2010)], [Cattafesta, L. et al. (2011)], ( ↑ electric curtain, ↑ corona discharge) (Source: TU Darmstadt, Institute of Gas Turbines and Aerospace Propulsion) DC, short for ↑ direct current DC discharge bar, ↑ ionizer DC discharge bar 107 <?page no="111"?> DC low-energy plasma (low temperature non-equilibrium plasma at atmospheric pressure). It is defined by electron densities up to 10 10 electrons/ cm 3 with electron temperatures up to 50 000 K and a much lower temperature (< 100°C) of the ions and neutral gas particles. Furthermore, the number of negative charge carriers (electrons/ ions) and the number of positive gas ions of plasma gas are not in equilibrium. Current-limited single electrodes (cathodes) are arranged opposite an anode at which a plasma is ignited after reaching the breakdown voltage. DC low-energy plasmas are suitable for separating even the smallest particles (< 1 μ m) from a gas stream ( ↑ misting tacker, ↑ air boundary layer). [SE Section 8.2.13] (Source: according to patent [Knopf, F., Op de Laak, M. (2008)]) DC power supply. Provides positive or negative voltage to the individual rows of pins in the DC discharge bar ( ↑ ionizer). They are usually integrated into the electrode and supply the pins with high voltage pulsed at different frequencies, depending on the manufacturer. Debye, Peter (1884 - 1966). Dutch physical chemist, developed, among other things, the theory of the polarizing effect of electric fields on molecules (dipole theory, Nobel Prize 1936) and the theory of the temperature dependence of the dielectric constant ( ↑ permittivity). ( ↑ dipole moment) Debye length. Distance in a conducting substance named after P. ↑ Debye at which the electric potential drops to 1/ e-fold due to ↑ shielding as a function of temperature and ↑ charge density. It describes the thickness of the diffuse layer of ions of one polarity. The ions of the opposite polarity are deposited by adsorption, e. g. on a pipe wall. ( ↑ charge double layer, ↑ spraying) Decadic multiples. Facilitate calculations with very large and very small numerical values, as they are often used in electrostatics (see table {Appendix M}). For example, they cover the range 10 15 Ω to 10 -15 S but may only be used en bloc with the SI prefix or its short form. In everyday use, the computational handling of powers of ten is sometimes prone to error. The clarity and reliability of calculation can be increased by using decadic multiples for simplification. Note that only decadic multiples of thousands are used in calculation. DC low-energy plasma 108 <?page no="112"?> For example: A resistance of 1.8 × 10 10 Ω is to be converted to ↑ Siemens [S], base: Siemens = 1 / Ohm. 18 G Ω = 1 / 18 nS = 0.056 nS = 56 pS Decanting, ↑ filling process Decay time, ↑ relaxation time decitex. Unit [dtex], defined in g/ 10 000 m, to measure yarns. ( ↑ denier) Decoupling. Electrical connection of the emission pins of ↑ charging electrodes and discharge electrodes ( ↑ ionizer) for touch protection. For this purpose, appropriate resistors (ohmic decoupling) or capacitors (capacitive decoupling) are used. [IEC/ TR 60479-5] De-electrification, ↑ depolarization De-electrifier, ↑ ionizer Defect electron. This describes the hole (gap) left by a ↑ valence electron of a semiconductor crystal when it moves away from its atomic bond after e. g. optical, or thermal excitation. As soon as a voltage is applied to the semiconductor crystal, this hole can be filled by a valence electron of an adjacent bond. Since a hole is created at the same place where it was before and this process is repeated continuously, a charge transport with the amount of a positive elementary charge is generated ( ↑ band model). Deflagration. ↑ Combustion process of a mixture of combustible gases, vapors, dust, and mists mixed with gaseous oxidizers. Locally initiated ignition causes burning without explosive phenomena, usually at a velocity well below 340 m/ s (speed of sound). Deflagration cannot be prevented by exclusion of oxygen. Reaction products flow in the opposite direction to the direction of propagation. Deflagration may transition to ↑ detonation and vice versa, but the transition is not defined. ( ↑ cracking process, ↑ pyrolysis), [Köhler, J. et al. (2008)], [Steen, H. (2000)] Deflection. Electrically charged particles are deflected along their paths of motion by an electric or magnetic ↑ field if the field lines are in the direction of their motion. The deflection of particles with field lines across to the direction of motion is stronger, the slower the particles are. ( ↑ Millikan experiment, ↑ separation of substances, ↑ useful application) Degree of homogenization. Defined by A. Schwaiger (1879 - 1954) as the degree of utilization η for the homogeneity of an electric field. It is used to optimize an electrode arrangement for high-voltage systems in which ↑ gas discharge is to be avoided. The homogeneous field of an ideal plate ↑ capacitor is optimal ( ↑ Paschen ’ s law, ↑ Townsend discharge). Deionization. Extinction of an independent ↑ gas discharge (e. g. an ↑ arc) after removal of the electric field. Deionization time. Time required to extinguish a gas discharge after a power interruption. Example: After lightning strikes a high voltage overhead power line, an arc may occur between a phase and earth. The affected phase is then disconnected and reconnected Deionization time 109 <?page no="113"?> after 1.2 s. During this time, the arc is extinguished, the gas section is deionized, and reignition of the gas discharge is prevented. Delay time for measurements, ↑ waiting time Delta. Angle between roll and web. There are no ordered static field conditions, because the film web charged by separation with different charge profiles is tangent to the coil or a guide roll with also different charge profiles. Considering the surface of the stretched web and the tangential inflow to and outflow from the coil, one can imagine an oscillating vectorial behavior of the field parameters with different charge signs and potential heights. The already oscillating electric field in the delta is periodically superimposed by the alternating field of a discharge electrode ( ↑ ionizer). Consequently, the arrangement of a discharge ionizer in the delta is generally not effective during ↑ winding/ unwinding and at the separation point of a guide roll. If the ionizers are placed in the direction of the web path in front of the delta, the web can be optimally discharged. ( ↑ web tension profile), [Schubert, W., Ohsawa, A. (2024)], [SE Section 5.4.1] Dendrites (Greek: déndron, “ tree ” ). Crystal-like ramifications similar to the ↑ Lichtenberg figures ( ↑ fractals) that can be produced on metals when the metal (e. g. lithium) is deposited below the charge zero point (e. g. on a negatively charged electrode) ( ↑ surface potential). According to a newer theory, during metal deposition (vapor deposition) tiny asperities can form that attract other metal ions as electrostatic concentration points and thus grow into dendrites. They can cause short-circuits in batteries, for example. [Santos, E., Schmickler, W. (2021)] Dendrites are also found on nerve cells and lead to synapses, where stimuli are transmitted electrically. The phenomena that occur during crystal growth comprise a separate field of knowledge. [Glicksman, M. E. (2015)] denier. Unit [den] defined in g/ 9000 m for the measurement of yarn (the lower the denier, the finer the yarn) ( ↑ decitex). Depolarization ( ↑ coercive field strength) ● Electrostatic depolarization: Cancellation of ↑ polarization of ↑ electrets, usually by melting (heating). [SE Section 2.15] ● Dielectric depolarization: Cancellation of dielectric polarization (de-electrification), e. g. in ↑ ferroelectrics by application of thermal or mechanical energy, or by application of initially strong, then decaying to zero, alternating electric fields. ● Magnetic depolarization: Removal of magnetic polarization (demagnetization), e. g. in ferromagnetic materials as before (alternating magnetic fields). Delay time for measurements 110 <?page no="114"?> ● Electrochemical depolarization: In the case of electrical elements, a gaseous layer of hydrogen is formed at the positive electrode (polarization), which increases the internal resistance of the current source. Oxidizing agents, such as manganese dioxide (MnO 2 ), cause hydrogen to combine with oxygen to form water, causing depolarization. Derived SI unit, ↑ SI unit Design specification. In ↑ Ex-areas, only electrical equipment that conforms to the relevant design specifications, e. g. [IEC 60079-11], may be used. Desorption (Latin: de-sorbere, sorbere, “ (to) suck up ” ). Release of a substance previously bound by ↑ absorption or ↑ adsorption (general term: sorption). Detergents, ↑ surfactants Detonation. ↑ Combustion process of a mixture of combustible gases, vapors, dust, and mists mixed with gaseous oxidizers (e. g. explosives) that occur at supersonic speeds (up to 9000 m/ s). When an explosive mixture is ignited in an elongated container (pipeline), the pressure in the direction of flame propagation can briefly reach up to 1000 times the initial pressure due to pre-compression. Such detonation waves have a highly destructive effect upon impact with obstacles. ( ↑ deflagration), [Köhler, J. et al. (2008)], [Steen, H. (2000)] Detour line. It is used for phase shifting, typically 0.5 λ . The cable length determines the delay time or the phase shift in the μ sor ns-range. Device. According to ↑ ATEX 114, this term covers devices, components, and protective systems for use in hazardous areas. ATEX 114 also applies to safety, control and regulating devices outside the hazardous area if these are necessary for the safe operation of devices in the hazardous area with regard to explosion hazards. The directive establishes essential safety requirements which are considered to be obligatory quality requirements. These are specified by mandatory and harmonized standards. ● Devices are machines, operating resources, stationary or mobile devices, control and equipment parts as well as warning and prevention systems, - which individually or in combination, are intended for the generation, transmission, storage, measurement, control, and conversion of energy and for the processing of materials and - which have their own potential ignition sources and can thus cause an explosion. ● Components are parts that are required for the safe operation of devices and protective systems without fulfilling an autonomous function. ● Protective systems are all devices, apart from equipment components, which are intended to stop incipient explosions immediately and/ or to limit the area affected by an explosion and which are placed on the market separately as systems with autonomous functions. For devices that have a potential ignition source and can therefore cause an explosion, the manufacturer must carry out a risk assessment in which he relates the explosion protection measures to the probability of an explosive atmosphere occurring. The ↑ explosion-related parameters must also be considered. If the device (e. g. a machine) is Device 111 <?page no="115"?> to be used in areas with a high risk of explosion, the explosion protection measures must be more extensive than in areas in which an explosive atmosphere occurs only rarely and for a short time ( ↑ equipment category, ↑ quenching distance). [11. ProdSV] Dew point. Temperature value at which the gas in a gas-vapor mixture is just saturated with the amount of vapor present at constant pressure. For example, the water vapor content of air has reached its highest level at the dew point (relative ↑ humidity = 100 %). The dew point is measured with a dew point hygrometer. When the air is cooled below the dew point, condensation occurs and ↑ fog or precipitation forms. The more water vapor in the air, the higher the temperature, and vice versa. Dew point hygrometer, ↑ humidity meter DGUV, short for German: Deutsche Gesetzliche Unfallversicherung e. V. Is the umbrella organization of the German statutory accident insurance institutions for trade and industry and the accident insurance funds. Diaphragm. A partition made of electrically insulating material that, due to its porosity, can be permeable to current and prevents the mixing of solutions in electrolysis cells ( ↑ electro-osmosis). Dielectric. Electrically non-conducting material ( ↑ insulator). When a dielectric is placed in the electric field of a capacitor, it causes a more or less strong ↑ polarization in all insulating materials to the extent that they try to reduce the field strength. The relative ↑ permittivity (formerly the dielectric constant) expresses the force that exists between the charges within the material. This relationship is illustrated by identical parallel plate capacitors A and B: Capacitor A contains air (in this case equivalent to ↑ vacuum) with relative permittivity ε r = 1. Capacitor A and B are identical, but B contains a dielectric instead of air. To charge capacitor A to a certain potential, an amount of charge Q 0 is required ( ↑ displacement current), which corresponds to its capacitance resulting from the given dimensions. On the other hand, in the case of a capacitor B with the same dimensions, an additional quantity of charge Q d is required to obtain the same potential. It is needed for the polarization ( ↑ dipole) of the dielectric. Accordingly, a larger amount of charge is released when capacitor B is discharged than when capacitor A is discharged, because the ↑ capacitance of the capacitor is larger. This polarization effect is expressed in the relative permittivity ε r > 1 of the dielectrics ( ↑ molecular dipole). Insulating films have ε r -values between about 1 to 5. In the case of ceramic insulators, ε r -values as high as 10 4 can be achieved, and in the case of light metal oxides, even higher than 10 8 . Since residual Dew point 112 <?page no="116"?> polarization always remains ( ↑ hysteresis), the total charge introduced is never released again ( ↑ electrostriction, ↑ piezo effect). {Appendix M.1} Dielectric absorption, ↑ absorption Dielectric constant, ↑ permittivity, {Appendix M.1.1} Dielectric field strength, ↑ breakdown field strength Dielectric loss. Occurs in a dielectric due to its electrical resistance and due to reelectrification phenomena (polarization of the ↑ molecular dipoles) in an alternating electric field (practical application: microwave heating). They can lead to heating of e. g. high voltage cables and thus reduce the breakdown strength. The dielectric losses are characterized by the ↑ dissipation factor and can be measured with a ↑ Schering bridge. Dielectric value (of a material), ↑ permittivity number, {Appendix M.1.2} Di-electrophoresis. Linear motion of matter (e. g. particles) is caused by polarization effects in an inhomogeneous electric field. The ↑ Coulomb force acting in this process is proportional to the volume as a function of the shape of the matter. Applications include the dielectric manipulation of particles, such as microorganisms, in a field formed by microelectrodes. The inhomogeneous field influences a ↑ dipole moment in the particle so that it moves according to the polarity in the field. The medium surrounding the matter must have a different polarizability than the matter. Diesel fuel (also known as diesel oil). A mixture of hydrocarbons with a high ↑ flash point (above 55°C), is classified as non-flammable according to the ↑ BetrSichV. Diesel fuel can become highly charged when flowing due to its low electrical conductivity. This can occasionally lead to charge-induced electric ↑ breakdown of insulating components (pipe, tank). Diesel fuel can be made conductive by adding antistatic agents. (According to TRGS 727 Appendix F, diesel fuel (technically pure, at 20 °C) has a conductivity of approx. 10 -13 S/ m.) Differential current. Sum of instantaneous values of currents flowing through all active conductors of a circuit at one point of the electrical system. [IEC 61008-1], [NFPA 70], [IEEE 80-2013] Diffusion. Equilibration processes in which particles (e. g. vapor molecules) move from locations of higher concentration to locations of lower concentration as a result of their thermal motion (even through apparently impermeable walls). Diffusion must be considered for containers or packaging made of ↑ plastics, through the walls of which volatile contents (e. g. gasoline) can easily diffuse to the outside (barrels, tanks, canisters). If the conductivity of plastics is improved (e. g. to prevent electrostatic charging) by incorporating conductive substances (e. g. carbon black and graphite ( ↑ carbon), ↑ metal fiber), this generally leads to an increase in diffusion along the internal contact surfaces between the conductive foreign substances and the polymer. Diffusion rate, ↑ MIE (minimum ignition energy) Dimensions of chargeable surfaces, ↑ chargeability Dimensions of chargeable surfaces 113 <?page no="117"?> DIN, short for German: Deutsches Institut für Normung e. V. (Institute for Standardization). DIN is a private organization registered as a non-profit association founded in 1917. ( ↑ standardization) DIN ISO. German standard adopted unchanged from an international standard, the ↑ ISO (International Organization for Standardization). DIN notification. Announcing the intended publication or withdrawal of a standard in order to give the public the opportunity to comment. [SE Section 9] DIN SPEC. Publicly available specification developed by a temporary committee that bypasses all the steps required to develop a standard. The goal is to quickly publish technologies or products that have not yet been standardized. DIN SPEC is a marketing tool for interested groups and is therefore not part of the German body of standards but can form the basis for a standard. DIN standards. Are the results of work at a national, European and/ or international level. Anyone can submit a proposal for a new standard. Once accepted, the standards project is carried out by the relevant DIN standards committee, the relevant Technical Committee (TC) of the European standards organization CEN (CENELEC for electrotechnical standards) or the relevant committee of the International Organization for Standardization ISO (IEC for electrotechnical projects) according to established rules of procedure. Diode (Greek: di, “ twofold ” , hodos, “ path ” ). Electrical component whose resistance depends on the polarity of the electric voltage. Diodes are electrical valves (rectification of an alternating current) and are realized as ↑ electron tubes (with two electrodes) or semiconductor components ( ↑ semiconductor diode) with at least one junction. Dip electrode, ↑ measuring electrodes for liquids no. 2 and 3 Dip tube, ↑ filling pipe Dipole ● Model of an arrangement of two equally strong magnetic poles (magnetic dipole) or two equally strong electric charges (electric dipole, ↑ dielectric) of opposite polarity in close proximity ( ↑ molecular dipole). ● Original design of a (bipolar) transmitting or receiving antenna. For the detection of electrostatic discharges ( ↑ spark detection device), the following arrangements can be chosen: - Two wire-shaped conductors, each as long as about 1/ 4 of the wavelength of the frequency to be received, placed either vertically on top of each other or horizontally next to each other (stretched dipole). - Two semicircles that together form a full circle with a small air gap. One conductor is connected to the core, the other to the shield of a 50 - 75 Ω coaxial cable and connected to a receiver. DIN 114 <?page no="118"?> - A folded dipole design, in which a single conductor approximately the length of the frequency to be received has its ends connected to a 50 - 75 Ω coaxial cable via a 4: 1 high-frequency transformer. Dipole force. Generated between two electric or two magnetic ↑ dipoles. It is directly proportional to the product of the ↑ dipole moments and inversely proportional to the fourth power of the distance between the two dipoles. The electric dipole force also contributes to the ↑ Van der Waals forces. Dipole moment. For two opposite equal point-charges +Q and -Q at distance d (vector) the dipole moment is: p = Q × d. The vector p points from the negative to the positive charge. The electric polarization P is equal to the spatial density of the electric moment of molecular dipoles. ( ↑ permittivity), [DIN 1324-1] Direct current (DC). Electric current in which charge carriers move in one direction in the same direction on average under the influence of a DC electric field ( ↑ current). Disaster management plan. Civil protection is part of the general emergency response and is the responsibility of the federal states. Their authorities are obliged to carry out hazard prevention planning for each large facility (e. g. chemical plant, tank farm, nuclear power plant) and to draw up a disaster management plan. Discharge. Neutralization or elimination of electrostatic charges, especially on the surface of an insulating material. Electrostatic charges inside ( ↑ electret) are not covered by this ( ↑ ionizer). ● Discharge by earth contact. Effective discharge is achieved by any contact to earth, but it must be noted that the required discharge time is mainly determined by the ↑ surface resistance of the object and the contacting surface. Depending on the circumstances, optimum contact can also be achieved by immersing the object in a wetting, conductive, residue-free and earthed liquid. ● Contactless discharge by neutralization using freely moving, oppositely charged gas ions from the surrounding atmosphere. The use of ionizers is the most common method of discharging and is particularly suitable for moving objects. It is performed by attaching pins at any distance from the charged object. A distinction is made between passive (earthed) and active (high voltage) ionizers. ● Contactless discharge by flame ionization, in which gases provide ions for discharge by thermal excitation ( ↑ flaming). ● Contactless discharge by glow discharge ( ↑ glow discharge installation), which causes spontaneous gas discharges at the surface under reduced atmospheric pressure, depending on the charge level ( ↑ electrodeless discharge). ● Discharge by ionizing radiation, ↑ gas discharge Discharge (physical), ↑ electrodeless discharge, ↑ electrostatic discharge, ↑ liquid discharge, ↑ spark discharge, ↑ gas discharge, ↑ charge dissipation, ↑ Lenard effect, ↑ air breakdown arc, ↑ self-discharge, ↑ partial discharge, ↑ UV radiation, ↑ flame ionization, ↑ material web Discharge bar, ↑ ionizer, ↑ ionizer in processing machines Discharge bar 115 <?page no="119"?> Discharge brush. Which is connected to the ↑ earth electrode and is available from many manufacturers in a variety of shapes. The bristles of the brush are made of conductive substances such as plastic, carbon, stainless steel, or other conductive fibers. Depending on the arrangement of the filaments, different ↑ corona inception voltages are required. In extreme cases, a compact arrangement of filaments is equivalent to a surface, which is almost ineffective for discharging charged surfaces. Discharging brushes do not have reproducible discharging characteristics. If the brushes become soiled, all ionization may stop because there are no protruding pins (conductive filaments) that would be stimulated to discharge by the ↑ surface charge density. Individual filaments can be caused to glow by high discharge currents and ignite any flammable gases or contaminants present. Contaminated brushes become an acute fire hazard. Passive discharge brushes with compact fiber fill are not recommended for use in hazardous areas. ( ↑ ionizer test), [SE Section 5.2.3.1] Discharge circuit, ↑ MIE (minimum ignition energy) Discharge current. This describes the current that flows when a load is applied to a charged accumulator ( ↑ accumulator, ↑ capacitor). Discharge current pulse, ↑ gas discharge Discharge curve. Represents the discharge curve for a charge accumulator ( ↑ accumulator, ↑ capacitor, ↑ charge double layer, ↑ relaxation time). The discharge curve also characterizes the course of current pulses generated by ↑ ESD test generators. In all ESD standards, the discharge curve is measured as the short-circuit current against the reference earth of the test generator. {Appendix M.6.2} Discharge mechanism, ↑ gas discharge Discharge of granules, ↑ bulk material discharge Discharge spark, ↑ spark discharge Discharge time. Time required to discharge a charge storage device ( ↑ accumulator, ↑ capacitor). In practice, for capacitances, 5 times the discharge ↑ time constant is taken as the time for a complete discharge. ( ↑ relaxation time), {Appendix M.6.3} Discharge time constant, ↑ time constant Disconnection in power installations. Disconnection on all sides of an installation, part of an installation or operating resources from all unearthed conductors ( ↑ work clearance permit). [EN 50110-1], [NFPA 70E] Dispersants. Surface-active substances that reduce the ↑ surface tension of liquids (e. g. water). Soluble and insoluble substances are made more finely dispersed to prevent their separation or segregation ( ↑ surfactants). Dispersion (Latin, “ dispersio ” ). A system of substances (mixture) consisting of two or more phases, in which one substance (dispersant, the dispersed phase) is distributed in another substance (dispersing agent) in the finest form ( ↑ emulsion, ↑ suspension). Both the dispersant and the dispersing agent can be solid, liquid or gaseous. If the dispersant is to be Discharge brush 116 <?page no="120"?> classified as chargeable due to low electrical conductivity, a significantly higher charge must be expected for dispersions than for pure liquids. The charge separation at the “ inner surfaces ” can considerably exceed the charge separation at the tube wall. Example: The charging when flowing gasoline by adding a small amount of water (ppm-range) becomes significantly larger ( ↑ charging - of liquids, ↑ continuous phase). Dispersity, synonym for ↑ fine particle size Displacement current. Electric current in insulators is not caused by a charge carrier transport but by a change in the ↑ electric flux density. The term displacement current was introduced by J. C. ↑ Maxwell because of the occurrence of magnetic field lines during charge movement in analogy to conduction current. For example, every conductor circuit containing a capacitor (with ↑ dielectric) represents a closed circuit. The displacement current is made up of a current for the ↑ polarization and a current from the change in electric field strength over time. The capacitance causes the displacement current in a circuit, although no charge carriers are transported through the capacitor. [Wedler, G., Freund, H.-J. (2018)] Displacement density. Antiquated term for ↑ electric flux density. Display. Device or component for the optical representation of information. ( ↑ electronbeam tube, ↑ liquid crystal display) Dissipation (Latin: dissipatio, “ fragmentation ” ). Conversion of a form of energy into heat energy ( ↑ dissipation factor). In the electrostatics also occasionally used instead of ↑ charge dissipation. Dissipation capability. Characterizes the ability of materials and objects to dissipate electrostatic ↑ charges to earth quickly enough to prevent hazards or disturbances. It is a material property related to electrical resistance ( ↑ leakage resistance, ↑ earth able point). It is defined by: - Volume resistivity ρ v between 10 4 and < 10 9 Ω m - Surface resistance R s between 10 4 and < 10 9 Ω , measured at 23 °C and 50 % RH - Surface resistance R s between 10 4 and 10 11 Ω , measured at 23 °C and 30 % RH Surface resistance is usually measured at 50 % RH. However, it is common for ↑ plastics to be used at lower relative ↑ humidities. Therefore, a “ safety margin ” with a factor of 100 was introduced for the measurement at 50 % RH to ensure that plastics measured at 50 % RH still have the ability to dissipate at 30 % RH. [TRGS 727 Section 2.13], [SE Section 3.5] ● The dissipation capability of protective clothing is usually achieved by incorporating conductive fibers into the high-resistance base material (e. g. cotton or polyester). Such material systems cannot be discharged in the sense of homogeneous dissipation. The electrostatic effect of dissipation capability consists of various physical interaction Dissipation capability 117 <?page no="121"?> mechanisms between the base fabric, the conductive fibers and the earthed body of the person. The surface charges can be discharged galvanically or electrostatically bound or neutralized by field effects. As a result, ignition effectiveness is lost. (group [EN 1149]) Dissipation factor (also loss factor). In every ↑ capacitor, losses occur during operation with alternating voltage or during switching on and off ( ↑ molecular dipole). These can be represented by a resistance parallel to the ideal capacitor. This results in a phase shift angle, called the loss angle, whose tangent (tan δ ) is called the dissipation factor. The dissipation factor is a measure of the dielectric losses, i. e. the energy extracted from the alternating electric field and converted to heat in the capacitor. For some materials, the dissipation factor is frequency dependent. Since the ↑ electric strength of insulating materials decreases with increasing temperature, insulating materials subjected to high electrical stress must have low dissipation factors. [IEC 61620], [IEC 60247] Dissipative, ↑ dissipation capability [TRGS 727 Section 2 (13)] Dissociation (Latin: dis-, “ apart ” , socius, “ companion ” ). Separation of molecules into smaller components. ● In electrolytic dissociation, such as in salt solutions, molecules break apart into electrically differently charged components ( ↑ ions). Example: Chemically pure water is an insulator. If copper sulfate (CuSO 4 ) is dissolved in water, the salt is separated into positively charged particles (Cu ++ ) and negatively charged particles (SO 4 - - ) ( ↑ electrolysis). The charged particles are mobile in the solution. They take over the charge transport and the water has become conductive ( ↑ electrolyte). ● In thermal dissociation, the molecules separate as a result of inelastic collisions during their thermal motion ( ↑ flame ionization). Distance Law 1. For a point source, the radiant power at the point of irradiation decreases with the square of the distance. For real sources, the distance law applies only in the ↑ far field. 2. For magnetic poles, the attractive (unlike poles) or repulsive (like poles) forces decrease with the square of the distance between the magnetized bodies. 3. For electric charges, the attractive (different polarity) or repulsive (same polarity) forces decrease with the square of the distance between the electrically charged bodies ( ↑ Coulomb ’ s law). Distribution network. It is the totality of all the lines and cables that run from the power generator to the installation of the consumer. Disturbance variable (electrostatic / electromagnetic), ↑ measurement error Diversity (Latin: diversus, “ turned away ” , “ opposite ” ). Design principles for safety systems, e. g. for chemical plants. To increase reliability, safety systems are not only designed multiple ( ↑ redundancy), but also “ diversified ” according to chemically or technically different principles. DKE, short for German: Deutsche Kommission Elektrotechnik Elektronik Informationstechnik in DIN und VDE. Is the German member of the International Electrotechnical Dissipation factor 118 <?page no="122"?> Commission ( ↑ IEC) and the European Commission for Electrotechnical Standardization ( ↑ CENELEC). As a National Standards Organization (NSO), it cooperates with ETSI (European Telecommunications Standards Institute) and is thus also responsible for the standardization projects dealt with in the corresponding international and European organizations, in particular IEC, CENELEC and ETSI. Donor (Latin: donator, “ giver ” ). ↑ Foreign atom in the semiconductor that can donate electrons to make it n-conducting ( ↑ electron conduction) ( ↑ band model). Materials are also called donors if they have a low ↑ electron emission energy and therefore release electrons upon contact with materials that have a higher emission energy ( ↑ acceptor, ↑ charge double layer, ↑ charging, ↑ triboelectric series). Donut dot. Quality defect in gravure printing where the screen dot has a “ donut ” shape. Donut dots can be caused by ↑ electrostatic print assist in gravure printing when the cell shape has a “ V ” -shape (Figure). There are also other causes of donut dots, such as incorrect squeegee positioning on the gravure cylinder. Donut dots are not expected to be with a “ U ” -shaped cell [SE Section 8.2.10]: (Source: www.vtt.fi) Doping. Is the insertion of foreign atoms into crystals (e. g. by diffusion, ion implantation) or polymers to increase the number of mobile charge carriers and thus the electrical conductivity of the material. Foreign atoms that donate electrons are called ↑ donors; Doping 119 <?page no="123"?> charge transport takes place through negative charge carriers (electrons). Foreign atoms that bind electrons are called ↑ acceptors; with them, charge transport takes place through “ positive charge carriers ” ( ↑ defect electrons or holes). Double insulation, ↑ insulation Double layer capacitor, ↑ capacitor Double layer charge, ↑ charge double layer Drop test. Large packaging (containers, barrels, etc.) for the transport of dangerous goods are, among other things, subjected to a drop test, which must be carried out after the test sample and its contents have been tempered to - 18 °C or lower. To prevent hazards due to electrostatics, the ↑ BetrSichV stipulates that transportable plastic containers with a volume of more than 5 l for flammable liquids with a flash point of up to 35 °C may only be used if they are sufficiently electrostatically dissipated or equipped with a sufficiently dissipative device. Permanent conductivity of plastics can currently only be achieved economically by adding carbon black ( ↑ carbon), which however reduces the ↑ cold impact toughness. As a result, large packaging means made conductive in this way often fail the drop test. [TRGS 727 Section 4.5.4 (3) 2c)], [BAM Ratgeber (2017)] Droplet charging, ↑ Lenard effect, ↑ atomization, ↑ Rayleigh instability, ↑ Rayleigh limit Dry cleaning. Use of solvents on textiles can cause electrostatic charging (charging and emptying of drums and equipment; cleaning by rubbing or brushing on worktables; and repeated lifting of containers filled with solvents). If the solvents used are flammable, protective measures must be taken. The Accident Prevention Regulations for Chemical Cleaning [DGUV Regel 100-500] require that measures be taken to prevent electrostatic charges when flammable solvents are used in cleaning equipment. The solvent must be made electrically conductive at the latest after it has been filled into the system. Since not all additives are equally effective, the operator should use only those additives for which the manufacturer guarantees sufficient conductivity when used properly (dosing instructions, including subsequent dosing). It is worth mentioning that from 1880 to 1892, there were more than 80 fires in German gasoline laundries, in which M. M. Richter determined electrostatic charge as the cause of ignition. He was also responsible for the idea of increasing the conductivity of gasoline by adding magnesium oleate to such an extent that no more charges could be generated. [Richter, M. M. (1893)], [EN 12921] Duromer (also known as thermoset). ↑ Plastic with spatial cross-linking, which has a lower tendency to electrostatic charging in comparison to other polymers. Dust. Dispersed distribution of solid substances initially in the air, which is usually deposited. It is divided into coarse and fine dust. Fine dust < 5 μ m is referred to as respirable (A-dust). The ↑ occupational exposure limit for A-dust is 1.25 mg/ m 3 and for Edust (inhalable) 10 mg/ m 3 [TRGS 900]. Lower limit values generally apply for carcinogenic, mutagenic, fibro genic, toxic or allergenic dust. In the technical sense, dust is a comminuted solid who ’ s electrostatic and explosion properties are significantly influenced by the increase in surface area associated with the degree of comminution. The following overview shows the enormous increase in surface Double insulation 120 <?page no="124"?> area that results from extensive ↑ crushing. A cube with an edge length of 10 mm results in the following with extensive comminution: Number of cubes Edge length [ μ m] Surface area [m 2 ] 10 3 1000 0.006 10 6 100 0.06 10 9 10 0.6 10 12 1 6 Since electrostatics is a surface phenomenon, dust have higher specific ↑ charges than ↑ granules. Dusty bulk materials are charged as a result of separation processes on the wall, e. g. when conveyed through pipes. These separation charges are superimposed in various ways by other charges (contact and separation of product particles) ( ↑ mass flow rate). Thus, a charged quantity of dust will always have positive and negative charges, with smaller dust particles being preferentially negatively charged and larger particles being preferentially positively charged. For example, when filling a silo, the coarse dust that settles on top is positively charged, while the fine dust that floats on top is negatively charged. If dust has a resistivity ρ D > 1 T Ω m, significant product charging must always be expected at transport speeds v > 1 m/ s ( ↑ cone discharge). Explosive dust include wood, flour, coal and ↑ plastic dust, but also ↑ light metal dust. In certain concentrations and with appropriate distribution in the air, dust can cause explosions if ignition sources are present. Great attention must therefore be paid to explosion prevention, including the installation of extraction systems. (DGUV: GESTIS- STAUB-EX, database on combustion and explosion properties of dust www.dguv.de/ ifa/ gestis/ gestis-staub-ex/ index.jsp) Dust can be divided into three resistance groups according to their chargeability: Low ρ D < 1 M Ω m Medium ρ D = 1 M Ω m to 10 G Ω m High ρ D > 10 G Ω m [TRGS 727] Dust-air mixture. Whirling up combustible dust creates dust-explosive mixtures in the range of their ↑ explosion limits. Dust charging, ↑ charging, ↑ dust Dust deposition. For most combustible dust, a dust deposit of about 1 mm thickness evenly distributed over the entire floor surface is sufficient to fill a room of normal height with an explosive ↑ dust-air mixture when whirled up. [TRGS 722 and 727] Dust explosion class (also known as pressure rise class). Provides information on the maximum rate of pressure rise ( ↑ K St value) of a dust explosion in closed apparatus (20 l sphere or 1 m 3 container) under defined conditions. It is calculated from ↑ explosion pressure, pressure rise velocity and container volume and is required for dimensioning ↑ explosion pressure reliefs. The dust explosion classes are marked by the following pressure rise velocities: Dust explosion class 121 <?page no="125"?> Dust explosion class K St value [bar × m/ s] St 1 up to 200 St 2 over 200 to 300 St 3 over 300 St 0 indicates that no ignition has occurred. The dust explosion class is not necessarily a measure of the hazard of a dust, e. g. it does not allow any conclusions to be drawn about the ↑ MIE, only in the case of St 0 dust can an explosion hazard be ruled out. [BIA Report 12/ 97] Dust explosion hazard. When whirled up in air, combustible ↑ dust can form an explosive mixture in which rapid combustion reactions with progressive pressure and flame front take place when a sufficiently strong ↑ ignition source becomes effective. ( ↑ hybrid mixture) Dust figures. Can occur on insulating objects that have been stored for a long time and were originally highly charged, such as injection molded parts. They reveal latent electrical ↑ charge distributions (charge structures) caused by the attraction of dust from the environment ( ↑ soiling). The ever-changing surface distributions also show how positive and negative charges coexist and balance or repel each other. ( ↑ dendrites, ↑ fractals, ↑ treeing) Dust filter, ↑ filter Dust ignition. To ignite deposited ↑ dust, energy is required to swirl it, initiate a ↑ cracking process, and then ignite the resulting gas. This means that when ignited by electrostatic ↑ gas discharges, they must be of sufficient length and energy to trigger all three stages ( ↑ propagating brush discharge). ↑ Brush discharges are generally too short, and there is no reliable evidence for ↑ super brush discharges. ( ↑ Godbert-Greenwald apparatus, ↑ hybrid mixture, ↑ measuring electrode), [SE Section 6.9.7] Dust protection by enclosure, ↑ type of protection “ t ” Dusting (due to electrostatic charging), ↑ contamination, ↑ soiling DUT, short for device under test, is an electronic component that is being tested for its susceptibility to electrostatic discharge ( ↑ ESD). For the required simulated discharge, the energy stored in the capacitor C is discharged into the DUT via a circuit consisting of an active resistor R and an inductive reactance X L . The simple circuit principle makes it possible to determine a variety of discharge curves depending on the values of capacitance, resistance and inductance. [IEC/ TR 61340-1] Dwell time. All electrostatically charged materials discharge more or less quickly depending on their ↑ conductivity. Accordingly, an adequate dwell time generally ensures a reliable discharge ( ↑ calming section, ↑ self-discharge). Dust explosion hazard 122 <?page no="126"?> The dwell time for liquids in conductive pipes or containers can be calculated using the formula t [s] = 100 / κ [pS/ m], according to which the liquid is discharged to a safe level before entering a container (t: time, κ : conductivity). Excluded from this are processes in which ↑ electrets have formed, e. g. insulating material parts formed by injection molding. [TRGS 727 Section 4] dyn. Unit of force agreed in 1873 in the CGS system (centimeter-gram-second) 1 dyn = 1 kg×m×s -2 = 10 -5 N. As of January 1, 1978, dyn is no longer allowed as a unit of force and has been completely replaced by the ↑ SI unit Newton [N]. dyn 123 <?page no="127"?> E Earth (the term ground is only used in the US). The conductive earth (soil) whose electric potential is set to zero at every point in the currentless state ( ↑ soil resistance). Earth (to earth). Connecting an electrically conductive part to the ↑ earth via an earthing device. Earth able point. The connection point for an earthing cable must be marked on objects from which electrostatic charges must be safely discharged. In the IEC 61340 standards, this earth connection point is generally referred to as an earth able point. [ISO 7010] Earth clamp. Clamping device with earth connection for the ↑ discharge of conductive objects, e. g. when ↑ container filling. The teeth of the pliers should be very sharp and applied with high spring force so that, for example, paint layers can be perforated safely. For control purposes, earth clamps can be equipped with a signal transmitter that monitors the earthing via an intrinsically safe circuit ( ↑ electric circuit). To prevent galvanic elements, different metals should not be used in the clamp (e. g. copper/ brass or brass/ stainless steel). The advantage of earth clamps made of dissipative plastic (approx. 1 M Ω ) is that, due to their inherent resistance, they do not cause an ignitable spark in the event of a delayed connection to, for example, a partially filled and thus charged drum. (Source: www.atc.nu) (Source: www.walkerling-shop.de) Earth conductor. Protective earthing conductor that obligates the main earth terminal or busbar to the earth. [IEC 60050] Earth electrode. One or more conductive parts that are in good contact with ↑ earth. Electrically independent earth electrodes are installed at such a distance from each other that the potential of the other earth electrode is not significantly affected by the maximum current flowing through one earth electrode. ● Natural earth electrode (in the sense of electrostatics), metal part in contact with the earth or groundwater, either directly or via concrete (foundation earth electrode), <?page no="128"?> whose original purpose is not earthing, but which acts as an earth electrode. This includes pipelines, sheet pile walls, concrete pile reinforcement, steel parts of buildings, etc. [IEC 60050] Earth fault. Conductive connection of a phase conductor or an operationally insulated line to neutral voltage with earth or earthed parts caused by a fault. Earth fault current. Electric current due to an earth fault (e. g. insulation fault). [IEC 60050] Earth-fault-proof. A feature of operating resources or current paths for which no earth fault is to be expected during ↑ operation as intended by the application of appropriate measures or means. [IEC 60050] Earth leakage current. Non-functional electric current flowing in a faultless circuit to earth or to a third party between conductive parts. (Others: touch current and patient leakage current). [IEC 60050] Earth leakage resistance. ↑ Leakage resistance between a conductive object and earth. Earth loop. It is formed by two separates ↑ earth electrodes on an electrical part (system, device, circuit). If electric or magnetic ↑ fields act on the resulting conductor loop, interference voltages can be influenced or induced in the system. An earth loop must always be avoided. Earth monitoring. It is performed with a variety of systems. There is a distinction between earth monitoring of the leakage path ( ↑ earthing) with only visual indication, with capacitive monitoring (i. e. which capacitance is connected) and with a switching unit for process enabling. They usually consist of an ↑ earth clamp (earthing contactor) on the object to be earthed, connected to an evaluation unit. Correct and continuous monitoring is usually indicated visually. Additional integrated contacts of the evaluation unit can enable a process and, if necessary, stop it if the earthing is insufficient. Special versions are available for ↑ FIBC-C, as these should be earthed at two points. Earth resistance meter. Device for testing the ↑ discharge resistance of a part to be earthed. The measuring range covers values up to 10 12 Ω with measuring voltages up to 1000 V. Earthing testers used in electrical engineering are generally unsuitable, since they can generally only measure resistances in the m Ω range up to several 100 Ω and the measuring voltage is in the low-voltage range. In the case of electrostatic earthing in hazardous areas, an approved earth tester (explosion proof) must be used or a ↑ work clearance permit must be issued. The figure shows an example of such a high-ohm tester for insulation and discharge resistances of 1 k Ω to 2 T Ω with measuring voltages of 32, 100, or 500 V. Earth resistance meter 125 <?page no="129"?> Earth tester, ↑ earth resistance meter Earthed radiator. Wire-shaped conductor, approximately half the wavelength of the frequency to be received, with one end in the air ( ≙ 377 Ω ) and the other end connected to the shield of a 50 - 75 Ω coaxial cable ( ≙ 0 Ω ) to a receiver. The core of the conductor is connected to the 50 - 75 Ω point of the conductor. ( ↑ dipole, ↑ spark detection device) Earthing. All means and measures to prevent dangerous contact voltages between a system and the earth. ● Reference earth. The part of the earth that is considered to be electrically conductive, outside the influence of earthing systems, and whose electric potential is set to zero by convention (IEC 60050-195). The measured values for the earthing of an installation are referred to the reference earth. Protective earthing. The safe connection of one or more points of an electrical network, system or operating resources to earth to protect persons in the event of faults. Working earthing. Safe connection of switched off active parts to earth, so that work can be carried out without risk of electric shock. ( ↑ work clearance permit) Operational earthing. Safe connection to a point of the operational circuit necessary for the proper and safe operation of equipment or systems. [IEC 60050] Functional earthing. Connection to a point in measuring, controlling or regulating circuit or to shielding to ensure the trouble-free operation of electrical equipment and systems (not protective earthing). Interference currents should be safely discharged, and electrical interference coupling prevented. In the case of measuring instruments, this is generally referred to as the “ measuring earth connection ” (intrinsically safe circuit ( ↑ electric circuit), ↑ equipotential bonding). ( ↑ measuring electrode), [IEC 61010-1] ● Electrostatic earthing. It is used to safely discharge electrostatic charges, e. g. for barrels on insulating wooden pallets, before starting any handling or technical processes. This is the case for a conductive object if its discharge resistance does not exceed 1 M Ω at any point, and for persons and objects if their capacitance-related ↑ time constant {Appendix M.6.3} is less than about 10 ms. In contrast to the protective earthing of electrical equipment, this “ electrostatic ” earthing does not have to be of low resistance. [TRGS 727], [IEC/ TS 60079-32-1 Section 7.8.1.3.1; 13.1] Note: Equipotential bonding (B) alone is generally not a safe earthing method, since such a series connection always carries the risk of breaking the earthing chain. Earthing Earth tester 126 <?page no="130"?> should always be done according to (A). [TRGS 727 Section 8; Appendix E], [IEC/ TS 60079-32-1 Section 13] ● Earthing of insulated conductive objects, e. g. metal screws in plastic flanges of glass apparatus, must only be earthed considering the surrounding ↑ Ex-zone and ↑ explosion group. Maximum allowed insulated capacitances in zones of hazardous areas are e. g.: Charged body Capacitance [pF] Potential [kV] Energy [mJ] Flange 10 10 0.5 Bucket 10 10 0.5 Aluminum label 7x10 cm (e. g. in rotary presses) 10 10 0.5 Small metal objects (e. g. shovel, hose nozzle) 10 - 20 10 0.5 - 1 Small containers up to 50 l 50 - 100 8 2 - 3 Metal containers from 200 - 500 l 50 - 300 20 10 - 60 Person 100 - 200 12 7 - 15 Large plant components directly surrounded by an earthed structure 100 - 1000 15 11 - 120 Truck/ Tanker 1000 - 1500 2 - 5 2 - 19 [SE Section 3.8], [TRGS 727 Section 8.3.5] ● Personnel earthing, which is intended to prevent persons from being charged, always requires some effort, the quality of which depends on the reliability required. For example, foot earthing straps may be sufficient. When working in ↑ Ex-areas, dissipative shoes and dissipative ↑ floors are considered adequate protective measures. In general, the leakage resistance to the earth should not exceed 10 8 Ω . When working in a seated position, it must be possible to discharge the charge only through the seating furniture. In areas where, for example, explosives are handled, 10 5 Ω must not be exceeded, and in rooms used for medical purposes, 5 × 10 4 Ω must not be exceeded. ( ↑ clothing), [IEC 61340-6-1] Wrist earthing has proven to be the most reliable method for handling electrostatically sensitive components. This earthing consists of a conductive wrist strap that tightly encloses the wrist and is connected to earth via an insulated earth cable (test voltage for insulation 4 kV) with a resistance of at least 1 M Ω and 0.25 W load capacity. The total discharge resistance to earth shall not exceed 5 M Ω . Foot earthing straps may be sufficient for shoes that do not have adequate dissipation capability. This requires constant or frequent contact between the conductive straps or chains attached to the ankle or shoe and an adequately dissipative ↑ floor. Due to their lack of reliability, these ribbons should not be worn by personnel working in hazardous areas, but only by visitors. [TRGS 727 Sections 7 and 8] ● Ship earthing. The term “ earthing ” is incorrectly used to refer to equipotential bonding. Ships are adequately earthed by the water that surrounds them. From an Earthing 127 <?page no="131"?> electrostatic point of view, earthing is not necessary and is not allowed because the currents that occur can be very high due to the interaction of capacitances. Stray currents can be caused by ↑ cathodic protection (CP) systems on ships and port facilities, but also, for example, by electric locomotives, which generate strong ↑ spark discharges when metal cables from ship to shore are connected ( ↑ ignition source). Active, equipotential bonding between the ship and the port facility must be ensured when loading and unloading (discharging) ships with products belonging to an ↑ explosion group ( ↑ explosion prevention). The ship-water-port facility system represents a voltage source ( ↑ galvanic element), which may result in spark discharges at the connection points of the loading hoses, loading arms or other conductive components when they are connected to or disconnected from the ship. If the ship and the berth have a CP, safe insulation, e. g. by means of insulating flanges (insulation resistance ≥ 1 k Ω to 100 M Ω ) in the piping to the mainland is sufficient [IEC/ TS 60079-32-1]. There must be no insulated conductor between ship and shore, e. g. by using two insulating flanges ( ↑ influence). If only one partner has CP, it must be disconnected [ISGOTT]. Unfortunately, despite the standards mentioned above, there are still no uniform regulations worldwide. Commonly used earthing systems for discharging electrostatic charges are not functionally suitable for ship earthing. ● Earthing of rail tank wagons. Due to the proximity of railroad electrical systems, stray currents may flow across conductive system components used in the filling of tank wagon, causing ignitable sparks upon contact with conductive earthed parts. For this reason, all system components, including eventually electrically insulated rail systems on which the tank wagon is located, must be securely earthed, using insulating flanges where necessary. The ↑ charging caused by the transport of liquids must be prevented by electrostatic earthing. Earthing lance, ↑ central conductor Earthing strap (foot earthing strap, wrist strap), ↑ earthing - personnel earthing Earthing system. A locally limited set of interconnected ↑ earth electrodes or metal parts acting in the same way and ↑ earth conductors. [IEC 60050] Earthing tongue (according to Harald Schulze). Earthing tongues (smooth or ribbed) connected to earth are used for passive discharge ( ↑ ionizer). This is a simple way to reduce electrostatic charges in all industrial areas. It can be used wherever ionizers with a power supply cannot be used and where low residual charges are not perceived as disturbing ( ↑ corona discharge). Initial investigations showed that the installation of earthing tongues at the end of transport pipes for filling silos had successfully eliminated the discharge of bulk material. [Shoyama, M. et al. (2024)] Earthing lance 128 <?page no="132"?> As passive components, earthing tongues can also be used in Ex-group IIA hazardous areas and at high ambient temperatures. The material of the earthing tongue is so flexible that injuries are unlikely. The earthing tongue can also be used for ↑ backspraying and thus for reducing charging on insulated, charged conductive objects ( ↑ St. Elmo ’ s fire). [Schulze, H. (1972)] Easily ignited mixture, ↑ most easily ignited mixture Ebert tube. A device developed in 1901 to determine the ↑ charge density in gaseous media. The gas under test is sucked through an electrode tube connected to one pole of a DC high-voltage source U. The voltage must be high enough to attract all gas ions to the concentric collector. The resulting current is fed back from the collector to the other pole of the high voltage source via a ↑ pico-ammeter. The charge density can be calculated from the collector current, the gas flow and the flow cross-section (between the collector and the electrode tube). The Ebert tube was developed into an aspiration condenser in 1909 and is often referred to as an ionometer. ( ↑ ionization) Eddy current. Electric current flowing without electrodes in vortices inside sufficiently large conductors. It is generated by ↑ induction when a conductor is either moved by a constant magnetic field or is subjected to an alternating magnetic field while at rest. Eddy currents can cause significant losses by extracting energy from the magnetic field and converting it to heat. This effect is used, for example, in eddy current brakes. ( ↑ skin effect) Edge field. Marking the ends of homogeneous ↑ fields. Depending on the shape of the electrode end, the field increases or decreases ( ↑ Rogowski profile). This is important, for example, for contact electrodes used for ↑ resistance measurements. The influence of the boundary field causes a widening of the current path and thus a reduction of the measured value. ( ↑ measuring electrodes for solids no. 1) The edge fields can also distort the reading when measuring field strengths. This can be remedied by ↑ homogenization of the electrostatic field according to the Rogowski profile as described in ↑ measurement error. Edge potential (electric). Value of the line integral along a closed path of the electric field strength. The edge potential disappears in the electric field of a stationary point charge (vortex-free electric field). An electric charge moving along a closed path has (Source: [Berger, Ch. (2011)]) Edge potential (electric) 129 <?page no="133"?> reached the potential energy of the initial state after one revolution and thus has not done any work. The edge potential is used to model electric fields, usually according to the formula Δ φ = ρ / ε ( Δ : Laplace operator, ρ : space charge, ε : permittivity), ( ↑ Poisson equation). Edge strip disposal. When processing material webs, edge trimming is often performed, which is usually removed as a continuous strip via injector nozzles ( ↑ venturi principle). At high material speeds and with insulating materials, ↑ brush discharges can occur in rapid succession at the entrance to the earthed nozzle. These continuous electromagnetic pulses can affect electronic components. In the case of non-earthed metallic injector nozzles, these can be charged by ↑ influence and cause ↑ spark discharges. The edge strips should be transported through earthed pipes. Contact of e. g. connected plastic hoses with earthed machine parts can lead to ↑ propagating brush discharges in the hose. Edge zone fixation. A molten film usually begins to shrink as it cools, so the edge of the film is often fixed to the cooling roller with a ↑ charging electrode (see arrow). ( ↑ cast process, ↑ useful application), [SE Section 8.2] Edison, Thomas Alva (1847 - 1931). American inventor: carbon grain microphone, phonograph, incandescent lamp, motion picture camera, etc. Edison effect. A phenomenon observed by T. A. ↑ Edison in carbon incandescent lamps in which electrons from a filament escape into the surrounding ↑ vacuum. The importance of this thermal ↑ electron emission was recognized by the German physicist Arthur Wehnelt in 1903 and has since been used in ↑ electron tubes and ↑ electron-beam tubes. EDV, short for German: Elektronische Datenverarbeitung (electronic data processing). Electrostatic discharges ( ↑ ESD) can damage the electronic components used in EDV equipment. Therefore, extensive protective measures are mandatory in the manufacture and use of IT equipment. [IEC/ TR 61340-1] Effect (triboelectric), ↑ charging (equipment-related) Edge strip disposal 130 <?page no="134"?> EFM, short for electrostatic field meter or E-field meter ( ↑ influence electrostatic field meter) ● EFM with influence principle. The principle of an electrostatic-mechanical “ parametric amplifier ” developed by H. F. C. ↑ Schwenkhagen in 1930 is still used today almost unchanged. Behind a conductive, rotating, earthed impeller (measuring chopper) is an influenceelectrode (sensor plate) connected to the input of an amplifier. The field lines of the electric field to be measured (e. g. from the plate (or object) in front of the measuring chopper) end either at the impeller itself or at the influence-electrode, depending on the position of the impeller. This causes an AC voltage drop proportional to the field strength at the input resistance R of the amplifier, which allows a field strength determination after rectification. For charge sign detection, a light beam is periodically interrupted by a reference chopper (2nd impeller) mounted on the motor shaft and a reference signal of the same frequency as the input is generated, amplified, and fed to a phase discriminator. Without extracting energy from the field itself, the field display is absolutely linear and calibrated to ± kV/ m. EFMs operating on this principle have sensitivities from about 1 V/ cm to 2 MV/ m (with aperture, influence electrostatic field meter). For rotating field modulators, the diameter of the measuring head ranges from about 20 to 100 mm. In this EFM, the measuring range can be extended by a factor of 10 to 2 MV/ m with a measuring aperture. Other EFMs based on the influence principle use piezo tuning forks instead of the rotating measuring chopper (measuring head diameter up to 1 mm, ↑ piezoelectric sensor). Measurement range typically up to ±50 kV. EFM 131 <?page no="135"?> (Source: Principle of Kasuga Denki KSD System) Depending on the measurement setup, high accuracy can be achieved. There is no energy extraction from the measured surface. ● EFM with potential matching. A self-compensating comparator with zero indicator supplies the measuring head with exactly the voltage until the field strength between the charged object and the measuring probe is zero. The distance to the target becomes irrelevant. Since there is no field between the target and the probe, there can be no measurement error due to field distortion. It should be noted that the field modulator can accept a correspondingly high voltage to earth (usually up to 20 kV, touch protection required! ). Due to the adaptation of the probe potential to the measured object, a “ zero adjustment ” must be performed after each measurement, otherwise the previously measured value could be integrated into the next measurement result. The arrangement shown in the figure allows an indication of the average potential, at least for the area covered by the field modulator. ● EFM with ionization principle. It is the reverse of an ↑ ionization chamber. The space between the surface to be measured and the probe is ionized by a weak radioactive preparation with a long half-life (Radium 226 , α -emitter). A (small) current flows from the EFM 132 <?page no="136"?> charged surface to the probe according to the prevailing field strength, which is amplified and displayed. Calibration is done in the field strength unit [kV/ m]. Advantage: The probe can be made explosion proof. Disadvantage: Influence on the object to be measured, since the surface to be measured is discharged by the ionization of the radioactive preparation ( ↑ ion source). [Masuda, S. (1973)] This measuring principle, which is also suitable for the detection of field strength changes at higher frequencies, is no longer used today. ● Contacting measuring device for charges, also known as “ contact voltmeter ” , preferably used in the ESD area to measure possible charges on electronic components in a field-free manner. This type of voltmeter has a very high input resistance of > 10 14 Ω , combined with an extremely low input capacitance of < 10 -14 F. This measuring device must be earthed after each measurement (zero reset). EFT, short for electrical fast transients, ↑ transient EFT recorder. For recording non-periodic high-speed of ↑ transients. EGB, short for German: elektrostatisch gefährdetes Bauelement (electrostatically sensitive component (ESD)). This includes electronic components, integrated circuits or assemblies that can be damaged by electrostatic fields or electrostatic discharges that occur during routine handling, testing and transportation. EHD, short for ↑ electro hydrodynamics Elastomer. Dimensionally stable but elastically deformable ↑ plastic ( ↑ caoutchouc, ↑ NBR, ↑ EPDM). Electret. First developed by the Swedish scientist H. Wilke in 1771 ( “ electrophorus perpetuus ” ). A ↑ dielectric polarized over its entire volume, which can exhibit an unchanging dipole moment over a long period of time (electrical counterpart to the permanent magnet, ↑ ferroelectric). Natural electrets are inter alia quartz and tourmaline. Electrets can be produced artificially, e. g. by melting a suitable dielectric (e. g. ↑ carnauba wax) and then slowly solidifying it again in a strong electric field (thermoelectret). This Electret 133 <?page no="137"?> process principle can be applied to some thermopolymers, such as polytetrafluoroethylene (PTFE), polypropylene (PP), polyvinylidene fluoride (PVDF), polystyrene (PS), polyethylene terephthalate (PET). For this purpose, the polymers must be heated in an electric field up to the ↑ glass transition temperature and during the subsequent cooling, polarized molecular chain segments “ freeze ” during the transition to the solidified state. This can be improved by adding fillers with high permittivity ’ s. Electrets are used as sound transducers, ↑ filter materials, etc. {Appendix A}, [SE Section 2.15] The metrological verification is performed with a special setup using capacitive measurement. [Sessler, G. M. et al. (1999)], ( ↑ influence field measurement probe) Electret microphone, ↑ microphone Electric circuit. With at least one power source and at least one load (device or component). Cables connect the power source to the consumer. ● System circuit. System of conductors and loads, e. g. all electrical operating resources of a system that are supplied from the same infeed point and protected by the same overcurrent protection device. Depending on how the loads are connected, a circuit may consist of a ↑ outer conductor (L1, L2, L3) and the ↑ neutral conductor (N) or of several or all outer conductors with or without a line to neutral conductors. However, if, for example, three two-pole loads (between L1 and N, L2 and N, and L3 and N) are Electret microphone 134 <?page no="138"?> connected in a three-phase system and each of these connections is individually fused, there are three separate circuits. ● Auxiliary circuit for additional functions, e. g. control, signal, and measurement circuitry. (IEC 60050-441) ● Intrinsically safe circuit. A circuit is intrinsically safe if no sparks or thermal effects occur that could lead to ignition of a specific Ex-atmosphere. Test conditions are defined that include normal operation and certain fault conditions. The intrinsic safety of a circuit is tested using a spark tester standardized in [IEC 60079-11], which is installed in the circuit at the point where the spark is to be simulated instead of, for example, the intended switch. The main components of such a spark tester are an explosion vessel with a volume of 0.25 l, in which a rotating contact arrangement is located to generate opening and closing sparks. The test gas used is the most ignitable mixture of the flammable substance in air that can be expected in the intended application of the circuit ( ↑ explosive test mixture). Intrinsically safe circuits must not be earthed to prevent potential carryover in the event of a fault. If earthing is required for electrostatic reasons, it must be done via a protective resistor > 200 k Ω . (IEC 60050-426) Electric curtain. System for transporting electrostatically charged particles by means of a moving electric field ( ↑ three-phase current). [Masuda, S. (1973)] In principle, it is an electrostatic counterpart to the ↑ maglev train. Charged particles are accelerated and carried along by the wave of the moving field. A large number of cylindrical electrodes are arranged in parallel under an insulating plate. They are continuously connected in groups of three to a three-phase high-voltage system L1 / L2 / L3. The travelling electric field emanating from these electrodes acts on the particles above through the insulating plate ( ↑ DBD actuator). Electric field, ↑ field Electric flux density. Derived ↑ SI unit ~ D [As/ m 2 ], vectorial quantity characterizing an electric ↑ field in addition to the electric ↑ field strength. Electrostatic charges in isotropic media are the source of the electric field strength ~ E and the rectified electric flux density ~ D. The electric flux density figuratively describes the “ density of field lines ” with relation to a surface ~ D ¼ " 0 ~ E þ ~ P and for the vacuum applies ~ D ¼ " ~ E ¼ " r " 0 ~ E ( ↑ displacement current, ↑ permittivity). Antiquated terms are: Electrical excitation, dielectric displacement or displacement density. Electric induction, ↑ influence Electric induction 135 <?page no="139"?> Electric shock must be classified as follows: ● Electric shock is a pathophysiological effect caused by an electric current passing through the body of a person or animal. If the muscle contraction at the point of contact makes it impossible to disengage, serious damage can occur as the current continues to flow. This electric shock from the power grid is life-threatening. The shock hazard limits are specified in [BS IEC 60479-2] ( ↑ danger of electric shock). ● Electrostatic shock. In contrast to electric shock, this is a single, brief effect on a living being as a result of electrostatic discharge. According to general opinion, it is not a direct health hazard (exception: ↑ propagating brush and ↑ super brush discharge), but secondary accidents due to muscle contraction and/ or startle reaction must always be expected ( ↑ perceptibility, ↑ implant, ↑ personal hazard). [TRGS 727 Annex D] Electric strength (breakdown strength). A measure of the electrical strength of liquid and solid insulators. It is the maximum field strength that can exist in the material without voltage breakdown ( ↑ spark, ↑ arc). It can only be determined if there is a uniform electric field between the electrode centers that decreases continuously toward the electrode edges ( ↑ Rogowski profile). The electric strength is given in [kV/ mm] for solids, [kV/ 25 mm] for liquids and [MV/ m] for gases. [IEC 60243-1] Electrical discharge machining (EDM) (also spark erosion). An undesirable phenomenon in the field of electrostatics caused by thermal material erosion on conductive materials. It can be caused by ↑ spark discharge as a result of high electrostatic charge, e. g. during electric breakdown of insulating lubricating layers in rolling bearings ( ↑ gas discharge mark, ↑ composite). Electrical disturbance. Must be considered when setting up the measuring setup. At very low (e. g. < 1 pA) or very high (e. g. > 100 G Ω ) values, they can destabilize the measured values by ↑ influence. Electrical disturbance can generally be prevented by providing a field-free space for shielding the measuring circuit ( ↑ Faraday cage). The earthing of the equipment and the shielding should be combined in one point of the measuring circuit, which is then connected to earth with low impedance. Special measuring cables should be used ( ↑ cable charging, ↑ measurement error). Electrical double layer, ↑ charge double layer Electrical equipment, ↑ operating resources Electrical installation of buildings. All associated electrical ↑ operating resources for a specific purpose and with coordinated parameters ( ↑ ignition source). [IEC 60050] Electrical overstress. An operating condition in which the maximum allowable component values (absolute maximum ratings) are exceeded, resulting in damage to the components affected. Electrical separation. A system-independent protective measure in which equipment is safely separated from the power supply and not earthed. Electricity. Thales of Miletus, 590 BC, is credited with the first observation of “ electric ” effects on amber ( ↑ electron). Since W. ↑ Gilbert, a general term for all phenomena Electric shock 136 <?page no="140"?> associated with stationary or moving electric ↑ charges and the resulting electric and magnetic ↑ fields. Both negative and positive forms of electricity are bound to elementary particles as carriers ( ↑ elementary charge). Negatively charged objects have an excess of electrons, while positively charged objects have a deficiency of electrons ( ↑ charging, ↑ current). The charge is equalized by the flow of electrons from the negatively charged object to the positively charged object ( ↑ Lichtenberg), e. g. via a ↑ conductor. In technical terms, however, the current is defined as the flow from the positive pole to the negative pole. ● Static electricity, ↑ electrostatic Electrification machine. A device for generating high electric voltage, used for demonstration purposes and now of historical interest only. Three principles were used for this purpose, namely the ↑ steam electrification machine, the ↑ influence electrifying machine, and the ↑ friction electrification machine. Electrization. Refers to the ↑ polarization of a ↑ dielectric. Electro adhesion. First described in 1923 as the “ Johnson-Rahbek effect ” . Electro adhesion uses the electrostatic fields specifically arranged by voltage and sign differences, e. g. for manipulating objects (e. g. in robotics). The part to be manipulated (regardless of whether it is an insulator or an electrical conductor) is exposed to an electrostatic field formed by alternating positive and negative electrode lines or opposite charges by using flexible fingers. When the part is in close proximity to or in contact with the field-generating electrode, localized charges are generated within the part that are opposite to the charges on the plate or the fingers of a gripper. Since opposite charges attract each other ( ↑ Coulomb force), an adhesive force is created between the partners, which immediately dissipate when turned off. ( ↑ useful application), [Gou, J. et al. (2020)], [Cacucciolo, V. et al. (2022)] Electro aerosol. ↑ Aerosol whose particles are charged, e. g. by corona charging ( ↑ useful application), and transported in a targeted manner by electric field forces (e. g. ↑ separation of substances, ↑ coating). Electro filter, ↑ separation of substances Electro fluid dynamics. Encompasses all processes in which electrical or electrostatic phenomena and flows are coupled independently of the carrier fluid (liquid or gas). Two classes can be distinguished: - Electrical phenomena generate, change or control flows (Examples: ↑ electro-osmosis, ↑ electrophoresis, ↑ ion propulsion system, plasma actuators, ↑ separation of substances, etc.). Electro fluid dynamics 137 <?page no="141"?> - Flows generate electrical or electrostatic phenomena, where under certain conditions ignition hazards may occur due to electrostatic charging. (Examples: triboelectric ↑ charging at the solid/ liquid, liquid/ liquid, liquid/ gas (e. g. air) boundary layers or targeted use of electrostatic charging when handling liquids or at laminar ↑ air boundary layers. ( ↑ polarity inversion) Electro hydrodynamics. Describes flow processes in insulating liquids through brought in charge carriers that are exposed to an electric field and thus moved by ↑ Coulomb force. ( ↑ electrophoresis, ↑ electro kinesis, ↑ electro-osmosis) Electro kinesis (Greek: kinesis, “ movement ” ) (electrokinetic phenomenon). Generic term for processes in which electrical double layers at the contact surface of different substances or phases (as a result of a ↑ contact potential) lead to movement processes in the presence of an electric field ( ↑ electro-osmosis, ↑ electrophoresis, ↑ cataphoresis). Electro lens, optical ↑ liquid lens Electro-osmosis (Greek: osmos, “ the pushing ” ). Movement of charged particles of a liquid through a diaphragm under the influence of an electric field. It is used, for example, in the drying of porous substances. ( ↑ electrophoresis) Electro smog. Colloquial term for ↑ Electromagnetic Compatibility of the Environment, general term for electromagnetic fields that are generated by technical equipment, e. g. by the electrical power supply or the use of electrical energy in the home and which are said to have harmful effects on health. ( ↑ skin effect) Electroactive polymer. Described by W. C. Roentgen in 1880. He had discovered that rubber bands suspended on one side and tensioned by a weight were stretched by electrostatic charge, which could be reversed by discharging. Electroactive polymers (EAP, sometimes called “ artificial muscles ” ) are ↑ polymers that change their shape when an electric voltage is applied, e. g. via conductive outer layers. A distinction is made between ionic electroactive polymers, in which the effect is based on ion transport within conductive polymers, and electronic (dielectric) electroactive polymers, in which charge transport causes electro strictive processes ( ↑ electrostriction). Recent research has been in the area of muscle replication for robotic systems. The advantages of electroactive polymers over ↑ piezo mechanics are high elongation (up to about 4 times), free formability, and low density. [Buchner, T. J. K. et al. (2024)] Electrode. Conductive partner in an electrostatic discharge system. The term is also used for a variety of devices: ↑ measuring electrode, ↑ ionizer, ↑ charging electrode, ↑ welding electrode. Electrodeless discharge. ↑ Gas discharge, induced under reduced pressure ( ≈ 10 Torr ≙ 1.333 kPa) in an insulating discharge vessel (e. g. glass or plasma sphere) when the gas is placed in a high-frequency electromagnetic field. Free charge carriers in the discharge vessel are accelerated to such an extent that gas discharge lights are produced as a result of impact ↑ ionization ( ↑ Kirlian photography). [SE Section 5.6] Electro hydrodynamics 138 <?page no="142"?> Electrodynamics. Describes all electromagnetic phenomena and is the theory of electricity. The term is also used to distinguish between useful (dynamic) electricity and static electricity. Electroluminescence. Excitation of ↑ luminescence by electrical ↑ gas discharges or the application of an electric field. A technical variant is the luminescent diode ( ↑ light emitting diode), in which a doped ↑ diode emits continuous visible radiation when a ↑ PN junction is driven in the forward direction by recombination of charge carriers. Electrolysis. A method of forcing chemical reactions that do not occur spontaneously for energy reasons by supplying electrical energy. It takes place in an electrolytic cell equipped with two electrodes, where reduction takes place at the negative pole ( ↑ cathode) and oxidation at the positive pole ( ↑ anode). Both processes occur simultaneously provided that the space between the electrodes is filled with an ↑ electrolyte solution. Electrolysis is used to obtain elementary gases (e. g. hydrogen) and very pure metals ( ↑ Faraday constant) as well as for ↑ electroplating. When measuring the conductivity ( ↑ resistance measurement) of liquids, possible electrolysis processes must be considered. ( ↑ measurement error, ↑ iontophoresis) Electrolyte. Any substance in which electrolytic ↑ dissociation takes place, and which can therefore transport electric charges in its solution, melt, or in a gel. Two types of ions must always be present: Anions (-) and Cations (+). Electrolytic capacitor, ↑ capacitor Electromagnetic Compatibility (EMC). It is defined as the ability of a device, system or installation to function properly in its intended electromagnetic environment without causing electromagnetic disturbances that would be intolerable for the devices, systems or installations present in that environment. The EU Directive [EU 2014/ 30], deals with interference caused to equipment by electromagnetic fields and requires that: - The generation of electromagnetic disturbance by a device must be limited to such an extent that the intended operation of other devices is possible, and - devices must be sufficiently resistant to external interference so that they can be operated as intended ( ↑ shielding). The test and measurement procedures for EMC are specified in [IEC 61000-4-1]. EMC law must also be applied to devices in which electrostatic ↑ gas discharges occur, since these also cause electromagnetic interference radiation (coupling via electromagnetic fields). Electrostatic charges can also cause discharge currents to flow directly into a device or component (e. g. via a charged person touching a contact). For this reason, the ↑ ESD defines further electrostatic protection measures in addition to the EMC Directive. The term EMC refers only to the effect of technical devices on each other [IEC 61000-3-3]. The biological effect of electromagnetic fields, e. g. on humans ( ↑ electro smog), is dealt with in EMCE ( ↑ Electromagnetic Compatibility of the Environment) [IEC 61000-4-2]. [26. BImSchV] Electromagnetic Compatibility Act (German: Elektromagnetische-Verträglichkeit-Gesetz [EMVG]). Is the German implementation of the European EMC Directive and was Electromagnetic Compatibility Act 139 <?page no="143"?> amended in 2017. The requirements of the EMVG partly exceed those of the EMC Directive. [EU 2014/ 30] Electromagnetic Compatibility of the Environment (EMCE). The 26th BImSchV (08/ 2013) ordinance to the Federal Immission Control Act [BImSchG] on electromagnetic fields; applies to the installation and operation of low-frequency systems (frequency 1 Hz to 9 kHz, voltage ≥ 1 kV) and high-frequency systems (frequency 9 kHz to 300 GHz, power > 10 W). The EMCE is limited to the EMC of technical systems, since no binding statements can be made about the effects of electromagnetic fields on biological systems ( ↑ electro smog). Cardiac pacemakers and other electronic ↑ implants (cerebral shunt, brain stimulator (Parkinson ’ s disease), tongue stimulator (sleep apnea), etc.) are externally adjusted by electromagnetic pulses and could therefore be disturbed. Electromagnetic field (EMF), ↑ electromagnetic radiation Electromagnetic radiation / electromagnetic wave. Have the same meaning and describe the propagation of a time-varying radiation field in space. They cannot be associated with electromagnetic ↑ fields. In this context, “ wave ” symbolizes propagation and “ radiation ” symbolizes energy transport. However, a further distinction is almost universally made in relation to wavelength λ [m] and frequency f [1/ s]: both are obligatory via the speed of light c (~ 3 × 10 8 m/ s): λ = c / f. For frequencies below about 500 MHz, the term waves are usually used; for higher frequencies, the term radiation is preferred. The spectrum covers the enormous range of about 10 2 to 10 23 Hz. (Source: H. Frank, Jailbird and Phrood) Electromagnetic radiation and electromagnetic waves are mutual couplings of electric and magnetic fields, where the E and M fields are perpendicular to each other. {Appendix M.1.4} Electromagnetic Compatibility of the Environment 140 <?page no="144"?> A temporal change in the electric field is always associated with a spatial change in the magnetic field and vice versa. For example, periodic (sinusoidal) sequences result in a “ radio wave ” , whereas aperiodic sequences result in a uniformly propagating interference pulse ( ↑ gas discharge). These electromagnetic signals are emitted and recorded via corresponding ↑ antennas. ( ↑ spark detection device). Their generation is explained by ↑ Maxwell ’ s equations. According to quantum dynamics, they have both a particle character (photons) and a wave character. They can propagate in ↑ vacuum as well as in media with the corresponding velocity. If there is a fixed phase relationship between the magnetic and electric field components with respect to their spatial and temporal radiation, they are called coherent (Latin: cohaerere, “ to hang together ” ) (e. g. laser radiation). Electrometer. Originally an electrostatic (continuous current less) measuring device for voltages and charges based on the mechanical attraction or repulsion forces between charges ( ↑ Coulomb force) (see figure as an example). These electrometers were preferably used for current less high-voltage measurements ( ↑ static voltmeter), so that versions with a voltage measuring range of 30 - 300 V ( ↑ Kirchhoff ’ s balance) were already available for laboratory use in the last century. Today ’ s electronic electrometers use highly sensitive semiconductor devices, such as ↑ metal oxide FETs. They measure the voltage range from μ V to kV with current consumption in the fA-range. Compared to static voltmeters, the latter can also display DC voltages with correct polarity in the mV-range. Electronic electrometers require an external power supply ( ↑ EFM). Electromotive force (EMF). Historical term for the force that separates electric charges to form an electric voltage, the ↑ open circuit voltage (measure of the EMF). (now Cell source voltage), (IEC 60050, IEV ref 114-03-11) Electron (Greek, “ amber ” ). Elementary particle with a negative electrical ↑ elementary charge of 1.602176634 × 10 − 19 C and a rest mass of m = 9.1 × 10 -28 g. They surround the positively charged nucleus of the ↑ atom and determine its chemical behavior ( ↑ valence electron). The number of electrons in an electrically neutral atom describes its atomic number. Electrons can move freely in the lattice structure of metals, which is the reason for their good thermal and electrical conductivity ( ↑ Wiedemann-Franz-Lorenz law). The conduction electrons available in a metal can be regarded as a confined ↑ electron gas. Note: The “ negative ” electron is sometimes called a negatron, so the term electron is also used as a generic term for ↑ positron and negatron. ( ↑ exo-electron, ↑ luminescent electron, ↑ trap electron) Electron avalanche. Multiplication of free electrons in a ↑ gas discharge. It occurs when more than one ↑ secondary electron and/ or more electron-ion pairs are formed by each accelerated electron. Electron beam. Free electrons propagating radially in a vacuum ( ↑ beta radiation), or the electrons emitted from the cathode of an ↑ electron-beam tube after thermal or electrical Electron beam 141 <?page no="145"?> excitation following their bundling by electric or magnetic fields (antiquated: ↑ cathode ray). Electron-beam tube. ↑ Display of ↑ oscilloscopes and radar devices or, more rarely, of computers and television receivers, which have already been replaced in many areas by ↑ liquid crystal displays resp. LEDs or OLEDs. The ↑ electron beam emanating from a hot cathode is controlled by a deflection system (electrical resp. magnetic) so that it covers the entire surface of a phosphor screen. The latter represents the front wall of the electronbeam tube and is coated on the inside with luminescent substances in which the kinetic energy of the electrons is converted into light pulses ( ↑ electron collision glow). Electron-beam tubes as screens have a positive electrode ( ↑ anode) on the inside, whose electric field also reaches the viewer through the screen. The resulting positive charge is perceived as disturbing when touched and is also responsible for increased dust accumulation from the surrounding air. This can be remedied by so-called “ screen filters ” , which are also intended to prevent the biological effects of electric fields ( ↑ electro smog). (Electron-beam tubes are now an extinct species.) Electron collision. Impact of an energetic electron on another atomic structure ( ↑ atom, ↑ molecule). In an elastic electron collision, the kinetic energy is conserved, and the electron merely changes direction. In an inelastic electron collision, part of the kinetic energy is used to ionize the hit particle (collision ↑ ionization). Electron collision glow. Luminous phenomenon after excitation of atoms by ↑ electron collisions whose kinetic energy is at least equal to the excitation energy of the atom. After about 10 ns, the excited atom returns to its ground state ( ↑ gas discharge) with ↑ emission of one or more light quanta ( ↑ emission spectrum). Electron conduction. Characterizes the charge transport by free (e. g. in copper 10 20 / mm 3 ) or only weakly bound electrons, whose migration speed of about 4 mm/ s is relatively low (distinction from ↑ ionic conduction). Electron conduction occurs in metals and in the ↑ conduction band of semiconductors ( ↑ band model, ↑ doping, ↑ defect electron). Electron conductor. ↑ Conductor 1st order, e. g. all ↑ metals ( ↑ proton conduction, ↑ ionic conduction). Electron emission (thermal). Electrons escaping from a heated metal surface ( ↑ Edison effect), whose kinetic energy increases by heating to such an extent that more and more of them are able to overcome the potential threshold at the metal surface and leave the ↑ crystal lattice ( ↑ electron emission energy, ↑ Galvani voltage). Electron emission energy (also (electron) work function). Energy that must be expended to move an electron from the surface of a material to the outside (e. g. exit from the cathode of a ↑ cathode ray tube into the vacuum). It can be provided by a temperature increase (thermal ↑ electron emission), mechanical impact (impact ↑ ionization), radiation ( ↑ photoelectric effect), and others. In the case of electrostatic charging, the electron emission energy determines the sign of the charge. If a material has a low electron emission energy, it is called a ↑ donor (release of electrons - positive). Materials with a high electron emission energy are called ↑ acceptors (accepting electrons - Electron-beam tube 142 <?page no="146"?> negative). ( ↑ charge double layer, ↑ Lewis ’ s acid-base concept, ↑ Brønsted-Lowry definition), [SE Section 2.4] Electron exchange, ↑ charging, ↑ charge double layer Electron gas. Not the correct term, but frequently used because of its clarity, for the entirety of the electrons freely available in ↑ metals. These are the electrons that are only weakly bound to the atomic nucleus ( ↑ conduction or ↑ valence band, ↑ band model), which can move freely through the entire volume of the metal. As a model, the electron gas can flow through the metallic conductor like an ordinary gas under the influence of a pressure difference. Electron shell. Represents the totality of the electrons that surround the nucleus of an atom and together with it form the ↑ atom. Electron theory. Term for all theories that attribute physical properties to the effect of electrons or corresponding charge carriers ( ↑ band model). Electron tube. Once the preferred electronic component, is now almost completely replaced by ↑ semiconductors. Electron tubes are highly evacuated vessels in which the ↑ electrons emitted by a glowing cathode ( ↑ Edison effect) migrate to an ↑ anode. Since a current can only flow from the ↑ cathode to the anode, an electron tube of this type ( ↑ diode) can be used to rectify an alternating voltage. The strength of this electron current to the anode can be influenced by electric voltages at a control electrode (control grid of a triode). In this way, small changes in voltage across the control grid cause large changes in anode current with almost no power. Due to their high input resistance, electron tubes were used for a long time for electronic ↑ electrometers but have now been completely replaced by ↑ metal oxide FETs. Many multigrid electron tubes are known tetrode, pentode, hexode, heptode, octode, enneode (nonode) and “ magic eye ” . They can also be used to modulate high-frequency signals, such as amplitude modulation (AM) and frequency modulation (FM). Electronvolt. Common unit of energy [eV] in atomic and nuclear physics. An electronvolt is the kinetic energy gained by an electron or other singly charged particle in a vacuum when passing through a voltage difference of 1 V. It corresponds to an energy of 1.6 × 10 -19 J. Electrophoresis (Greek: phoreus, “ carrier ” ). Migration of electrically charged colloidal or suspended particles in an electric field ( ↑ electro kinesis, ↑ cataphoresis, ↑ iontophoresis as a medical procedure). Electrophoresis is used as a method of physical analysis (capillary electrophoresis). Electrophorus (Greek: elektron, “ amber ” , pherein, “ to carry ” ). First described by J. C. ↑ Wilcke and further developed by A. ↑ Volta, it is still used today to illustrate the phenomenon of separation charging. The electrophorus consists of “… a round, thin (about 2 mm), very smooth cake of resinous electrical materia resting on an equally large, smooth disc of metal … . Furthermore, in the middle of the cake there is a highly conductive … lid that fits tightly to the cake. ” [Cavallo, T. (1785)] Electrophorus 143 <?page no="147"?> G.Ch. ↑ Lichtenberg owned an electrophorus with a diameter of approx. 2 m, the lid of which had to be lifted with a pulley, with which he could generate sparks of up to 35 cm. Electrophotography, ↑ xerography Electroplating. Makes it possible to create metal coatings on conductive or surfaceconductive insulators ( ↑ chemo galvanic metallization). The object to be coated is placed as the ↑ cathode in an electroplating bath whose ↑ electrolyte contains the dissolved salt of the metal to be coated (e. g. copper sulfate solution for copper plating). The ↑ anode consists of the metal to be coated, which is continuously added to the electrolyte. Electrorheological fluid (ERF). A product based on an anhydrous dispersion of polymer particles in, for example, silicone oil. Schematic illustration shows that applying an electric field to an ERF polarizes the particles. They align in a chain, increasing the dynamic viscosity within milliseconds. When the electric field is removed, the original viscosity is restored. These viscosity changes can be used to control power transmission in hydraulic systems, e. g. in electrorheological clutches, vibration dampers, in data processing as a “ joystick with feeling ” for cursor positioning (help for the visually impaired), torque converters, etc. [DIN 51480-1]. In addition, so-called switchable films, in which polymer-dispersed liquid crystals (PDLC) become transparent when a voltage is applied, are a widespread application. ( ↑ Kerr effect) Electroscope. A device for the powerless detection of electric charges ( ↑ thread electrometer), whereby these are fed to a metal rod with a rotating pointer placed inside an earthed circular ring. The charge of the same name causes the pointer to spread out ( ↑ Coulomb ’ s law) until its restoring moment due to gravity is equal to the electrostatic force. Electrospray ionization. A process in which an analytical solution is dissolved into positively or negatively charged ions (e. g. aerosols of 10 μ m) through a capillary connected to a counter electrode at high voltage. As the solvent evaporates, the droplets become smaller and ↑ atomization occurs ( ↑ Rayleigh limit, ↑ Taylor Cone). This is the principle used in mass spectrometry. Electrostatic. The four fundamental forces of physics (forces of nature) are: - Gravity - Electromagnetic interaction Electrophotography 144 <?page no="148"?> - Weak interaction (weak nuclear force) - Strong interaction (strong nuclear force) Electromagnetic interaction is divided into magnetostatics and electrostatics, which is the teaching of static electric charges and the forces they exert on their surroundings. They manifest themselves in attractive forces for unequal charges and repulsive forces for equal charges ( ↑ Coulomb ’ s law). This leads to the existence of two different electric charges: positive and negative. They are assigned an atomic structure ( ↑ elementary charge): Negative charge has an excess of ↑ electrons ( ↑ donor), positive charge represents a shortage of electrons ( ↑ defect electrons, ↑ acceptor). The charge carriers (electrons or ↑ ions) are stationary in ↑ nonconductors and mobile in ↑ conductors. In IEC 60050-121 the term “ electrostatics ” is defined as: Set of phenomena associated with electrostatic fields in the absence of electric current. ● System comparison with electrical engineering. Two fields of knowledge with different approaches have emerged from a common origin. Essentially, the only units they have in common are current, voltage, and resistance, albeit with considerable differences in their dimensions. As a result, fundamentally different measurement methods must be used, and completely different instruments are required to perform the same measurement tasks in both fields. The difference between the two fields can be illustrated by the fact that electrostatics is a current system; the electrostatic “ generators ” produce currents in the dimension of micro-amperes, which - depending on the level of the load resistance - result in voltages up to the kV-range. Electrical engineering, on the other hand, is a voltage system in which fixed mains voltages are assumed for all applications (e. g. household: 230 V, automobile: 12 V). Electrostatic: Current system (typical values) 1 μ A Voltage >> 100 kV “ Fuse limit ” (maximum field strength in the atmosphere) 3 MV/ m Earth leakage resistance (measurement voltage < 100 V) 100 M Ω Insulation resistance (e. g. for measurements) > 100 T Ω Electrical engineering: Voltage system (typical values) 230 V Current 1 A “ Fuse rating ” (maximum line load) 10 A Earth fault resistance (touch voltage < 50 V) 10 Ω Insulation resistance (2 k Ω / V) according to [IEC 60204-1] ≥ 500 k Ω Electrostatic attraction (ESA). Unequally electrically charged bodies attract each other ( ↑ Distance Law 3, ↑ Coulomb ’ s law). Electrostatic charging, ↑ charging Electrostatic discharge ( ↑ ESD). In principle a reversal of the term electrostatic ↑ charging, is generally used for ↑ gas discharge. ( ↑ discharge) Electrostatic disturbance, ↑ measurement error Electrostatic disturbance 145 <?page no="149"?> Electrostatic field, ↑ field Electrostatic field meter, short ↑ EFM or E-field meter, ↑ influence electrostatic field meter Electrostatic generator. Convert mechanical energy into electrical energy ( ↑ charging). Although it has no significance in terms of electrical power supply, it is still used today in specific cases to generate high voltages at low currents. In historical order, these are ↑ electrophorus, ↑ friction electrification machine, ↑ steam electrification machine, ↑ influence electrifying machine, ↑ Kelvin generator, ↑ Van de Graaff generator and ↑ pelletron, although only the last two are still of technical importance. Today, high voltage is generated almost exclusively by transformers and ↑ high-voltage cascades with downstream rectifiers ( ↑ high-voltage generators). Electrostatic hazard. The ↑ hazards or disruptions caused by electrostatic ↑ charges, and particularly the resulting ↑ gas discharges, can be divided into the following groups: - Damage to or destruction of ↑ ESDS (electrostatic sensitive devices) - Ignition of ↑ combustible substances ( ↑ ignitability of gas discharges) - Pre-exposure of photographic emulsions (e. g. X-ray film) - Danger to persons (extremely rare, ↑ workplace ordinance, ↑ implant) Electrostatic interaction. Based on molecular charge differences, whereby a distinction is made depending on their level: - Ionic bonds are the strongest electrostatic interactions with long ranges. - Hydrogen bonds are weaker with a short range. ( ↑ Van der Waals forces) Electrostatic loudspeaker, ↑ loudspeaker Electrostatic motor, ↑ motor Electrostatic print assist (ESA). Is used in the ↑ gravure printing process: An electric potential of approximately 500 V is applied between the earthed print cylinder and the ESA impression roller, which presses on the web. For example, with a substrate thickness of 50 μ m, an electric field of 10 MV/ m is generated {Appendix M.5}. The resulting electric force deforms the membrane of the ink surface in the cell so that the ink is virtually “ pulled ” onto the web. The geometric conditions influence the ink transfer ( ↑ donut dot). Depending on the type of ESA, the steel core of the impression roller has a semi-conductive rubber coating with a certain volume resistivity to ensure reliable printing. ( ↑ charging electrode, ↑ ionizer in processing machines) Electrostatic field 146 <?page no="150"?> ENULEC is a family-run company with a long tradition of providing customized solutions for electrostatic problems in the fields of printing, coating and converting. As the global market leader for highly effective ESA systems, the company offers a module-based technology concept to achieve the highest quality standards in printing while maintaining high efficiency and maximum safety standards. ENULEC technology fulfills these standards both in traditional manual machine control and state-of-the-art as an autonomous automated control system of the electrostatic charge during the entire production process. ENULEC GmbH Rudolf-Diesel- Str. 7 22946 Trittau GERMANY Telephone: +49 (0) 4154 4229 Fax: +49 (0) 4154 3780 E-mail: info@enulec.com ENULEC is a family run company with a ENULEC GmbH INNOVATIVE INNOVATIVE ELECTROSTATIC ELECTROSTATIC SOLUTIONS SOLUTIONS Global Network www.enulec.com STATE OF THE AR <?page no="152"?> Electrostatic ribbon tacking. In paper or film web processing machines, multiple webs are typically joined at high transport speeds (15 m/ s or more). The laminar ↑ air boundary layers adhering to the webs can cause significant production and quality problems. To prevent this, two charging electrodes of different polarity are placed opposite the superimposed webs (strand) and electric charges are applied to the outer sides of the strand. The force vectors of the electric charges are perpendicular to each other and thus hold the strand together. The material must have sufficiently high resistance. [SE Section 8.2.3] Electrostatic shielding. Protective devices are made of a suitable material, which shields the part to be protected from the penetration and effects of electrostatic fields as an open separating layer or as a closed capsule (e. g. ↑ Faraday cage). The key measure of shielding quality is attenuation (e. g. ↑ HBM). Electrostatic shock, ↑ electric shock Electrostatic space thruster, ↑ ion propulsion system Electrostatic treatment, ↑ separation of substances Electrostatic voltmeter, ↑ static voltmeter Electrostatically conductive. In addition to conductive substances, electrostatically conductive also refers to originally insulating materials that have a correspondingly low resistance due to conductive additives (e. g. carbon black ( ↑ carbon), ↑ metal fibers) or chemical processes (intrinsic ↑ conductivity) have a correspondingly low resistance. Materials are considered electrostatically conductive if they have: - Volume resistivity ρ v ≤ 10 4 Ω m or - Surface resistivity ρ s ≤ 10 5 Ω □ For liquids, a high conductivity κ is defined for the range > 10 000 pS/ m. [TRGS 727], [IEC/ TR 61340-1] Electrostatically dissipative. Refers to materials that will equalize or dissipate electrostatic charges within a defined short period of time and therefore generally will not cause hazards or malfunctions. Materials with electrostatic dissipation capability are those with: - Volume resistivity ρ v between 10 4 and 10 9 Ω m or - Surface resistivity ρ s between 10 5 and 10 12 Ω □ For liquids, an average ↑ conductivity κ is defined for the range > 50 pS/ m < κ ≤ 10 000 pS/ m. [TRGS 727], [IEC/ TR 61340-1] Electrostatically sensitive component, ↑ ESDS (electrostatic sensitive devices) (Source: www.eltex.de) Electrostatically sensitive component 147 <?page no="153"?> Electrostatics museum. Compared to the “ Deutsches Museum ” in Munich, the “ Physikalisches Kabinett ” in Görlitz (Germany) has probably the most solid collection of electrostatic devices from the Baroque period. Since 2002 the collection of A. T. von Gersdorf (1744 - 1807), a friend and colleague of G.Ch. ↑ Lichtenberg, has been processed there. [Herrmann, C. (2016)] Electrostriction (Latin: stringere, “ to string ” ). In solids the elastic change in shape of a ↑ dielectric in an electric field as a result of electric ↑ polarization independent of the field direction ( ↑ piezo effect, ↑ electret). Electrum. A term for a naturally occurring or artificially produced alloy of gold and silver. Element. Energy source in which chemical energy is converted into electrical energy ( ↑ primary cell). If this conversion is reversible, i. e. such an element can be discharged and recharged, it is called an ↑ accumulator. Elementary charge. Smallest positive or negative electric charge detected to date with the size of the electron e = 1.602176634 × 10 - 19 C. All detectable electric charges are integral multiples of the elementary charge ( ↑ Millikan experiment, ↑ natural constant). Elementary dipole, ↑ molecular dipole Eliminator, ↑ ionizer Eloxal layer. An acronym for the electrolytic oxidation of aluminum. ( ↑ anodized layer) Elstatik-Stiftung. German foundation established by Günter and Sylvia Lüttgens in 1999 with the purpose of promoting scientific work on research and teaching in the field of electrostatics and electrical energy efficiency. (www.elstatik.de) EMC, short for ↑ Electromagnetic Compatibility EMCE, short for ↑ Electromagnetic Compatibility of the Environment EMF, short for the rejected term ↑ electromotive force (IEC 60050, IEV ref 114-03-11) EMF, short for electromagnetic field, ↑ electromagnetic radiation EMI, short for electromagnetic interference. Is the effect of single or repeated ↑ gas discharges on the operation of an electronic device. EMI shielding gasket. Flexible, elastic and conductive sealing material that helps eliminate EMC problems at electrical equipment ( ↑ Electromagnetic Compatibility). Emission (Latin: emissio, “ to send out ” , “ to let out ” ). Emission of wave or particle radiation. Spontaneous emission: ↑ electron collision glow. Emission current suction voltage method, ↑ ionizer test Emission energy (also work function). Material property belonging to the properties of a substance ( ↑ electron emission energy). Electrostatics museum 148 <?page no="154"?> Emission spectrum. Spectrum of radiation emitted by excited atoms of a substance ( ↑ electron collision glow). The frequency of the emitted radiation corresponds to the energy level of the electron transition. Substances that are excited to glow as a result of high temperature show a continuous emission spectrum (temperature emitters, e. g. incandescent lamps). Gases excited to glow ( ↑ gas discharge) provide an emission spectrum consisting of individual spectral lines (line or atomic spectrum) or a large number of spectral lines (band or molecular spectrum) that is characteristic of the atoms or molecules of the gas in question ( ↑ gas discharge light). EMP, short for electromagnetic pulse. It is caused by high-energy electrostatic ↑ gas discharges such as ↑ lightning ( ↑ LEMP), nuclear weapon explosions in the upper atmosphere ( ↑ NEMP), etc. EMP propagates as a non-conductive electromagnetic field phenomenon and causes rapidly increasing transient currents in conductive structures (e. g. cables), which can cause damage to connected electrical equipment. Appropriate ↑ transient protection can prevent damage to systems, equipment or components. Employer ’ s Liability Insurance Association (German: Berufsgenossenschaft (BG)). A public-law corporation that is responsible for statutory accident insurance and with the task of preventing work-related accidents (prevention) or, after they have occurred, of supporting the injured person (rehabilitation), his or her relatives or surviving family members (compensation). It issues accident prevention regulations and develops safety regulations (German: TRBS, TRGS, ↑ BetrSichV), compliance with which is monitored by supervisors. It advises employers on occupational health and safety issues. Emulsion (Latin: ex, mulgere, “ to milk ” ). A liquid in which fine particles (diameter 1 - 100 μ m) are dispersed in another liquid that is not miscible with it (e. g. oil in water or cow ’ s milk). If the continuous phase has a low conductivity, high electrostatic charges can occur due to the large contact surfaces. ( ↑ dispersion) There are several ways to separate the fine particles of an emulsion using electric fields: ↑ electro kinesis, ↑ electrophoresis, ↑ cataphoresis. [SE Section 7.3.8], [TRGS 727 Section 4.11(3)] EN, short for European standard. European standards in the field of electrical engineering are referred to as regional standards and also as CENELEC standards according to the ISO/ IEC definition. Enamel (French: èmail, from Middle Latin: smeltum, “ molten glass ” ). Glass flux colored with metal oxides for coating metals and ceramics, that is corrosion resistant and has good stickiness. Enamel coatings (glass-lined) are often used as corrosion protection in chemical reactors. During stirring chargeable ↑ dispersions, ↑ micropores can form in the enamel at the liquid level. They are caused by high liquid charge and the resulting electric ↑ breakdowns (punctures). An earthed metal layer (often silver) can be added to prevent electrostatically induced pores throughout the entire enamel coating ( ↑ gas discharge mark). For conductive liquids in large containers, damage to the enamel is not expected, because with a volume resistivity of 10 12 Ω m and a coating thickness of 2 mm, only a few [m 2 ] of wetted surface are required to achieve a volume resistance of 10 8 Ω . For small vessels, a ↑ Hastelloy ® lead seal is recommended. [TRGS 727 Section 4.4.5], {Appendix D} Enamel 149 <?page no="155"?> Encapsulation. ↑ Type of protection for explosion-protected electrical operating resources. Enclosure. Basic protection of equipment against certain external influences and protection against direct contact. (IEC 60050-151), [Rudnik, S., Pelta, R. (2018)] Energy (Greek: enérgeia, “ acting force ” also “ work ” ). Symbol W with the derived ↑ SI unit [ J], named after J. P. ↑ Joule. In evaluating electrostatic ignition hazards, the energy released in a ↑ spark discharge is compared to the ↑ MIE required to ignite a substance. {Appendix M.6.1.1} Energy level, ↑ electron emission energy, ↑ contact surface Engler, Carl (1842 - 1925). German chemist, developed a method for determining ↑ viscosity, studied firedamp explosions, and elucidated the ignition processes of ↑ hybrid mixtures. Entering confined spaces. When entering or rappelling into containers, silos, manholes or confined spaces, dangerous charges can occur if the person carries out activities there. [TRGS 727 Sections 7.3 and 7.6] EOS, short for electrical overstress. Describes the short-term (< 1 ms) overloading of electronic components that results in immediate or delayed failure and can be reversible or irreversible. EPA, short for electrostatic protected area, ↑ ESD protected area EPDM, short for ethylene-propylene-diene caoutchouc of the M group according to [ISO 1629]. Versatile synthetic caoutchouc with non-polar behavior. EPL, short for ↑ equipment protection level Epoxy resin. A curable liquid or solid polymer consisting of two or more epoxy groups obtained by condensation of epichlorohydrin with aromatic hydroxyl compounds. Uses: casting resin (coating of electronic components), adhesive, coating raw material. Equilibrium moisture content. It is determined after a sufficient storage time in a product or material in relation to the ambient climate. It is particularly important when measuring electrostatic properties ( ↑ hysteresis, ↑ test climate, ↑ sorption isotherm, ↑ water activity). Equipment and Product Safety Act (German: Geräte- und Produktsicherheitsgesetz [GPSG]). Formerly the Equipment Safety Act (German: Gerätesicherheitsgesetz (GSG)) has been replaced by the Product Safety Act (German: Produktsicherheitsgesetz [ ↑ ProdSG]) since 2011/ 12/ 1. Equipment category (equipment grouping). Directive 2014/ 34/ EU ( ↑ ATEX 114) divides equipment into three equipment groups and five other equipment categories. The basic requirements are: Encapsulation 150 <?page no="156"?> Equipment group I Equipment for mines susceptible to firedamp (mine gas/ dust) Category M1 Category M2 Very high level of safety High level of safety Safe even if two independent faults occur Shut down if an explosive atmosphere is present Equipment group II Installations in all other non-mining hazardous areas Category 1 Category 2 Category 3 Very high level of safety High level of safety Normal level of safety Safe even in the event of rare faults and when two independent faults occur Safety even in the event of an expected malfunction and in the event of a fault Safe during normal operation Equipment group III Equipment for all dust hazardous locations except mines IIIA IIIB IIIC Combustible lint (fluff ) Non-conductive dust Conductive dust Zone 20, 21, 22 Zone 20, 21, 22 Zone 20, 21, 22 [IEC 60079-0], {Appendix D} Equipment protection level (EPL). Classification of equipment according to its potential to become an ignition source. For application, equipment is divided into categories that are assigned to ↑ Ex-zones. The code letter “ G ” stands for gas and vapor atmospheres and “ D ” for dust atmospheres. (Source: ↑ Physikalisch-Technische Bundesanstalt) Equipment category EPL Level of protection Zone use Gas and vapor atmospheres 1G Ga Very high 0, 1, 2 2G Gb High 1, 2 3G Gc Normal 2 Dust 1D Da Very high 20, 21, 22 2D Db High 21, 22 3D Dc Normal 22 Mine susceptible to firedamp M1 Ma Very high Continued operation in Ex-atmosphere M2 Mb High Switch off in an Ex-atmosphere [SE Section 1.6], [IEC 60079-0], {Appendix D} Equipment protection level 151 <?page no="157"?> Equipment Safety Act (German: Gerätesicherheitsgesetz (GSG)). Act on technical work equipment was replaced in 2004 by the Equipment and Product Safety Act (German: Geräte- und Produktsicherheitsgesetz (GPSG)), which in turn was replaced on 2011/ 12/ 1 by the Product Safety Act (German: Produktsicherheitsgesetz [ ↑ ProdSG]). Equipotential bonding. Often incorrectly used synonymously with ↑ earthing or grounding; electrical connection that brings bodies, electrical operating resources and external conductive parts to the same or approximately the same potential. [IEC/ TS 60079- 32-1] Equipotential lines. Give a two-dimensional view of the potential curve. The figure shows the equipotential lines (dashed) and the corresponding field lines (solid) between a positively charged cylindrical electrode and an earthed plane surface. Since the electrode and the earthed surface are conductive, they represent the reference potential lines. Depending on the selected resolution, a corresponding number of equipotential lines can be displayed between them. [Fongsuwan, C. et al. (2019)] Equipotential surface (Latin, “ level area ” ). Area of equal (time-constant) potential in a ↑ field that can be represented as a potential gradient. It results from the connection of all points in space that are at the same potential. By definition, field lines are always vertical on an equipotential surface. In the electrostatics, every conductive surface represents an equipotential surface. The equipotential surface of a point-charge are spherical surfaces with the charge as the center of the sphere. The movement of an object along the equipotential surface causes no energy transfer (neither input nor output) because such movement follows a constant potential. The figure shows in two dimensions the equipotential surface between two cylindrical electrodes which are at potentials of + 30 V and - 30 V with respect to their surroundings. The potential differences between the individual lines are set to 5 V each. ( ↑ Rogowski profile) Equipment Safety Act 152 <?page no="158"?> Equivalent circuit. Used to illustrate the electrical properties of a system, e. g. a human being (Figure). For example, ↑ container filling explains the charging and discharging process when filling a barrel using an equivalent circuit. Equivalent energy. Symbol W, a term introduced by N. Gibson, that a ↑ gas discharge has equivalent energy when it is just beginning to ignite an explosive mixture. It is to be considered only in this context and only for a defined mixture. The ↑ ignitability of explosive mixtures is quantified by their ↑ MIE using a spark discharge of energy. Ignition energy values can be assigned to electrostatic gas discharges only to a very limited extent because the definition of ↑ energy does not allow conclusions to be drawn about how it is released, since neither volume nor time is specified. [Gibson, N., Lloyd, F. (1965)] ESA / ESA impression roller, ↑ electrostatic print assist ESD, short for electrostatic discharge. Charge transfer between bodies at different electric potential, triggered by direct contact or by an electrostatic field. ESD refers to the problem that electronic components can be damaged or destroyed by electrostatic discharges (usually < 1 μ s) ( ↑ ESD protected area). The illustration shows the symbol for the EPA (electrostatic protected area) Further information, mostly on testing techniques: ↑ CDM, ↑ DUT (EUT), ↑ EMP, ↑ EOS, ↑ ESDS, ↑ HBM, ↑ LEMP, ↑ MM, ↑ SG. [IEC 60749-27] ESD Association. A non-profit industry association in the USA. It is a voluntary association of interested industry professionals formed to expand awareness of ESD through standards and education in the areas of ↑ EOS and ↑ ESD. It is the only organization accredited by the American National Standards Institute (ANSI) to write and develop standards for electrostatics. ESD correlation. Tests e. g. with HBM pulses on semiconductor components ( ↑ DUT) can be performed on different ↑ ESD test systems. The measurement result is the charging voltage of the HBM discharge network at which the DUT was damaged by the subsequent HBM pulse, the so-called failure threshold. ESD Forum e. V. An independent non-profit association in Germany. The association consists of members from universities, industry and public institutions and pursues the goal of researching the effects of electrostatics in the field of microelectronics and making the results available to the general public. ESD gun. Design of an ↑ ESD test generator in the form of a gun to easily perform ↑ HBM tests on devices. ESD guns have interchangeable test probes, one that resembles the shape of a finger and is used for proximity testing, and a very tapered test pin that can puncture layers of paint to conduct the test pulse directly to the housing of a device under test ( ↑ DUT). ESD guns are primarily categorized by their maximum charging voltage, which for most models is in the range of 8 - 20 kV for most all models. [IEC 61000-4-2] ESD protected area. Area in which ↑ ESDS can be handled with the lowest risk of damage ( ↑ ESD) due to electrostatic discharging. An ESD protected area is established so that a ESD protected area 153 <?page no="159"?> certain level of electrostatic charge cannot be exceeded at the lowest expected humidity. Dissipative tables, chairs, floors, wrist straps, shoes, and nonchargeable clothing are used, as well as ↑ ionizers if necessary. An electrostatically sensitive component ( ↑ DUT) may only be handled in an ESD protected area if its ↑ ESD voltage sensitivity or failure threshold, i. e. the electrostatic charge above which damage can be caused by a discharge, is higher than the maximum achievable charge in the ESD protected area ( ↑ personnel earthing tester). ESD protection. The term is most often used in combination with “ ESDS ” and is intended to protect electronic equipment from static electricity. ESD protective coating. By adding conductive pigments (e. g. carbon black ( ↑ carbon), metal powder), electrically conductive coatings can be achieved which are applied to insulating plastic housing (preferably on the inside) and thus protect the ↑ ESDS contained therein. ESD simulation. Method for simulation of electrostatic effects - electrostatic discharge test pulse shapes for the machine model ( ↑ MM). [IEC 61340-3-2] ESD test generator. Used to test the immunity of electronic devices to electrostatic discharges. It is also referred to as an HBM tester because interfering discharges are often caused by electrostatically charged persons. The design is usually the ↑ ESD gun. ESD test system. Used to test microelectronic components or devices containing such components for their immunity to ESD pulses ( ↑ CDM, ↑ DUT, ↑ HBM, ↑ MM, ↑ SG). ESD voltage sensitivity. This describes the maximum voltage (electrostatic charge) up to which ↑ ESDS will not be damaged by electrostatic discharge ( ↑ ESD). However, this classification into CDM classes based on maximum voltage values is sometimes controversial because it does not consider the effects of exposure time, current flow and converted energy. ESDA ® method (electrostatic detection apparatus). The aim of the method is to make optically invisible print traces visible during the non-destructive examination of preferably handwritten documents and certificates based on electrostatic principles. The document to be examined is placed on a conductive, earthed plate. A very thin film (e. g. PET) is placed over the document, manually fixed with a ↑ charging electrode ( ↑ corotron) and charged. If there are optically invisible differences in thickness, the ↑ charge bonding is higher at precisely these points than at other points. ( ↑ charge compression, ↑ charge distribution). The volume conductivity ( ↑ volume resistance) of the document must be high enough for the film to adhere well. The different charge profiles can be made visible with suitable ↑ toners ( ↑ lycopodium). (Source: urkundenlabor.de) ESD protection 154 <?page no="160"?> ESDS, short for electrostatic discharge sensitive device. Integrated circuits or assemblies and devices that can be damaged or destroyed by electrostatic fields or electrostatic discharges. This can occur during handling, testing or transportation. Ether (Greek: aither, “ the upper air, celestial air ” ). Common name for diethyl ether {Appendix B}. Because of its low ↑ MIE and relatively large ↑ explosion range, ether, as an electrostatically chargeable ( “ excitable ” ) and ignitable liquid, was often used in Baroque experiments to demonstrate the danger of ↑ static electricity (e. g. personnel charging). In physics of that time, it was regarded as a substance at rest in itself (light ether) filling the entire world, which as a hypothetical medium should explain the mediation of remote effects (electric and magnetic ↑ fields, light, etc.). Only Einstein proved the untenability of this hypothesis with his theory of relativity (1905). When ether is used for inhalation anesthesia, explosive mixtures can form, which have often led to explosions during operations. Protective measures against electrostatic charges are therefore required in rooms used for medical purposes. [TRGS 727], [IEC 61340-6-1] EUT, short for equipment under test, ↑ DUT Ex-area also hazardous area (potentially explosive region). Area in which a dangerous ↑ Ex-atmosphere of combustible gases, vapors, mists or dust can occur under ↑ atmospheric conditions due to local and operational conditions and in which independent flame propagation is possible after ignition ( ↑ explosion). Hazardous areas are divided into ↑ Exzones according to the probability of the presence of explosive mixtures, whereby the equipment used must meet protection criteria defined in ↑ categories. According to the ↑ BetrSichV, the employer must classify these regions into “ Ex-zones ” , considering the results of a risk assessment. [TRGS 721 to 725, 727] Ex-atmosphere (explosive atmosphere). Mixtures of gases or vapors with each other or with mist or dust, including common admixtures (e. g. moisture), in which the combustion process is transferred to the unburned mixture under ↑ atmospheric conditions after ignition has occurred. [TRGS 723] Excess charge. Sum of charges Q, which, e. g. after ↑ charging on both sides of a ↑ material web, becomes effective towards the outside and can thus be detected ( ↑ bipolar charge layer, ↑ charge transfer, ↑ charge double layer). Under atmospheric conditions, the excess charge can reach a maximum of 26 μ C/ m 2 ( ↑ surface charge density). However, depending on the permittivity of the material web, this amount can be greatly exceeded because the surface charge density of the top side behaves like a capacitor to that of the bottom side ( ↑ charge bonding). If the electrical strength of the web is exceeded, breakdown occurs ( ↑ propagating brush discharge, Excess charge 155 <?page no="161"?> ↑ super brush discharge). Excess charges can be eliminated by ↑ ionizers ( ↑ ionizers in processing machines). Exhaust system. In the presence of gases or vapors of flammable liquids or dust, ventilation systems must be provided in workplaces to prevent hazardous ↑ Ex-atmospheres. They must be designed as object exhaust systems at the expected discharge points (in the case of dust, the fan casing and impeller should be capable of discharging). Since flammable gases are usually denser than air, and flammable vapors are always denser, they will gradually sink to the ground - unless they are completely captured by the exhaust system - and should also be exhausted there (ground exhaust). With such validated and monitored exhaust, large areas that would originally be classified as ↑ Ex-zone 1 can now meet Zone 2 requirements. This is advantageous for the electrostatic area as no further protective measures are required except in special cases. ( ↑ PTS), [IEC 60079-0], [TRGS 722 Section 4.6.3], [TRGS 724] ● Object exhaust / exhaust hoods. Device for direct exhaust (gases, vapors and dust) at the point of release, the need for which results from the ↑ risk assessment when handling ↑ solvents. In the case of warm or hot solvents, their vapors may rise and require extraction. In the context of engineering ↑ ventilation, this is a procedure to avoid a widespread ↑ Ex-atmosphere. ● Floor exhaust. An important part of ↑ explosion prevention. It should always be combined with object exhaust; the latter has priority. Exo-electron. It is generated without energy supply from freshly vaporized metal surfaces. It only has a low energy of around 1 eV ( ↑ electronvolt). Exothermic reaction. Self-heating, which is possible when the rate of heat production is greater than the rate of heat loss to the environment. The chemical reactions that cause self-heating can occur already below room temperature. However, they are usually so slow that the heat released is usually quickly to the environment, and the system remains at a constant temperature. However, by hindering the dissipation of heat or by increasing the ambient temperature (e. g. during storage), the reaction rate may increase to the point where the conditions necessary for ignition are reached. Among other parameters, the volume/ surface ratio of the reaction system, the ambient temperature and the dwell time are decisive. The resulting high temperatures can lead to the ignition of an ↑ Ex-atmosphere as well as to the generation of glow nests and/ or fires. Any combustible substances (e. g. gases or vapors) that may be generated during the reaction can themselves form an explosive atmosphere with the ambient air and thus considerably increase the danger of such systems as a source of ignition. A combination of several effects may occur, e. g. in the case of sedimentation of self-igniting dust, if the glowing nests initially formed by selfignition become ignition sources for an explosive atmosphere. [TRGS 721] Explosimeter (combustible gas detector). Device for checking the presence of an ↑ Exatmosphere at the measurement location ( ↑ clearance measurement, ↑ work clearance permit). Explosimeters must be regularly calibrated to the gases to be detected. ( ↑ calibration, ↑ gas warning device) Exhaust system 156 <?page no="162"?> Explosion. Sudden oxidation or decomposition reaction involving an increase in temperature, pressure or both. It is possible only with a certain mixing ratio of combustible substance (gas, dust) and air, and results in rapid independent flame propagation (about 10 m/ s under atmospheric conditions). ( ↑ flame reaction, ↑ deflagration, ↑ detonation, ↑ combustion process), [EN 1127-1], [IEC 60079-0] Explosion accident of Bitburg (Germany). In 1954, a serious explosion occurred in a military fuel storage tank. The tank was partially filled with ↑ kerosene and its free volume should be inerted with carbon dioxide (CO 2 ) for demonstration purposes during a firefighting exercise. Shortly after the fuel injector was opened, i. e. before inerting had been achieved, the fuel vapor in the tank ignited and destroyed it. There were fatalities and injuries. The initially incomprehensible event could only be explained in subsequent tests. It was found that during the expansion process of the CO 2 gas, a partial sublimation to CO 2 snow occurs due to strong cooling ( ↑ CO 2 fire extinguishing system). This ↑ aerosol becomes highly electrostatically charged as it flows through the outlet line and leads to the formation of a ↑ space charge cloud in the storage tank, which can trigger ↑ cluster discharges of sufficient ↑ ignitability on metal fixtures. Since any preventive CO 2 inerting (i. e. before a fire has occurred) is associated with this ignition risk, false activations of CO 2 fire extinguishing systems should be avoided at all costs. [SE Section 7.3.8.2], [Schön, G. (1956)] Explosion class. This term, which has been invalid since 1988, was changed to ↑ explosion group. Explosion group. Gases and vapors that may form the environment of explosionprotected operating resources are classified into three groups according to ↑ MESG (maximum experimental safe gap), which is correlated to ↑ MIE (minimum ignition energy) as a first approximation ( ↑ charge transfer - measurement). Explosion group MIE [mJ] Example I (mining) ~ 0.2 Methane IIA ≥ 0.2 Acetone, Gasoline, Cyclohexane, Cyclopropane IIB < 0.2 up > 0.02 Ethanol, Ethyl ether, Ethylene oxide IIC ≤ 0.02 Acetylene, Carbon disulphide, Hydrogen Explosion groups are used to limit the allowable dimensions of chargeable surfaces ( ↑ chargeability) and to evaluate the ↑ ignitability of ↑ gas discharges by measuring the charge transfer. Recently, however, it has become apparent that there are several flammable gases and vapors, particularly in the transition region from IIA to IIB (maximum experimental safe gap 0.9 mm), whose MIE is ≥ 0.2 mJ, but which would have to be assigned to explosion group IIB. The decision was made to include all “ borderline ” substances in the more critical group (i. e. IIB). [TRGS 727 Section 2], [IEC 60079-0] Explosion hazard. An explosion hazard may exist when flammable gases, dust or flammable liquids are produced, stored or processed and when gases, vapors, mists (liquid Explosion hazard 157 <?page no="163"?> droplets) or dust are mixed with air. The explosion hazard assessment must be performed whether or not an ↑ ignition source is present. Explosion limit. A mixture is explosive only within certain substance-specific limits. The explosion limit is usually given in [vol. %]. If the concentration of the sufficiently mixed (dispersed) flammable substance in air exceeds a minimum value (lower explosion limit), an explosion is possible. Such an explosion will not occur if the concentration exceeds the maximum value (upper explosion limit). Explosion limits change under conditions other than ↑ atmospheric conditions, e. g. higher oxygen content, lower air pressure. The explosion limit itself is not part of the explosion range. Unlike gases and vapors, ↑ dust-air mixtures cannot be homogeneous due to local and temporal variations in dust concentration. For this reason, the upper explosion limit in particular is not as important as for vapor-air mixtures. Often, in an inadmissible simplification, the total amount of dust in the total volume of an apparatus (e. g. atomizing dryer) is taken as dust concentration and a uniform distribution is assumed. However, there may be completely different local dust concentrations, since a summary estimate cannot describe the concentrations in the partial volume. Explosion limits vary with pressure and temperature. ( ↑ vapor pressure curve), {Appendix B}, [SE Section 1.2], [Hirsch, W., Brandes, E. (2014)] ● Lower explosion limit (LEL) denotes a fuel concentration below which a mixture is too “ lean ” to allow flame propagation after ignition has occurred. For most gases and vapors, the LEL is between approximately 30 and 100 g/ m 3 . It can also be defined by the ↑ flash point for flammable liquids. For dust, the LEL values are more imprecise due to the local and temporal instability of the dust distribution ( ↑ lean mixture). ● Upper explosion limit (UEL) indicates a fuel concentration above which a mixture is “ too rich ” to allow flame propagation after ignition without further oxygen supply. For most gases and vapors, the UEL is between 200 and 1000 g/ m 3 . For dust, the values for the UEL can only be given with reservations due to the local and temporal instability of the dust distribution ( ↑ rich mixture). The UEL is much higher for mixtures with oxygen than for mixtures with air. Explosion point. Safety related parameter, divided into lower explosion point (LEP) and upper explosion point (UEP). The explosion point is the temperature at which no ignition is observed at the saturated vapor concentration. The concentrations associated with that temperature are called the LEL and UEL ( ↑ explosion limit). The LEP is slightly below the flash point. The explosion point thus defines the lower and upper temperature limits of the explosive range of a substance. The explosion point is pressure dependent. [Steen, H. (2000)] Explosion pressure. Maximum value of the pressure (overpressure above the initial pressure) which occurs in a closed container during the combustion of an explosive mixture. For gases, vapors and dust of organic compounds mixed with air under ↑ atmospheric conditions, an explosion pressure of about 6 - 10 bar is reached in approximately cubic containers. In containers with a length/ diameter ratio > 5, an ↑ explosion may become a ↑ detonation after a sufficient start-up distance. Explosion limit 158 <?page no="164"?> Explosion pressure relief (explosion venting). In the broadest sense, includes anything that serves to open an originally closed apparatus in which the ↑ explosion occurs, either temporarily or permanently, in a safe direction when the response pressure is reached during or after an explosion. The purpose of the relief device is to ensure that the equipment is not stressed beyond its explosion resistance. For example, bursting discs or explosion doors can be used for this purpose. Safety valves are not suitable for this purpose. A ↑ quench tube, for example, can be used to collect the released substances. The time relationship between the progress of the explosion and the response of the pressure relief system is the primary consideration in sizing the explosion pressure relief system. Explosion pressure relief is not permitted if the substances released by it endanger persons or damage the environment. [TRGS 724] Explosion pressure shock-resistant design. Containers and apparatus are constructed to withstand the pressure shock occurring within them in the event of an explosion to the extent of the expected explosion pressure. However, permanent deformation is permissible. After an explosion, the affected parts of the plant must be checked for deformation. [TRGS 724] Explosion pressure-resistant design. Vessels and apparatus are designed to withstand the expected explosion pressure without permanent deformation. The calculation and design rules for pressure vessels are used for design and manufacture. The design pressure is based on the expected explosion pressure. [TRGS 724] Explosion prevention. Includes all measures that are suitable for preventing or limiting explosions when flammable gases, vapors, mists or dust are used, so that no personal injury and, as far as possible, no damage to property can occur. Explosion prevention is categorized as: ● Primary explosion prevention: Avoiding or limiting hazardous ↑ Ex-atmospheres (e. g. mixtures outside their ↑ explosion limits, ↑ inerting). ● Secondary explosion prevention: Avoidance of ↑ ignition sources, the scope of protective measures depends on the probability of occurrence of explosive atmospheres ( ↑ Ex-zone). ● Constructive explosion prevention: Which limits the effects of an explosion to a harmless level by means of constructive measures (e. g. ↑ explosion pressure-resistant design, ↑ explosion pressure shock-resistant design, ↑ explosion pressure relief, ↑ explosion suppression). Explosion prevention measures for electrical equipment are covered in the IEC 60079 series of standards, and those for mechanical equipment are covered in the IEC 80079 series of standards. (Source: REMBE ® GmbH Safety+Control) Explosion prevention 159 <?page no="165"?> Explosion prevention document. If the user of a facility has determined in the risk assessment (§ 3 of the Operational Safety Regulation [ ↑ BetrSichV]) that the generation of a hazardous explosive atmosphere cannot be safely prevented, he must ensure that an explosion prevention document is prepared, regardless of the number of employees. This document must show that appropriate precautions have been taken to ensure explosion prevention (including the prevention of electrostatic ignition sources) before work commences. The explosion prevention document must show: - Identification and evaluation of explosion hazards - A list of precautions taken to prevent explosions - Classification of the hazardous areas into zones (layout of the plant explosion zone plan) in accordance with § 5 and Appendix 3 of BetrSichV - Compliance with the minimum requirements according to Appendix 4 of BetrSichV. This includes organizational and general measures as well as the selection of suitable equipment and protective systems according to the respective zone in accordance with Directive ↑ ATEX 114. The explosion prevention document should therefore contain at least: - A list of operating resources according to ATEX in defined hazardous areas - Safety matrix and associated checklists - Escape and rescue route plan - Operating instructions - Hazardous materials/ hazardous material register - Maintenance concept - Risk assessment - Effectiveness test In accordance with the ATEX 114, the relevant ↑ explosion-related parameters for gases, liquids and dust must be observed. The form of the explosion prevention document is not prescribed, but it can be useful to use a sample form and its explanation (www.baua.de). The employer must keep the explosion prevention document up to date to meet the protection obligations and ensure a consistent level of safety. [TRGS 721] Explosion-proof design. Plant components such as vessels, apparatus and piping can be designed to withstand an internal explosion without rupture. The following types of explosion-proof design are generally distinguished: - ↑ explosion pressure-resistant design - ↑ explosion pressure shock-resistant design [TRGS 724] Explosion range. Concentration range of flammable gases, vapors, mists or dust under ↑ atmospheric conditions in which independent flame propagation is possible after ignition, i. e. the range in which they are explosive. The explosion range is limited by the ↑ explosion limits. Explosion prevention document 160 <?page no="166"?> Explosion-related parameters. To be considered for the preparation of the ↑ explosion prevention document. They can be obtained from various databases (Chemsafe, GESTIS substance database, GESTIS dust-Ex, GDL, ISCS database, GSBL database) or, if necessary, determined in a suitable laboratory: ↑ MIE, ↑ ignition temperature, ↑ explosion limit (LEL, OEL), ↑ limiting oxygen concentration, ↑ flash point, ↑ explosion group, ↑ temperature class. Additional for dust: ↑ particle size, ↑ median value, ↑ glow temperature, ↑ explosion pressure, maximum pressure rise over time, ↑ K St value, ↑ dust explosion class, ↑ hybrid mixture, ↑ aerosol-air mixture. Explosion risk (integrated explosion prevention). The following criteria must be considered when determining the risk of explosion: - The likelihood of the occurrence of an explosive mixture. - The likelihood of an effective ignition source. - The extent of damage that can be expected if the explosive mixtures are ignited. Explosion suppression. Prevents the maximum ↑ explosion pressure from being reached in the event of an ↑ explosion by rapidly blowing extinguishing agents into containers and equipment. This means that equipment protected in this way only needs to be designed for reduced explosion pressure. Unlike ↑ explosion pressure relief, the effects of an explosion are limited to the interior of the equipment. Explosion suppression systems essentially consist of a detector system that detects the onset of an explosion and the pressurized extinguishing agent containers whose outlets are released by the detector signal. [TRGS 724 Section 2.7] Explosion tube, ↑ Hartmann tube Explosive atmosphere, ↑ Ex-atmosphere Explosive test mixture. Defined fuel gas-air mixture used for testing electrical ↑ operating resources (intrinsically safe circuit ( ↑ electric circuit)) for use in hazardous areas (e. g. also for ↑ ionizers on high voltage). Explosives. Chemically uniform solid, liquid or gelatinous mixture of substances which, when ignited without the addition of an oxidizing agent (oxygen), undergoes a rapid reaction throughout its volume with corresponding heat development. Since explosives require relatively strong ignition initiators, so-called primary explosives (detonators) are used to initiate the reaction, the ↑ MIE of which is extremely low (in some cases even lower than that of hydrogen). Therefore, during blasting operations, measures must be taken to prevent electrostatic charging (e. g. of the blasting lines) to prevent unwanted ignitions. During the production and processing of primary explosives, very strict requirements must be met to prevent electrostatic charging. ( ↑ Explosives Act), [TRGS 727 Section 8], [Köhler, J. et al. (2008)] Explosives Act. The German Explosives Act [SprengG] regulates the handling and movement as well as the import and transit of explosives and blasting accessories. The substances are classified according to their intended use as explosives, pyrotechnic articles, detonators, igniters and other explosive substances. There are specific regulations in each country, e. g. USA: ATF Regulations. Explosives Act 161 <?page no="167"?> Ex-symbol. Symbol for ↑ explosion hazard and ↑ explosion prevention. The areas in which hazardous atmospheres may occur must be marked with the danger triangle according to ↑ ATEX 137 at all access points, regardless of the hazard zones assigned to them. All operating resources used in hazardous areas must be tested and approved accordingly and bear the appropriate mark in accordance with ATEX 114 (hexagon). This indicates that a type of equipment has been tested by a conformity assessment body within the EU and that the manufacturer has determined, as part of a routine test, that the equipment conforms to the type. External ionization. Generation of charge carriers in gases by processes of ↑ ionization independent of the current flow through the gas. Extinguishing system, ↑ CO 2 fire extinguishing system Extra-low voltage. Includes direct voltages up to 60 V and alternating voltages up to 25 V, at which there is not yet a ↑ danger of electric shock ( ↑ safety extra-low voltage). [IEC 60364-4-41] Ex-zone (hazardous area, risk area), (explosion prevention zone). Classification of hazardous areas according to the frequency and duration of the occurrence of hazardous explosive atmospheres. This must be done by the employer in the documentation of the risk assessment ( ↑ explosion prevention document). Classification according to [ ↑ GefStoffV]: Zone 0 is an area in which an explosive atmosphere consisting of a mixture with air of flammable gases, vapors or mists is present continuously, for long periods or frequently. Zone 1 is an area in which an explosive atmosphere consisting of a mixture with air of combustible gases, vapors or mists is likely to occur occasionally during normal operation. Zone 2 is an area in which an explosive atmosphere consisting of a mixture with air of combustible substances in the form of gas, vapor or mist is not likely to occur in normal operation but, if it does occur, will persist for a short period only. Zone 20 is an area in which an explosive atmosphere in the form of a cloud of combustible dust in air is present continuously, for long periods or frequently. Zone 21 is an area in which an explosive atmosphere in the form of a cloud of combustible dust in air is likely to occur occasionally in normal operation. Zone 22 is an area in which an explosive atmosphere in the form of a cloud of combustible dust in air is not likely to occur in normal operation but, if it does occur, will persist for a short period only. Normal operation is the condition in which the equipment is used within its design parameters. If in doubt, the more stringent zone should be selected. Layers, deposits and accumulations of combustible dust must be considered in the same way as any other cause that may lead to the formation of a hazardous explosive atmosphere. Ex-symbol 162 <?page no="168"?> The North American “ Division ” system (NEC (USA), CEC (Canada)) defines only two probabilities of ignitable mixtures: Division 1: The ignitable gases, vapors or dust particles are present continuously or intermittently during normal operation; to be compared with Zones 1 and 0. Division 2: The ignitable mixtures are unlikely to occur during normal operation (rarely and only for a short time); comparable to Zone 2. EYE Meter ® . Mobile detector for ↑ ESD and ↑ EMI events and measuring device for EM fields and RF signals (3M Electronic Solutions) ( ↑ spark detection device). EYE Meter 163 <?page no="169"?> F Face shield. The face shield of a respirator can become dangerously charged at any time. If soiling and the resulting need for cleaning, e. g. wiping, is expected, it must be conductive or dissipative in Ex-zone 1. Fahrenheit, Daniel Gabriel (1686 - 1736). German physicist founded scientific thermometry and developed a liquid (mercury) thermometer with a three-point calibration, the mean calibration point of 100 °F corresponding to the temperature of the human body. Fahrenheit. Degrees Fahrenheit [°F] is a unit of temperature used primarily in Englishspeaking countries. The temperature scale was divided into 180 equal parts by D. G. ↑ Fahrenheit, in which the solidification point for water was set at 32 °F and the boiling point at 212 °F. A temperature difference of 1 K (1°C) corresponds to a temperature difference of 5/ 9 F. The temperature in degree ↑ Celsius is calculated using the formula: y°C = (x°F - 32) × 5/ 9. Far field. Region in which a field behaves essentially as if the field magnitudes emanated from a single point. The field strengths decrease with the square of the distance from that point ( ↑ Coulomb ’ s law). Far field shielding. Shielding of devices or components against external field influences ( ↑ Electromagnetic Compatibility). For example, the ↑ Faraday cage is used to shield against external electric fields, and the ↑ Permalloy TM is used to shield against magnetic fields. Farad. Derived ↑ SI unit [F] of the electrical ↑ capacitance C, named after M. ↑ Faraday. A capacitor has a capacitance of 1 F (1 As/ V) when it is charged to a voltage of 1 V by a charge of 1 C (1 As). In electrostatics, the smaller unit pico-farad [pF] is commonly used. {Appendix M.6} Faraday, Michael (1791 - 1867). English physicist and chemist, best known for his proof of electromagnetic ↑ induction and his fundamental work on electrolysis ( ↑ Faraday constant). He is credited with establishing that the interior of a conductive hollow body is always free of fields ( ↑ Faraday cup, ↑ Faraday cage). Faraday cage. In analogy to the ↑ Faraday cup (field-free interior), rooms can be protected against electric fields by a conductive shell that is closed on all sides. It does not have to be completely closed, since an electrically conductive wire mesh will keep practically all field lines away from the interior. The mesh size must be smaller than the wavelength of the alternating electromagnetic fields. The name “ cage ” comes from the fact that M. Faraday put small animals (e. g. mice) and not least himself into the wire housing during demonstration experiments. The principle of the Faraday cage can be found in many applications: Shielding for ↑ resistance measurements in the T Ω -range, car bodies as protection against lightning strikes ( ↑ lightning protection), shielding of ESD-sensitive electronics. [SE Section 3.9] <?page no="170"?> Faraday constant. Symbol F, also known as the electrochemical equivalent, is a proportionality factor that indicates the quantitative relationship between the current flow and the amount of substance deposited during ↑ electrolysis ( ↑ voltameter). The Faraday constant is the product of ↑ Loschmidt ’ s number N L and the ↑ elementary charge: N L × e = 96485.3365 × 10 -8 C/ mol (CODATA 2006). Faraday cup (also called Faraday cylinder). The inside of a conductive hollow body is field-free, so that the ↑ charge of an inserted charged object is transferred to the Faraday cup and can be detected with an electrometer (R i > 10 15 Ω ) ( ↑ influence). For example, the charge of an insulating material can be measured. The charge Q is calculated from the total capacitance C of the measurement setup and the measured voltage U {Appendix M.3, M.4 and M.6}. A falling charged particle transfers its charge to the Faraday cylinder without touching the wall. ( ↑ charging - falling drop), [SE Section 3.10] Faraday cup electrometer (FCE). A simple form of electrical measuring device for measuring the charge of particles. It consists of an insulated filter mounted in a Faraday cup and the electrometer. The FCE is used in aerosol research to determine the specific charge [C/ g] of particles. Faraday ’ s laws. Studied and defined by M. ↑ Faraday in 1833, quantitative relationships between the current flow through an ↑ electrolyte and the amount of substance deposited on the electrodes (basic laws of ↑ electrolysis). ● 1st Faraday ’ s law: The amount of substance of the electrolytic decomposition products is proportional to the charge passed through. The charge is an integral multiple of the elementary charge (e = 1.602176634 × 10 -19 As). On this basis, the unit Faraday ’ s laws 165 <?page no="171"?> ↑ ampere [A] was defined in 1898 in the “ Law concerning electrical units of measurement ” : It is represented by the invariable electric current which, when passing through an aqueous solution of silver nitrate, precipitates 0.001118 g of silver in one second. ● 2nd Faraday ’ s law: The mass of an element deposited by a given quantity of charge is proportional to the atomic mass of the deposited element and inversely proportional to its valence, i. e. to the number of monovalent atoms that can combine with this element. Federal Institute for Materials Research and Testing (German: Bundesanstalt für Materialforschung und Materialprüfung (BAM)). Scientific and technical federal authority under the auspices of the Federal Ministry of Economics and Technology. It is the successor organization of the State Materials Testing Office founded in 1871 and is engaged in materials research and testing with the aim of advancing safety in technology and chemistry. In accordance with its guideline “ Safety in technology and chemistry ” and its statutory tasks (including those arising from the hazardous goods, explosives and chemicals legislation), BAM is responsible for the safe and environmentally compatible use of technical equipment and products and for the provision of reference methods and materials. Federal Institute for Occupational Safety and Health (German: Bundesanstalt für Arbeitsschutz und Arbeitsmedizin (BAuA)). Federal institution with research and development tasks, which acts as a federal agency at the interface between science and politics. It performs tasks assigned to it by law or by the Federal Ministry of Labor and Social Affairs or, in agreement with the latter, by other federal ministries. It performs governmental tasks with international activities in the field of the regulation of industrial chemicals and the authorization and evaluation of biocidal products. As the Federal Chemicals Agency (German: BfC), the BAuA is the legally responsible authority for tasks related to the REACH, CLP, and Biocide Regulations. Under the Product Safety Act (German: ProdSG), the BAuA is mandated to support the state authorities responsible for market surveillance and to provide information on the safety of consumer products and work equipment. At www.baua.de, the Technical Rules for Industrial Safety (German: TRBS) and the Technical Rules for Hazardous Substances (German: TRGS) can be viewed and downloaded as PDF files free of charge. Felici generator. A further development of the ↑ Van de Graaff generator in which a rotating plastic cylinder is used to transport the charge instead of a rotating belt. The advantages of the Felici generator are its smaller size and lower gas friction losses when operating in a pressurized vessel ( ↑ Paschen ’ s law). [Felici, N. (1957)] Typical characteristics of a Felici generator are U = 100 kV, I = 10 mA, η ~ 80 %. Ferroelectric. Dielectric with a thermodynamically stable phase that undergoes a spontaneous dipole orientation (electric ↑ polarization) below a certain temperature, the ↑ Curie point. This polarization can be reversed with losses by an external Basic structure of a single-pole drum generator with reversing according to N. Felici. Federal Institute for Materials Research and Testing 166 <?page no="172"?> electric field ( ↑ depolarization, ↑ hysteresis), counterpart to the permanent magnet. Examples of substances: barium titanate ( ε r = 1200, inorganic, for electrets), triglycine sulphate (organic as ↑ pyroelectric infrared sensor). FET, short for field effect transistor, ↑ metal oxide FET FIBC, short for flexible intermediate bulk container (also big bags, bulk bags, super sacks). Large bags with a volume of several 100 to over 1000 l. They are made of woven tape (preferably polypropylene) and are coated on the inside to make them dustproof/ food safe or have a film ↑ liner. They have straps to hold the load and usually have a sealable opening at the top and bottom for filling and emptying. As FIBCs are usually made of insulating or chargeable materials, measures must be taken to prevent electrostatic charges if they are used for flammable bulk materials and/ or if they are handled in potentially explosive environments. FIBCs are classified into types A through D according to their electrostatic properties: A has no specific protection against electrostatic ↑ gas discharge from its surface and may therefore only be used for non-flammable products and only in non-hazardous areas. B is intended for use in hazardous areas with a ↑ MIE > 3 mJ. The dielectric breakdown voltage of its fabric is < 6 kV to prevent ↑ propagating brush discharges. All conductive objects in the vicinity - including people - must be earthed during filling/ emptying. C The fabric contains conductive threads with a parallel spacing of ≤ 20 mm, or a grid spacing of ≤ 50 mm and is designed so that the ↑ leakage resistance from its earthing points and carrying loops to all parts of the container R A < 100 M Ω . For this type, earthing is mandatory during filling and emptying ( ↑ earth clamp, ↑ earth monitoring). The type C FIBC must have one or more earthing points. The carrying loops can be made of conductive substance or contain conductive threads and can therefore be considered as an earthing point. This does not apply if the hooks for the carrying loops are coated with insulation. All conductive objects in the vicinity - including people - must be earthing during filling/ emptying. D with antistatic properties that may cause part of the charge to be discharged by ↑ corona discharge. Earthing of the FIBC is not required, but FIBC type D is subject to the following limitations: - MIE of the surrounding atmosphere ≥ 0.14 mJ, - Charging current through bulk material supplied must not exceed 3.0 μ A, - All conductive objects in the vicinity - including people - must be earthed during filling/ emptying (this is due to the corona discharge operating principle of this type of container). FIBCs of types B to D must be marked with appropriate labels for their intended use and, if necessary, must be used only with liners of types L1, L1C, L2 and L3 specifically prescribed for the FIBC type. [TRGS 727 Section 6.6], [IEC 61340-4-4], [IEC 61340-4-11], [ISO 21898] Fiber bridge sparkover. In the case of ↑ type of protection “ o ” (oil immersion), the aging of the insulation, e. g. when using ↑ pressboard, can cause the fibers aligned in the electrical field to separate and form a bridge, resulting in “ sparkover at a fiber bridge ” . These bridges can also lead to heat generation ( ↑ Joule ’ s law), causing moisture or low-boiling liquid Fiber bridge sparkover 167 <?page no="173"?> components to evaporate and initiating the breakdown of the resulting gas bubbles. ( ↑ dendrites) Fiber brush. An essential component of a ↑ discharge brush. Reducing the number of fiber brushes increases their discharging effect ( ↑ corona inception voltage). [SE Section 5.2.3] Field. In physics, a field is generally understood to be a spatial area in which each point is assigned to a defined value of a physical quantity. In this logic, a distinction is made between: - Scalar fields (e. g. density, temperature) which are completely defined by specifying a numerical value or unit of measurement. - Vector fields (e. g. electrostatic or magnetic field strength) which represent a directed quantity and differ from scalar fields by the additional specification of a specific direction. Vector fields can be visualized using ↑ field lines, which are oriented lines whose tangents indicate the direction and magnitude of the field quantity acting at each point in space. In a narrow sense, electric and magnetic fields are force fields: A force is exerted on an appropriate object placed in the field. The electromagnetic field is to be distinguished from these descriptions of a field, because it describes the propagation of a time-varying radiation field in space ( ↑ electromagnetic radiation, also known as electromagnetic wave), which represents the transport of energy by radiation. ● Natural field of Planet Earth. The Earth is surrounded by magnetic and air-electric fields. At the Earth ’ s surface there is a DC electric field caused by the ionizing effect of cosmic rays on higher layers of air (ionosphere) and by the movement of air in the atmosphere. Under normal weather conditions, it varies between 0.1 and 0.5 kV/ m and decreases with altitude. It can reach 30 kV/ m and more under a thunderstorm cloud ( ↑ thunderstorm lightning, ↑ thunderstorm electricity). Sensitive people can perceive electric fields as low as 1 kV/ m, some animal species probably even earlier. At 10 kV/ m and above, people experience tingling of the skin or raising of body hair. While research has shown that the Earth ’ s magnetic field serves to protect life on Earth (it repels the high-energy particle radiation “ solar wind ” emitted by the Sun), there is no reliable information yet on a corresponding benefit of the air ’ s electric field. Weather conditions such as foehn winds also change the ion content of the air and thus the electric field. The biological effects on the human organism are controversial. - 95 % of the Earth ’ s magnetic field is caused by a geodynamo in the liquid ferromagnetic core of the Earth. It can be recognized by the fact that a freely moving magnetic needle always points in a certain direction (north-south, compass). At the Earth ’ s magnetic poles, the field lines emerge vertically and run almost parallel to the Earth ’ s surface near the equator (called the magnetosphere, about 100 km thick). Since the magnetic field lines exit vertically near the Earth ’ s poles, the solar wind can penetrate the Earth ’ s atmosphere there and cause the ↑ aurora borealis. [Müller, U., Stieglitz, R. (2003)] - The Earth ’ s electrostatic field has been proven by measurements: The Earth ’ s sphere can be understood as a spherical capacitor, and as a whole is negatively charged (about 10 5 C), with the surrounding ionosphere ( ↑ Heaviside layer) having a corresponding positive charge. The resulting field strength at the Earth ’ s surface averages about 200 V/ m, in clear weather about 100 - 130 V/ m. Fiber brush 168 <?page no="174"?> ● The magnetic field is important in the context of electrostatic ↑ gas discharges because, with the appropriate strength, it leads to the formation of a ↑ plasma via the ↑ pinch effect with the resulting gas heating and thus to ↑ ignitability. ( ↑ permeability) ● Force effects in the field ( ↑ field lines) (North pole red; South pole blue) Field constant. Proportionality factors in the electric or magnetic ↑ field: ● ↑ Permittivity (absolute) ε 0 = 8.8541878128 × 10 -12 As/ Vm of matter-free space (electric field constant of vacuum, also called influence constant, formerly dielectric constant), quotient of displacement density and field strength, unit: Coulomb per square meter [C/ m 2 ], ● ↑ Permeability (absolute) μ 0 = 1.25663706212 × 10 -6 Vs/ Am (magnetic field constant, also called induction constant), quotient of magnetic flux and magnetic field strength in matter-free space, unit: Henry per meter [H/ m]. {Appendix M.1}, ( ↑ natural constant) Field decay method. Comparable to the ↑ relaxation time measurement ( ↑ CPM), it is used to determine the electrostatic properties of flat structures such as films, paper, or textiles. The sample is clamped in an earthed frame, charged in a defined manner by corona charging ( ↑ useful application), and the decay time for 50 % of the charge is determined with an ↑ EFM after charging is complete. [Matschulat, U., Schubert, W. (2023)] Field decay method 169 <?page no="175"?> Field distortion. The potential curves resulting from the field distortion are easily recognized by a joint plot of ↑ equipotential lines (dashed) and ↑ field lines (solid). The figure shows a charged film on an earthed plate. The field is directed towards the earth ’ s potential and can therefore not or only marginally be measured in this region. [SE Section 2.11.2] Field effect operation. Mode of operation of a ↑ semiconductor consisting of an n-type conductor into which two p-type zones are laterally diffused. The electric field between the p-zones more or less constricts the electron current through the n-conductor ( ↑ metal oxide FET, ↑ PN junction). Field effect transistor, ↑ metal oxide FET Field emission. Direct emission of electrons from cold electrodes at field strengths above 100 kV/ mm only under high ↑ vacuum ( ↑ tunnel effect). Even at very low gas pressures, a ↑ gas discharge would occur at lower field strengths. Field emission is used in electron microscopes, for example. Field equation. Mathematical equations ( ↑ Maxwell ’ s equation) that describe the electric and magnetic ↑ field. Field induced model, ↑ FIM Field lines. Can represent electrostatic (electric) and magnetic fields. They are curves running through space in the direction of the associated vectorial field quantity ( ↑ equipotential surface). At each point of the field lines, the direction of the field is determined by the corresponding tangent. (A particle at point A would move in the direction of the tangent with the force ~ F .) The density of the field lines is a measure of the field strength. ( ↑ electro fluid dynamics) ● Electric field lines can be caused by a single pole (+ or -) and, by definition, start at the positive electrode, radiate into space, or end vertically at the negative electrode. The figure shows a homogeneous electric field between the flat electrodes and an inhomogeneous electric field that decreases in strength toward the outside ( ↑ edge field). Field lines cannot cross at any point. Field distortion 170 <?page no="176"?> ● Magnetic field lines are always based on two poles (north and south) and by definition run outside a magnet from north to south and inside from south to north. They are always closed lines. Accordingly, magnetic poles always occur in pairs. ● Field line image. The abstract term “ field lines ” can be understood by visualizing the course of electric and magnetic fields. For the latter, it is sufficient to scatter iron filings on a glass plate and arrange the magnetic poles underneath. Electrostatic field line images can be made in an electric field, for example, by aligning non-conducting particles dispersed in an insulating liquid (traditionally: corn grits in castor oil). Field mill, ↑ EFM, ↑ influence electrostatic field meter Field penetration. If shielding is provided by conductive earthed grids ( ↑ Faraday cage, ↑ lightning protection), the larger the mesh size, the greater the field penetration must be expected. The same applies to shielding through electrically weak conductive layers. Field measuring probes ( ↑ EFM, ↑ influence electrostatic field meter) are placed behind a measuring aperture in an earthed shield, the diameter of which determines the field penetration ( ↑ resolution capacity and sensitivity). Field penetration also means the penetration of an electric field through an insulating material ( ↑ dielectric). Field penetration must be considered when ↑ filling process made of electrically insulating materials, such as plastic drums or plastic bags, ↑ FIBC etc., and when arranging ↑ ionizers. In the case of highly charge-generating processes in glass apparatus, charging may be caused by the field penetration. [TRGS 727 Section 4.13] Field strength. Symbol E, unit [V/ m], vectorial quantity effective at a given location in a ↑ field. The field strength is inversely proportional to the distance s. It is a measure of the force F exerted on a charge Q in the electric field (F = Q × E). Under certain conditions, the charge state of an object can be determined by the electric field strength emanating from it with an ↑ EFM. ( ↑ measurement error), {Appendix M.3 and M.3.1.2} Field strength measurement (electrostatic). The field strength emanating from a unipolar charged object characterizes its state of charge. An accurate field strength measurement is only possible in a homogeneous electric field. The usually earthed measuring head always detects the vectorial sum of the E-field and causes ↑ field distortions, as the field lines are concentrated towards the measuring head, resulting in too high measured values ( ↑ measurement error, ↑ EFM). This can be remedied by a compensation method, in which the field strength signal is fed to a comparator, which in turn feeds a DC voltage to the sensor head until the field strength between the sensor head and the object becomes zero. The potential of the sensor head potential then corresponds exactly to the surface potential (potential-free (field-free) measurement) of the object ( ↑ charge distribution, ↑ potential measurement). Field strength meter, ↑ EFM, ↑ influence electrostatic field meter Field strength meter 171 <?page no="177"?> Field theory (electrostatic). Fundamental mathematical-physical formalism that makes it possible to treat any physical phenomenon that can be represented by a field or a field quantity according to uniform aspects and thus to arrive at concrete statements about its state quantity. According to the field theory, forces are exerted on a charge by electric fields emanating from other charges. For example, the force between two point-charges can be understood as an interaction between the second charge and the field emanating from the first charge. Filament measuring chamber. Adapter for ↑ influence electrostatic field meter for measuring the electrostatic charge of filaments. The maximum charge (Q)/ area (F) for a filament of 1 m length can be calculated: The ↑ surface charge density is σ max = 26 μ C/ m 2 . Q = Q max × F and U = Q / ε 0 (absolute permittivity ε 0 = 8.85419 × 10 -12 As/ Vm (electric ↑ field constant)), {Appendix M.1 and M.3}. Fill jet / free jet. Leakage of liquids from pipes, e. g. when filling containers. This can lead to ↑ charging of the liquids if they spray and splash ( ↑ Lenard effect). “ Friction ” of the liquid against the surrounding atmosphere does not cause charging. [TRGS 727 Section 4] The figure shows a possible measurement setup with an ↑ EFM with a voltage probe. ( ↑ filling pipe), [SE Section 3.14.5] Filling, ↑ filling process, ↑ storage Filling pipe. When filling insulated containers (drums, ↑ RIBCs, ↑ tanks), conductive, earthed filling pipes must be used to dissipate charges from the liquid and prevent droplet formation and spray mist ( ↑ spraying). In the case of flammable flowing liquids, the filling pipe should always be routed as a dipping pipe to below the level of the liquid to prevent ↑ brush discharges. Conductive containers must always be earthed. The ↑ flow velocity must not exceed the limit values according to [TRGS 727 Section 4]. When filling without a dipping pipe, this limit value must be reduced by half. If this is not possible, it must end at or just below the cover level (maximum 20 mm). Field theory (electrostatic) 172 <?page no="178"?> Filling process. When charged bulk materials or liquids are fed into containers ( ↑ FIBC, ↑ RIBC), charge accumulation occurs. This can lead to ↑ cone or ↑ brush discharges on the product surface. In the case of containers made of insulating materials ↑ field penetration occurs, so that gas discharges can also be initiated externally. Electrically conductive vessels can be charged by the charged product through ↑ influence and/ or ↑ ionization ( ↑ charge transfer) and must therefore be continuously earthed during the filling process to prevent discharge sparks. It should be noted that a direct discharge of the product to the conductive and earthed container is only possible to a limited extent, the charge transfer mainly takes place by ionization ( ↑ container filling). [TRGS 727 Sections 4 and 6] Filling speed. To reduce the ↑ charging of flammable liquids, the filling speed must not exceed a limit that depends on the size of the container and the diameter of the filling pipe. [TRGS 727 Section 4] Filling stations. Where gasoline is handled are required to take measures to prevent explosions ( ↑ explosion prevention). This also applies to electrostatic ignition sources, e. g. caused by charging when the fuel flows into the ↑ tank. Protective measures consist of redundant earthing of the vehicles ( ↑ refueling): - Dissipative tires on dissipative surfaces in the refueling area. - Conductive dispensing hoses provide a conductive connection between the vehicle filler neck and the earthed dispenser. - ↑ Gas swing adsorption to avoid explosive atmosphere outside the filler neck. Film (also foil) (Latin: folium, “ leaf ” ). Film is usually made of plastic (foil includes metals), gives rise to a variety of sources of electrostatic charging and the resulting hazards and malfunctions ( ↑ gas discharge), of which the following are only examples: - ↑ Charge separation during unwinding ( ↑ brush discharge) - ↑ Charge accumulation during winding (brush discharge, ↑ propagating brush discharge, ↑ super brush discharge) - Charge separation during removal from the stack ( ↑ adhesion, brush discharge) - Charge accumulation during de-stacking ( ↑ repulsion, super brush discharge) If the film contains a conductive inner layer, e. g. aluminum coated with polymer on both sides ( ↑ composite), an influenced charge can build up on it, leading to ↑ spark discharges ( ↑ ionizer, ↑ material web). Note: Freshly manufactured film tends to ↑ telescoping when wound. Film thickness, ↑ bipolar charge layer Filter (Latin: filtrum, “ felt strainer ” ). Used among other things, to separate partially charged solid particles from the gas stream, the charge of which accumulates in the filter ( ↑ separation of substances). Even if there are no moving parts in the filter, ↑ charging and the resulting electrostatic hazards can still occur during cleaning (compressed air, vibration). If explosive mixtures are present in the filter that can be ignited by ↑ brush discharges, electrically dissipation-capable and earthed ↑ filter materials must be used. For less flammable mixtures, it is sufficient to prevent ↑ spark discharges; at a minimum, all Filter 173 <?page no="179"?> conductive filter components must be earthed. Depending on the design of the filter, such conductive parts that are used to shape or reinforce the filter medium, for example, may be concealed. This is especially true for filter hose support elements. They can be earthed, for example, by providing a mandatory connection to the cleaning jet in the earthed head plate via conductive tape sewn to the top ends of the hose. When using dissipation-capable filter media, such earthing generally occurs automatically. The figure shows this using the example of a hose filter to be cleaned with compressed air. Filter material ● Filter material for dust, gases, and vapors. If an explosive atmosphere is likely to occur due to dust ( ↑ MIE ≤ 3 mJ), gases or vapors, conductive or dissipative filter materials must be used. Their properties and ↑ earthing must be permanently maintained and regularly tested. Otherwise, the earth connection may be interrupted, for example, during cleaning with a pulse of compressed air, causing a fire. [TRGS 727 Sections 5.7 and 6.5] ● Filter materials for liquids can electrostatically charge insulating liquids flowing through them, largely independent of their own conductivity. The greater the flow resistance and velocity in the filter material, the greater the ↑ charging. ( ↑ dwell time) FIM, short for field induced model ( ↑ influence charge in a component). When an electrostatically charged object is brought close to a component, charge movement can occur in its microstructure. The resulting potential differences cause corresponding damage within the circuits. Depending on the nature of the component, different variants of the FIM can be used. Fine particle size (fineness). Characterizes the appearance of solids, e. g. by specifying the ↑ particle size ( ↑ dust). Fine structure - The decomposition of otherwise apparently simple processes, which only become visible at sufficiently high resolution. - The corpuscular structure of matter at submicroscopic dimensions. Filter material 174 <?page no="180"?> Fingerlin. S. Lüttgens ’ synonym for contamination of measurement surfaces by hand perspiration and hand grease. Finishing. Treatment process after actual production, especially for textiles, to achieve certain properties and utility values (e. g. dissipation capability). ( ↑ refinement, ↑ clothing) Fire, ↑ combustion process Fire classes. Intended for the practice of firefighting, represent a division into five classes of application areas of fire protection agents in fire extinguishing equipment: Class Description acc. [EN 3-7] Class Description acc. [NFPA 10] A for solid substances that produce glowing embers (apart from light metals): water, ABC powder, extinguishing foam A Fires in ordinary combustible materials, such as wood, cloth, paper, rubber, and many plastics. B for liquid flammable substances: ABC powder, carbon dioxide (CO 2 ) B Fires in flammable liquids, combustible liquids, petroleum greases, tars, oils, oil-based paints, solvents, lacquers, alcohols, and flammable gases. C for gaseous combustibles: ABC powder, carbon dioxide (CO 2 ) C Fires that involve energized electrical equipment. D for combustible light metals: metal fire powder (dry sand, if necessary, never water) D Fires in combustible metals, such as magnesium, titanium, zirconium, sodium, lithium, and potassium. F for edible fats and oils: foam or special extinguishing agent K Fires in cooking appliances that involve combustible cooking media (vegetable or animal oils and fats). Fire extinguishing agent. General term for any solid, liquid or gaseous substance used to fight fires. They are classified according to ↑ fire classes. Water is undoubtedly the most common extinguishing agent (cooling effect); however, it must not be used for metal fires and burning liquids that are not miscible with water (e. g. gasoline). Because flammable liquids are always less dense than water, they float when water is added, increasing the surface area of the fire. For liquids that can be mixed with water in any ratio (e. g. ethanol), the addition of water raises the ↑ flash point. Once this exceeds the temperature of the burning liquid, the temperature falls below the lower ↑ explosion limit and the flame extinguishes. ( ↑ CO 2 fire extinguishing system) Fire safety. All employees, regardless of the requirements of the job, should be trained in basic fire safety. Appropriate drills, such as fire extinguisher use, are recommended. Ignorance of electrostatic ignition hazards combined with inappropriate extinguishing attempts can have devastating consequences. Fitting, ↑ armature Fixation (electrostatic). Charged insulating films (e. g. by ↑ corona charging, ↑ useful application), when approaching conductive parts, cause ↑ image charges in the latter, Fixation (electrostatic) 175 <?page no="181"?> resulting in an attractive ↑ Coulomb force. In a sense, they hold themselves together with their charge. This effect is used, for example, when plastic films are sandwiched between polished metal plates to prevent scratches, when text or graphic films need to be held in injection molds prior to the injection process, when film webs need to adhere to metal rollers (in winding and stretching processes), etc. ( ↑ in-mold labeling) Fixed connection of a cable, ↑ connector Flame. Visible reaction of fuel and oxygen whose color indicates whether it is burning in a ↑ lean (bluish) or ↑ rich (yellow/ red) mixture ( ↑ explosion limit). Flame arrester vent. Based on cooling combustible gases below ignition temperature ( ↑ MESG, ↑ Davy, ↑ quenching distance). Flame ionization. In gases, thermal excitation can cause electrons to separate ( ↑ ionization) because of their thermal motion during inelastic “ collisions ” of atoms or molecules. The ↑ ions formed in this way are predominantly positively charged and can cause discharges at larger distances due to thermal buoyancy ( ↑ ionizer) or lead to charge accumulation ( ↑ cloud dipole in volcanic eruptions, ↑ thunderstorm electricity). Flame ionization detector (FID). A detector for organic compounds developed by McWilliam and Dewar (1958) and used primarily in combination with gas chromatographs. It measures the change in conductivity of an oxyhydrogen gas flame (hydrogen and oxygen) as a result of the introduction of the substance to be analyzed into the flame (thermal ionization up to > 3000°C). The ionization of the gas to be analyzed causes the current of 300 V/ cm and approx. 1 pA to rise sharply and the released electrons are collected e. g. with capacitor plates or a grid (insulation resistance > 10 13 Ω ) and detected by suitable electronics [Leibnitz, E., Struppe, H. G. (1984)]. Flame propagation. Flames generated in an Ex-atmosphere can have a volume approximately ten times that of the Ex-atmosphere before ignition. Therefore, if the flame propagates in one direction, long jet flames can be expected. In a stoichiometric fuel/ air mixture ( ↑ stoichiometry), the flame front spreads at a speed of about 10 m/ s under atmospheric conditions. If the combustible atmosphere is in a closed volume, the expansion of the gas heated by the heat of reaction ( ↑ exothermic reaction) leads to a brief increase in pressure to about 10 bar, which decreases after cooling and can even cause negative pressure. [TRGS 721 and 723] Flame reaction. After ignition, the flame reaction within the explosion range is determined by the prevailing fuel concentration. Flame retardants. In the case of combustible solids, added flame retardants are intended to limit, slow or prevent fires. In the case of textiles, it should be noted that water-soluble flame retardants can be washed out. [SE Section 7.5.10] Fixed connection of a cable 176 <?page no="182"?> Flameproof enclosure, ↑ type of protection “ d ” Flameproof joint, ↑ type of protection, ↑ MESG Flaming. Process to increase the ↑ surface energy of insulating materials prior to further processing (e. g. gluing). In addition, the ↑ electrostatic discharge of the surface ( ↑ corona pretreatment) takes place. Flammable liquid according to the valid classification ( ↑ Globally Harmonized System - GHS) and the ↑ CLP Regulation: Category Criterion Hazard warning (H-phrase) Label (CLP) 1 Flash point < 23°C Initial boiling point < 35°C H 224 Liquid and vapor Extremely flammable Danger 2 Flash point < 23°C Initial boiling point > 35°C H 225 Liquid and vapor Highly flammable Danger 3 Flash point < 23°C and < 60°C H 226 Liquid and vapor Flammable Warning (4) * (Flash point > 60°C and < 93°C) H 227 Combustible liquid Warning No symbol * Only in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS), not adopted in the CLP Regulation. ↑ Combustible liquids are the generic term that includes flammable liquids. According to [TRGS 509], ↑ liquids are considered combustible if their flash point is ≤ 370 °C. [SE Section 1.2.2.2] Note: In divergence from the GHS, NFPA 30 (USA) defines the terms combustible and flammable at different temperatures, particularly for liquids, as follows: - Combustible: substances with a flash point above 100 °F (37.8°C) and below 200 °F (93.3°C). - Flammable: substances with a flash point below 100 °F (37.8°C). These substances are highly flammable at normal room temperature. Flammable liquid 177 <?page no="183"?> Flange. Annular disk firmly connected to a pipe ( ↑ armature). ● In the case of conductive pipes, the electrical connection between the pipes must be ensured via the flange. In the case of standard electrically insulating gaskets, this can only be achieved by screwing the flanges together, i. e. they must not have an electrically insulating coating. Lap joint flanges (loose flange) must be in good contact with the pipe. In hazardous areas, flange connections should always be checked for adequate electrical volume resistance and electrically bypassed if necessary. ● On electrically insulating piping (glass or plastic), conductive flanges can be charged by the influence of the charging liquid flowing through them. They must be earthed in hazardous areas, although earthing may be waived for ↑ glass apparatus with a diameter < 50 mm in ↑ Ex-zone 1. [TRGS 727] Flash point. Symbol T F , unit [°C], the lowest temperature determined under ↑ atmospheric conditions in a defined test apparatus at which a flammable mixture begins to form above the liquid surface (lower ↑ explosion limit). According to the ↑ BetrSichV, flammable liquids are divided into: - Flammable: T F < 55 °C and > 21°C - Highly flammable: T F < 21°C - Extremely flammable: T F < 0 °C and initial boiling point < 35°C Different methods for determining the flash point are permitted in different countries. Deviations in the resulting numerical values must be considered for safety-related specifications. For this reason, the explosion prevention regulations stipulate that the risk of explosion can only be safely excluded if the processing temperature is at least 5 K below the flash point for pure liquids and at least 15 K below the flash point for solvent mixtures ( ↑ fog, ↑ ink mist). Caution: The flash point of a mixture may be lower than that of the individual components. {Appendix B}, [TRGS 721] Flash protection. ↑ Ionizers are typically operated with a voltage of 5 - 8 kV (AC) and therefore require contact and flash protection. This is to prevent interference with, for example, data lines ( ↑ Electromagnetic Compatibility). These protection requirements are met by installing a resistive or capacitive current limiter. Flashing. ↑ Gas discharge, also a term for the unwanted exposure of photographically sensitive surfaces due to the high levels of blue and ultraviolet light in the region caused by the nitrogen ( ↑ atmosphere). This flashing can be countered by using ↑ antistatic agents, ↑ ionizers, appropriate optical filters, and an optimized processing environment. ( ↑ Lichtenberg figure) Flashover strength. Value of electrical strength at which current flow between two poles is just prevented at a boundary layer. The flashover strength is lower than the ↑ electric strength. In addition to the material parameters at the contact surfaces, the flashover strength is influenced by ↑ pollution, ↑ temperature and ↑ humidity, type of voltage, and duration. ( ↑ creepage distance, ↑ clearance) Flange 178 <?page no="184"?> Flint ● Rock of finely crystalline silica that produces sparks when struck. ● Industrially manufactured metal pin made of cerium-iron (mixed metal of Ce, Fe and other rare earths), which produces sparks when rubbed (mechanical lighter (mechanical ↑ sparks)). Floating ball. Hollow plastic balls (approximately 10 - 100 mm in diameter), that are poured onto liquids where they form a uniform layer. Regardless of the ball diameter, 91 % of the liquid surface is always covered, reducing evaporation or heat loss. From an electrostatic point of view, floating balls must be conductive or dissipative and can only be used with liquids with sufficient ↑ conductivity. They must be connected to earth (e. g. via the liquid) otherwise they may become dangerously charged. [TRGS 727 Section 4.3.3] Floating roof tank, ↑ tank Flocking, ↑ coating Floor. Earthing the floor is one of the most important protective measures for dissipating electrostatic charges. The leakage resistance must not exceed the value of 100 M Ω in Exareas of Zones 0, 1, 20 and 21 and the value of 10 6 Ω in areas where substances are handled in accordance with the ↑ Explosives Act. For measurements, [IEC 61340-4-1] and [IEC 61340-4-5] must be used. These define the electrostatic properties of a floor as follows: - Electrostatically conductive floor (ECF): resistance < 1 M Ω - Dissipation capability floor (DIF): resistance between 1 M Ω and 1 G Ω - Astatic floor (ASF): A person walking on the floor must not be charged with more than 2 kV ( ↑ walk-in charge). The leakage resistance of a floor depends on the conductivity of the floor covering material and the floor substructure (e. g. screed). The influence of the latter on the leakage resistance decreases as the floor area increases, because a large area reduces the total resistance of an electrically conductive floor covering and increases the capacitance of the floor covering to earth. Both effects counteract any potential increase in potential. For this reason, additional earthing measures (e. g. earthed metal strips in the screed) are not required for conductive floor areas > 10 m 2 , even if the screed is laid on an insulating film ( ↑ leakage resistance of the floor). [TRGS 727 Sections 7 and 8], [IEC/ TS 60079-32-1] - Natural stone flooring is considered to have permanent discharge capability. - Concrete flooring is considered to have permanent electrostatic dissipation capability if cement has been used in its manufacture, resulting in the bonding of water of crystallization. [TRGS 727 Annex H] - Ceramic flooring, such as fired tiles, is generally considered to have inadequate dissipation capability. Better conductivity can be achieved by moistening with water (e. g. by frequent wet cleaning). Accordingly, measuring the leakage resistance with a damp blotting paper under the electrode generally leads to an incorrect evaluation. Recently, permanently dissipative unglazed ceramic tiles have become available whose dissipation capability does not depend on wetting (Eladuct ® ). The floor covering can be Floor 179 <?page no="185"?> kept moist and thus dissipative for a longer period by wetting it with a water-glycerin mixture. (This function must be checked regularly.) - Floor covering made of plastic or similar materials are generally not conductive. By incorporating conductive additives (e. g. ↑ carbon (graphite, carbon black), metal fibers), plastic floors can be made permanently conductive. The principle of ↑ high-voltage perforation has proven effective for thin insulating plastic films on a dissipative substrate. In this way, generally adequate charge dissipation can be achieved via the perforation at high charge potentials. ● Cover the existing floor - Additional covering of dissipative floors or their covering is not permitted if this restricts the dissipative function. In addition, the often-used unacceptable covers made of cardboard or paperboard pose the risk of solvent vapors accumulating in their pores and thus creating flammable atmospheres. [TRGS 727 Section 7.2] - Floor covering during spray painting. Floor coverings are acceptable for nonelectrostatic painting operations. However, floor coverings must be changed periodically to prevent high fire loads. Also, make sure the person is earthed during cleaning. In electrostatically assisted painting operations, covers are allowed only if they do not interfere with the earthing of the sprayer through the floor. Covers with unknown volume resistance are not acceptable. [TRGS 727 Section 5.5] Floor exhaust, ↑ exhaust system Floor pan. A spill containment basin in which a liquid-carrying device or a liquidcarrying container is placed. The purpose of the sump is to absorb any spillage and prevent it from spreading throughout the facility and surrounding area. In most cases, a sump is made of concrete and then requires a coating on its surface for waterproofing. If there are ↑ flammable liquids in the tanks, the coating must have electrostatic dissipation capability and be earthed. When installing floor pans, consider the function of any existing floor ↑ exhaust system. Flow velocity ● Flow rate of liquids, depending on factors such as ↑ conductivity, contamination, cross section of the filling line, dimensions of the container (tank), location and type of ↑ container filling. Single-phase liquids are generally not dangerously charged in conductive, earthed pipes at flow velocities of up to 7 m/ s. For two-phase or multiphase liquids, e. g. due to heavy contamination, the flow rate must be limited to 1 m/ s. The same applies to liquids with low conductivity (e. g. pure hydrocarbons such as toluene with < 10 - 11 S/ m). ● Flow rate for gases/ vapors, provided there are no particles in the flow, no electrostatic ↑ charging will occur. In pipelines, the flow velocity is generally not more than 20 m/ s. No limits are specified. However, fans can have much higher flow velocities in the area between the wall and the impeller, where even the smallest particles can initiate chargegenerating processes if insulating materials are used. Therefore, all parts of exhaust systems in Ex-zones 1 and 2 must be conductive and earthed. [TRGS 727 Section 5.6] Floor exhaust 180 <?page no="186"?> Fluidized bed process. It is a state of constant movement and mixing of solid particles under the influence of an ascending gas stream. A liquid-like state is achieved, i. e. objects of higher density can be immersed by gravity alone (useful application: ↑ coating, cleaning). As a result of electrostatic charging, the particle agglomerates ( ↑ agglomeration), either in the desired way (e. g. granulation) or in an undesired way which can have a lasting negative effect on the sintering result (remedies: including the use of ↑ antistatic agents). Fluorination. Surface treatment of plastics under the influence of gaseous fluorine. This transforms a μ m-thick layer on the surface of the polymer into a functional thin film that creates a barrier effect. Fluorination is often used to reduce the ↑ diffusion of vapor molecules through container walls, especially those made of polyethylene. After the fluorination of automotive gasoline tanks, several ignitions occurred during initial refueling, which were undoubtedly due to the increased electrostatic charging tendency of the fluorinated interior surfaces. An explanation for the higher charging tendency caused by fluorination is probably to be found in the highest possible electronegativity of fluorine ( χ F = 3.98). Fog. Generally, an ↑ aerosol of liquid suspended particles, in the narrower sense condensed water steam ( ↑ air conductivity, ↑ dew point). Since droplet dispersion in technical applications is often produced by spraying liquids, the terms spray, spray jet or aerosol are more commonly used. Upon atomization, flammable liquids can form explosive ↑ aerosol-air mixtures even at temperatures below their ↑ flash point. Food. It can be made more durable or easier to process by using pulsed electric fields (PEF). Both plant and animal cells (e. g. microorganisms) are reversibly or irreversibly affected by PEF in bioprocess engineering. Liquids can thus be sterilized, or, for example, potato chips can be produced much more effectively and energy-efficiently (up to 90 % water and energy savings). Product quality can also be significantly improved when drying fruit, for example. [Parniakov, O. et al. (2021)] (Source: www.elea-technology.com) Foot earthing strap, ↑ earthing - personnel earthing Forbidden band. It is located between the ↑ conduction and ↑ valence bands in the ↑ band model and is also called the gap energy. Electrons in the forbidden band cannot take on any energy values, except for impurities. Force field (electrostatically). Like gravity, the forces between bodies are a precisely calculable natural phenomenon whose magnitude and direction can be clearly represented Force field (electrostatically) 181 <?page no="187"?> by “ lines of force ” . The concept of an electric field was introduced by M. ↑ Faraday. ( ↑ Coulomb force) Forced ventilation. Outdated term for the pressurized enclosure type of explosion protection ( ↑ type of protection “ p ” ). Foreign atom (impurity atom) in the semiconductor. Non-lattice atom in the crystal ( ↑ doping). Even a few foreign atoms can have a strong influence on the electrical properties of a semiconductor. Foundation earth electrode. Conductive part, usually installed as a loop in a foundation (usually concrete) and provided with a connection point. ( ↑ earth electrode) Fractals (Latin: frangere, “ to break ” ). Description of complex structures (fractal geometry) by B. Mandelbrot (1924 - 2010). Thus, proliferating, delicate patterns in nature can be understood as forms of fractal growth, whereby various processes, such as crystallization, movement of air bubbles in liquids, high electric potentials at electrodes, etc., can lead to similar forms of branching patterns (self-similarity). In electrostatics, it is the ↑ Lichtenberg figures whose growth is initially caused by a high electric field strength. With the onset of a ↑ gas discharge, an electrically conductive channel begins at the peak where the field strength is greatest. These pins become longer and longer and branch out. An example of fractal growth is shown by the traces of electrostatic discharges in a highly charged PMMA plate with punctual lateral contact to earth. ( ↑ dendrites, ↑ treeing) Franck-Hertz experiment. Experiment performed by J. Franck and G. ↑ Hertz in which the quantum nature of atomic energy levels is characterized by ↑ electron collisions for a particular type of ↑ atom. ( ↑ electronvolt) Franklin, Benjamin (1706 - 1790). American politician, printer, writer, and scientist began researching electricity and the electrical spike effect ( ↑ corona effect) in 1746. He proposed using the spike effect to discharge electricity from thunderstorms. This led to the construction of “ Franklin ’ s lightning rod ” on a merchant ’ s house in Philadelphia in 1760, which was partially melted by a lightning strike soon after but protected the house from lightning damage ( ↑ lightning rod). Franklin was the first to coin the terms “ plus ” and “ minus ” for polarity. [SE Section 4.2.4] Freeze charging, ↑ charging Frequency (Latin: frequentia, “ frequency ” ). Symbol f with the derived ↑ SI unit [Hz], named after H. ↑ Hertz. It defines the number of oscillations per unit of time, i. e. the number of periodically repeating processes occurring in one second. Frequency discriminator (phase discriminator) (Latin: discriminare, “ to separate ” ). A module used in ↑ EFM to provide signals for positive or negative values. Depending on the sensitivity, values from 1 V/ m to breakdown field strength (3 MV/ m) can be recorded. Fresh air, technical ↑ ventilation Friction electrification machine. Electrification machine in which a rotating body (ball, disk or cylinder made of glass) is “ rubbed ” against a friction material (e. g. leather with Forced ventilation 182 <?page no="188"?> amalgam coating) originally held by hand ( ↑ cylinder electrification machine). An alternative is the ↑ influence electrifying machine. Frictional charging. The term “ frictional (tribo)electricity ” , created in the Baroque period, is incorrect in that friction can only produce heat, not electricity. Frictional charging is intended to express the fact that ↑ charging is preceded by intensive contact caused by friction. In fact, materials can hardly be brought into contact without some friction. Friction that precedes the separation process (by increasing the number of contact points) can increase the level of charge and also lead to a reversal of the charge sign ( ↑ charging phenomenon), caused, for example, by a local increase in temperature ( ↑ violin bow effect). Intense friction can also lead to a material transition, which also represents the possibility of charge transfer. ( ↑ material web, ↑ coating, ↑ charge transfer - measurement) Full-body protective suit, ↑ personal protective equipment Full load. State of maximum power output for machines. Fullerene, ↑ carbon Functional earthing, ↑ earthing Functional extra-low voltage (ELV). Protective measure in which the circuits are operated with a rated voltage of up to 50 V AC or 120 V DC, but which does not meet the requirements for safety extra-low voltage and is therefore subject to additional conditions. Fundamental forces of physics, ↑ electrostatic Funnel (Latin: traiectorium, “ device for pouring ” ). Device for pouring liquids or bulk materials into narrow openings. In ↑ Ex-areas, funnels, if made of conductive material, must always be earthed to avoid electrostatic hazards. When transferring flammable liquids, especially into containers made of insulating material, the outlet tubes ( ↑ filling pipe) of the earthed funnels should lead close to the bottom of the container. [TRGS 727] Funnel 183 <?page no="189"?> G Galvani, Luigi (1737 - 1798). Italian physician and naturalist studied electrical phenomena on frog leg nerves with two different metals connected and interpreted the muscle contractions as animal electricity. This was disproved by the experimental results of his contemporary A. ↑ Volta. Galvani voltage. Electric potential difference Δ φ inside substance A and the inside of substance B at their ↑ contact surface named after L. ↑ Galvani. The effort to release electrons determines the level of the Galvani voltage ( ↑ charge double layer). Galvanic connection. Directly electrically connected, as opposed to inductive or capacitive ↑ coupling. Galvanic element. In modern times, electrochemical power generation was attributed to L. ↑ Galvani, based on the conversion of chemical energy into electrical energy (A. ↑ Volta). It can be designed as a battery ( ↑ primary cell) or as an accumulator ( ↑ secondary cell). During excavations in 1936, archaeologists discovered the so-called Baghdad battery, in which a copper sheet and an iron rod were found in a ceramic vessel. Tests showed that this battery could produce 0.5 V. [König, W. (1936)], [Der Spiegel (1978)] Galvanometer. A highly sensitive moving-coil meter, occasionally equipped with an inertia-free light pointer (mirror galvanometer), which allows measurements down to the pA-range. Nowadays largely replaced by electronic ↑ pico-ammeters. ( ↑ influence electrostatic field meter) 592. The mirror galvanometer of Gauss and Weber (Source: [Wilke, A. (1898)]) <?page no="190"?> Gamma radiation. Short-wave ↑ electromagnetic radiation (wavelength between 10 -10 and 10 -15 m) emitted by a radioactive nucleus ( ↑ radioactivity). Gamma radiation is very penetrating and can only be attenuated by high-density materials (e. g. lead). In contrast to ↑ alpha and ↑ beta radiation, its ionization effect is low. Gap energy. Smallest energy difference between two allowed bands, separated by a ↑ forbidden band. ( ↑ band model) Gas. Substance that is completely gaseous at a vapor pressure > 3 bar and 20 °C or at a pressure of 101.3 kPa. ( ↑ smoldering gas) ● Ideal gas consists of molecules or atoms whose dimensions are very small in relation to their distance, and which do not exert any forces on each other. These particles behave like “ rigid ” spheres and are in constant motion. The laws of conservation of energy and momentum apply to collisions between particles and with boundary surfaces. Gases are generally non-conductive; they become conductive only by high temperature or ionization. [Wedler, G., Freund, H.-J. (2018)] ● Gas properties are classified as follows: - Combustible gas has an ↑ explosion range under atmospheric conditions. - Oxidizing gas can react with combustible substances in such a way that they burn much faster than in air (e. g. oxygen, ↑ ozone). - Inert gas neither supports combustion processes nor is it combustible itself (e. g. nitrogen ↑ inerting). - Gas hazardous to health Gas can only be charged by ↑ ionization, but not by separation processes ( ↑ charging). The occasional charging of flowing gases, e. g. compressed air, is always due to entrained ↑ aerosols. Gas detector, ↑ gas warning device Gas discharge (electrostatic). A physical phenomenon that occurs when an electric current passes through a gas. It is subdivided into: ↑ corona discharge, ↑ brush discharge, ↑ super brush discharge, ↑ cone discharge, ↑ propagating brush discharge, ↑ spark discharge, ↑ dark discharge and ↑ thunderstorm lightning. In high-voltage engineering, the term ↑ partial discharge is used ( ↑ ignitability). In contrast to metals, gases are not electrically conductive. Only when a gas discharge occurs can an electric current flow through gases. The charge carriers required for a gas discharge are positive and negative ↑ ions as well as free electrons, which are caused by external ionization (non-independent discharge) based on high-energy radiation (UV, laser, X-ray, gamma radiation) and thermo-ionization (high temperatures, ↑ flame ionization). When an electric field is applied to a gas section, the charge carriers are caused to move according to their polarity, with their velocity being determined by the field strength and the frequency of elastic collisions with the molecules of the surrounding gas (gas pressure) ( ↑ Paschen ’ s law). As the field strength increases, the electron velocity reaches a critical value at which the collisions become inelastic (impact ↑ ionization), and the gas molecules release electrons by becoming positively charged themselves. This leads to an avalanche-like increase in charge carriers (electrons and positive ions), which are Gas discharge (electrostatic) 185 <?page no="191"?> moved to the electrodes according to their polarity and release ↑ secondary electrons there if the impact energy is high enough. The resulting carrier movement - also called “ selfsustained discharge ” - represents an electric current with an avalanche-like increasing tendency. In homogeneous electric fields, such a gas discharge starts under ↑ atmospheric conditions at a field strength of ~ 3 MV/ m. In the case of inhomogeneous field distributions, it always starts at the location of the highest field strength, i. e. the smallest radius of curvature and thus the highest field line density ( ≤ 1 mm as corona discharge, ≥ 1 mm as brush discharge ( ↑ Rogowski profile)). Irrespective of this, gas discharges are not expected to occur at voltages below about 300 V due to the close electrode spacing ( ↑ quenching distance). Figure 1 shows how, according to the rules of electrodynamics, every electric current flow is surrounded by a magnetic field, including the ion current (D), which initially flows in a diffuse region between the electrodes. The resulting magnetic field lines (M) have the shape of concentric circles around the current path and tend to shorten ( ↑ Lorentz force). Thus, a self-compression of the initially diffused gas discharge is initiated, resulting in a corresponding heating (compression heat). This process starts (like ionization) at the smaller sphere as the site of the highest field strength. This compression process, also called the ↑ pinch effect, to a ↑ plasma (P) eventually continues along the entire path of the gas discharge and is completed only when there are no neutral gas molecules in the current path, but only ions and electrons. The high temperature of plasma is ultimately the cause of the ignitability of gas discharges in flammable mixtures. If the electrostatic charge source has only a small amount of energy ( μ J-range), it will be depleted after the initial plasma entrapment due to energy consumption during gas compression, and the process will stop shortly after starting (brush discharge). The process can be repeated with the addition of a new supply of electric charge. On the other hand, if the charge source has a higher amount of energy (mJ-range and more), a situation as shown in Figure 2 occurs. With sufficient charge replenishment, the gas discharge is compressed along its entire path by the enveloping magnetic field to form a plasma, which has very low electrical resistance in contrast to the original insulating gas atmosphere. In addition to the heating of the gas and the resulting high ignition potential, this results in a near short-circuit between the electrodes. If continually adding more charges this will finally lead to the development of a continuously burning arc discharge (electric arc). However, if the supply of electrical energy is limited, as in the case of an electrostatic discharge or the discharge Gas discharge (electrostatic) 186 <?page no="192"?> of a capacitor, then the electric field also collapses with the “ short-circuit ” effect of plasma, the charge is consumed, and the current flow approaches zero. This deprives the confining magnetic field of its basis, and it collapses as well. This results in the emission of a nonperiodic damped ↑ electromagnetic radiation or wave in the kHz to GHz frequency range. The reason for this is that already during the pinch effect a mutual coupling between the magnetic and the electric field has been established, with the latter leading. From the point of view of electrostatics, the following criteria apply to gas discharges (apart from corona discharges): - If plasma is formed, combustible gases and dust can be ignited by its high temperature. - Plasma is always associated with the emission of an electromagnetic wave (interference pulse of electromagnetic radiation), so that it is possible to determine whether qualitatively ignitable gas discharges occur by means of a ↑ spark detection device or, for example, a radio receiver (AM-range). ● The power density of gas discharges is the main factor in determining the ↑ MIE. It is the amount of energy per unit time, related to the unit volume. This can be approximated by precise specifications for the spark gap (electrode spacing, diameter) and the damping in the discharge circuit (ohmic and inductive resistance) ( ↑ Hartmann tube). ● The detection of gas discharges is manifested by: - Electric current - Luminous appearance ( ↑ gas discharge light) - High-frequency electromagnetic radiation in the kHz to MHz range, noise (hissing, popping, thundering) - Ozone and nitrogen oxide formation Luminescent phenomena and ozone and nitrogen oxide formation can be detected immediately, but weak gas discharges can only be detected over short distances. Highfrequency radiation, on the other hand, can be detected over longer distances with appropriate receivers. Noise and high-frequency radiation are caused by the ↑ pinch effect. Gas discharge detection, ↑ spark detection device, ↑ gas discharge Gas discharge detector. A device for detecting and evaluating the electromagnetic pulses caused by ↑ gas discharges (except corona discharge) and their high-frequency components by means of an antenna and a corresponding receiver (e. g. oscilloscope). Approximate conclusions can be drawn about the course of the discharge, its strength and its presumed location. It is particularly suitable in hazardous areas in processing plants of e. g. ↑ material webs. It can also be used to check the effectiveness of built-in discharge bars ( ↑ ionizers). Gas discharge figure, ↑ Lichtenberg figure, ↑ charge distribution Gas discharge light. It is always accompanied by radiation emission in the visible and/ or adjacent ultraviolet range. It is caused by gas atoms or molecules excited by impact ionization as their electrons fall back to their original energy state. This results in photon Gas discharge light 187 <?page no="193"?> emission with a substance-specific emission spectrum, which may consist of single spectral lines (e. g. oxygen) or a large number of adjacent spectral lines (e. g. nitrogen) ( ↑ atom). In the case of atmospheric gas discharges (e. g. ↑ thunderstorm lightning), most of the radiated energy occurs in the region of the nitrogen spectra, corresponding to the composition of air (about 21 % oxygen and 78 % nitrogen). The latter is mainly in the blue and near-ultraviolet region, so that only a relatively small fraction of the radiation is visible ( ↑ flashing). Gas discharge mark. Usually, tiny due to low energy release, but typical and therefore allow conclusions about the type of gas discharge ( ↑ ignitability of gas discharge). (Damage to electronic components is not described here.) ● ↑ Corona discharge leaves no visible marks, but the ↑ wettability of polymer surfaces exposed to it can be altered. ● ↑ Brush discharge causes ice flower-like charge distribution patterns (dust attraction) on insulating material surfaces, which become visible through ↑ toner or dust from the environment ( ↑ charge distribution). Surfaces of different signs are directly adjacent. Charge equalization is shown in the ramifications between partial surfaces. Cloudy regions indicate negative charges. ● ↑ Cone discharge does not leave a mark on the bulk cone itself, but where it hits the silo wall it can cause tiny erosion marks that can be seen under optical magnification. ● ↑ Super brush discharge. There are no studies to date on possible markings from this type of discharge. ● ↑ Propagating brush discharge has higher energies and causes branching melt marks on thermos-polymers. Again, better detection is possible with toner or similar. Perforations on polymers (pores) caused by this discharge often remain undetected. If such discharges start repeatedly from the same perforation, melting, decomposition and burning processes can occur. For example, antler-like burn marks can be seen on insulated metal tubing of pneumatic conveying systems, ending in a more or less burntout hole. If the material to be conveyed is combustible, ignition may also occur in the pipe, especially during a vacuum conveying ( ↑ Paschen effect). ● ↑ Spark discharge causes erosion or melting marks or even annealing colors on the electrodes, depending on the energy. Pores in the glass lining of vessels and agitators have been observed. They occur when insulating liquids with undissolved conductive components are moved, resulting in high field strengths in the ↑ enamel layer. Such Gas discharge mark 188 <?page no="194"?> pores usually go unnoticed until corrosion damage occurs. To remedy this, a conductive and earthing layer (e. g. silver) under the top enamel layer has proven effective. This dissipates the liquid ’ s charge to earth before it can create an electrical field in the protective enamel layer. (Source: Pfaudler GmbH) In addition, during ↑ winding/ unwinding, such high charges can be generated that ↑ electrical discharge machining occurs in the earthed bearings (Photo). ( ↑ composite), [Schubert, W., Ohsawa, A. (2024)] Gas discharge tube. Sealed chamber for targeted application of ↑ gas discharges (lighting, switching). At reduced pressure (low-pressure gas discharge), the gas discharge starts at field strengths of about 10 kV/ m ( ↑ glow lamp, fluorescent tube). If, on the other hand, high radiation densities are required, a high-pressure gas discharge is used with starting field strengths of 10 MV/ m (mercury vapor, high-pressure xenon lamp). Since gas discharges always have an increasing current tendency, gas discharge tubes must always be operated with a current limiter (e. g. series resistor) to protect them from overloading. Gas flow. Pure gases, i. e. those free of liquid or solid ↑ aerosols, do not become electrostatically charged ( ↑ charging) when flowing. This statement is only of theoretical importance, since gases almost always carry aerosols that cause significant charging even at low concentrations, e. g.: Gas flow 189 <?page no="195"?> - Plant-related: Flash rust in pipes, oil mist from compressors, whirled up deposits. - Process-related: Expansion leads to cooling and falling below the ↑ dew point temperature and thus to the formation of a liquid aerosol ( ↑ wet vapor) or to ↑ sublimation and the resulting solid aerosol (e. g. in a ↑ CO 2 fire extinguishing system). Gas ion, ↑ ion Gas molecules. The presence of gas molecules on surfaces of any kind is an essential factor for the ↑ charging generated by contact and separation. The gas molecules are adsorbed on the surfaces (e. g. carbon dioxide). If the substances are placed on top of each other without friction, the gas molecules from the surrounding atmosphere, which usually adhere to the surface in several layers, keep the contact surfaces at a distance, a circumstance that is largely eliminated by friction. In this atomic or molecular region, there are almost never physically clean surfaces, i. e. surfaces that are not contaminated with other molecules ( ↑ glow discharge installation). Gas phase. Refers to the gaseous substances of a chemical reaction system whose components are present in various ↑ states of matter. In the case of flammable substances, the gas phase can form an explosive atmosphere ( ↑ combustion, ↑ solvent vapor). Gas purification, ↑ separation of substances Gas swing adsorption (vapor recovery system). Used to return the displaced gas volume when filling containers, especially with liquids: - Recirculation of inert gas from a protected container to be filled into the dispensing container. - Recirculation of displaced vapors during filling to prevent them from escaping into the environment (e. g. vehicle fuel tank). As an ↑ Ex-atmosphere may be present throughout the recirculation area, attention must be paid to the hazards of electrostatic charging. Gas warning device. Used to detect explosive or harmful gases and vapors. Gas detectors are designed to monitor the atmosphere and warn of explosive atmospheres, health hazards and oxygen deficiency or trigger protective measures to avert hazards ( ↑ work clearance permit, ↑ clearance measurement, ↑ explosimeter). [DGUV Information 213-057] Gasket (seal). Component of plant systems at the interface of components. They are divided into static seals ( ↑ flange) and dynamic seals (seal in a ball valve). They are usually made of insulating materials. As such, they often represent an interruption in the dissipation capability of a system. This must be considered, especially in hazardous areas. PTFE seals with metal inserts are often used. These must be earthed (e. g. metal insert with earth lugs) in piping regardless of the nominal size (DN), unless it can be demonstrated that hazardous charges are not expected. Gasoline (petrol, lighter fuel). A general term derived from Arabic for a mixture of hydrocarbons used primarily as a fuel. Gasoline has low conductivity and is therefore classified as a chargeable liquid ( ↑ chargeability). The relevant ↑ flash points and boiling points are decisive for the evaluation of the explosion hazard, so that gasoline is classified Gas ion 190 <?page no="196"?> as highly flammable or extremely flammable according to the applicable classification system for ↑ flammable liquids, depending on its quality. [SE Section 1.2.2.2] Due to its low flash point (< - 35°C) and electrostatic chargeability, gasoline for Otto engines requires appropriate protective measures when ↑ refueling ↑ cars. ( ↑ CAS number) Gasoline vapor. 5 ml of gasoline produces about 1.6 l of gasoline vapor (gas), which forms an explosive mixture with air with a volume of about 200 l at the lower ↑ explosion limit (LEL). GefStoffV, short for German: Gefahrstoffverordnung (Hazardous Substances Ordinance): - Regulates the classification, labeling and packaging of dangerous substances and certain products as well as the handling thereof (dangerous goods) - Regulates the measures for the protection of persons when working with hazardous substances - Regulates restrictions on the manufacture and use of hazardous substances, mixtures and products - Regulates the placing on the market of hazardous substances and mixtures Geiger-Müller tube (also counter tube). Gas-filled detection device for ionizing radiation based on the principle of an ↑ ionization chamber. While the ion current is used to detect radiation, the gas pressure and gas composition of the counter tube are selected in such a way that the initial ionization leads to ↑ gas discharges through further impact ↑ ionization, which trigger countable pulses at the ↑ anode. A counter tube has a thinwalled, cylindrical outer electrode made of metal or conductive glass (possibly with an additional window that allows ↑ alpha radiation to pass through), in which a thin, insulated coaxial wire or a slim pin (tip counter) is installed as a counter electrode. Counter tubes can also be operated (low voltage) in such a way that the output pulses are proportional to the primary ionization (proportional counter). Alpha and ↑ beta radiation can be detected separately due to its different specific ionization, whereby it is also possible to determine the energy of the radiation. ↑ Gamma radiation can be detected by shielding against alpha and beta radiation. German Commission for Electrical, Electronic & Information Technologies in DIN and VDE, ↑ DKE GGBefG, short for German: Gefahrgutbeförderungsgesetz (Dangerous Goods Transportation Act). Basic law for the transportation of dangerous goods (formerly ↑ GGV) ( ↑ ADR). - Dangerous Goods Ordinance for road, rail and inland navigation - Dangerous Goods Officer Ordinance - Dangerous Goods Exemption Ordinance GGBefG 191 <?page no="197"?> - Portable Pressure Equipment Ordinance - Guideline for the design type approval procedure for packages for the transport of radioactive material, radioactive material in special form and low dispersible radioactive material (R 003) - Dangerous Goods Costs Ordinance GGV, short for German: Gefahrgutverordnung (Dangerous Goods Regulation). It has been replaced by [ ↑ GGBefG]. GHS, short for ↑ Globally Harmonized System Gilbert, William (1544 - 1603). Physician in England, developed a common theory of electricity and magnetism on an empirical basis. Glass. Main raw materials are silica sand, lime, soda and potash. The difference between glass and other amorphous solids is that glass changes to the liquid state when heated in the region of the ↑ glass transition temperature, while non-glass amorphous substances crystallize. ● Silicate glass. Predominantly solid, amorphous, inorganic substance produced by supercooling a melt without crystallization. It is not a solid in the true sense of the word, but an infinitely slow flowing liquid. In electrical engineering, it is an insulating material, and no protective measures are generally required in ↑ normal climates if it is only exposed to low friction and is not located in ↑ Ex-zone 0 [TRGS 727 Sections 4 and 8]. ● Quartz glass. Pure silicon oxide (SiO 2 ) without the usual small additions of other substances (e. g. calcium oxide or sodium carbonate). It has a much better electrical insulation capacity and is therefore used in measuring cells ( ↑ measuring electrode) that are exposed to high thermal and/ or chemical stresses. It is transparent to UV radiation. ● Borosilicate glass. Particularly chemicaland temperature-resistant glass that is also transparent to UV radiation. [SE Section 7.7.4] ● Many polymers (e. g. Plexiglas ® ) are referred to as organic glass, as they also fall into the glass category due to their amorphous structure and glass transition, although they have a completely different chemical composition to silicate glass. Glass apparatus. If chargeable liquids are processed in a glass apparatus under conditions where a dangerous charge is to be expected, protective measures must be taken, in particular earthing measures, e. g. on metal flanges, valves, metal measuring instruments - graded according to ↑ Ex-zones. A ↑ field penetration can cause ↑ brush discharges from the surfaces of the glass apparatus if the ↑ surface temperature is significantly higher than the ambient temperature and the relative humidity is low. If no strong charge-generating processes are to be expected, metal flanges need only be earthed in accordance with their nominal diameter (DN). [TRGS 727 Section 4.13] Ex-zone (risk area) Substances of Ex-group IIA; IIB Substances of Ex-group IIC 0 for all DN for all DN 1 for DN ≥ 50 for all DN 2 for DN ≥ 50 for DN ≥ 50 GGV 192 <?page no="198"?> Glass transition temperature (T g ). Characterizes the transition of amorphous or semicrystalline polymers from the liquid or rubber-elastic state to the glassy (hard-elastic) state and vice versa. The phenomenon of the glass transition temperature is caused by the thawing or freezing of longer chain sections in the polymer ( ↑ Brownian molecular motion). When the glass transition temperature is reached, there is a permanent change not only in the viscosity but also in the ↑ permittivity number. Globally Harmonized System (GHS). The GHS for the classification and labelling of chemicals was introduced in 2009 under the auspices of the United Nations to eliminate the differences in the existing international systems and to further raise standards in the areas of occupational safety, health, environmental and consumer protection and the transport of dangerous goods ( ↑ liquid). The recommendations of the UN with its GHS system have not been fully adopted by the EU, but they have been primarily adopted. There are also references to the REACH regulations. Implementation is based on the ↑ CLP Regulation, which regulates the classification, labelling and packaging of substances and mixtures in accordance with the ↑ GefStoffV. The German BG RCI ’ s GHS converter (www.gischem.de) allows the new GHS/ CLP classification to be automatically determined from the previous classification. Only the following two symbols must be used: - Flame (GHS02): Do not rub or tap substances, prevent fire, sparks and any heat generation. Substances are flammable; liquids form explosive mixtures with air; form flammable gases with water or are self-igniting. Keep away from open flames and heat sources, keep containers tightly closed, store in a fireproof place. - Flame above circle (GHS03): Substances have an oxidizing effect and intensify fires. When mixed with combustible substances, explosive mixtures are generated. Keep away from combustible substances and do not mix with them, store in a clean place. Glossing. Gas discharge under reduced pressure, especially for cleaning surfaces ( ↑ glow discharge installation, ↑ Paschen ’ s law). Glove, ↑ personal protective equipment Glow discharge. Independent ↑ gas discharge emanating from cold electrodes, which draws its charge carriers mainly from the space charge. The strength of the glow discharge depends on the current flowing through it ( ↑ glow lamp). Glow discharge installation. Device for removing adsorbed water skins on substrates such as plastic films, glass, and metal substrates (also with insulating top layers such as painted surfaces or anodized aluminum layers). Under a reduced gas pressure of approx. 1 - 2 × 10 -2 bar a low-pressure plasma is generated with an alternating voltage of approx. 2 kV and 40 kHz, with which weakly adhering, loosely bound atoms and molecules can be detached, and the surfaces activated (maximum ↑ surface charge density, impact ↑ ionization) (see photo next page). Glow discharge installation 193 <?page no="199"?> (Source: VON ARDENNE Corporate Archive, Photo: A. Müller) Glow-electrical effect ( ↑ Edison effect). A phenomenon in which electrons escape from glowing metals (thermal ↑ electron emission at a ↑ hot cathode). Glow lamp. Lamp, that is well suited for the qualitative detection of electrostatic charging on insulating material surfaces and between charged, non-earthed, conductive objects. It is sufficient to pass the glow lamp by hand over the surface to be tested; earthing is not necessary. In the vicinity of charged surface elements, ↑ brush discharges occur at the electrodes of the glow lamp, which appear as short glow light pulses. A phase tester can also be used to check the voltage in electrical circuits. Glow light. The visible radiation emitted during a ↑ glow discharge (e. g. glow indicator tube). Glow temperature. Lowest temperature at which a 5 mm thick layer of dust (100 mm diameter) on a heated exposed surface begins to glow. To prevent ignition of the dust, the surface temperature must be 75 K below the glow temperature. In the USA, the glow temperature is determined by a 0.5-inch-thick layer in a modified ↑ Godbert-Greenwald apparatus. [DGUV Information 213-065] Glycerol monostearate (GMS). Antistatic agent, preferably used to antistatically finish polyethylene and polypropylene. Godbert-Greenwald apparatus. It consists of a temperature-controlled heated tube (up to 1000°C) through which a fuel-air mixture (usually a ↑ dust-air mixture) flow. The lowest temperature at which the dust particles ignite by contact with the heated surface is determined ( ↑ minimum ignition temperature of the whirled-up dust). This parameter is used, for example, to determine the allowable surface temperatures for drying processes. Glow-electrical effect 194 <?page no="200"?> Gold leaf electroscope. ↑ Electrometer in which a piece of gold leaf is made to deflect ( ↑ Coulomb force). Gradient. Describes the change in a physical or mathematical quantity ( ↑ vector) per unit length and points in its strongest direction. In mathematics, gradient is denoted by [grad] and is used in field theory, among other things. Granules. Coarse ↑ bulk material, the particle size of which generally does not fall below the dimension of 1 mm. Graphene, ↑ carbon Graphite, ↑ carbon Gravity. A property of bodies recognized by I. ↑ Newton that they attract each other because of their mass. All bodies are subject to the effect of gravity ( ↑ charge accumulation, ↑ super brush discharge). Gravity is used for separation during ↑ separation of substances. Gravure printing (also intaglio printing). A process in which printing areas are recessed into the surface of the flat or round printing form by engraving, embossing, impressing or etching. The surface is cleaned prior to printing so that only the recessed areas contain ink, which is transferred to the substrate during the printing process. Electric fields are used in the rotary process as ↑ electrostatic print assist to improve the process flow (speed, quality). ( ↑ corona pretreatment, ↑ material web, ↑ ionizer, laminar ↑ air boundary layer, ↑ electrostatic ribbon tacking, ↑ composite) Grid. Generally, a system of (intersecting) lines or a system of small areas formed by lines. Conductive earthed grid structures on insulating surfaces can be used to divide large surfaces into smaller sections and thus limit hazardous electrostatic charging. ( ↑ area limitation, ↑ RIBC), [TRGS 727 Section 3], {Appendix D} Ground, ↑ earth GS mark. German “ Tested Safety ” seal of approval for ready-to-use products according to § 21 ↑ ProdSG. The award is limited to a maximum of five years or to a defined production quota. Guard electrode, ↑ measuring electrode Guard ring circuit. Used for surface and volume resistance measurement. ( ↑ measuring electrode, ↑ resistance measurement, ↑ measurement error) Guericke, Otto von (1602 - 1686). German physicist, engineer and natural philosopher. His remarkable work in the field of electrostatics (construction of a ↑ friction electrification machine (1663), ↑ levitation experiment to determine the quantity of charge) was eclipsed by the spectacular vacuum experiments (Magdeburg hemispheres). (Source: www.Schuetz.net) Guericke 195 <?page no="201"?> Guide roller. An essential transport element in processing systems for material webs, on which ↑ charging is always generated by contact and separation. ( ↑ banana roller, ↑ delta, ↑ ionizer) Guideline. Can be instruction, principle, or regulation. In the German understanding, it represents the prevailing opinion of experts the Stand der Technik ( ↑ state of the art). ( ↑ ATEX 137) Guide roller 196 <?page no="202"?> H Hair hygrometer, ↑ humidity meter Half-life. Period, in which a decreasing physical quantity has decreased to half its initial value, e. g. ↑ relaxation time and radioactive decay. Hall, Edwin Herbert (1855 - 1938). American physicist discovered the physical phenomenon named after him, the ↑ Hall effect. Hall effect. Effect discovered by E. H. ↑ Hall in 1879. When a current flows longitudinally through a rectangular metal plate and a magnetic field is applied perpendicularly, a potential difference, the Hall voltage, is created between the long sides. The Hall effect can be used to determine the type and density of charge carriers in a semiconductor. Halogenation. It is a chemical reaction in which one or more halogen atoms are introduced into an organic compound. One of the effects of halogenation is to reduce the flammability of a substance. The extinguishing effect of halons is based on the anticatalytic extinguishing effect, i. e. the combustion reaction is chemically interrupted. When exposed to heat, halons release free radicals that attach themselves to the burning material instead of the oxygen required for combustion, thus bringing the reaction to an abrupt halt. Halogens (from Greek háls, “ salt ” , “ salt-forming ” ). Group name for the element ’ s fluorine, chlorine, bromine, iodine, the rare radioactive astatine, and tennessine ( 294 Ts), which was first artificially produced in 2010. Carbon tetrachloride (CCl 4 ) was first used as a fire extinguishing agent around 1914. By 1994, the halon mixtures had changed, with bromine, chlorine and fluorine being used as components (tetra or halon extinguishers). Due to its toxicity, its use as a fire extinguishing agent was banned in 1996, with a few exceptions. Hand area. Region that a person can reach from a standing position. [prEN ISO 14738] Hand pallet truck. Industrial trucks, usually for pallets, also with integrated weighing device. Like all vehicles in ↑ Ex-zone 1, they must be earthed. Hand pallet trucks may only be used if they have a discharge resistance to earth of maximum 10 8 Ω . Packaging means or containers that are filled or emptied on hand pallet trucks must also be earthed ( ↑ ATEX 114). Hartmann tube. Laboratory device developed by J. F. Hartmann and J. Nagy (USA 1944) to determine the pressure curve over time in dust explosions ( ↑ dust explosion hazard). It is also used for explosive test mixtures of gases and vapors. <?page no="203"?> “ The Hartmann tube is a closed, vertical tube with a capacity of about 1200 cm 3 . The dust to be tested is filled into the tube and, after the apparatus is closed, is swirled up by emptying an upstream compressed air chamber (50 cm 3 , 7 bar) via a mushroom-shaped distributor cap (atomizer). A high-voltage spark gap in the lower third of the tube serves as an ignition source. The measuring chain consists of a pressure transmitter, an amplifier, and a recording device. ” or a rotating cover whose opening angle is recorded over time and thus allows conclusions to be drawn about the rate of pressure increase ( ↑ dust explosion class) (measured value recording). If defined electrical energies are applied to the high-voltage spark gap (e. g. from a charged capacitor), the values for the ↑ MIE can also be determined in the Hartmann tube. [Berthold, W., Löffler, U. (1981)] Hastelloy ® . Common brand name for highly corrosion resistant alloys of molybdenum and nickel with very low electrical resistivity in the range of 1.3 - 1.5 μΩ m. This alloy is well suited as an earthing point for conductive liquids in reaction vessels and is conductively connected to the vessel. Hazard. Describes a condition or material that has the inherent property of a hazard and therefore can be a permanent source of harm or injury. ( ↑ risk assessment, ↑ personal hazard, ↑ danger) Hazard class. This labeling of flammable liquids was replaced in 2003 by the German ↑ BetrSichV. It no longer differentiates between water solubility and viscosity, but according to ↑ flash point ( ↑ CLP Regulation). Hazardous area, ↑ Ex-area, ↑ Ex-zone Hazardous quantity (hazardous ↑ Ex-atmosphere). It is present, if the safety and health of employees or third parties could be impaired in the event of ignition; protective measures are mandatory. A quantity of 10 l or more in an enclosed room, regardless of the size of the room, is generally considered to be a continuous hazardous quantity. Smaller quantities can also be hazardous in the immediate vicinity of people (e. g. workplaces with glass equipment (flame effect, splinters)). A hazardous quantity can be prevented or restricted by limiting the quantity and concentration ( ↑ inerting, ↑ exhaust system). These measures must be monitored. What is to be considered is a hazardous quantity outdoors must be evaluated on a case-by-case basis. A hazardous quantity must be determined separately: - Gas-air mixture: Flammable quantity greater than one ten-thousandth of the room volume (e. g. for 100 m 3 room volume ~ 10 l). However, the ↑ Ex-area is only the area in which this atmosphere can occur ( ↑ Ex-zone). - Dust: For many combustible ↑ dust, a layer of less than 1 mm is sufficient to fill the room completely with an explosive ↑ dust-air mixture when whirled up ( ↑ dust explosion hazard). [TRGS 721 and 722] Hazardous substances. Substances, mixtures and objects that may pose a risk to humans, animals and other important public goods ( ↑ GefStoffV). This includes substances to which an ↑ occupational exposure limit (OEL) has been assigned. Hazardous substances that can lead to fire and explosion hazards are divided into ↑ explosion groups. Hastelloy 198 <?page no="204"?> Hazardous Substances Ordinance, German short [ ↑ GefStoffV] HAZMAT, ↑ dangerous goods Hazmat officer. The person responsible for ensuring that all obligations relating to the transportation of dangerous goods are considered to the extent necessary and for monitoring compliance with the regulations. In Germany, all companies that transport hazmat are required to appoint a hazmat officer. He must be able to provide proof of EU training with a final examination. [GbV] HBM, short for human body model, ( “ replica of the human body ” - regarding electrostatic discharges). HBM simulates the discharge pulse that is generated when a charged person touches a semiconductor component or device. Equivalent circuit: A capacitor, which represents the capacitance C p of a person against earth (reference earth), is charged by the high-voltage generator via a series resistor R v when the switch is in the appropriate position. This switch is also used for the defined triggering of the discharge pulse via a resistance R p simulating the person from the electrode E through the component ( ↑ DUT) or device ( ↑ EUT) to be tested to reference earth. Different variants of HBM are used in both cases. An HBM circuit is integrated into an ESD test system appropriate to the application. The characteristic curve of the ESD tester is recorded with the measuring resistor R m . During the actual test, the device under test (DUT or EUT) is connected between the electrode E and the reference earth instead of R m . ● HBM for testing (semiconductor) components. The capacitance C p is set to 100 pF and the body resistance R p to 1.5 k Ω . This original HBM model is defined in MIL-STD 883 (Military Standard USA). The usual setup is called an ESD test system and is a complex electronic device controlled by a computer. It can currently be used to automatically contact and test components (DUTs) up to a maximum of 1024 pins. The discharge curve across the measuring resistor R m (minimum value 0 Ω ) is a unipolar current pulse that has an exponential rise and fall in all component standards. The ↑ rise time between 10 and 90 % of the maximum current must not exceed 10 ns. The decay time (discharge ↑ time constant), i. e. the time taken for the current to fall from maximum to 37 %, shall be 150 ± 10 ns. The maximum current of the discharge curve should be equal to the charge voltage/ body resistance ratio R p = 1.5 k Ω ± 10 %. In addition, many standards define a maximum ↑ ringing at the peak of the discharge curve, which allows the exact level of the maximum current to be interpreted. For this purpose, during the test of the ESD test system, the discharge curve is converted into a voltage curve using a very fast inductive current sensor ( ↑ current transformer, ↑ current clamp), which is visualized using an ↑ oscilloscope. The maximum current, rise time, decay time and ringing tolerances are checked against the discharge curve image. In its ANSI/ ESD STM5.5.1 standard, the ↑ ESD Association has for the first time defined an additional measurement for HBM with R m = 500 Ω in addition to the measurement of the discharge curve shape in the short-circuit case (R m = 0 Ω ). This allows the ESD test HBM 199 <?page no="205"?> systems to be evaluated regarding their ↑ parasitic elements. This discharge curve, which is heavily attenuated compared to the 0 Ω -measurement, can still have a maximum rise time of 20 ns with a minimum peak current of 66 % of the 0 Ω -measurement. ESD test systems that significantly exceed this requirement have historically differed from ideal ESD test systems due to a lack of correlation between test results. ● HBM for the device test. Here, the capacitance C p is set to 150 pF and the resistance R p to the EUT is set to 330 Ω . Other values are also used in older standards. The usual design is a pistol-shaped package ( ↑ ESD gun). The waveform consists of an initial fast unipolar pulse with a rise time of 1 ns, followed by a slower, deeper, also unipolar pulse. This simulates the initial discharge of charge from the contacted surface of the person, followed by a delayed discharge of charge from the rest of the body, represented by the body resistance R p . Compared to the HBM for semiconductor devices, three different types of discharge are distinguished: - Contact discharge via a pinned test electrode that can penetrate the paint coating of a metal package. - Air breakdown arc with a rounded test electrode (imitation of a fingertip) by sparkover onto the package. - Discharge onto a conductive, earthed coupling plate, which either forms the base of the test object or is arranged vertically at 0.1 m from it. In contrast to contact or air breakdown arc, the pulsed field generated by the equalizing current through the coupling plate acts as a disturbance. [IEC 61000-4-2], [IEC 60749-26] Heat of compression generated: - By mechanically reducing the volume of a gas by increasing the pressure on all sides (compressor). - By the formation of a magnetic field as a result of a current flowing through a gas, which leads to a plasma ( ↑ pinch effect, ↑ plasma, ↑ gas discharge). [SE Section 4.1.2] Heaviside layer. Discovered by the English physicist O. Heaviside (1850 - 1925) together with the American engineer A. E. Kennelly (1861 - 1939). These are electrically conductive layers (due to many free electrons and ions) in the ↑ ionosphere, which among other things reflect short waves and thus orbit the Earth (enabling worldwide radio reception). Helicopters. An extreme case from an electrostatic point of view. A helicopter has a capacitance of about 1000 pF (measured on the ground). Due to the triboelectric effect, especially on the rotor blades, an electrostatic charge can build up, depending on air pressure and humidity. This requires special precautions that must always be taken before rescuing people, e. g. an earth wire on the helicopter that must touch the ground. [BS IEC 60479-2], [DGUV Information 214-911] Heat of compression 200 <?page no="206"?> (Source: DRF-Luftrettung, Bautzen heliport) Helmholtz, Hermann von (1821 - 1894). German physicist, director of the Physikalisch- Technische Reichsanstalt in Berlin (now the German ↑ Physikalisch-Technische Bundesanstalt). Among other things, he studied electrostatic phenomena and in 1879 postulated the existence of an electrical double layer at the ↑ contact surface between a solid and an electrolyte [Helmholtz, H. v. (1879)]. Helmholtz double layer, ↑ charge double layer Hertz. ↑ SI unit [Hz] of the ↑ frequency f, named after H. ↑ Hertz. It describes a periodic process: 1 Hz = 1 oscillation/ second = 1/ s Hertz, Gustav (1887 - 1975). German physicist was awarded the Nobel Prize in Physics together with J. Franck for stimulating atoms by electron collisions ( ↑ Franck-Hertz experiment). Hertz, Heinrich (1857 - 1894). German physicist, who was the first to demonstrate the generation and detection of electromagnetic waves (radio transmitters). High frequency. (HF) pulse, term for the frequency range of electromagnetic oscillations above the hearing limit ~ 20 kHz to 300 MHz. High frequency is emitted, among other things, when the ↑ pinch effect occurs during ↑ gas discharges ( ↑ spark detection device). All modern telecommunications also use the properties of high frequency for wireless signal transmission (radio) or for very fast wired signal processing. Most of the interference signals that ↑ Electromagnetic Compatibility deals with are radio-frequency interference ( ↑ electromagnetic radiation). [SE Section 3.6.2.2] High-ohmic resistance. Effective ↑ resistance greater than 1 G Ω . It is preferably used in circuits of ↑ electrometers and ↑ pico-ammeters and as ↑ voltage divider ( ↑ shunt) for high voltage measurements. High resistance carbon film resistors are considered less stable and have high ↑ temperature coefficients. In contrast, metal oxide resistors with temperature coefficients of 0.1 % per Kelvin have much better stability. High-pressure cleaning. High-pressure liquid jet cleaning process for reactors, vessels, etc. Highly electrostatically charged mists can be generated not only by the ↑ spraying of High-pressure cleaning 201 <?page no="207"?> chargeable liquids, but also - at correspondingly high pressures and the resulting high ↑ separation speeds - with conductive liquids (e. g. water). This leads to ↑ space charge clouds ( ↑ Rayleigh limit), which cause ↑ brush discharges on conductive devices. The charge is increased by a second, immiscible phase. When cleaning containers up to about 1 m 3 with water jets, no ignition hazard is expected if the flow rate is < 7 l/ s and the pressure is < 1.2 MPa. [TRGS 727], [Steen, H. (2000)], [Baumann, F. (2023)] High voltage. Generally, it refers to all voltages above 1000 V. In the electrical power supply, networks are divided into the following nominal voltage ranges: - Low voltage: 230 - 400 V (residential, commercial, agricultural) - Medium voltage: 10 - 60 kV (local substations, industry) - High voltage: 66 - 115 kV (large cities, power plants) - Extra-high voltage: > 220 kV (interconnected, national and international) High-voltage cascade (Italian: cascare, “ to fall ” ). Device for generating high DC voltages (MV-range) in which an applied AC voltage is rectified and multiplied by ↑ diodes and ↑ capacitors. It was developed by the Swiss physicist H. Greinacher (1880 - 1974) and is used to generate high voltage ( ↑ useful application, ↑ accelerator). ( ↑ ionizer), [SE Section 5.3.2] High-voltage generator - Often used in electrostatics to operate ↑ ion sources, where both AC and DC high voltage is used to eliminate interfering charging ( ↑ ionizer). DC high voltages are required for ↑ useful applications ( ↑ separation of substances, ↑ coating, ↑ xerography). In all cases, the protective measures against dangerous ↑ electric shocks specified in the relevant safety regulations must be observed (e. g. protection against dangerous body currents, protection against direct and indirect contact, etc.). - A machine that converts mechanical energy into electrical energy. In the past it was often called an electrostatic generator (e. g. ↑ Van de Graaff generator, ↑ pelletron, ↑ influence electrifying machine). High-voltage perforation. Targeted electrical perforation ( ↑ breakdown) of very thin insulating layers to allow electrostatic charge dissipation to a conductive, earthed substrate (e. g. for a plastic floor coating) and for micro perforation, e. g. to make films breathable. The pore size can be controlled by a series resistor in the discharge circuit of the perforation electrode or by additional charge storage in capacitors. ( ↑ corona pretreatment) High-voltage system, ↑ low-voltage system Hobbock (also drum, barrel or pail). Container for liquid or solid substances, mostly made of metal, which must be earthed in ↑ Ex-areas. Hobbocks made of insulating materials are not suitable for use in explosive gas or vapor atmospheres. Hoist. Winches for lifting loads, electric hoists, storage and retrieval systems and cranes of all types. In ↑ Ex-areas, hoists must be designed in such a way that they discharge the electrostatic charge of suspended loads to earth (e. g. ↑ FIBC). Hole, ↑ defect electron High voltage 202 <?page no="208"?> Hole conduction. Current flow in semiconductors made possible by ↑ defect electrons. Homogenization of the electrostatic field. Necessary for a reproducible measurement with an ↑ EFM in relation to the measurement object. The size, type and method of homogenization depend largely on the measuring device used ( ↑ influence electrostatic field meter, ↑ measurement error). When the earthed measuring device approaches the test object, the field lines are concentrated at the meter head, resulting in a significant increase in field strength (1). With one-sided homogenization (2), the field strength at the sensor head can be higher than in the undisturbed homogeneous field, as the field lines emanating from the backside B of the object are also deflected to the sensor head (vectorial addition). Although the field is homogeneous, the field strength is distorted by approximately the field strength component of the back side. Only if two earthed homogenizing plates are arranged parallel to each other (a = a ’ ) and the object to be measured is placed in the middle of them (3), the field strength of the field emanating from the charged object can be expected to be recorded correctly. The dimensions of the homogenization plates have a significant influence on the ↑ degree of homogenization. Sufficient homogenization is achieved when the ratio of the plate edge length L to the object distance (a + a ’ ) is at least 2 : 1. [SE Section 3.13.1] Homogenous field, ↑ field Hose (Middle High German: sluch, “ peeled snakeskin ” ). Flexible tube for conveying liquids, dust or gases ( ↑ hose lines). Hose line (also hose assembly). Is used to transport liquids, gases and solids dispersed in gases ( ↑ pneumatic conveying) and always consist of the fittings (e. g. flange or screw connection) at the ends and the flexible hose. The dangers of electrostatic charging are many. For example, it must be possible to shield the field of a charged liquid from the outside. The hoses used for this purpose are equally varied and must meet the relevant regulatory requirements (conductive: R < 10 3 Ω / m, dissipative: R > 10 3 Ω / m to < 10 6 Ω / m, insulating: R > 10 6 Ω / m). For use in ↑ Ex-zones, they are differentiated according to their construction and divided into conductivity classes: Hose line 203 <?page no="209"?> ● M hose line has electrically conductive wire inserts that cross each other regularly and are connected directly to the fitting. The resistance must be R ≤ 10 2 Ω over the entire length. ● Ω hose line is made of conductive or dissipative material, with metal inserts if necessary. The resistance must R ≤ 10 6 Ω be over the entire length. ● Ω CL or Ω T hose line conduits have dissipation capability on the inner and outer layers, which are interconnected by any intermediate insulating layers. A support wire, if present, is connected at one end only. ● Ω M or MT hose line are constructed in the same way as Ω CL hose line, but there is a metallic bond between the fittings. The fittings and hose lines always form a unit. Repairs or adaptations (e. g. shortening) of hose lines permitted in hazardous areas should only be carried out by specialists who know how to make the necessary contacts to ensure conductivity and can carry out the corresponding tests. [DGUV Information 213-053] The color coding of the hose line complies with [EN 12115]. [ISO 8031], [IEC/ TS 60079-32-1], [TRGS 727 Section 4.9] Examples of hose marking (Source: www.elaflex.de) Hot cathode. Negative electrode in which electrons are emitted from the cathode material by supplying energy (heat). The amount of electrons emitted per unit of time depends on the cathode area, the ↑ electron emission energy and the temperature. Hot surface. An ↑ ignition source defined in the technical regulations. It must be considered if equipment that can heat up (pipes, motors, lights) are located in areas where flammable substances are present ( ↑ temperature class, ↑ ignition temperature, maximum ↑ surface temperature, ↑ Godbert-Greenwald apparatus). [TRGS 720] Housing. The part that protects a device from certain external influences and provides protection against direct contact from all possible access directions. In connection with Hot cathode 204 <?page no="210"?> ↑ Electromagnetic Compatibility, the housing also has the function of ↑ shielding. Enclosures for electrical equipment used in ↑ Ex-areas must be tested in accordance with [IEC 60079-0]. Human being. The human body consists of 80 - 85 % water in infants, with increasing age this proportion decreases to about 70 %. Depending on the condition, healthy skin has the ability to dissipate, the inside of the body is very conductive and therefore almost free of fields ( ↑ implant). There are diseases where there is no body sweat (e. g. a certain form of diabetes) and measures for personnel ↑ earthing in the ↑ Ex-area cannot be effective ( ↑ personnel charging). If a person holds a (gold-plated) hand electrode and a second electrode made of zinc in their hands, a current flows from hand to hand because the body fluids serve as an electrolyte and the distance between the two metals in the electrochemical ↑ voltage series is also effective ( ↑ galvanic element). The human being - is to be regarded as a conductive object and is subject to the effects of ↑ influence, - can transport charges as an isolated body ( ↑ charge abduction), - can be charged by motion ( ↑ clothing, ↑ walk-in charge), although no more than 19 kV has been measured so far, - cannot be charged to more than a maximum of 40 kV ( ↑ corona charging) as an insulated body by external influence (contact or ↑ corona discharge), - can store ↑ charge depending on body volume (electrical capacitance approx. 70 - 150 pF) and discharge it in an ignitable spark, - senses electrostatic discharges from about 2 kV and - generates functional currents that can be measured (e. g. ECG). Human body model, ↑ HBM Humidification. Hygroscopic insulating materials, e. g. dry paper, can be moistened by precipitating water in the form of aerosols with the aid of an electric field ( ↑ coating (Figure), ↑ remoistening). Humidity (air humidity). Temperature and moisture are the variables that define a climate. Humidity describes the amount of steam contained in the air. When the air is saturated with water steam, fog forms. When this state is reached as the air cools down, the associated temperature is called the ↑ dew point temperature (expressed in [°C]). The electrostatic behavior of substances is more or less affected by humidity, depending on their ↑ water activity. ( ↑ humidity meter) ● Absolute humidity. Which indicates how much [g] of water steam is contained in one standard cubic meter of air, or how much [kg] of water steam is contained in one [kg] of air. ● Relative humidity (short RH). Is the percentage of the maximum possible amount of water steam is present in the air at a given temperature. Thus, 100 % RH corresponds to Humidity 205 <?page no="211"?> the maximum amount of water steam (saturation) that a gas mixture (e. g. air) can contain. Below this value, the water steam pressure and therefore the percent RH, is proportional to the total barometric pressure. Since the maximum possible water steam pressure depends on temperature, RH also depends on temperature. In a closed system, it increases as the temperature decreases and vice versa. Humidity meters (atmospheric). The electrostatic properties of many materials are always subject to the influence of the environment ( ↑ climate). For the necessary measurements of ↑ humidity, various types are available based on chemical, electrical, mechanical or thermodynamic methods. In addition to the devices listed, there are also ↑ absorption, capacitive ( ↑ thin film technology), and optical methods. Aspiration psychrometers are an absolute measurement method, in contrast to hair hygrometers, lithium chloride humidity sensors and electronic devices with semiconductor sensors (e. g. use of a hygroscopic layer as ↑ dielectric in a ↑ capacitor). ● Aspiration psychrometer. A device based on the thermodynamic principle. The air to be measured is passed in a constant flow past a dry thermometer and a thermometer moistened with distilled water. As a result of the heat of vaporization extracted from the humid thermometer, this shows a lower temperature than the dry one. The lower the humidity, the greater the temperature difference between the two thermometers (psychrometric difference). The relative humidity can be determined using the so-called Sprung psychrometer formula or from corresponding tables. ● Hair hygrometer. Uses the property of degreased hair to shorten with decreasing relative humidity and lengthen with increasing humidity ( ↑ sorption, ↑ hygrometer). In the device, the hairs are spring-loaded at one end and connected at the other end to a lever system that transmits their change in length to a pointer. On the associated scale, which is divided into percentages of relative humidity, the 100 % point is used as the value for ↑ calibration. The ↑ hysteresis that occurs results in a system-related inaccuracy. As the device is sensitive to drying out, it should be placed in humid air to regenerate if the display appears incorrectly. The device can be checked in the following way: Place it in a container with the base covered with water. After closing the lid, leave it in the container for at least 5 hours. An atmosphere saturated with water steam is created in the container, i. e. it must display 100 % RH. If necessary, it can be adjusted to this value using the calibration screw. ● Dew point hygrometer (also dew point mirror or condensation hygrometer). Hygrometer for measuring the water steam content of air, which is used especially at low temperatures. A reflective surface is slowly cooled by the ↑ Peltier effect, and condensation occurs on it when the dew point temperature of the surrounding air is reached. The relative ↑ humidity can be determined from the dew point temperature and the air temperature. Humidity meters (atmospheric) 206 <?page no="212"?> (Source: www.pruemmfeuchte.de) ● Lithium chloride humidity sensor. The method is since lithium chloride LiCl (3), as a highly hygroscopic salt, absorbs water from the ambient air. A fabric (2) impregnated with the salt solution encloses an insulating tube (1) in which a heating coil (4) and a temperature sensor are integrated. Humidity sensor (electronic). Capacitive or resistive system in which the electrical properties of a hygroscopic substance change depending on the relative humidity of the surrounding gas. - The capacitive measuring principle is based on the change in the dielectric properties of a hygroscopic polymeric plastic as a function of the relative humidity. - The resistive measuring principle is based on measuring the impedance of a hygroscopic liquid, the ↑ electrolyte. Such “ electronic ” humidity sensors are characterized by their small size, short response times, good reproducibility and wide measuring ranges. ( ↑ thin film technology) Hybrid mixture (Latin: hybrida, “ of two origins ” , “ hybrid ” ). While investigating firedamp explosions, C. ↑ Engler (1885) found that methane-air mixtures can already be ignited below their lower ↑ explosion limit (LEL) if some coal dust (also below its LEL) is added. Hybrid mixtures are mixtures of combustible dust and combustible gas. They can already be formed from a concentration of the combustible gas phase as low as 10 % of the LEL. In addition, the influence of combustible gases or vapors on the individual safetyrelated parameters of the dust must be evaluated. For example, even at low combustible gas concentrations, the ↑ MIE of the hybrid mixture is significantly lower than the MIE of Hybrid mixture 207 <?page no="213"?> the pure ↑ dust-air mixture. If the MIE of the mixture is not known, the MIE of the fuel gasair mixture can be used as a worst-case estimate. [Hesener, U., Beck, M. (2016)], [EN 14034-2 and 14034-3] Hydro- (Greek: hydro, “ water ” ). Prefixed term meaning “ water ” . Hydrogen. An element discovered by H. Cavendish in 1766 with the chemical symbol H (hydrogenium). It exists in the ↑ standard condition as the molecule H 2 and is a colorless, odorless, nontoxic gas. Hydrogen has a density of 0.09 kg/ cm 3 and is about 14 times lighter than air. It has a very high diffusion capacity and can be absorbed or adsorbed ( ↑ adsorption) by many substances. When released, it rises and spreads very quickly. Unfavorable architectural conditions in which hydrogen can accumulate should be avoided. The ↑ explosion limits are very wide: LEL 4 vol. % and UEL 77 vol. % with a ↑ MIE of 0.02 mJ. [DGUV Information 209-072] Hydrophilic. Describes substances that absorb water (e. g. ↑ paper) and thus have a lower electrical resistance ( ↑ water activity) at higher humidity than when dry. Hydrophobic. Describes substances that do not absorb water or are water-repellent, e. g. PTFE ( ↑ water activity). Hygro- (Greek: hygros, “ moist ” , “ wet ” ). Prefixed term meaning “ humidity ” . Hygrometer. Used to measure ↑ humidity. Hair hygrometers are often used, which are characterized by their simplicity but do not have a high level of accuracy ( ↑ hysteresis). Aspiration hygrometers and electronic hygrometers, which are based on capacitive and resistive ↑ humidity sensors, fulfil higher requirements. ( ↑ humidity meter), [SE Section 3.16.2] Hygroscope (Greek: hygros, “ moist ” , skopein, “ to look ” ). Device for estimating the ↑ humidity, e. g. hair hygrometer. Hygroscopic. Property of substances (e. g. ↑ silica gel and calcium chloride), absorb moisture (e. g. from the air) and thus have a drying effect on their surroundings. Hysteresis (Greek: hysteros, “ later ” ). The “ lagging ” of an effect behind the variable physical quantity that causes it. A residual effect (remanence) remains when the causal variable falls to zero. It is a manifestation of ↑ relaxation. Example: Dielectric hysteresis manifests itself in a residual polarization after the electric field strength disappears ( ↑ dielectric). The same is true for magnetic hysteresis; residual magnetism remains. Hysteresis effects also occur when materials are wetted and dried ( ↑ sorption isotherm, ↑ coercive field strength). Hydro- 208 <?page no="214"?> I I/ O shielding gasket, ↑ EMI shielding gasket IBC, short for intermediate bulk containers. Originally a container for the intermediate storage of bulk materials, today generally bulk containers with a volume of several 100 to several 1000 l. A distinction is made between rigid containers for liquids ( ↑ RIBC) and flexible containers for powdery or granular bulk materials ( ↑ FIBC). [TRGS 727], FIBC: [IEC 61340-4-4], RIBC: [IEC 61340-4-11] Idling, ↑ no-load operation IEC, short for International Electrotechnical Commission. It is an international standardization organization based in Geneva (founded in London in 1906) for the field of electrical engineering and electronics. Some standards are developed jointly with ↑ ISO and are given the prefixes of both organizations, such as “ ISO/ IEC ” . The IEC Statutes cover all electrical engineering, including power generation and distribution, electronics, electromagnetism, electrostatics, electroacoustics, and telecommunications, as well as general disciplines such as technical vocabulary and symbols, Electromagnetic Compatibility, metrology and performance, design and development, reliability, safety, and the environment. IECEE, short for International Certification System for Conformity Assessment to Safety Standards for Electrotechnical Equipment and Components. ( ↑ IEC) IECEx, short for IEC System for Certification to Standards relating to Equipment for use in Explosive Atmospheres, based on IEC standards. IECQ, short for IEC Quality Assessment System for Electronic Components. ( ↑ IEC) Ignitability. The type of ↑ ignition source and the willingness to ignite of an explosive mixture determine its ignitability ( ↑ equivalent energy). [Steen, H. (2000)] The ↑ ignition temperature required for ignition is only reached if the current flow during a ↑ gas discharge leads to the ↑ pinch effect and thus to the ↑ plasma. There are several parameters to consider that affect the intensity and thus the ignitability: Discharge type Influencing factors ↑ Corona discharge Generally, not considered ignitable ↑ Brush discharge Radius of the electrode and the size of the charged area ↑ Super brush discharge Number of partial charges of the same polarity and the distance between them ↑ Cone discharge Charge density in the bulk volume ↑ Propagating brush discharge ↑ Surface charge density of the charged surface and thickness of the insulating material ↑ Spark discharge Quantity of capacitively stored energy <?page no="215"?> For atmospheric conditions, the following classifications between discharge types and flammable/ combustible substances can be established from practical experience: Discharge type Gases/ vapors 0.2 - 2 mJ Dust 3 - 10 mJ Dust > 10 mJ Corona discharge no no no Brush discharge yes no no Super brush discharge yes suspicious improbable Cone discharge yes suspicious improbable Propagating brush discharge yes yes yes Spark discharge calculable calculable calculable Note: It should be noted that even a small increase in the amount of ↑ oxygen in the air will significantly reduce the ignition energy required. Substances of ↑ explosion group IIC (e. g. acetylene or ↑ hydrogen) and primary ↑ explosives are not considered. - Corona discharge. It has not yet been possible to ignite explosion group IIC substances by corona discharge under atmospheric conditions in stationary test rigs and experiments. It is therefore safe to assume that there is no ignition hazard for explosion group IIA and IIB substances. It is therefore a simple and safe way of eliminating annoying and dangerous charging in a wide range of applications. It should be noted, however, that as the radius of curvature increases (bending or rounding of the ionization pin due to contamination), corona discharges may change to brush discharges where ignition cannot be excluded. In dynamic systems (fast-moving, non-dissipative material webs and any existing insulated, charged, conductive surfaces (e. g. aluminum ↑ label)), there may be a sudden increase in charge that could possibly cause ignition ( ↑ capacitance). It is therefore advisable to connect the pins with high resistance (> 100 M Ω ) to smooth the charge profiles. No studies are known to date. [SE Section 4.2.2.1] - Brush discharge. In these discharges, the distance to the charged object is much smaller than in a quasi-continuous corona discharge. The field strength in the gap is greater, resulting in higher ionization and a stronger current pulse. The ↑ pinch effect always occurs in the region of the highest field strength, i. e. the discharge path in the air heats up, resulting in a risk of ignition of surrounding flammable gases. Depending on the charge present on the insulating material, the phenomenon is of short duration. Ignitability can be determined by measuring the ↑ charge Q on the object, e. g. with a ↑ coulometer. If the charge is less than the MIQ of the substance involved, general experience shows that a flammable gas-vapor-air mixture cannot be ignited ( ↑ charge transfer - measurement). [SE Section 4.2.2.2] - Cone discharge. In any case, it has the ignitability for gas-vapor-air mixtures and can probably ignite dust with an MIE < 10 mJ. - Super brush discharge. Ignitability depends on the number of individual charges stacked on top of each other (e. g. plastic trays or film rolls) and occurs in any case for gas-vaporair mixtures ( ↑ charge accumulation). To date, it has not been possible to ignite dust with an MIE > 1 mJ. [Forestier, S. et al. (2016)] Ignitability 210 <?page no="216"?> - Propagating brush and spark discharge. Due to the energy content converted in them, they are always considered ignitable for gas-vapor-air mixtures and for dust. ● Ignitability through mechanically generated sparks. “ Ignitability is the sum of all elements of the combustion mechanism of a particle that is able to optimally transfer the maximum amount of heat available to the gaseous environment. ” [Steen, H. (2000) Section 2.4.3] Ignition. The term is only useful for substances that are capable of continuing a selfsustaining combustion process ( ↑ explosion range). This defines an ignition ( ↑ ignition source) as the initial stage of this process. Ignition energy, ↑ MIE Ignition hazard assessment (IHA). The discharge currents generated by electrostatic charges are generally so small that they do not present an immediate ignition hazard. Hazards arise only when the ↑ charge is accumulated in some way. It must first be determined whether the materials involved in a charging process are chargeable or conductive (charge dissipative). In the latter case, the risk of ignition can be largely eliminated by constant earthing ( ↑ influence). Earthing chargeable (insulating) materials does not lead to charge dissipation but is possible via a ↑ corona discharge ( ↑ ionizer, ↑ earthing tongue). However, if at least one of the materials involved is chargeable, ignition hazards must be expected ( ↑ area limitation). A conductive, unearthed part represents a ↑ capacitance that can lead to ↑ spark discharges. {Appendix D} Ignition induction time. Characteristic time from ignition to transition to self-sustaining ↑ flame propagation for a given flammable mixture. [Steen, H. (2000) Section 2], [TRGS 723 Section 5.9] Ignition point, ↑ ignition temperature Ignition sensitivity. Characterization of the electrostatic behavior of substances or substance mixtures towards gas discharges by their ↑ MIE and ↑ MIQ. Ignition sensitivity 211 <?page no="217"?> Ignition source. According to scientific knowledge and common experience, an ignition source is defined by its ability to ignite certain combustible materials when mixed with air. The evaluation of a large number of fire and explosion incidents led to the definition of 13 different ignition sources some 40 years ago. Despite much research, it has not been possible to change this number so that it remains valid worldwide: Ignition source Examples 1 Hot surfaces Hot engine or electrical machine components 2 Flames and hot gases Naked flames such as welding torches, exhaust gases 3 Mechanically generated sparks Sparks from grinding, drilling or hammering on metal 4 Electrical equipment Switching, short-circuiting or faulty electrical equipment 5 Electric currents, cathodic corrosion protection Unwanted electric currents leaking through defective insulation 6 Static electricity Discharge of static charge, spark discharges, brush discharges 7 Lightning Direct strike of lightning into a building or facility 8 Electromagnetic fields (low frequency: 10 4 to 3 × 10 11 Hz) Powerful high-frequency transmitters such as those used in broadcasting or telecommunications systems 9 Electromagnetic waves (high frequency: 3 × 10 11 to 3 × 10 15 Hz) Laser beam or intense infrared radiation 10 Ionizing radiation Radioactive radiation from X-ray sources or nuclear facilities, UV lamps 11 Ultrasound High-frequency ultrasonic vibrations, such as those produced by cleaning or welding equipment. 12 Adiabatic compression and shock waves. contaminated flowing gases Sudden pressure increases in gases due to compression or explosions 13 Chemical reactions, including selfignition of dust Exothermic reactions such as self-ignition of coal dust or chemical reactions that release heat Some of these ignition sources can ignite all types of combustibles (e. g. flames, lightning). For others, additional parameters must be considered, such as the ↑ ignition temperature for hot surfaces and the ↑ MIE for static electricity. [SE Section 7] Ignition temperature. ↑ Explosion-related parameter describes the lowest temperature at which a combustible substance or an optimally ignitable fuel-air mixture can just be ignited on a hot surface under ↑ atmospheric conditions and the combustion process continues independently without the addition of heat ( ↑ operating temperature). It is used as a reference value for explosive mixtures and allows them to be grouped and categorized [Steen, H. (2000)]. It depends on many parameters: - Pressure and reaction mechanisms of the substances involved, Ignition source 212 <?page no="218"?> - Structure and material of the hot surface (e. g. concave, convex, roughness, catalytic effect), - Homogeneity of the substance and the gas-vapor-air mixture and its dynamics (e. g. turbulent flow). To determine the ignition temperature, it is therefore necessary to select a method that corresponds to the most unfavorable conditions in practice. Combustible gases and vapors are classified into ↑ temperature classes according to their ignition temperatures. A similar categorization does not exist yet for dust. For dust, it should be noted that only equipment whose surface temperature on surfaces on which dust deposits are effectively prevented is not more than 2/ 3 of the ignition temperature in continuous operation may be used in operating areas endangered by dust explosions. In the case of dust deposits on hot surfaces, in addition to the danger of ↑ smoldering fire, the development of ↑ smoldering gases and their ignition potential due to electrostatic ↑ gas discharges must also be considered. Ignition temperature data for various substances can be found in ↑ Chemsafe and [Nabert, K., Schön, G. (1970)]. [DIN 51794], [IEC 60079-10- 1], [ISO/ IEC 80079-20-2], [ASTM D2155-18] Ignition voltage. Can be determined experimentally using a ↑ Hartmann tube. Using a plastic tube charged by rubbing, a charge is transferred to the ↑ capacitance of the meter (about 50 pF) by ↑ influence. This allows the stored energy to be calculated {Appendix M.6} and the spark gap in the Hartmann tube to be adjusted. It can also be used to ignite an ignitable mixture for demonstration purposes. Image charge (also called “ virtual charge ” ). This is the reason why charged particles adhere to electrically neutral surfaces. Electric fields have the property of causing opposite pole ↑ charges on nearby conductive surfaces by electrostatic ↑ influence. For example, if a positively charged insulating film is brought close to a conductive object, negative influence charges become active on its surface. A charge movement occurs on the surface of the object facing the charged surface. Since this influenced charge always has the opposite sign to the original charge, the charged insulating particle is attracted to the conductive object ( ↑ Coulomb force), regardless of whether the latter is earthed or not. In this way, the Coulomb forces of attraction become active, so that the particles are increasingly accelerated towards the object, since the force increases quadratically with the reduction of the distance. When the insulating particle finally reaches the object, it is held there by its “ image charge ” ( ↑ useful application, ↑ influence electrifying machine). {Appendix M.3.1} Impact ionization, ↑ ionization, ↑ impulse excitation, ↑ recombination Impedance, ↑ alternating current quantity Implant (electronically controlled). For example, cardiac pacemakers or other electromedical devices worn in or on the body (e. g. insulin pumps) are increasingly being used. Electrostatic discharges from charged persons through contact with earthed objects or Implant (electronically controlled) 213 <?page no="219"?> from charged conductive objects to persons can cause electrical impulses in the organism. Their effects on the organism, e. g. excitation and conduction in the heart and in electronically controlled implants, depend on the discharge current and energy and possibly other parameters. However, an electrostatic discharge usually causes only a single, very short current pulse because the electrostatic charge is discharged with it (electrostatic shock, ↑ electric shock). People with implants cannot usually be affected by constant or slowly changing external electrostatic ↑ fields because they do not penetrate the body surface. The inside of the body is electrostatically conductive and therefore almost free of fields and thus shielded from the effects of these fields ( ↑ charging - of persons). [TRGS 727] specifies a value of maximum 2 mJ for cardiac pacemakers, which was arbitrarily set. [EU 2013/ 35], [BMAS Forschungsberichte 400-D and 451] Impression roller. Term for the impression cylinder in gravure printing presses. The steel core of the impression roller has a semi-conductive rubber coating with a certain volume resistivity, depending on the functional system, when using ↑ electrostatic print assist (ESA). This property is severely limited if impression roller cleaning is neglected. For example, the solvent usually removes only the ink residues, not the abrasion of the components of the ↑ paper. An impression roller is explicitly mentioned in [TRGS 727 Section 3], but it must always be regarded as a counterpressure cylinder. (see figure at ↑ ionizer in processing machines) Impulse excitation. Describes for a microphysical system the energy transferred from an impacting particle T (electron, ion or atom) to another particle, which puts the latter into an excited state ( ↑ gas discharge, ↑ ionization, ↑ electroluminescence). In ion impulse excitation, an ion collides with the other particle, in electron impulse excitation, it is an electron that transfers energy to the particle and puts it into an excited state; and in atom impulse excitation, both collision partners are atoms. Conversely, an excited atom in a collision can transfer its energy to an electron, which then enters a state of higher kinetic energy (collision excitation of the second type). ( ↑ Penning effect) Impulse test (surge withstand voltage). Dielectric strength of an insulating material to voltage pulses of a specified waveform and amplitude. ( ↑ creepage distance) Increased safety, ↑ type of protection “ e ” Induced voltage. It is generated when a conductor loop is moved in a magnetic field in such a way that the number of field lines passing through it changes, or when the magnetic field strength of stationary magnets and conductors is changed by changing the current in a coil ( ↑ self-induction, ↑ induction). The faster the magnetic flux in the coil (Source: www.spektrum.de/ lexikon/ physik) Impression roller 214 <?page no="220"?> SERVICE SLEEVES ROLLERS <?page no="222"?> changes, the greater the voltage. Such influences must be avoided in electrostatic measurement setups. Induction voltage can also be caused by indirect near-field effects of ↑ thunderstorm lightning. Inductance. Symbol L, ↑ SI unit [H], named after J. Henry. It indicates the ratio between the voltage U and the change in current overtime dI/ dt. A coil has an inductance of 1 H if a voltage of 1 V is induced with a uniform current change of 1 A in 1 s (reactance ( ↑ alternating current quantity)). Inductance is usually used to describe ↑ self-induction. The antagonist is ↑ inductive coupling. Induction (Latin: inductio, “ the bringing in ” ). An electric voltage is induced in an electrical conductor when it moves in a magnetic field, the direction of which depends on the direction of movement of the conductor and the direction of the magnetic field ( ↑ induced voltage, ↑ inductance). Induction is therefore a dynamic phenomenon. The opponent of induction is ↑ influence. ( ↑ Lenz ’ s law) Note: In IEC 60050-121, the term “ influence ” is translated as “ induction ” . This equation often leads to misunderstandings. In physical terms, electrical induction and electrostatic influence are two completely different things: - In electrical induction, a voltage is induced in a conductor that crosses the magnetic field lines. If the conductor moves parallel to the field lines, no voltage is induced. A nonconductor does not experience any change. - In the case of influence, the charge distribution in an electrical conductor is changed regardless of the direction of movement and a nonconductor can be polarized. ( ↑ useful application) Induction coil, ↑ Wagner ’ s hammer Induction constant, ↑ field constant Inductive coupling. Influence of two adjacent current-carrying conductors by their magnetic fields. When the current in one conductor changes, a voltage is induced in the other conductor. ( ↑ measurement error, ↑ inductance, ↑ self-induction) Inductive coupling 215 <?page no="223"?> Inductor, ↑ spark inductor, ↑ Wagner ’ s hammer Inert gas. Gas that is added to explosive mixtures to achieve explosion protection by reducing the oxygen content ( ↑ inerting). Nitrogen, carbon dioxide, inert gases and water steam are used, for example. The inert gas must be tested for a possible reaction with the substances to be inerted (e. g. ↑ light metal dust can react with CO 2 ). Inerting (Latin: inert, “ inactive ” , “ inert ” ). It is one of the most common protective measures used for primary ↑ explosion prevention. For this purpose, the oxygen content of the air is reduced to such an extent that ignition is no longer possible even under otherwise, optimal conditions (e. g. ↑ MIE at a stoichiometric ratio of about λ = 1). This value is called the ↑ limiting oxygen concentration, which also depends on the ↑ inert gas used for oxygen reduction. As a first approximation, inerting process is achieved when the oxygen content is reduced to below 10 % ( ↑ gas swing adsorption). A differentiation is made between: ● Partial inerting process: The oxygen concentration in the mixture is reduced so that it is no longer explosive. ● Total inerting process: The ratio of the amount of inert gas to the amount of combustible substance is so high that the mixture will not become explosive even if any amount of air is added. An essential requirement for the effectiveness of the inerting process is to monitor it with suitable measuring equipment. An alarm threshold must be set below the maximum allowable oxygen concentration. [TRGS 720], [TRGS 722 Section 2.3.3], [TRGS 727 Section 5.3] Influence (Latin: influere, “ to flow into ” ) Note: “ Electrostatic induction ” is the term used in English, whereas “ electrostatic influence ” has become established in German as a more precise term due to the Latin origin of the word. An electrostatic field (E-field) has the ability to move charges on conductive objects ( ↑ Coulomb force) depending on the potential strength and the distance, if they are actively brought into the field or randomly enter its area of influence. This process, known as influence, causes a charge displacement on the surface of a conductive - originally electrically neutral - body. If one of the displaced charges (+ or -) is diverted to the earth, the body is charged with the opposite polarity after it is removed from the field. It then has a real excess charge, which is exactly the same amount as the quantity of charge that has flowed off, but with the opposite sign. For the process of influence, it is irrelevant whether it occurs on stationary or moving parts. Influence can therefore be defined as a static phenomenon. ( ↑ image charge), [SE Section 2.12], [Westphal, W. H. (1970)] Inductor 216 <?page no="224"?> (A) Capacitor with two parallel plates, (B) two metal plates are brought into the field, (C) the metal plates are separated, (D) the metal plates are removed from the field. (A) An uncharged conductive part enters an electrostatic field. (B) The absolute values of the +/ excess charges on the surface are exactly the same. From an atomistic point of view, some electrons of the conductive part are moved by attractive forces in the direction of the positive charge of the field, leaving behind a positive charge of the same magnitude at their original location ( ↑ displacement current). If the conductive part is then removed from the electric field (without a short earthing), the displaced charges spontaneously equalize again, and the part is uncharged. ● Influence on ionizers. There are currently many ↑ ionizers in use whose high-voltage is generated via an integrated ↑ high-voltage cascade (24 V supply voltage). Especially with fast-moving material webs, pulses emitted by these ( ↑ charging phenomenon) can destroy the ionization components. A suitable overvoltage protector can be installed to protect the cascade structure. [Schubert, W., Ohsawa, A. (2024)] Influence charge. This describes the charge available after an influence process ( ↑ charge measurement). Influence charging, ↑ useful application, ↑ charging Influence constant, ↑ field constant Influence electrifying machine. ↑ Electrification machine in which two plastic discs covered with metal strips rotate in opposite directions on a common axis at a small distance from each other. Two metal strips facing each other are charged in opposite directions by ↑ influence and their charges are removed by sliding contacts. Voltages of about 100 kV can be achieved with currents of about 30 μ A. The charge generated by the Wimshurst machine is stored in ↑ Leiden jar (LF - see photo next page). Influence electrifying machine 217 <?page no="225"?> Influence electrostatic field meter. Based on the principle developed by H. F. C. ↑ Schwenkhagen, H. ↑ Kleinwächter has further developed the influence electrostatic field meter. Combined with a voltage measuring head, it has the characteristic of an electrometer that can detect up to 10 aA (10 -17 A). There are two voltage measuring heads: ● 2 kV (Breakdown voltage at about 4 kV, when this is exceeded, a characteristic ↑ sawtooth curve occurs when an oscilloscope is connected.) ● 40 kV (breakdown voltage at about 60 kV, R i > 10 15 Ω , C i = 10 pF) H. ↑ Künzig has shown a variety of additional applications in combination with the influence electrostatic field meter and the associated voltage probe: - It can be used as a ↑ coulometer according to the relationship Q = C × U {Appendix M.3}. Influence electrostatic field meter 218 <?page no="226"?> - With an additional resistor connected in parallel, it can be used as a ↑ pico-ammeter in the range up to 10 -12 A. - With the same circuit as the pico-ammeter and an additional controllable voltage source, it can be used as an ↑ ohmmeter to determine the continuity of high resistance as a function of the measured voltage. For resistance values of R x > 10 13 , the entire measurement setup must be enclosed in an earthed Faraday cage. Only the display instrument U can be outside the cage. - By changing the resistance to R ≥ 10 12 Ω , it can be used as a tera-ohmmeter to determine high resistance continuity resistances as a function of the measured voltage. ( ↑ measuring electrode, ↑ hysteresis) Influence electrostatic field meter 219 <?page no="227"?> - Chemical production processes often take place in closed systems and are not directly amenable to electrostatic charge measurement and detection. Knowing that a ↑ corona discharge is not ignitable, an earthed slender pin can be inserted into the production area under test (spray tower, vessel, etc.) to allow an electric current to flow out to earth. The voltage can be measured using an influence electrostatic field meter with a voltage measuring head as a ↑ static voltmeter and a sensing resistor. If no current is flowing, i. e. the voltage across the resistor is close to 0 V, it is unlikely that charges will occur in the container. The experiment can be repeated without the measuring resistor to measure the potential in the container. It should be noted that even small changes in production parameters can significantly affect electrostatic charging. (Note: The safety requirements applicable to the production area must be observed.) Influence field measurement probe (IFM). It is a special principle of electric field measurement. As early as 1978, a measuring device based on this principle was sold by the company VEB Statron (GDR) [Statimeter II (1978)]. W. Löbel (1930 - 2021) described the procedure in 1993: The measuring device is designed to measure only the ↑ charge displacement caused by a test object by ↑ influence on the IFM. The field strength must not cause ↑ ionization of the air between the test object and the IFM, as this would otherwise be charged (measurement error). If the insulating materials used have leakage resistance < 10 14 Ω , long-term measurements may drift. To obtain meaningful measurements, the measuring plate is equipped with a guard ring ( ↑ guard ring circuit, ↑ Rogowski Influence field measurement probe 220 <?page no="228"?> Manufacturer since over 50 years: • Electric field meter for production and laboratory (according to the induction field-mill principle) • Charge Plate Monitor • TERA Ohmmeter • ESD wrist strap-/ shoetester • Grounding monitoring devices • ESD-protected access control • Customized developments TERA Ohmmeter L aboratory Equipme nt W rist strap-/ Shoetest er C harge Plate Monito r Electric Field Meter Forschungs-, Entwicklungs-, Produktionsu. Vertriebsges.m.b.H www.kleinwaechtergmbh.de Examples of our product range are shown. On our homepage you will find detailed information about these and other products. +49(0) 7622 667652-0 info@kleinwaechtergmbh.de Krummattstraße 9 - 79688 Hausen im Wiesental Manufacturer since over 50 years: Manufacturer since over 50 years: • Electric field meter for production and laboratory (according to the induction field-mill principle) • Charge Plate Monitor • TERA Ohmmeter • ESD wrist strap-/ shoetester • Grounding monitoring devices • ESD-protected access control • Customized developments W rist strap-/ -/ - Shoetest er C harge Plate Monito r Meter www.kleinwaechtergmbh.de www.kleinwaechtergmbh.de Examples of our product range are shown. On our homepage you will find detailed information about these and other Manufacturer since over 50 years: Manufacturer since over 50 years: • Electric field meter for production and laboratory (according to the induction field-mill principle) • Charge Plate Monitor • TERA Ohmmeter • ESD wrist strap-/ shoetester • Grounding monitoring devices • ESD-protected access control • Customized developments TERA Ohmmeter L aboratory ry r Equipme nt Electri Examples of our product range are shown. On our homepage you will find detailed information about these and other products. +49(0) 7622 667652-0 +49(0) 7622 667652-0 Manufacturer since over 50 years: Manufacturer since over 50 years: • Electric field meter for production and laboratory (according to the induction field-mill principle) • Charge Plate Monitor • TERA Ohmmeter • ESD wrist strap-/ shoetester • Grounding monitoring devices • ESD-protected access control • Customized developments ric Field Examples of our product range are shown. On our homepage you will find detailed information about these and other products. <?page no="230"?> profile, ↑ electret (measurement)). The IFM can also be used to detect short-term field changes (dF/ dt) in the high kHz-range. It can also be used to monitor the manufacturing processes of conductive textiles. [Löbel, W. (1995)], [Vogel, Ch. (2014)], [Haase, J., Löbel, W. (1995)], [EN 1149-3 and 1149-5] Influencing factors. The generation and dimensions of electrostatic charges depend on many factors. In addition to the separation speed, the factors shown must be considered. When handling dust, its concentration, particle size and similar factors must also be considered. Inherently conductive, intrinsic ↑ conductivity Initial conductivity. After applying a DC measurement voltage to a sample of high electrical resistance, the measurement current decreases asymptotically to a limit. This is caused by dielectric ↑ polarization and/ or ion migration to the electrodes ( ↑ electrolysis). This current reduction to the final measured value can take seconds or weeks. After reversing the polarity of the measuring voltage, the measuring current can be up to 2 times the original initial current. Therefore, ↑ resistance measurements on insulating materials must always be made with DC voltage and the measurement times must be specified. Initial voltage, ↑ gas discharge, ↑ breakdown voltage Ink deposition (e. g. gravure ink). It is generated in the electric field, especially in high-speed coating machines ( ↑ Lichtenberg figure). Such ink depositions can be conductive for discharging but can also be heated by the current flow and ignite flammable gas mixtures. [SE Section 8.2.10] Ink jet printer, ↑ coating Ink mist. At high speeds and extremely high motion of the coating materials (e. g. printing ink), they foam strongly, bubbles rise, burst and form charged aerosols (ink mist). These aerosols are attracted by the charged ↑ material Ink mist 221 <?page no="231"?> web (e. g. paper or film) or charged by influence and can travel around the coating unit until they settle on earthed surfaces and contaminate the machine ( ↑ ink deposition). Paint mist usually escapes from the outlet side of a coating unit, as the inlet side is covered by, for example, the squeegee. Paint mist can be reduced by using ↑ ionizers. Under certain technical conditions, ink mist can be prevented by using ↑ charging electrodes ( ↑ misting tacker). [SE Section 8.2.10] Inliner. Inner lining of containers and hollow bodies ( ↑ liner). In-mold labeling / in-mold decoration (IML / IMD). It is used in the production of injection molded or blow molded parts for decoration (e. g. labels) to eliminate process steps such as printing or coating. Two processes are used: - Direct charging of the decoration/ label in the injection mold. - Indirect charging of the decor/ label outside the injection mold. The film printed with the decor must be of high resistance and adapted to the mold for electrostatic adhesion. Charging causes the decor to adhere firmly to the mold ( ↑ core dummy charging). ( ↑ useful application) Inner bag, ↑ liner Input capacitance (formerly also referred to as the self-capacitance of a measuring device). It is always proportional to the capacitance of the charged object when measuring a ↑ charge (e. g. with a ↑ coulometer) or a voltage (e. g. with an ↑ electrometer). The resulting capacitive voltage division must be considered when determining the measured value. Input resistance. In electrostatic measurements, the input resistance of the measuring instrument is much more important than in electrical engineering, since it puts a noticeable load on the usually very weak electrostatic ↑ voltage sources and can thus lead to incorrect measurements. Both the input resistance and the ↑ insulation resistance should not be less than 100 T Ω . Inspection attest. An antiquated term for ↑ work clearance permit. Inspection body (accredited), ↑ notified body Inliner 222 <?page no="232"?> Inspection interval. Corresponding inspection intervals are specified for many objects and documents, e. g. an interval of 30 months applies to RIBC for use in Ex-areas. Instructed person. The employer must take precautions to ensure that the work equipment is used and/ or maintained only by suitable, instructed or authorized employees. The same applies to the handling of substances or mixtures within the meaning of the [ ↑ GefStoffV]. In ↑ Ex-areas, this also includes all measures to be taken to prevent electrostatic ignition hazards (e. g. earthing). [ ↑ BetrSichV], [TRGS 727] In the field of electrical engineering, these instructed persons are instructed by a specialist about the tasks assigned to them and the possible dangers of improper behavior and work only under their direction/ supervision. They are also instructed on the ↑ personal protective equipment, necessary protective measures and safety devices. Insulated (electrostatic). This describes conductive substances that are not (electrostatically) earthed ( ↑ conductors). [TRGS 727] Insulating material. A general term for a material that limits the respective form of energy (e. g. electricity, temperature) to the region intended for it. It must be evaluated differently for use in electrical engineering and in ↑ electrostatics. An insulating material with a ↑ surface resistivity ρ s > 10 9 Ω is considered electrostatically chargeable. ( ↑ comparative tracking index, ↑ chargeability) Insulation. preventing an electrically conductive connection (functional insulation). ● Basic insulation is applied to active parts to provide basic protection against dangerous body currents. It may only be removed by destruction. ● Reinforced insulation provides protection against hazardous body currents and must be at least double insulation. It may consist of several layers that cannot be tested individually, such as additional or basic insulation. ● Supplementary insulation is independent of the basic insulation and provides protection against hazardous body currents in the event of failure of the basic insulation. ● Double insulation consists of basic insulation and additional insulation. [IEC 61010-1] Insulation resistance. Electrical resistance of an insulation material between two conductors. It is determined according to [IEC 62631-3-3]. In electrical engineering, insulation resistance defines the quality of an insulation, especially regarding dangerous body currents ( ↑ danger of electric shock). In ↑ electrostatics, the significance of insulation resistance is primarily in measurement technology, where it marks the ↑ input resistance of ↑ electrometers. Insulation resistance meter. An electrical measuring instrument that can also be used in electrostatics. It is generally intended for insulation measurement (operational insulation 2 k Ω / V), but the ↑ leakage resistance required in electrostatics in the range up to 200 M Ω can also be measured. Insulation resistance meter 223 <?page no="233"?> Insulation value. An important criterion for measuring accuracy, e. g. at ↑ CPM. These values should be in the range > 10 16 Ω . For measuring devices with a lower insulation value (around 10 13 Ω ), the measuring accuracy is reduced (tolerance between ± 1 % and ± 5 %). [IEC 61340-4-7] Insulator ● Component used to electrically isolate live parts from each other and/ or from earth. ● General term for electrically insulating material. ( ↑ insulation value) A. Wilke defined insulator in 1898 as follows: “ The extraordinary readiness with which the current follows the path of the conductor is in some respects a disadvantage, because the current takes any path it finds practicable for its circuit, and its paths are not always the ones we require. We must therefore take care to prevent the current from taking any detour, to force it to take the path we want …” [Wilke, A. (1898)] Interaction. Connection by mutual influence. All forces known from the everyday world, as far as they do not originate from gravity, are generally caused by electrical, electromagnetic or electrochemical interactions ( ↑ electrostatic, ↑ adhesion, ↑ cohesion, etc.). Interfacial resistance. Electrical resistance, at the contact surface of two similar or dissimilar materials. In the electrostatics, not entirely correct term for the generation of ↑ charging in the range of contact points of the same or different materials ( ↑ charge double layer). Depending on the magnitude of the electrical ↑ surface resistance R s of the substances involved, a charge equalization will occur during the separation process via the last common contact points, the temporal occurrence of which is determined by the ↑ time constant τ = R × C {Appendix M.6.3.1}. If the capacitance C in this equation is replaced by the quotient Q / U, the charge flowing back during the separation process of the two parts can be calculated from this: Q ¼ U R Accordingly, high separation speeds only allow a low charge equalization depending on the respective resistance values and thus lead to high charging and vice versa. ( ↑ surface reverse current). As a result, charging occurs even if only one of the materials involved has a correspondingly high resistance. This also applies when insulating material and metal are separated. Interlocking devices. Shutters of electrical equipment in the ↑ Ex-area. It is used to maintain a ↑ type of protection and must be designed so that its effectiveness cannot be defeated by simple means (e. g. with a screwdriver or clamp). [IEC 60079-0] Intermediate bulk container, ↑ IBC Internal resistance of an electrostatic voltmeter should not be less than 1 P Ω (10 15 Ω ). ( ↑ adaptation, ↑ voltage source) Intrinsic conductivity (Latin: intrinsecus, “ within ” ), ↑ conductivity Intrinsic safety, ↑ type of protection “ i ” Insulation value 224 <?page no="234"?> Intrinsically safe circuit, ↑ electric circuit Ion (Greek: ión, “ wandering ” ). Electrically charged molecular or atomic particle formed from electrically neutral particles by the addition or removal of electrons. Ions with an excess of electrons are negatively charged and migrate to the positive pole, the ↑ anode, and are termed ↑ anions; conversely, a deficiency of electrons results in a positive charge and migration to the negative pole, the ↑ cathode, and are termed ↑ cations. Ions are generated from neutral particles ( ↑ atom) by ↑ dissociation (chemical and thermal), impact ↑ ionization, ↑ electromagnetic radiation ( ↑ photoionization), ↑ ionizing radiation, ↑ secondary electron. Ion blower nozzle. In high voltage ↑ ionizers, the corona tip is combined with a compressed air nozzle to assist free ion flow (i. e. ions not bound to field lines). This allows the ionized air to be transported over greater distances. Ion blower nozzles are also used to remove electrostatic particles (dust): The ions and electrons neutralize the charges, and the airflow carries the particles away. The illustration shows an ion blower nozzle as a rotating nozzle. Ion current. Term for the current flowing through an ionized path under the influence of an electric field (e. g. ↑ ionizer test, ↑ charge transfer, laminar ↑ air boundary layer, ↑ useful application). Ion dose. Amount of ionizing radiation, until 1985 marked by the unit Roentgen [R]. Its derived SI unit is ↑ Coulomb per kilogram [C/ kg]. Conversion: 1 R = 258 μ C/ kg. It is defined by the amount of ionizing radiation of spatially constant energy flux density that causes a charge of 1 C in 1 kg of air by generating ↑ ions of one sign. Ion exchangers. Substances that absorb negative or positive ↑ ions from solutions and release a corresponding number of ions in return. In water softening, for example, sodium ions are exchanged for calcium or magnesium ions. Ion propulsion system. Developed back in the 1960s, it is based on the recoil principle of a jet of gas ions (usually xenon) traveling at around 50 km/ s. The ions are accelerated by electrical (including high frequency) fields, which allow the ion speed to be precisely controlled. Such thrusters are used for satellite control, among other things. [Bock, D., Tajmar, M. (2018)] Ion pump ● Ion pump for liquids. Insulating (dielectric) liquids are ionized and can then be transported in equally insulating lines by corresponding electric fields emanating from external electrodes ( ↑ electrorheological fluids, ↑ di-electrophoresis, ↑ electrophoresis, ↑ electro-osmosis, ↑ iontophoresis). (Source: Eltex Elektrostatik GmbH) Ion pump 225 <?page no="235"?> ● Ion pump for gas. Used to generate an ultra-high ↑ vacuum. The residual gas molecules still present are ionized by electron radiation and transported out of the vessel to be evacuated by electric fields. Ion source (also ionization source). Term generally used for devices in which gas ions are released in sufficient quantities to eliminate interfering electrostatic charges, e. g. ↑ corona discharge, ↑ alpha and ↑ beta radiation, ↑ flame ionization, ↑ ionizer. Ion spray bar, ↑ ionizer Ion wind (also known as the electric wind). It is generated during the ↑ corona discharge as a stream of air directed away from the pin. It is caused by the ↑ electrons emitted by the pin in the strong electric field (ionizing the air), which entrain the gas molecules. The ion wind increases with increasing temperature and decreasing viscosity of the surrounding gas. [SE Section 6.9.5] Ionic conduction. Represents an electric current generated by the migration of ions in a solid (e. g. salt), liquid ( ↑ electrolyte) or gas ( ↑ gas discharge) under the influence of an electric field ( ↑ antistatic agents). In contrast to ↑ electron conduction in metals ( ↑ conductor 1st order), ionic conduction always involves significant mass transport ( ↑ ion pump) and is therefore slower (conductor 2nd order). Since the mobility of ions increases with increasing temperature, ionic conduction is strongly temperature dependent. Ionization. A process in which ↑ ions are released through the supply of energy. Negative ions are generated by attaching one or more electrons to an electrically neutral atom or molecule ( ↑ anion), positive ions by splitting off one or more electrons ( ↑ cation). ● Primary ionization is the prerequisite for a ↑ gas discharge. It depends on the velocity of the particle, its specific charge, and the absorber. This energy is expressed in ↑ electronvolt [eV]. The ionization energy, which is sufficient to release the weakest bound electron from an atom, is given by: - High-energy photons (UV, X-ray, gamma radiation (photoionization), - Thermal motion of the particles at high temperatures, e. g. in flames (thermal ionization), - Electrical high voltage at a sharp pin, where ions with sufficiently high kinetic energy strike atoms or molecules and knock ↑ electrons out of their orbits (impact ionization), or - Electromagnetic radiation. The resulting positively charged ions and the released electrons are available for charge transport, known as gas discharge in gases. ● Secondary ionization occurs when ionization depends on external electric fields that accelerate the generated charged particles within a free length of path ( ↑ mean free path) to such an extent that impact ionization occurs at the next collision with other particles. Ion source 226 <?page no="236"?> Under atmospheric conditions, impact ionization always occurs at field strengths above 3 MV/ m, but no longer at voltages below 300 V ( ↑ quenching distance). Ionization bar, ↑ ionizer Ionization chamber. Device for detecting and measuring the intensity of ionizing radiation by measuring the electric current generated when the ↑ gas in the measuring chamber is ionized and thus becomes electrically conductive. It consists of a container filled with air or another gas and two electrodes placed in the container and held at a defined potential (plate ↑ capacitor). When ionizing radiation passes through the gas volume, ↑ ions and ↑ electrons are generated, which reach the electrodes under the influence of the electric field and cause a current. Provided there is no impact ionization and no further ion formation, this current is a measure of the incident radiation intensity. The figure schematically shows ionization, i. e. charge separation, by a beta emitter under atmospheric conditions. Ionization device. Active ↑ ionizers (sometimes in combination with fans) permanently installed on ceilings or walls in processing rooms for electrostatically sensitive components (ESDS) to increase the ion concentration in the room air. This can reduce interfering charging, but basic measures to protect against ↑ ESD, e. g. earthing, cannot be replaced by an ionization device. Ionization field meter, ↑ EFM Ionization fire detector ● Detector that responds to combustion gases and consists essentially of a double ↑ ionization chamber, each half of which is ionized uniformly by a weak, long-lived radioactive compound. This takes advantage of the effect that combustion gases attenuate the ↑ ionization artificially generated in a measuring chamber by a radioactive emitter (usually americium 241 ). Depending on the applied DC voltage (e. g. 100 V at an electrode distance of 10 mm), an ↑ ion current flows, the value of which is highest in smoke-free air. If smoke enters the measuring chamber, the ion current is reduced compared to the smoke-free reference chamber. If a predetermined differential current is exceeded, an alarm is triggered by an electronic system. Commercially available smoke detectors are generally based on IR (infrared) technology, in which an IR light-emitting diode is continuously illuminated. When smoke Ionization fire detector 227 <?page no="237"?> enters, the IR light is scattered by the smoke, detected by a sensor, and a signal is generated. ● Flame detector. A live wire grid structure in a tube that uses ↑ flame ionization. Ionization causes the air to become conductive, and a current begins to flow between the wires, causing a voltage drop across the resistance. Ionization pin. The condition of the pins is critical to the operation of an ↑ ionizer. Environmental conditions can cause the pins to corrode. This increases the surface area of the pin, greatly reduces the number of emitted carriers, and decreases the efficiency of the ionization pins. Corrosion or burn-off may be observed especially with DC-positive powered pin rows. - Insulating contamination reduces the effectiveness of the ionization pins. - Conductive contamination can lead to ignition. In some cases, there are solutions where a sharp-edged disk is used instead of the ionization pin. Ionizer (also known as an ionizing bar, discharge bar, or similar). The ionizer is used to provide the surface of a charged object with the opposite pole charge necessary for neutralization. Active ionizers should not be used with ↑ composites with conductive layers. All types of ionizers must be expected to degrade over time ( ↑ ionizer test). ● Passive ionizer. Single or multiple pins connected to earth, which can cause current flow and thus discharge ( ↑ discharge brush, ↑ earthing tongue) in relation to electrostatically charged surfaces (e. g. insulators or insulated conductive parts). The ↑ ionization pins can be wired with resistors to limit the discharge current per pin. (Source: SIMCO Netherlands, “ ThunderIon ” ) Ionization pin 228 <?page no="238"?> When using passive ionizers, residual charges ( ↑ corona discharge, ↑ corona inception voltage) will always remain if the ↑ breakdown field strength of the air is not reached, depending on the distance to the charged counterpart. [SE Section 5.2.3] (Design by Eltex) ● Active ionizers have pins or rows of pins that are typically connected to a ↑ highvoltage generator in the range of 4 - 10 kV. Electrons are emitted from the pin at 3 kV (at standard conditions) and cause impact ↑ ionization. A blue glow is visible in the dark, the atmosphere is ionized, the electrons are available for charge transport and the air becomes conductive. Since the ↑ recombination of these gas ions is relatively fast (their lifetime is only milliseconds), they can only be transported over short distances. The effective range of ionizers depends on: - Amount of charge of opposite polarity ( ↑ Coulomb force) - Time during which the opposite polarity charge is in the region of the active ionizer - Distance to the object to be discharged - Presence of earthed parts in the active area of the ionizers - Presence of condensation With AC high-voltage supply ionizers emit positive ions and electrons sequentially at their pins according to the applied frequency and following a sine or square wave curve. With DC high-voltage supply ionizers usually have rows of polarity separated tips that are usually operated at high operating voltages. They require a large free space around the electrode because a large proportion of the ions generated flow directly to earth potential via earthed parts and do not even reach the substrate to be discharged. Active ionizers are available as separate electrodes or with an integrated high-voltage power supply. For protection against contact and lightning, the pins are usually fitted with upstream resistors or capacitors (only for AC at 50 Hz). Both are justified and are also tested and approved in increased safety versions for hazardous areas, but they differ significantly for highly charged, moving ↑ material webs. Ionizers with ohmic current limiting have an all-current discharge to earth potential, which acts as a passive ionizer (Figure a) in the voltage-free state, provided the ↑ high-voltage cascade is not integrated into the ionizer. Ionizer with capacitive current limiting (Figure b) has no ↑ galvanic connection from the emission pin to the earth. At high surface charges, these ionizers become limited. For example, at an operating voltage of 5 - 8 kV and a charge peak coming from the web ( ↑ charging phenomenon), the capacitor (i. e. the current limiter) is overcharged and ↑ spark discharges to an earthed part are possible. [Künzig, H. (2008)] Ionizer 229 <?page no="239"?> With AC or DC ionizers, high-resistance or conductive contamination can reduce performance. High-impedance contamination reduces the emission current; lowimpedance contamination can cause ↑ parallel connection of the safety resistors, resulting in spark discharges, or allow the current caused by the ionization pins to flow to earthed parts. Filigree contamination (Figure) can act as an ↑ ionization pin, glowing at high discharge current and causing an ignition hazard. External cable contamination places a capacitive load on the ionizers. When used properly, the surfaces of the parts to be discharged are not affected by the ionization of the air ( ↑ ozone). [SE Section 5] ● Radioactive ionizers. The natural radioisotope polonium 210 is used in radioactive ionizers. The particle radiation ( ↑ alpha radiation) generated during radioactive decay has such a high ionization density that it can be used as an ionizer to eliminate with electrostatic charges. The Po 210 in these ionizers is enclosed in a foil. Radioactive ionizers must be replaced every 12 - 15 months due to their short half-life. Because of the German [StrlSchV], their use is no longer acceptable (except in the USA, https: / / nrdstaticcontrol.com/ ). Ionizer test. The effectiveness of active or passive ↑ ionizers can be expected to deteriorate over time. The condition of the ↑ ionization pins and any non-repairable contamination conditions are critical, so it is necessary to test the emission capability of the ionizers. Ionizer test 230 <?page no="240"?> The measurement setup shown applies to all types of ionizers. It has a plate potential (metal plate) of ± 0 to ± 20 kV. This potential is changed manually on the HSP generator so that the emission current of the discharge bar is displayed on instrument I as a function of the plate voltage of the currently tested discharge bar. This measurement setup eliminates the interfering internals that are always present in processing machines. [Bondar, W. A. et al. (1971)] Ionizer test 231 <?page no="241"?> For passive ionizers, diagram 3a shows that discharge efficiency begins at a plate voltage of approximately 3 kV (plate distance 10 mm). For ↑ discharge brushes, the following applies: The denser the filament fill, i. e. the denser the brush, the worse the discharge start. With single pins the discharge current starts at 3 kV, with densely packed brushes only at 8 - 10 kV ( ↑ corona inception voltage, ↑ earthing tongue). With active ionizers (diagram 3b), it can be demonstrated that an emission current already flows to the plate at 0 V potential of the plate and a distance of 10 mm from the ionizer. This can lead to the opposite effect of the ionizer if no corresponding electronics in the high-voltage supply prevent this. A ↑ CPM is therefore of limited use for ionizer efficiency testing. However, [IEC 61340-4-7] specifies a test procedure for 1000 V with the CPM over a period of 1 - 5 min for stationary objects. Common CPMs resolve charge decay with an accuracy of up to 0.1 s (plus measurement tolerance of 2.5 % and greater). Long time intervals are too low a resolution for high performance ionizers. Active ionizers with resistive circuitry have a passive discharge effect on the CPM in a voltage-free state. AC ionizers emit more negatively charged particles than positive ones, which a CPM detects and thus causes misinterpretation. The CPM cannot resolve transient changing charge profiles, either in time or magnitude. However, this ionizer test does not indicate whether the ionizers, when installed, will meet the requirements of a high-speed web processing machine. Short-term charge changes in the ms-range ( ↑ charging phenomenon) and high-voltage potentials > ± 100 kV are possible and detectable. [SE Section 5.2.1.1] Ionizers in processing machines. The correct placement of ionizers is critical to the success of static elimination of webs due to the large number of separation points. In general, both sides of the web should be discharged. The first ionizer should be positioned at the point where the web separates from the roll ( ↑ charging). An ionizer opposite a conductive, earthed roll is useless because the electric ↑ field is directed toward the earthed roll ( ↑ measurement error (field strength measurement)). Contrary to popular belief, these do not discharge, as they are always contaminated with abrasion, dust or other particles in the molecular range. [Lorenz AG (1937)], [Reuter, K. (1965)], [Ohsawa, A. (2013)] Since charging occurs again at each separation point, ionizers may have to be arranged again behind subsequent rollers. Because complete neutralization (discharge) is hardly possible, an ionizer should definitely be provided at the rewind. If the charging of the film only interferes with the rewinding of the web, it would be sufficient to discharge only there. ( ↑ super brush discharge, ↑ danger of electric shock) Because of the ignition risks due to electrostatic charging, the ionizers are recommended according to [TRGS 727 Section 3.3 Example 1] and should be arranged according to the adapted principle sketch. It should be noted that the positions shown in the figures Ionizers in processing machines 232 <?page no="242"?> are only an example and must be adapted to the specific conditions in a coating system ( ↑ roller coating system). 1 - ionizer; 2 - brush discharge, if 1 is not installed; 3 - dust particles that are attracted during high charging; 4 - winding station for unwinding and rewinding; 5 - heavy brush discharge; 6 - counterpressure cylinder (impression roller, central cylinder or similar); 7 - application unit for highly flammable coating materials, Zone 0 tank area; 8 - floor, conductive or dissipative in Zone 1; 9 - continuous dryer; [IEC/ TS 60079-32-1 Sections 6.38 and 12.5.3] IEC/ TS 60079-32-1 adapted to CI flexo press. Ionizing radiation. ↑ Nuclear radiation that ionizes directly or indirectly as it passes through matter, provided the required ionization energy is achieved. Directly ionizing radiation consists of electrically charged particles such as electrons, protons, and alpha particles. UV-rays, X-rays, gamma rays and neutrons rays ionize indirectly and therefore to a lesser extent by releasing secondary electrically charged particles via elementary processes ( ↑ electromagnetic radiation). Ionizing radiation 233 <?page no="243"?> Ionometer, ↑ Ebert tube Ionosphere. Part of the atmosphere in which the gas molecules are largely ionized by space radiation ( ↑ cosmic radiation, photoionization). The ionosphere is divided into the following layers according to their different reflection properties for electromagnetic waves (especially short waves): - D-layer (approx. 80 - 100 km) - E-layer (approx. 100 km, Heaviside layer) - F-layer (approx. 150 - 500 km) Disturbances in the ionosphere (e. g. due to eruptions on the surface of the sun) lead to a loss of shortwave reception and can cause luminous phenomena ( ↑ aurora borealis). Iontophoresis (ancient Greek: pherein, “ to carry ” ). Medical procedure for the percutaneous introduction of ions foreign to the body (e. g. suitable medication) using a weak electrical ↑ direct current. The current strength is around 0.2 - 0.3 mA/ cm 2 electrode surface and maximum 60 V. [Steuernagel, O. (1969)] ISO, short for International Organization for Standardization. An international association of national standards committees founded in 1946 and based in Geneva. Germany is represented there by ↑ DIN. Isotopes. Chemically identical substances whose atomic nuclei have different numbers of neutrons (mass number) for the same number of protons (atomic number). Artificial radioactive isotopes are used in electrostatics as ↑ ion sources for measurements and discharges. ITO layer (short for indium tin oxide). Transparent semiconductive coating, preferably on films ( ↑ composites) in the field of flexible electronics. By using active ↑ ionizers, charges can be stored in ITO layers, which can be dissipated in ↑ spark discharges and destroy the ITO layer. Ionometer 234 <?page no="244"?> J Jet pump / jet vacuum cleaner. Device operates according to the ↑ Venturi principle, in which high charges occur inside due to the transport of solid or liquid particles. Therefore, jet pumps or jet vacuum cleaners for use in ↑ Ex-areas may only be made of electrically conductive material and must be earthed. [TRGS 727 Section 4] Joule. Derived ↑ SI unit [ J] of energy W (work) and the amount of heat Q ( ↑ MIE), named after J. P. ↑ Joule. It replaces the antiquated unit of heat quantity ↑ calorie [cal]. {Appendix M.6.1.2} Joule, James Prescott (1818 - 1889). British brewer and physicist established the ↑ Joule ’ s law named after him in 1840. Joule ’ s law. Describes the amount of heat Q (Joule ’ s heat) generated at an electrical resistance R by the flow of current I in time t. The energy converted into defined ↑ spark discharges is used to determine the ↑ MIE of combustible mixtures. {Appendix M.6.1.2} Joule-Thomson effect. A process named after J. P. ↑ Joule and W. Thomson in which the temperature of a gas changes after an adiabatic pressure drops, i. e. without heat exchange with the environment. This results in a drastic drop in temperature, which leads to condensation or sublimation (e. g. CO 2 fire extinguisher from liquid to solid, snow cannon). Friction at the exit point can cause the particles to become highly charged, resulting in ignitable gas discharges. (Not to be confused with the ↑ Thomson effect.) Junction capacitance (depletion layer capacitance). Capacitance at the junction of a semiconductor ( ↑ variable-capacitance diode). As a result of the depletion of the layer, a capacitance is created between the p-type and n-type material, which can be changed by applying a cut-off voltage ( ↑ PN junction). <?page no="245"?> K Kaolin. A filler used, among other things, in the manufacture of paper. Kaolin consists mainly of aluminum oxide (Al 2 O 3 ) and silicon oxide (SiO 2 ), whose ↑ permittivity ’ s can be responsible for the formation of ↑ electrets in the paper during ↑ corona pretreatment. Karl-Fischer titration. Chemical method for determining absolute water content ( ↑ water activity). An amount of iodine proportional to the water content of the test sample is released from the Karl-Fischer solution and measured by titration. Karl-Fischer titration can be used for both solid and liquid samples. Sample preparation is required for solid samples because the proportionality between the water contained and the amount of iodine released is only present for very small samples. Kelvin. ↑ SI unit [K] of the thermodynamic temperature T, named after W. ↑ Kelvin. Temperatures can be measured and specified in Kelvin, ↑ Celsius [°C] or ↑ Fahrenheit [°F]. Temperature differences are only specified in [K]. Kelvin, William Lord Kelvin of Largs (1824 - 1907), formerly Sir William Thomson ( ↑ Thomson bridge, ↑ Thomson effect). English physicist introduced the temperature scale named after him in 1848. Kelvin generator (also water droplet generator). Designed by W. ↑ Kelvin in 1867, which utilizes two essential effects of electrostatics as an ↑ influence electrifying machine: The ↑ influence and the ↑ Faraday cage. The water droplet generator consists of five components: The water container (A) with two droplet formers, two collection cups (B, C) and two influence rings (B ’ , C ’ ). To visualize the effect, a gas discharge lamp (G) with an upstream spark gap (F) is connected to the collection cups. Mode of operation: A large number of small droplets run out of an uncharged water container in rapid succession, where a minimal asymmetry in charge of a single water droplet starts the process of self-excitation and a high potential is generated as a result of mutual influence. Since the polarity is based on the asymmetry of the initial charge, the sign of the charge for the individual droplet string cannot be predicted. External influences such as electric fields can also initiate the process of self-excitation. The attractive forces of unequal charges cause positively charged water droplets to be generated in the example on the right and fall into the collection cup, which is insulated from its surroundings. The positive charge accumulates on the right-hand cup and in turn acts in the same way on the negative charge in the left-hand cup. By increasing the voltage between the cups and thus the influence rings, the charging effect becomes stronger and stronger. The electrical energy is gained from the <?page no="246"?> gravitational force acting on the drops. As the potential increases, the repulsive forces between the cups and droplets with the same polarity deflect them in a horizontal direction until they no longer hit the cup. The generator has now reached its highest possible voltage (about 10 - 15 kV, depending on the design). If the voltage exceeds the striking distance of the built-in spark gap before this point, a spark discharge occurs, causing the gas discharge lamp to flash. Kelvin voltmeter. Electrostatic high-voltage meter. In a plate ↑ capacitor with rounded electrode edges ( ↑ Rogowski profile) to prevent ↑ corona discharges, there is a rotatably mounted plate whose deflection is transmitted to a pointer by a lever mechanism. A potential applied to the voltage measurement electrode generates a homogeneous electric field that exerts an attractive force ( ↑ Coulomb force) on the moving plate. The deflection of the plate is a measure of the strength of the electric field or the magnitude of the applied voltage. Kerosene (Greek: keros, “ wax ” ). General term for the fractions obtained from the distillation of petroleum between gasoline and diesel fuels (boiling point about 150 - 250°C). Kerosene is generally not explosive at room temperature, as its flash point is in the range of 30 - 40 °C. Kerosene is classified as a highly chargeable liquid. ( ↑ antistatic agents, ↑ cation-active substance) Kerr, John (1824 - 1907). British physicist discovered the electro-optical effect in 1875 and the magneto-optical ↑ Kerr effect in 1876. Kerr effect ● Electro-optical Kerr effect. In some transparent bodies, an electric ↑ field (e. g. nitrobenzene in a plate ↑ capacitor) causes the molecules to align, resulting in optical anisotropy that leads to birefringence. A light beam passing through the medium perpendicular to the electric field lines is split into two linearly polarized beams. When the light beam passes through a polarizer in front of this Kerr cell and is then passed through an analyzer, field changes cause proportional changes in brightness with almost no inertia (Kerr cell shutter). ● Magneto-optical Kerr effect. When light is reflected by mirrors made of ferromagnetic materials, its polarization is changed by the degree of magnetization. Key figures, ↑ explosion-related parameters Kirchhoff, Gustav Robert (1824 - 1887). German physicist, established in 1845 the rules for calculating current and voltage ratios in electrical conductor systems ( ↑ Kirchhoff ’ s rules). Kirchhoff ’ s balance (also voltage balance). Electrometer whose principle of operation is based on the attraction ( ↑ Coulomb force) of two oppositely charged plates ( ↑ electroscope). Kirchhoff ’ s balance 237 <?page no="247"?> Kirchhoff ’ s rules. Behavior of the electric current along current paths. ● Kirchhoff law for nodes (also Kirchhoff current law). At each current node, the sum of the incoming currents I i is equal to the sum of the outgoing currents I o , so that the following holds for the currents I k : X I i ¼ X I o X n k ¼ 1 I k ¼ 0 ● Kirchhoff law for meshes (also Kirchhoff voltage law, Kirchhoff tension law). In any closed circuit, the sum of the generated voltages U g is equal to the sum of the consumed voltages U c , so that the voltage U m applies: X U g ¼ X U c X n m ¼ 1 U m ¼ 0 Kirlian photography. A method named after the Russian technician S. D. Kirlian for the photographic detection of high-frequency, high-voltage discharge patterns (electrodeless ↑ gas discharge). A blue-light sensitive photographic material is placed between a flat electrode and the earthed test object. Depending on the type, shape and electrical conductivity of the object, characteristic, often radial exposure patterns are produced. The use of Kirlian photography in medical diagnostics is controversial. Kleinwächter, Hans (1915 - 1997). German engineer and university professor, rocket, and solar scientist, further developed the ↑ EFM of H. F. C. ↑ Schwenkhagen ’ s ↑ influence electrostatic field meter. Klydonograph. An antiquated analog method for determining the magnitude and polarity of electric voltages using a photographic layer or glass plate dusted with sulfur powder between two electrodes (pin and plate), on which characteristic ↑ Lichtenberg figures are depicted during a discharge. Klystron. An electronic tube in which the ↑ time-of-flight effect is used for amplification. In this way, high oscillator powers in the GHz-range ( ↑ microwave oven) can be achieved. Knife electrode, ↑ measuring electrode for solids no. 1 Kraft paper, ↑ paper K St value. ↑ Explosion-related parameter, basis for the calculation of pressure relief areas, which is based on the rate of pressure increase [bar × m/ s] in the event of an explosion of a ↑ dust-air mixture in a 1 m 3 container. ( ↑ dust explosion class), [EN 14034-2] Künzig, Hermann (1937). H. ↑ Kleinwächter ’ s closest colleague and a versatile German engineer with extensive practical experience in almost all areas of electrostatics ( ↑ EFM). His expertise was sought by many users all over the world. Together with G. Lüttgens and others, he wrote the first editions of the textbook Static Electricity, Understand- Master-Apply. Kirchhoff ’ s rules 238 <?page no="248"?> L Label (French: étiquette). A sign for marking objects, particularly in the field of electrostatics, is used on objects (e. g. bulk packaging) to indicate electrostatic hazards and disturbances. Depending on their size, aluminum labels have sufficient capacity to store a spark that is ignitable for flammable gases and vapors. ( ↑ packaging) Labeling. Each package containing dangerous goods must be clearly and permanently marked with a label (hazard label) ( ↑ ADR). [ ↑ GGBefG] Lacquer. As a ↑ coating can affect the electrostatic properties of materials, especially the charge dissipation of metallic components (e. g. ↑ flange). In the case of internally coated vessels and piping, a sufficiently high ↑ breakdown voltage of the coating can lead to the formation of ↑ propagating brush discharges. Electrically conductive coatings on components made of insulating materials can prevent electrostatic charging and provide ↑ shielding against electric and electromagnetic fields. Laser, short for light amplification by stimulated emission of radiation. A light source that emits coherent wave trains of constant frequency and phase. Laser radiation differs from a conventional light source in its monochromaticity (single color), spatial and temporal coherence (constant phase reference), and very low beam divergence (low beam fanning). ( ↑ lightning protection, ↑ electromagnetic radiation) Laser printer. While in photocopiers the latent ↑ charge image is generated analogously from the reflection of the original image on the ↑ photo semiconductor, in laser printers the exposure and thus the charge dissipation on a photo semiconductor film or drum is performed digitally by a program-controlled laser beam. Due to its high precision, the laser beam produces very accurate images. ( ↑ xerography) Latch-up. This describes a damaging switching process in a highly integrated semiconductor device that is similar to the ignition process of a ↑ thyristor. Since many semiconductor functions must be placed side by side in a very small space, thyristor-like arrangements can occur by chance. Such a “ parasitic ” thyristor can be ignited by the external influence of electrical impulses (e. g. as a result of ↑ influence) and trigger a destructively high current in the semiconductor device. To control the sensitivity of semiconductor devices to ↑ ESD-induced latch-up, ↑ ESD test systems are often equipped with ↑ DUT power supplies that remain in operation during ESD pulse loading, monitor the DUT ’ s current consumption, and detect the sudden increase in supply current in the event of a latch-up. [IEC 60749-29] Lattice theory, electrical property, ↑ crystal lattice Law of Conservation of Charge. In a closed physical system, the total charge of all positive and negative charges remains constant for all processes taking place in it. ( ↑ charging) <?page no="249"?> Law of Induction. Established by M. ↑ Faraday. A voltage is induced in a conductor loop, the magnitude of which is equal to the change in magnetic flux over time. ( ↑ self-induction, ↑ induction) Layer thickness (also coating thickness). To avoid electrostatic hazards, the layer thickness of an electrically insulating ↑ coating ( ↑ lacquer) on conductive substrates (e. g. metal) must be considered from two points of view: - Containers and tanks for liquids may be coated with chargeable insulating materials if their layer thickness does not exceed given limit values (restriction for fluorinated polymers). ( ↑ container filling) - Containers and system parts for fine particle size solids ( ↑ pneumatic conveying, ↑ silo) may only be coated with insulating materials under restriction, as otherwise there is a hazard of ↑ propagating brush discharge. [TRGS 727], [IEC/ TS 60079-32-1], {Appendix D} LCD, short for ↑ liquid crystal display Leader. Term for the pre-discharge of ↑ gas discharges (e. g. ↑ thunderstorm lightning). Leak test. Used to verify the tightness and strength of components and equipment used for transportation, storage of media and/ or as reaction vessels. It must be performed hydrostatically (liquid-filled). On the other hand, pressurized gas systems must be tested with the appropriate gas due to the easier permeability of gases at leakage points. ( ↑ pressure test), [TRGI 2018], [SE Section 7.3.1] Leakage capacitor. ↑ Capacitor that acts as a short-circuit in high-frequency AC currents. Because its reactance ( ↑ alternating current quantity) decreases with increasing frequency, it can reduce unwanted high-frequency currents in low-frequency or DC circuits. Leakage current. Unwanted electric current on the surface of an insulating component or insulator. It can be generated by foreign substances (e. g. moisture, dirt) and cause heating, material changes, etc., resulting in malfunctions and personal injury. Leakage current is also generated by overloading (e. g. power strips), which generates heat and changes the effectiveness of the insulation (fire hazard). Leakage resistance (also known as earth resistance or resistance to earth). Symbol R E , unit [ Ω ], describes the electrical resistance, which is measured between an electrode ( ↑ earth able point) applied to an object and a reference system (e. g. earth). According to the standards, a ↑ measuring electrode with a circular area of 20 cm 2 must be used to measure leakage resistance to earth. The ↑ resistance measurements should be carried out with a DC voltage of at least 100 V, preferably 500 V. [IEC 60079-32-2], [TRGS 727 Section 2.9] ● Leakage resistance of safety footwear and safety gloves. Due to unclear standards, it has become common practice in the field of prevention of hazards due to electrostatic charges to test the leakage resistance in the hand-person-shoe system with an appropriate testing device ( ↑ personnel earthing tester). [IEC 61340-4-5] Law of Induction 240 <?page no="250"?> ● Leakage resistance of a floor. According to [IEC 61340-4-1], a cylindrical measuring electrode (diameter 65 ± 5 mm, weight 2.5 kg) can be used to determine the leakage resistance of a floor. The surface of the electrode should be dry and in full contact with the object (e. g. ↑ measuring electrode for solids no. 7). Since other test methods may also be used, the test method to be used for acceptance and its limits should be determined prior to delivery of a floor covering. [TRGS 727 Section 8.2], [SE Section 3.5.6] ● Leakage resistance of textiles. Shall be determined according to the standard group [EN 1149]. Lean mixture. It is a mixture of flammable gases or vapors in air below the lower ↑ explosion limit, it cannot be ignited. ( ↑ vapor pressure curve, ↑ flame) LED, short for ↑ light emitting diode Leiden jar. The oldest type of ↑ capacitor, consisting of a glass cylinder covered on the inside and outside with metal layers (e. g. tin foil) with sufficient insulating distance to the edge. The Leiden jar was invented independently of each other in 1745 by the Leiden physicist P. van Musschenbroek and the Pomeranian physicist E. J. von Kleist and was a prerequisite for effective electrostatic experiments because the charge of the electrostatic generators, which only supplied weak currents, could be stored in it. ( ↑ influence electrifying machine) LEL, short for lower ↑ explosion limit LEMP, short for lightning emitted magnetic pulse, ↑ thunderstorm lightning Lenard, Philipp (1862 - 1947). Slovakian physicist, Nobel Prize winner for cathode ray research ( ↑ Lenard effect). Lenard effect ● Waterfall electricity (formerly ballo electricity). When liquid droplets are splashed and atomized, electrical ↑ charging occurs. In polar liquids (e. g. water), molecular ↑ dipoles are oriented toward the contact surface with the surrounding gas (e. g. air) for energy reasons. Their positive polarity is directed into the liquid, while their negative polarity is directed outwards. The ↑ anions present in the liquid attach themselves to the positive dipole ends, which in turn bind ↑ cations from the liquid. However, due to thermal molecular motion, not every available site is occupied by a cation (in water at 20 °C, this is the case for about every 25th dipole). Accordingly, the outer layer of a water droplet has a low negative charge, which is why the air near a waterfall is always negatively charged. When a droplet breaks up, negatively charged ↑ aerosols are created, leaving behind positively charged “ droplet shells ” . According to the principle of charging by separation, the level of charge also depends on the ↑ separation speed and the conductivity. [Alty, T., Currie, B. W. (1929)], ( ↑ charging - freeze charging) ● Strong ↑ ionization of gases (especially air) by UV light. Length of path, ↑ mean free path Length of path 241 <?page no="251"?> Lenz, Heinrich (1804 - 1865). Russian physicist of German origin was primarily concerned with electrical and magnetic phenomena and formulated ↑ Lenz ’ s law in 1834. Lenz ’ s law. States that the current caused by ↑ induction always counteracts its cause ( ↑ self-induction). This leads, among other things, to the limitation of the ↑ rate of current rise of electrostatic discharges in electrical conductors ( ↑ ESD, ↑ spark discharge). Lenz ’ s law is a special consequence of the law of conservation of energy, because if it were not valid, the current-carrying ↑ conductor would move at an accelerated rate, the induction current would be amplified and a perpetual motion machine would exist. Levitation experiment. First performed by O. v. ↑ Guericke (1672) to determine the charge on “ electricity carriers ” , e. g. small floating particles (B). Guericke had placed a slowly sinking body (feather fluff, soap bubble or similar) in air in a vertical electric field consisting of two capacitor plates (A, C), arranged one above the other. If the particle had the same charge as the lower plate, it experienced an upward force against ↑ gravity. According to Coulomb ’ s law, which was later established, the charge of a particle in a state of equilibrium can be calculated from the particle mass and the field strength. This principle was used by J. S. E. ↑ Townsend (1897) and R. A. ↑ Millikan (1910) to determine the value of the ↑ elementary charge “ e ” . This principle is used in electrostatic separation devices ( ↑ separation of substances). Lewis, Gilbert Newton (1875 - 1946). American physical chemist. The acid-base concept is named after him. Lewis ’ s acid-base concept. Generally, refers to an ↑ ion as an acid α (acceptor) that can accept an electron pair from another ion, called a base β (donor) ( ↑ contact potential). Plastics with Lewis acidic surfaces, such as PVC, tend to be negatively charged and plastics with Lewis based surfaces, such as PA, PET or PS, tend to be positively charged. The larger the parameters, the greater the electrostatic negative or positive charge of the materials. ( ↑ Brønsted-Lowry definition) Lichtenberg, Georg Christoph (1742 - 1799). German physicist, best known as a writer of aphorisms. Initiator of a critical, mathematically based method of research that made a strict distinction between speculation and fact. He developed the definition of electricity that is still valid today from the two competing methods of his time regarding the nature of ↑ electrostatics (the unitary theory knew only one electrical substance, whose abundance or deficiency was denoted by plus (+) or minus (-), and the dualistic theory with the assumption that there are two types of electrical fluids, namely ↑ phlogiston and acid). He first gained worldwide recognition with the discovery of the star-shaped discharge Guericke levitation experiment (A, C - capacitor plates, B - shreds of gold leaf), [Pohl, R. W. (1957)] Lenz 242 <?page no="252"?> formations resulting from surface charges, the ↑ Lichtenberg figures, later named after him. Lichtenberg discharge, ↑ propagating brush discharge, ↑ Lichtenberg figure Lichtenberg figure. While grinding resin cakes flat ( ↑ electrophorus), G. Ch. ↑ Lichtenberg discovered small star-shaped formations ( ↑ dendrites, ↑ fractals) in the resulting resin dust, for the generation of which he found out different surface charges ( ↑ excess charges). Positive and negative charges gave different images. Lichtenberg recognized the possibility of securing the shape of the figure and thus using it to distinguish between positive and negative charge. When visualizing ↑ charge distributions, positive charges show staror antler-shaped marks, while negative charges are speck-shaped. Life-triggered mode. Oscilloscope mode in which the strongest electrostatic discharge that occurred can be determined from a large number of discharges by slowly increasing the trigger level after triggering by a discharge. [SE Section 3.6.2] Light emitting diode (LED). ↑ Semiconductor diode whose operation causes electrons to pass from the ↑ conduction band to the ↑ valence band, emitting energy in the form of light ( ↑ band model, ↑ OLED). Light metal. Metal and alloy with a density of less than 5 g/ cm 3 . It is characterized by relatively high stiffness and relatively low weight. Technical light metals required in large quantities include aluminum (Al) and magnesium (Mg). When these metals are processed and the metal dust (Al: ↑ MIE < 1 mJ) or abrasion that are generated in the process are produced, considerable hazards must be expected. The dust (mean diameter < 500 μ m) are flammable and explosive when stirred in air. In combination with water-miscible cooling lubricants or during wet separation, ↑ hydrogen and thus ↑ oxyhydrogen gas may be formed. To determine the required ventilation systems, the amount of hydrogen produced can be determined using the reaction equation: e. g. 2 Al + 3 H 2 O → Al 2 O 3 + 3 H 2 (oxidation of e. g. 1 kg Al produces 111 g H 2 with a gas volume of 1.24 m 3 ). Combustion of e. g. Mg produces very high combustion temperatures of about 2500 °C, which can lead to “ thermolysis ” of water with subsequent oxyhydrogen gas reaction (explosion). If work clothing is contaminated with light metal dust, there is an increased risk of fire for employees. [DGUV Regel 109-001], [DGUV Information 209-090] Lightning. A general term based on its luminous appearance for ↑ thunderstorm lightning. Lightning arrester (also gas arrester). ↑ Gas discharge tube filled with a specific gas at a defined pressure, in which overvoltage pulses can be dissipated by igniting a gas discharge ( ↑ surge arrester, ↑ transient). With a gas arrester, a ↑ breakdown voltage can be determined more accurately than with air gaps. Lightning arrester 243 <?page no="253"?> Lightning death without marks. ↑ Thunderstorm lightning can cause cardiac death in humans, even if the lightning strike occurs at some distance from the person and leaves no visible marks (burns). The high lightning currents of 100 kA and more generate extremely strong magnetic fields in their immediate vicinity for a duration of about 100 μ s, which can induce an induction current in the human body. If this happens at a critical time of the heartbeat, the life-threatening “ atrial fibrillation ” can occur. ( ↑ step voltage) Lightning detection system. Like all magnetic field coupled gas discharges [SE Section 4.1.1], thunderstorm lightning also emits high-frequency electromagnetic waves, so-called ↑ spherics. Their frequency band is in the kHz-range, but they can interfere with radio reception up to the MHz-range due to their harmonic content. Spherics have an almost global range but can only be received with special receivers (infra-long wave). On this basis a worldwide lightning detection system exists. In some countries (including Germany), due to the EU Directive on Electromagnetic Compatibility (EMC), commercially operated receiver systems are available that can detect lightning strikes with an accuracy of about 200 m and in real time (www.aldis.at). They indicate the polarity of the lightning and whether it was a partial, single or multiple flash. Lightning discharge, ↑ thunderstorm lightning, ↑ silo, ↑ dust Lightning protection ● External lightning protection. Lightning protection always requires an electrical shielding of the object to be protected ( ↑ Faraday cage). For this purpose, a very widemeshed grid is built over the building contour using appropriate metal conductors. The lightning interception system generally consists of a ridge conductor and, if necessary, interception rods on objects protruding above the roof (chimneys, ventilation pipes). All metal equipment on the building (gutters, antenna pipes) is connected by the shortest possible route to the lightning protection system, which in turn is connected to an earthing system ( ↑ foundation earth electrode). Due to the high current rise in values during ↑ thunderstorm lightning, the ↑ self-induction in the line system must be kept low. This is achieved by external lightning protection, which primarily serves to protect the building. [IEC 62305-1, NFPA 780, BS EN 62305 and AS/ NZS 1768] ● Internal lightning protection. Requires measures beyond external lightning protection to prevent harmful electromagnetic effects of the lightning current on sensitive electronic components within the protected area ( ↑ SG). To this end, inductive and capacitive coupling to lightning current carrying lines should be kept as low as possible. Further measures (protection of persons, installations and electronic equipment) are ↑ equipotential bonding and ↑ surge arrester. [Plumhoff, P. et al. (2010)] ● Lightning protection for people. How to protect yourself from lightning, how to behave correctly during a thunderstorm, what to consider for lightning protection and what to do in case of accidents caused by lightning - all this is explained in a very detailed and comprehensible way in the VDE leaflets “ Blitzschutz ” , which are available free of charge in the eWebshop VDE shop.vde.com/ en/ blitzschutz. ● For large-area lightning protection (e. g. airports), the first promising tests for triggering upward flashes with high-frequency laser pulses were carried out in 2020. Lightning death without marks 244 <?page no="254"?> The power of these pulses (1 ps) is in the TW-range. They create an ionization channel for flash triggering. [Produit, Th. et al. (2020)] Lightning pulse, ↑ thunderstorm lightning Lightning rod (ground rod). In 1750, B. ↑ Franklin succeeded in catching lightning with long, upright metal rods. This principle was later introduced as the lightning rod. The purpose of the lightning rod is to provide the undirected pre-discharge of the thunderstorm lightning with a defined starting point for the counter-discharge and thus the object to be struck, so that the lightning current can flow safely to earth. Unfortunately, lightning strikes have also been shown to occur in the vicinity of lightning conductors. Since lightning conductors do not always work reliably, more extensive ↑ lightning protection is required for the objects to be protected. [DEHN Blitzplaner ® ] ↑ Thunderstorm lightnings are undoubtedly the most spectacular gas discharge of static electricity and has been a source of fear and terror for mankind since the beginning of time. Throughout the ages, the founders of religions have exploited this fact by attributing the power of thunderbolts to their respective deities. Their priests were thus in the comfortable position of being able to manipulate the wrath of their gods and use it as a magical force against humans, animals, and buildings. The flash of lightning and the rumble of thunder were considered divine punishment. Only the invention of the lightning rod by B. Franklin (1752) freed mankind from the mysticism of thunderstorms. Not surprisingly, because of this loss of authority, all houses of worship around the world were soon equipped with lightning rods (first in Germany in 1769 on St. Jacob ’ s Church in Hamburg). In the collection of aphorisms by G.Ch. Lichtenberg there is a remarkable sentence on this subject: “ The fact that preaching takes place in churches does not make the lightning conductors on them obsolete. ” [Lichtenberg, G.Ch.] In Germany, the work of Adolph Traugott von Gersdorf (1744 - 1807) from Upper Lusatia had a lasting influence on the study of lightning conductors. Lightning strike. Can endanger living beings (by direct strike or indirectly via ↑ step voltage), destroy buildings and trees, cause fires and explosions in facilities with combustible substances (tank farms) and cause faults and damage to electrical wiring systems and devices ( ↑ lightning death without marks, ↑ thunderstorm lightning). Limiting oxygen concentration (LOC). Maximum concentration of ↑ oxygen in a mixture of combustible dust with air and ↑ inert gas at which no independent flame propagation (explosion) can occur. It depends on the combustible gas or vapor and the inert gas used. The limiting oxygen concentration is determined by laboratory experiments in which a dust sample is blown with compressed air into a test apparatus (volume 20 l or 1 m 3 ) and ignited with a ↑ ignition source (2 kJ or 10 kJ) ( ↑ Hartmann tube). A safety margin is subtracted from the concentration determined, which then defines the maximum allowable limiting oxygen concentration. Fluctuations in the limiting oxygen concentration in production plants must be considered, and an alarm threshold must be set as part of any necessary metrological monitoring that detects the increase in the O 2 concentration and still allows sufficient time to comply with the limiting oxygen concentration. [TRGS 407] Limiting oxygen concentration 245 <?page no="255"?> Line electrode, ↑ measuring electrode for solids no. 2 Linear accelerator. Evacuated particle accelerator in which elementary particles ( ↑ electrons, ↑ protons or heavier ions) are accelerated to very high energies (up to several mega- ↑ electronvolt) along a straight path by electrostatic fields or electromagnetic waves. Liner (either integrated or as a liner bag). Usually made of insulating material, should always be prevented in ↑ Ex-areas, as high ↑ potentials can build up on them during filling or emptying. They must be treated as insulating containers. Conductive liners in insulating containers should also be prevented or they must be permanently earthed. If liners are used in ↑ FIBCs (types B, C and D), these must be evaluated as a unit because their behavior is changed as a result. ( ↑ ADR, Section 6.9.2.2.3), [TRGS 727 Section 6] Liquid. A substance in a liquid ↑ state of matter that can become charged when flowing ( ↑ charging). In the past, the term “ combustible ” was used in connection with liquids. This term is incorrect, because it is not the liquid that burns, but the vapor it releases at the surface. In 2002, the ↑ BetrSichV defined the classification of “ inflammatory liquid ” , which is still valid today. In 2009, a ↑ Globally Harmonized System (GHS) was introduced, which will be mandatory from 2015, and the classification of liquids was modified. This was accompanied by the designation of inflammatory liquid as “ flammable liquids ” , in accordance with English usage. In general, however, it makes sense to use the terms flammable, highly flammable and extremely flammable ( ↑ flammable liquid). Liquid charging, ↑ charging - of liquids Liquid crystal. Found in organic liquids with crystalline structures (elongated molecules). It is often used for display purposes by causing a color change when the temperature rises or a change in the orientation of the molecules in the electric field, and thus optical transparency ( ↑ liquid crystal display). Liquid crystal display (LCD). Used in digital displays and computer screens, among other applications. It is a thin cell of plane-parallel plates with liquid crystals between them and an electrically conductive transparent grid. When an electric voltage is applied to a few opposite points on the lattice, the resulting field changes the transparency of the liquid crystals in that element, and when color filters (red, green, blue) are used, a color image can be generated. Numbers, letters, and images can be displayed by controlling the dots. Liquid crystal displays require external light for viewing, but as an electrostatic process they have very low energy consumption in contrast to self-illuminating LEDs. Liquid discharge. Occurs as ↑ self-discharge of charged liquids but may also be required for safety reasons at high flow velocities or after passing through filters. To discharge the liquid, ↑ calming sections can be installed in the pipe system, which must be dimensioned so that the average flow time is 100 s ( ↑ relaxation time). Another way to reduce the space charge density is to install ↑ ionizers on high voltage in the pipe wall with the pins pointing inwards. In this region, the tubes must have an insulating coating on the inside. The effectiveness of these “ liquid charge reducers ” developed in the USA has been proven, but they are rarely used in Europe. ( ↑ earthing tongue) Line electrode 246 <?page no="256"?> Liquid electrode, ↑ measuring electrode for solids no. 18 Liquid encapsulation, ↑ type of protection “ o ” Liquid fire, ↑ combustion process Liquid lens (electrostatic lens). An optical lens consisting of various liquids (e. g. oil and water) whose focal length can be varied precisely and extremely quickly by applying voltage. Static electric fields are used for this purpose. Alternatively, ↑ electroactive polymers are used. Manufacturers use technologies ranging from electrowetting and shape-changing polymers to acousto-optic tuning to control the radius of curvature and refractive index of the liquid lens. Liquid measuring cell, ↑ measuring electrode for liquids Liquid toner. An electrically insulating liquid with dispersed pigments. It is used in electrostatic ↑ copying processes to develop the latent electric ↑ charge image (e. g. in Hewlett-Packard (HP) digital printers). List of hazardous substances. List (with reference to the corresponding ↑ material safety data sheet) of the hazardous substances used in a company. ( ↑ explosion prevention document) Lithium chloride humidity sensor, ↑ humidity meter Lithium-ion accumulator. Currently the most common accumulator for high performance parameters with high ↑ power density up to 300 Wh/ kg. It should be noted that lithium-ion accumulators are rechargeable, whereas lithium-metal batteries are not. Depending on the technology used, these values are currently: - Lithium cobalt oxide (LCO): 150 - 200 Wh/ kg - Lithium manganese oxide (LMO): 100 - 150 Wh/ kg - Lithium nickel manganese cobalt oxide (NMC): 150 - 220 Wh/ kg - Lithium ferrous phosphate (LFP): 90 - 120 Wh/ kg - Lithium-nickel-cobalt-aluminum oxides (NCA): 200 - 260 Wh/ kg - Lithium titanium oxide (LTO): 70 - 80 Wh/ kg [Cadex Electronics Inc. (2019)], [Wu, F. et al. (2021)] A rechargeable lithium-ion accumulator typically consists of the cathode (lithium metal oxide in various compositions), the anode (usually made of graphite), and the separator, a nanoceramic layer that is permeable to lithium ions, and the water-free electrolyte. (double layer ↑ capacitor) Loop impedance. Sum of the impedances ( ↑ alternating current quantity) in a current loop, consisting of the individual impedances of the current source, the outer conductor from one pole of the current source to the measuring point, and the return conductor from the measuring point to the other pole. Lorentz, Hendrik Antoon (1853 - 1928). Dutch physicist discovered the ↑ Lorentz force named after him and established the classical electron theory in 1895, Nobel Prize in Physics 1902. Lorentz 247 <?page no="257"?> Lorentz force. Force exerted on a charge moving through a magnetic field ( ↑ induction). The Lorentz force is used, for example, to direct an electron beam from a vertically influencing magnetic field onto a circular path ( ↑ cyclotron). Lorentz plasma. Plasma model in which only the interaction between free electrons and positive ions is considered, but not the interaction between the free electrons themselves. Loschmidt ’ s number. Symbol n 0 , is the quotient of the ↑ Avogadro ’ s number N A and the molar volume V m . It indicates the number of atoms or molecules contained in a volume of 1 cm 3 of an ideal gas under standard conditions (T 0 = 273.15 K = 0 °C and p 0 = 101.325 kPa): n 0 = N A / V m = 2.69 × 10 19 cm -3 ( ↑ mole) Loss. In electrostatics, refers to the heat generated in the ↑ dielectric of ↑ capacitors after an electric voltage is applied. This loss is due to the finite resistance of the dielectric and the finite conductivity of the metal winding, plus an additional loss component (dielectric aftereffect). ( ↑ dissipation factor) Loudspeaker. Electro-acoustic transducer for emitting sound in which a membrane is excited by electrical energy to vibrate and thus become a sound source. The sound pressure generated in the medium (e. g. air) can be converted into auditory sensations by the human eardrum, for example. The pressure can be generated in electromagnetic, electrodynamic, ↑ piezoelectric and electrostatic transducers (Figure). The latter are a complex alternative to the other systems. In their simplest form, they consist of a conductive membrane placed at a short distance from an electrode. The voltage between the membrane and the electrode is supplied by the output of an amplifier in accordance with the sound signal. These voltage variations cause changes in the attractive forces on the membrane with corresponding deflections ( ↑ Coulomb force). The required voltages are in the kVrange and require correspondingly high pow er in the output stage of the sound amplifier. Low voltage. Used to describe electrical alternating voltages ≤ 1000 V RMS value ( ↑ Low Voltage Directive) and ≤ 1500 V for direct voltages. Low Voltage Directive. Serves to ensure the level of protection of electrical appliances regarding the health and safety of people, pets/ domestic animals and property. The scope includes all electrical appliances with a rated voltage range between 50 and 1000 V for alternating current and between 75 and 1500 V for direct current, insofar as they are technical equipment or parts thereof within the meaning of the ↑ ProdSG. [EU 2014/ 35] Low-voltage system (formerly high-voltage installation). Electrical installation containing equipment for the generation, conversion, storage, transmission, distribution, and Lorentz force 248 <?page no="258"?> consumption of electrical energy for the purpose of performing work, e. g. in the form of mechanical work or for generating heat and light. The distinction to other types of electrical installations by voltage (e. g. more than 50 V), current or power is not always clear. [IEC 60050] Lower explosion limit (LEL), ↑ explosion limit Lower explosion point (LEP), ↑ explosion point Lowry, Thomas Martin (1874 - 1936). English chemist, known for his acid-base theory, which he published independently of J. N. ↑ Brønsted in 1923. Luminescence (Latin: lumen, “ light ” ). General term for all luminous phenomena that are not based on thermal radiation (cold glow, cold light). Individual atoms and molecules are stimulated to release the energy supplied by light emission (from UV to IR radiation). Their intensity is often proportional to the number of excited atoms or molecules. Depending on the type of excitation, a distinction is made between: ● ↑ Electroluminescence in electric fields or electrostatic discharge processes ( ↑ gas discharge) ● Ion luminescence when the luminescent material is excited by ions ● Cathode luminescence when the luminescent material is excited by electron beams ● Piezo luminescence under external pressure with elastic deformation ● Thermoluminescence caused by heat when atoms are already excited ● Photoluminescence with optical excitement ● Chemiluminescence during chemical reactions (bioluminescence (fireflies) in living organisms) ● Triboluminescence, fracto-luminescence when the material is broken or rubbed together ● Mechano-luminescence caused by mechanical impact on solids or liquids ● Sono luminescence caused by sound, high pressure on bubbles in liquids (implosion) ● Radioluminescence caused by radioactive radiation ● X-ray luminescence caused by X-rays or gamma radiation Luminescent electron. The most easily excited electron in the outer shell of an atom. When excited (e. g. by ↑ ionization), this outer electron is transported to a higher-energy quantum state and emits the excitation energy as a ↑ photon at a substance-specific frequency when it returns to its ground state (luminous phenomenon in ↑ gas discharge). Luminescent substance. Conversion of visible (light) or invisible (e. g. UV) ↑ electromagnetic radiation and electron radiation into visible radiation by fluorescence (nonluminescent) or phosphorescence (luminescent). Lycopodium. Tiny spores of the “ cob lycopodium ” (Latin: lycopodium clavatum), which form a fine yellowish powder (median value 32 μ m), popularly known as witches ’ flour. Due to its consistent quality, lycopodium is used as a test substance for dust explosion tests ( ↑ MIE) and for visualization of ↑ charge distributions. In ancient times, the flame-like burning of whirled up lycopodium was considered a way to attract and render harmless ↑ thunderstorm lightning. Lycopodium 249 <?page no="259"?> M Machine (Greek: mechane, “ tool ” ). Mechanical device that converts a primary form of energy into another form of energy desired for a specific purpose, e. g. ↑ Van de Graaff generator, ↑ influence electrifying machine, ↑ motor. Machine model, ↑ MM Maglev train (magnetic levitation). Works on the principle of a linear drive with spacing by strong magnetic fields (force effect in the ↑ field). The electrostatic counterpart is the ↑ electric curtain. Magnesium powder, ↑ light metal Magnetic field, ↑ field, ↑ natural constant Magnetic induction, ↑ induction Magnetization. This describes the orientation of the elementary magnets (Weiss domains) of ferromagnetic materials (magnetic ↑ polarization). Magnetography. A digital printing process developed after 1980, in which small magnetic heads “ write ” the magnetic layer under a layer of graphite. The toner adhering to this layer is transferred electrostatically to the substrate and then fixed “ cold ” (approx. 50°C) using xenon flash lamps ( ↑ corona charging). Main earthing terminal. Terminal is used to connect the protective earthing conductor, the equipotential bonding conductor and, if applicable, the functional earthing conductor to the earth conductor and the earth electrodes. Major accident (force majeure). Malfunction in which a hazardous substance is released and may cause serious hazard to people, animals, plants, property or the environment. “ An event that immediately or subsequently leads to a serious hazard or property damage inside <?page no="260"?> or outside the operating area … in the operating area from EUR 2 million and … outside the operating area from EUR 0.5 million. ” [12. BImSchV] Major Accidents Ordinance. 12th Ordinance on the Implementation of the German Federal Immission Control Act [12. BImSchV]. It defines the term “↑ major accident ” , specifies the prevention of major accidents, accident prevention and the requirements for the prevention and limitation of major accidents, and defines the scope of the resulting obligations for plant operators by means of threshold quantities for certain hazardous substances. The requirements of the Hazardous Substances Act and the ↑ CLP Regulation are also primarily relevant. International regulations include the Seveso Directive (EU), SOLAS (maritime shipping), IHR (WHO). MAK value, short for German: maximale Arbeitsplatz-Konzentration (maximum workplace concentration), ↑ occupational exposure limit Marking. Graphic or visual representation corresponding to the substances or mixtures classified according to hazard classes and categories. Electrical operating resources must bear the name of the manufacturer, type designation and information on the connected loads in a clearly visible place. Special requirements apply to electrical operating resources in Ex-areas for which information on the ↑ category has been required since 1997. Marks of electrostatic discharge, ↑ gas discharge mark Mass flow rate (electrostatic determination). Compared to gases and liquids, the mass flow rate of bulk solids is difficult to determine. One method is an electrostatic measurement method based on the detection of particle charges resulting from the separation ↑ charging during material transport. The charge of the bulk material flow is transferred to a sensor by ↑ influence, which provides a current noise ( ↑ bandwidth) corresponding to the mass throughput from the superposition of many individual charges. When two sensors are placed at a defined small distance, similar noise signals are generated with a corresponding time offset, from which the flow rate and transport velocity can be determined using a correlation calculation. Material moisture. It is an important parameter in determining the properties of a material, which in turn determines its ability to be further processed, including print quality and, in the food, beverage and cosmetics industries, the shelf life of the product. For cellulose-containing materials (e. g. paper), surface and bulk resistivity decrease almost linearly with increasing water content. Water content can be measured by chemical, electrical, optical, or thermogravimetric methods. Near infrared spectroscopy ( ↑ NIR spectroscopy) can be used as an almost ideal method. In the thermogravimetric method, water is removed from the sample by increasing the temperature, infrared radiation or microwaves, and the weight loss is evaluated. Since other materials besides water can evaporate and contribute to the loss of mass, measurement errors cannot be ruled out. [SE Section 3.16.2.2] Material pairing. Influences the ↑ charging when separating the partners if only one of the materials involved has a correspondingly high resistance, i. e. charging also occurs when separating a material pair consisting of insulating material and metal, and in the Material pairing 251 <?page no="261"?> same way for both, only with a different charge sign. It should be noted that conductive metal rollers are often hard-coated and therefore generally no longer conductive. A special case is the material pairing of rollers in processing equipment, which are coated differently depending on the requirements. Common coatings are: - NBR (nitrile butadiene rubber, polar) - PU (polyurethane, polar) - EPDM (ethylene-propylene-diene rubber, non-polar) - Silicone (non-polar) The literature describes that ↑ Coehn ’ s rule is no longer valid if one of the partners is nonpolar ( ↑ charging phenomenon). [Kanamaru, K., Takada, T. (1939)], [SE Sections 2.5 and 2.14] Material property number. A term often used in electrical engineering for the ↑ permittivity number of insulation materials. Material safety data sheet (MSDS). Information on hazardous substances or preparations that the manufacturer must provide with the first shipment. The MSDS must comply with the “ REACH Regulation ” , Art. 31 [REACH EC, Annex II] and the Hazard Communication Standard (HCS). The content is internationally comparable. It is structured as follows: 1st Product identification 2nd Composition/ information on ingredients 3rd Hazard(s) identification 4th First aid measures 5th Fire-fighting measures 6th Accidental release measures 7th Handling and storage 8th Exposure controls/ personal protection 9th Physical and chemical properties 10th Stability and reactivity 11th Toxicological information 12th Ecological information 13th Disposal considerations 14th Transport information Material web. Webs of paper, film, textiles, metals and their ↑ composites, and glass (for electronic applications) are used in a wide range of industrial processes. Investigations related to the interpretation of ↑ charging phenomenon on material webs have shown that electrostatic problems can hardly be interpreted or answered satisfactorily in the conventional way, i. e. with the classical theory of the Helmholtz double layer ( ↑ charge double layer) ( ↑ surface reverse current density). The generation of different ↑ charge profiles cannot be predicted. ● During the unwinding or separation of the material web from a roll, there is an exchange of electrons between the donor D, e. g. the roll, and the acceptor A, the Material property number 252 <?page no="262"?> Trust KELVA, the innovator in industrial web cleaning. 7 000 installations worldwide. 20 cm to 10 m web width. Suitable for almost any material and surface. www.kelva.com YOU HAVE SOMETHING AGAINST DUST? SO DO WE! <?page no="264"?> material web (Figure). However, the web can also be a donor, and the guide roll an acceptor. Many factors affect how charging occurs: - Material: Thickness, surface, and volume resistances (R s and R v ), surface roughness, components of the material web, web tension - Contact pairs: Elastomer coated rollers, bare or coated metal rollers - Dynamic factors: Web speed, contact intensity (e. g. contact pressure or web tension), difference between web speed v and circumferential speed v u of the roller, wrap angle, temperature, and relative humidity ● During the rewinding of webs can be observed three phenomena: - The uneven ↑ charge distribution creates a rolled ↑ capacitor whose energy can be converted into a propagating brush discharge (especially in the case of composite materials). - An accumulation of charges of the same name occurs, which can lead to a ↑ super brush discharge ( ↑ charge accumulation). - Particularly in the case of freshly extruded films, cooling and/ or mechanical tension cause very slight relative movements within the coils, which are usually tightly wound, resulting in equally high charges due to the high contact pressure, which becomes visible during unwinding. ( ↑ useful application, ↑ charging electrode, ↑ ionizer in processing machines, ↑ Van de Graaff generator, ↑ Lewis ’ s acid-base concept, ↑ Brønsted-Lowry definition, ↑ surface charge density), [Schubert, W., Ohsawa, A. (2024)] ● Discharge of material webs. In general, passive or active ionizers are used. The latter must be able to support a high level of passive discharge current. At high charging potential and high web speed, the passive discharge at the ionizer increases almost exponentially with the onset of the corona inception voltage (> 2500 V, ↑ breakdown field strength). It can also cause a ↑ polarity inversion that should not be ignored; a positive charge partially becomes a negative charge and vice versa. If the distance between the ionizer and the web is too small, this effect is increased. Material web 253 <?page no="265"?> The primary cause of this is the high passive DC discharge current flowing from the pins to the web surface. The greater the product of the web charge and speed, the greater this current flow. This DC current also simultaneously causes the laminar air boundary layer to change into a turbulent boundary layer directly above the material web. A certain proportion of discharge ions (which have the opposite charge to the originally charged web) also become part of the turbulent air boundary layer and are carried along with ( ↑ potential). As a result, the web that was initially discharged under the ionizer becomes charged again after passing with the ions from the turbulent air boundary layer and their opposite polarity. This phenomenon was first systematically investigated experimentally and described by F. Knopf. [Knopf, F. (2017)] Maxwell, James Clerk (1831 - 1879). British physicist who, among other things, founded modern electrodynamics and the electromagnetic theory of light. Maxwell ’ s equations. Fundamental equations of electrodynamics formulated by J. C. ↑ Maxwell, describe the relationship and interactions between electric charge and electromagnetic ↑ field and provide the proof that an electromagnetic field propagates as a wave at the speed of light ( ↑ electromagnetic radiation). 1st Electric charges are sources of field lines ( ↑ Coulomb force). 2nd Magnetic point-charges do not exist. Magnetic field lines are always closed. 3rd A magnetic field changing with time generates an electric vortex field. 4th is the inverse of the 3rd equation: A time-varying electric field generates a magnetic vortex field ( ↑ pinch effect). Mean free path. Term introduced by R. J. E. Clausius in 1858 in the kinetic theory of gases, usually denoted by λ . It is the average distance that a particle (e. g. electron, atom or molecule) can travel freely before it suffers an impact, or the distance between two successive impacts (impact ↑ ionization). It is inversely proportional to pressure, so that the particle density and thus the possibilities for energy and matter transport decrease with decreasing pressure. For gases in the standard condition, the path length is between 30 nm (for chlorine Cl 2 ) and 180 nm (for helium He). The term can be applied to any system of interacting particles. ( ↑ vacuum, ↑ Avogadro ’ s number, ↑ Paschen ’ s law). Measurement accuracy. The degree of approximation of the measured value to the actual or agreed value. Due to the variability and non-uniformity of the materials of the test samples and the strong influence of ↑ humidity, additionally burdened by the effects of ↑ hysteresis, the measurement accuracy of electrostatic measurements is significantly lower than in electrical engineering. ( ↑ calibration uncertainty, ↑ measurement error) Measurement chopper, ↑ EFM Measurement error. In the field of electrostatics, measurement errors occur mainly in ↑ field strength measurements and ↑ resistance measurements and must therefore be reduced by the following measures. Instruments should always be calibrated or checked with known reference samples ( ↑ calibration). In general, it should be noted that electrostatic parameters cannot usually be measured very accurately and reproducibly because they are affected by the slightest inhomogeneities. Therefore, they typically have a Maxwell 254 <?page no="266"?> measurement uncertainty of up to about 30 %, although this is already considered for safety-related limit values. In principle, all parts and devices used for measurement must be earthed ( ↑ earthing). For more information on ↑ measurement accuracy for resistance measurements, refer to various standards and guidelines/ documents, including [TRGS 727]. It is recommended to repeat measurements on several samples or on several tests. Statistical evaluation methods can contribute to a better interpretation of the results. Measurements according to [IEC 60079-0] are not recommended, as a wide range of measurement errors may occur when following the procedures specified therein. The [IEC/ TS 60079-32-1] and group [IEC 61340] should always be used. [Pidoll, U. v. (2019)] ● When measuring field strength, the field should be homogenized ( ↑ homogenization) by means of symmetrically arranged conductive earthed plates and insertion of the ↑ EFM into the plate plane. Due to the high effort involved, this measurement setup is generally limited to special cases. Instead of measuring the field strength at the surface of the charged object, it may be more appropriate to make a ↑ potential measurement. When setting up test rigs for moving ↑ material webs, it is important to ensure that there are no interfering and field-distorting installations. Possible “ flutter movements ” ( ↑ web tension profile) of the web can be marginalized by arranging large homogenization plates (much larger than the distance between the measuring sensor and the material web). [SE Sections 5.4 and 8.2.12] Due to the difficulties in homogenizing the E-field on material webs, a measuring arrangement opposite a roller is often chosen, which is supposed to enable a stable measurement [Taylor, D. M., Secker, P. E. (1994)]. This arrangement does not provide meaningful measurements because - the E-field of the web (E = U/ a, [V/ m]) is directed towards the nearest earth potential and thus towards the roller, and Measurement error 255 <?page no="267"?> - the detection range of an EFM extends well beyond the contact area between the web and the roller and all fields of the incoming and outgoing web are included in the displayed measured values. If the web touches the earthed roll, the distance a tends to zero. This means that the field is bound and mirrored in the material thickness ( ↑ image charge). [Schubert, W., Ohsawa, A. (2024)] If possible, charged surfaces should always be measured against an unobstructed background, since flat objects in the vicinity or behind can influence the measurement. In the case of insulating surfaces, the ↑ charge distribution and thus the outgoing electric field strength is generally not homogeneous. EFMs can only record an average value corresponding to the measurement area and may not be able to detect small areas of charge with sufficient accuracy. The same applies, for example, to the measurement of thin threads ( ↑ filament measuring chamber). The electrostatic charge of strongly curved surfaces can also only be detected with error. An EFM with a small aperture or the use of a contact measurement with an electrostatic voltmeter can therefore be useful. Particularly with highly charged surfaces, if the distance of the EFM is too small, this can lead to pre-discharges that falsify the measurement result. Humans can also be a source of error. ● When resistance measurement, a current must flow which generates a more or less strong electromagnetic field. Therefore, the following measures should be taken to prevent measurement errors: - Keep conductor loop areas small through compact design. It is especially important to avoid earth loops. Due to inductive coupling ( ↑ inductive coupling), interference currents (AC currents) also flow through the power supplies of the measuring devices involved. - Shielding the measurement circuit with magnetically soft materials of very high permeability. Shielding of magnetic fields is only possible with thick-walled materials. Iron-nickel-copper alloys are used for this purpose ( ↑ Permalloy TM ). - Limiting the range in the measurement circuit. Although electrostatics only measures DC voltage or DC current, the measurement circuit must also be designed to operate (transient response) at low frequencies. By ensuring that only frequency components up to a limit frequency (e. g. 3 Hz) form the display, interfering alternating currents are evaporated and the noise of the resistances involved is limited. - Resistance measurements in the range > 10 12 Ω should be performed in a ↑ Faraday cage. ● Measuring volume resistance. It is recommended to use a guard ring circuit (principle circuit diagram), which also serves to shield the measurement circuit: Current is supplied from battery (B) via the current-limiting protective resistor (R) and terminal (A) to the lower electrode (in contact with the sample). The measuring current passing through the sample is received by the upper electrode and fed back to the ↑ ammeter via the measuring terminal (M) and thus to the other battery terminal. Measurement error 256 <?page no="268"?> To prevent a leakage current originating at the lower electrode and flowing across the sample surface from also reaching the ammeter, it is intercepted by the annular “ guard ring electrode ” surrounding the upper electrode and fed directly back into the battery via the guard ring terminal (S), bypassing the ammeter. ● Measuring the surface resistance largely independently of the influence of the volume resistance ( ↑ shell effect) is also possible with a guard ring circuit. In the case of flat, thin insulating material structures (films), it is always problematic to differentiate between surface and volume resistance. The principle-circuit is shown: The current is supplied from the battery (B) via the current-limiting protective resistor (R) via terminal (A) to the left-hand strip-shaped contact electrode, from where it passes via the sample surface to the right-hand contact electrode. There it is taken up, conducted via measuring terminal (M) via the ammeter and back to the other battery terminal. Since a residual current can flow through the insulating mounting parts (B 1 and B 2 ) of the electrode holder, they are attached to a conductive plate (P), which is connected to the protective ring terminal (S). Fault currents thus bypass the ammeter and return directly to the battery. ● For ↑ capacitance measurements, make sure that stray capacitances (e. g. the person performing the measurement, capacitance of the measurement cable) and stray voltages (AC voltage fields, e. g. fluorescent lamps ( ↑ gas discharge tube)) are kept as low as possible by keeping a sufficient distance (person at least 50 cm, fluorescent lamp at least 2 m). The capacitance to be measured must be isolated from earth, otherwise the earth leakage resistance could also be detected. Measuring cables should be as short as possible. [IEC 60079-32-2] ● Measurement error due to various circumstances - Movement of the test cable. The relative movement of the cable components leads to “ triboelectric currents ” between the cable insulation, the measuring conductor, and the shielding ( ↑ triboelectricity, ↑ cable charging, noise effect). This cable charging causes measurement errors when measuring high resistances Measurement error 257 <?page no="269"?> (> 10 12 Ω ), low currents (< 10 -12 A) or low voltages. The same applies to ↑ charge measurements in the range < 10 -12 F. [SE Section 3.16.3] - Unsuitable cable insulation material. Only cables with insulation materials such as silicone or PTFE should be used for all measurements. PVC or similar insulation is not suitable. - Electrical and electromagnetic fields emitted by powerful devices in the vicinity of the measurement must be avoided. - The temperature of liquids has a considerable influence on their ↑ conductivity. - In the case of multiphase liquids with a low conductivity phase or solid particles, a waiting time of 30 minutes must be observed before a measurement (static conductivity). [TRGS 727 Section 4.8] - Changes in test climates. Preparation of samples in the climatic chamber and measurement in the laboratory with a different climate will cause measurement errors. For example, textiles should be conditioned and measured in the same room. - Photoelectric effects (sunlight) can affect the permittivity of very sensitive measurements. Therefore, such measurements should be made in dark cells. - Avoid unprotected transport of samples from the climate chamber to the measuring station. Measurement field strength. The field strength applied to the test object when determining ↑ surface resistance or ↑ volume resistance. It is calculated from the measurement geometry and the applied measurement voltage. For ↑ resistance measurements on insulating materials, the measurement field strength should be at least 10 kV/ m to minimize interference ( ↑ contact potential, ↑ influence). However, it must not be so high that the sample is noticeably heated by the measurement current. The figure shows a recommendation for the measurement field strength depending on the expected resistance values. [SE Section 3.5.2] Measurement interferences. Usually caused by external influences ( ↑ influence, ↑ electromagnetic radiation, person not earthed, ↑ charges moving in the environment). Most of them can be avoided by measuring in a ↑ Faraday cage. Measurement technology. Enables the assignment of values, whereby ↑ voltage, ↑ current, ↑ resistance, electrostatic ↑ field strength, ↑ capacitance and ↑ permittivity can be measured for the evaluation of electrostatic charging. In addition, influencing variables that can change the electrostatic behavior (e. g. ↑ humidity, ↑ temperature) must also be measured. Conclusions about the behavior of an object can only be drawn to a limited extent from its properties since interactions with the environment and possible contact partners must be considered. An example of an object property is electrical resistance. It indicates the time in which an applied charge can be expected to be dissipated. The electrostatic behavior of the object can only be determined by a more or less close contact Measurement field strength 258 <?page no="270"?> (friction and separation test), the result of which can be used to draw conclusions about the amount of charge to be expected. Measurement voltage. Since the dissipation capability of objects is often relevant to safety, it must be verified by measurement. Various specifications can be found in [IEC 60079-32-2], [IEC 61340-2-3 and 61340-4-1]. Since many antistatic materials show a significant drop in resistance at test voltages of several 1000 V, the regulations recommend a test voltage of 10 000 V for these test samples to determine the antistatic property. Higher test voltages are not required. ( ↑ measurement field strength) Resistance [ Ω ] Measurement voltage [V] Measurement time [s] < 10 4 10 ± 5 15 ± 5 10 4 to 10 8 100 ± 5 65 ± 5 10 8 to 10 12 500 ± 25 65 ± 5 > 10 12 1000 ± 50 65 ± 5 The meaningfulness of the measurement time of 15 s at < 10 4 Ω must be questioned. Measuring aperture, ↑ EFM Measuring cable. Only suitable, clean cables with good insulation (e. g. silicone rubber) should be used for ↑ resistance measurements. They should not touch conductive objects during the measurement. The electrical capacity of the measuring cable must be considered and the influence of external electromagnetic fields on it must be avoided ( ↑ Faraday cage, ↑ measurement error). Measuring cables for the transmission of low charges between piezo sensors and charge amplifiers are subject to special requirements (e. g. oil-filled measuring cables). Measuring cell, ↑ measuring electrodes for liquids Measuring climate, ↑ test climate Measuring device. Used to quantitatively record physical and other properties. For direct electrostatic measurements, only powerless measuring movements can be considered, which are referred to as ↑ electrometers or ↑ static voltmeters. As an extension of the measuring range of these devices, e. g. by a ↑ voltage divider, always leads to a load on the current source, amplifier-fed multi-range measuring devices with a high resistance input are used. The usual electrical measuring devices for measuring voltage, current or resistance have an incorrect ↑ adaptation to the electrostatic ↑ voltage sources due to their low internal resistance. An explanation can be found in ↑ electrostatic - system comparison. It should be emphasized that the insulation measuring device from electrical engineering can be used to measure the ↑ leakage resistance (M Ω to G Ω -range). When handling measuring devices, the terms ↑ calibration, ↑ adjustment, and ↑ verification must be observed. ( ↑ tera-ohmmeter) Measuring electrode. Technical device for measuring ↑ resistances and temperaturedependent ↑ conductivities (for liquids) in electrostatics. It is used to determine both the electrical properties and the electrostatic behavior of objects ( ↑ shell effect). Different Measuring electrode 259 <?page no="271"?> measuring electrodes are used depending on the type of surface (hard, soft, stony). Various standards and regulations contain corresponding weight specifications for the contact pressure of measuring electrode on solid materials. This is usually achieved by the dead weight of the electrode or the person making the measurement or the standardized spring pressure. The measuring electrodes should have standardized configurations, otherwise their dimensions must be described in the test report. The test procedure and the specification of the measuring instrument must comply with the relevant normative specifications ( ↑ measurement error); measuring cables suitable for the measurement task must be used ( ↑ cable charging). To ensure comparability of the measurement results, the surface resistances for homogeneous solids should be converted to specific surface resistivities. In general, both the measuring electrode and the measurement sample should be acclimatized for at least 24 hours at 23 ± 2 °C and a relative humidity of 25 ± 5 %. Possible ↑ influencing factors on the measurements must be considered. The expected measurement result should be within the measuring range of the ↑ tera-ohmmeter. This should have the following connections: Power supply (A), measuring cable (M), guard ring (S), earth (E). ( ↑ measurement error (guard ring circuit), functional ↑ earthing). A guard ring circuit must always be used for high-resistance surface resistance values > 10 8 Ω . The most common measuring electrodes are listed below. [IEC 60079-32-2], [IEC 61340-2-3 and 61340-4-1], group [EN 1149], [SE Section 3.5] ● Measuring electrodes for solids (for measuring surface resistance R s and volume resistance R v ) are generally made of stainless steel and usually have a conductive rubber coating (volume resistance < 10 3 Ω , typically 3 mm thick, Shore A 50 - 70 (rubber hardness)). In general, the test specimen may have any shape but must be a solid. Special measuring electrodes are required for powder spills (note particle size). Other electrodes are available for clothing and textiles, e. g. [IEC 61340-4-9]. - 1) Parallel electrode (also knife electrode). Two parallel linear measuring electrodes for contacting insulating materials to determine R s (see figure for dimensions). The knife edges are made of flexible material or conductive soft rubber compounds to provide good contact on non-planar surfaces. Comparable electrodes can be used based on the dimensions shown. Even in the old IEC 60167 from 1964, the dimensions were specified in such a way that the ↑ edge field effects can be neglected (today [IEC 62631-3-3]). (Conversion factor: ρ s = R s × 10, ↑ measuring electrode for solids 5a) Measuring electrode 260 <?page no="272"?> - 2) Line electrode. Two narrow electrodes made of conductive paint (conductive silver paint or colloidal graphite) for determining R s on insulating materials. A possible influence of the solvent on the surface must be observed and prevented! - 3) Spring-tongue electrode. A set-up electrode described in the withdrawn DIN 53 482 for measuring R O . It consisted of two thin, regularly cut spring plates, 100 mm long, which were pressed onto the surface of the specimen at a distance of 10 mm using an insulated weight. [IEC 62631-3-2] Now replaced by electrode 4) due to poor contact with the test surface. (Source: www.fischer-messtechnik.de) - 4) Conductive rubber electrode. Modification of electrode 3) with attached conductive rubber strips 1 mm thick and weighing 2 kg, or stamped electrode with attached conductive soft material (e. g. 33 Shore A, maximum 1.5 Ω / cm, 3 mm thick), used to measure R s on insulating materials. It should conform to the contours of the specimen for better contact. To avoid measurement errors, the resistance of the electrode to the resistance of the sample to be measured must be negligibly small. If the resistance values are unknown, start with low voltages. At the preferred measurement voltage of 10 kV for dissipative and antistatic samples, the contact strips must be insulated with foam between them to prevent arcing. This type of measuring electrode is preferable to electrode 2). [IEC/ TS 60079-32-1] Measuring electrode 261 <?page no="273"?> - 5) Square measuring electrode a. For measuring the surface resistivity ρ s (in this context also called R □ ). The measurement is carried out between two narrow parallel measuring electrodes with a length L equal to distance A. If the resistance distribution is homogeneous, the surface resistance remains constant for measuring areas of A = L! [TRGS 727], [IEC 61340-2-3], [EN 1149-1] b. ( ↑ Roller tester) For cylinders, rollers, etc. to determine R s or R v . Recommended electrode shape for measuring cylindrical bodies (two electrodes 10 × 100 mm 2 , distance 100 mm). - 6) Cylindrical electrode. Standard electrode for flat samples to determine volume resistivity ρ v and ↑ leakage resistance of ↑ floors. It is also used to determine the electrical resistance of textiles (point-to-point resistance). [IEC 61340-4-1 and 61340-4-9]: diameter 65 ± 5 mm, 2.5 ± 0.25 kg (soft samples), 5.0 ± 0.25 kg (hard samples); [ISO 10965]: diameter 65 ± 2 mm, 5.0 ± 0.1 kg (all grades); [ASTM F150-06]: diameter 63.5 mm, 2.5 kg (all types). - 7) Tripod measuring electrode (also three-point electrode). It is used to check the insulation resistance of floor systems in relation to the dissipation capability of people. It consists of an equilateral triangle, which is to be pressed for the measurement with the weight of the measuring person (at least 300 N). In case of ceramic flooring, the cylindrical electrode 6) is useful. An intermediate layer of moistened blotting paper is not recommended because it introduces moisture into the floor covering and thus falsifies the measurement result. [EN 1081], [IEC 62631- 3-1] (Source: www.warmbier.com) Measuring electrode 262 <?page no="274"?> - 8) Two-point probe a. According to [IEC 61340-2-3] for resistance measurements on small non-planar objects. b. Tripod electrode. According to [IEC 61340-4-11] for uneven or vertical surfaces. It can also be used, for example, on handling systems for reconditioning ↑ IBC or as roller tester. A factor of 7 must be used to convert to surface resistivity R □ . (Source: www.warmbier.com) (Source: www.kleinwaechtergmbh.de) - 9) Ring electrode. Center electrode (M) surrounding a ring electrode separated by an air gap. When measuring R s , the ring is used as a power supply (A), and when measuring R v , the ring is used as a guard ring (S) ( ↑ measurement error). [IEC 61340-2-3] If R s < 10 8 Ω , the ring electrode for measuring R v must not be connected to (S), otherwise an excessively high residual current may cause an impermissible reduction in the measurement voltage. [EN 1149-2] The surface resistivity {Appendix M.7.1.3} can be calculated from S ¼ 2 R S log e d 2 d 1 d 2 ¼ d 1 þ 2g (A simple conversion factor from R s : ρ s = R s × 19.8) The volume resistivity {Appendix M.7.1.4} according to V ¼ R V d 1 ð Þ 2 4h Measuring electrode 263 <?page no="275"?> - 10) Cavity cylinder electrode. The ring electrode mentioned in [EN 1149-1] can be fitted with an insulating cylinder to determine the ρ v of bulk materials. In addition to the intended use for yarns, fibers and fiber short cuts (e. g. flock), powders can also be filled in, which are then compressed under the electrode ’ s own weight with a pressure of 2.5 ± 0.25 kPa (the particle size must be considered). The standard does not provide for conversion of the measured value to a defined volume, but this is possible in an idealized form, considering the dimensions and geometry of the measuring electrodes: The measuring surface is 20 cm 2 and the electrodes are 10 mm apart when the cylinder is full. This results in a factor of 0.02 m, by which the measured resistance value must be multiplied to arrive at ρ s with the unit [ Ω m]. {Appendix M.7.1.4} - 11) The powder cell. According to [TRGS 727 Section 6] is filled from above with the bulk material (e. g. dust/ powder). The upper weight electrode is then slowly lowered onto the bulk material. The distance between the electrodes is determined by the amount of sample and the bulk behavior (bulk density) of the dust and changes with each test series. This electrode is preferably used for cone discharge evaluation. The area of the tamped cell is 20 cm 2 . The resistivity of the material can be calculated as R × A / d = ρ (R - measured resistance, A - area through which current flows, d - distance between electrodes). - 12) Channel measuring cell. Characterized by a constant sample volume with a defined electrode surface and distance. Excess sample material is wiped off after filling. This measuring electrode is preferably used for the evaluation of fine particle size bulk materials regarding their behavior after penetration, e. g. in a housing. [ISO/ IEC 80079-20-2] specifies measuring voltages: 105 ± 10 V, 500 ± 25 V and 1000 ± 50 V Measuring duration 10 s, if the measured value is not constant, the measuring duration is increased to 65 ± 5 s. Measuring electrode 264 <?page no="276"?> - 13) Concentric measuring cell. J. Lucas (IBExU, Freiberg) used a measuring cell constructed from ring electrodes for the investigation of lignite dust in 1989. This consists of three ring electrodes arranged one above the other with a rod electrode in the middle. The material to be measured is not compressed by an electrode weight but is compacted as required for different bulk densities. - 14) Cylinder electrode. Electrode described in the withdrawn DIN 53 482 for measuring the R v of tubular specimens, analogously also for cables, pipes and hoses. The electrode consisted of an inner and outer metal electrode attached to a section of the specimen. - 15) Textile strip electrode. According to [DIN 54345-5] for resistance measurement on textile fabrics for textile strips maximum 350 × 50 mm 2 . (Source: www.fischer-messtechnik.de) Measuring electrode 265 <?page no="277"?> - 16) Pin electrode. According to [IEC 60243-1], for determining the breakdown strength of insulating materials. A distinction is made between: a) Conical pin electrodes (diameter maximum 5.5 mm), to be inserted into rigid materials with a minimum thickness of 1.5 mm and a center-tocenter distance of 25 ± 1 mm. b) Parallel cylindrical pin electrodes shall be used for testing high dielectric strength materials greater than 15 mm thick. The measurement result is determined equally by the surface and volume resistivity of the material. - 17) Bar electrode. For measuring the ↑ insulation resistance of materials in the form of strips, bands or thin rods. It consists of two metal clamps with the dimensions 10 × 10 × 50 mm 3 placed 25 mm apart. Since it is supported only by the test piece itself, there are no incorrect measurements due to shunts due to insulating fasteners. [IEC 62631-3-3] - 18) Liquid measuring electrode. To ensure better contact, it is allowed to use solid electrodes in addition to those mentioned above, such as those previously described in IEC 93. The liquid is confined by stainless steel rings with sharp edges on the bottom. There is no information on the type and resistance of the electrode liquid. (Mercury, although suitable in principle, is not recommended for continuous use or at elevated temperatures because of its toxicity.), [IEC 62631-3-3] - 19) Measuring electrode for gloves. To measure the leakage resistance of gloves and finger cots when worn. This electrode guarantees the ↑ CAFE system according to [ANSI/ ESD STM15.1] (constant area and force electrode). The weight of the electrode is 460 g. - 20) Handheld electrode. When testing the dissipation capability of people, it is always advisable to test the entire “ system ” consisting of the person, the footwear and the floor. The handheld electrode is available in different versions, gold-plated, silver-plated or steel. Measuring electrode 266 <?page no="278"?> - 21) Measuring electrodes for hose lines. They are very diverse and complex to use. The arrangement of the various measuring electrodes for determining the longitudinal, surface (internal and external) and volume resistance as well as the resistance from hose fitting to the hose body is described in [ISO 8031]. The measuring voltage is 500 V. ● Measuring electrodes for liquids to determine ↑ conductivity. - 1) Conductivity measuring cell. From the variety of electrodes used, it is recommended to use the one shown in accordance with [DIN 51412-1] to determine the static conductivity. - 2) Dip electrode for fast series measurements. Two 1 cm 2 measuring electrodes arranged in parallel and insulated from each other, immersion depth 1 cm, cell constant = 1/ cm. There is a protective electrode between the electrodes to prevent parasitic currents between the electrode plates. - 3) Dip electrode for measurements for the evaluation of electrostatic hazards (e. g. conductivity of kerosene) without high accuracy. Two insulated, preferably concentric arranged surfaces are immersed to a specified depth in the low-viscosity liquid to be measured. An inner electrode pin is connected to the input of a measuring device to determine the ↑ volume resistance, while a surrounding cylindrical electrode supplies the measuring current. To determine the resistivity of the liquid under test, the measured value (resistance value) must be multiplied by Measuring electrode 267 <?page no="279"?> the ↑ cell constant. The cell constant is calculated from the ratio of the electrode area to the electrode spacing. - 4) Measuring cell for determining conductivity and permittivity in combination with the EPSILON+ measuring system (www.flucon.de). To avoid electrolysis in liquids, measurements are performed with an alternating voltage of 1.5 V (AC), a frequency of 20 kHz for the determination of the electrical conductivity and a frequency of 100 kHz for the determination of the dielectric constant. The electrical conductivity κ can be measured in the range from 1 × 10 -9 to 6 × 10 -4 S/ m via the capacitance of the measuring cell, which is designed as a tubular capacitor (outer electrode - A, inner electrode - I). The measuring range of the permittivity ε is 1 - 10. In combination with a temperature control unit, the behavior of both values can be recorded at increasing temperatures up to 170 °C. The method is based on [IEC 60247]. ( ↑ alternating current quantity, ↑ resistance measurement) ● Measuring electrode as special application - Sphere electrode. Established electrode for electrostatic measurements, shaped like a knuckle or thumb, diameter 20 - 25 mm. Specially used for measuring transferred charges on the ↑ coulometer and as a hand test/ preliminary test for determining the MIE of dust. Measuring electrode 268 <?page no="280"?> Principle of ↑ dust ignition (Source: Dr. U. v. Pidoll) Measuring spark gap, ↑ spherical spark gap Mechanical sparks. ↑ Sparks caused by friction, impact, and grinding processes. Median value. ↑ Explosion-related parameter for bulk material, describes the average particle size (50 % by weight of the dust is coarser and 50 % by weight is finer than the median value). The particle size distribution of dust is determined by sieve analysis. Using the finite element method, the median value can be used to calculate the energy of a ↑ cone discharge (CD): W CD = 5.22 × d 3.36 × g 1.46 W CD [mJ] is the maximum expected ↑ equivalent energy of a cone discharge, d [m] is the vessel diameter, and g [mm] is the median value. [TRGS 727 Section A.3.6] Medical device. The medical device worn permanently or temporarily on the body (e. g. hearing aid, insulin pump, 24-hour blood pressure monitor, etc.) may pose a hazard in hazardous areas due to the integrated power supply as an ignition source. Investigations by the German ↑ Physikalisch-Technische Bundesanstalt and the Berufsgenossenschaft Rohstoffe und chemische Industrie (BG RCI) ( ↑ Employer ’ s Liability Insurance Association) have not yet been completed. ( ↑ implant) Melt marks. ↑ Propagating brush, ↑ cone, ↑ super brush, and ↑ spark discharges can leave tiny melt marks at their point of impact. If they keep hitting the same spot, they can cause corrosion damage. Stronger melt marks can be expected from spark discharges on the surfaces of the electrodes involved. ( ↑ gas discharge mark, ↑ thunderstorm lightning), [SE Section 4.2.4] Mercury. Liquid ↑ metal at room temperature, is well suited as a material for ↑ electrodes. However, its high toxicity (mercury vapors are released in dangerous quantities even at room temperature) makes it unsuitable for general use. Mercury 269 <?page no="281"?> MESG, short for maximum experimental safe gap. Classification of gases and vapors in ↑ explosion groups regarding their ability to penetrate a standardized annular gap [IEC 80079-20-1]: Maximum gap width (MESG) [mm] Ex-group ≥ 0.9 IIA > 0.5 to < 0.9 IIB ≤ 0.5 IIC Application: e. g. when selecting ↑ flame arrester vents or pressure-resistant enclosures ( ↑ type of protection “ d ” ). The MESG is the maximum gap opening for the most easily ignited mixture (not necessarily stoichiometric) at which no ignition failure occurs. It correlates with the ↑ minimum ignition current (MIC). The MESG decreases with increasing temperature and pressure and in the presence of oxidants stronger than air. The MESG can be increased by the addition of inert gas. [Zakel, S. et al. (2020)] Metal. Except for ↑ mercury, all metals are solid at room temperature. They can form intermetallic compounds (alloys), which are also called metals. They are good conductors of heat and electricity and are classified as ↑ conductors 1st order ( ↑ electron conduction). As molten metals solidify, the metal atoms group together to form ionized ↑ crystals. The electrons released in this process are also called ↑ electron gas due to their large number and random direction of motion, similar to the particles of a gas. They are available for ↑ charge transport and for charge transitions during separation charging. In the ↑ triboelectric series, metal always takes the place of the ↑ donor ( ↑ light metal). Metal fibers. Mainly made of stainless steel (a few micrometers in diameter and a few millimeters in length) are added to plastics in a manner similar way to ↑ carbon fibers to make them electrically conductive (e. g. to avoid ESD problems). Metal oxide FET, short for metal oxide field effect. Transistor, in which the gate is separated from the channel by a metal oxide layer. This design allows input resistances > 100 T Ω . Metal oxide FETs are used, for example, in the input stage of high-ohmic voltmeters (e. g. ↑ electrometers). Metal paper capacitor, ↑ capacitor Meter. ↑ SI unit [m] for the length l. One meter is the length of path that light travels in a ↑ vacuum for 1/ 299792458 s. mho. Backwards notation of Ohm. ( ↑ conductivity) Micro perforation, ↑ perforation Micronizer, ↑ air jet mill Microphone. For converting airborne or structure-borne sound into electrical signals. The microphone is the inverse of the electrostatic ↑ loudspeaker. MESG 270 <?page no="282"?> ● Capacitor microphone. Based on the change in capacitance (change in distance) between the diaphragm and the backplate. ● In an electret microphone (actually an electret capacitor microphone). Either the diaphragm or the backplate is an ↑ electret. The electret film (e. g. PE < 6 μ m) is usually coated with a metallized layer to increase the ↑ surface charge density. The film creates an electrostatic field between the two, which is set into vibration by the sound, causing a change in capacitance and a change in potential at the counter electrode. No voltage source is required. Both pieces of information can be processed by amplifiers as an electrical input signal. Micropore (also puncture). It is often generated by ↑ propagating brush discharge on the insulating packaging means ( ↑ liner) in the metal vessel. However, electrostatic discharges seldom lead to ignition because they mainly start on the container wall below the surface of the bulk material, where ignition is not possible due to the lack of atmospheric oxygen. They leave marks in the form of “ ice flower ” patterns ( ↑ dendrites, ↑ fractals) and often in the form of micropores. These do not lead to significant leakage, but microorganisms, for example, can enter the product through them and cause product contamination. ( ↑ FIBC) Microscopy. Non-contacting ↑ scanning force microscopy. Microwave oven. High-frequency device for heating materials in which ↑ molecular dipoles are set into strong oscillations (internal frictional heat) by a strong alternating field (frequency: 2.45 GHz). Because microwaves are very dangerous, especially to the eyes, the equipment must have reliable ↑ shielding. Microwave ovens are mainly used in households. In industry they are used to heat rubber parts and plastic parts and as dryers. Controlled microwave heating can also be used to eliminate unwanted ↑ electrets. MIE, short for minimum ignition energy E min , unit [mJ]. ↑ Explosion-related parameter describing the flammability of an explosive mixture with respect to electrostatic ignition. To initiate a ↑ combustion process in a fuel-air mixture, the energy of the ignition source must exceed a certain limit, which depends on both the type and concentration of the fuel. The MIE describes the smallest amount of electrical energy stored in an ideal ↑ capacitor that, under defined test conditions, is sufficient to ignite the ↑ most easily ignited mixture of fuel (gas or dust) and air at atmospheric pressure and room temperature when discharged across an ignition-optimized spark gap. The MIE decreases with increasing pressure and temperature, as well as with more oxidizing agents than air. The MIE is usually determined according to [ISO/ IEC 80079-20-2] in the ↑ Hartmann tube. {Appendix B], [ASTM E582-21], [ASTM E2019-03], [SN EN 13821], [TRGS 727], [SE Section 1.2.3] Migration (of antistatic agents). For the ↑ dissipation capability, thermoplastics are equipped with ↑ antistatic agents that migrate to the surface over a period of time. When Migration (of antistatic agents) 271 <?page no="283"?> the surface is subjected to heavy loads, the antistatic agents are used up and the dissipation capability is lost. Millikan, Robert Andrews (1868 - 1953). American physicist who, among other things, determined the ↑ elementary charge and was awarded the Nobel Prize in Physics in 1923. Millikan experiment. Experimental determination of the electrical ↑ elementary charge. In this experiment, very small, charged oil droplets are held in suspension against gravity in the vertical electric field of a plate ↑ capacitor. The field strength between the plates can be regulated by the voltage divider Sp and thus a defined state of the droplet with the charge Q can be set. In the floating state, F E + F G = 0. The charge of the droplet can be determined from the field strength and the droplet mass. A large number of repeated measurements on different droplets show that all values determined for the charge are multiples of the smallest unit of charge, the elementary charge. The Millikan experiment can also be performed in a modified form: The particles to be studied fall through the horizontal field of an elongated capacitor, to whose plates a sawtooth voltage is applied. If the mass of the particles is known, their charge can be deduced from the deflection of the particles, considering Stokes ’ law of friction. Mineral separation. ↑ Separation of substances, which can also be carried out electrostatically. Minimum ignition charge, ↑ MIQ Minimum ignition current (MIC). ↑ Explosion-related parameter. In a standardized procedure [IEC 80079-20-1], the ignitability of gases and vapors is determined using a standard circuit. The reference number for the tested substance, also known as the minimum ignition current ratio (MIC ratio), is determined for the minimum ignition current for methane. The values for the ↑ MESG have been adjusted to those of the minimum ignition current: Explosion group II A II B II C Maximum experimental safe gap (MESG) > 0.9 mm 0.5 - 0.9 mm < 0.5 mm Minimum ignition current (MIC) > 0.8 mm 0.45 - 0.8 mm < 0.45 mm ( ↑ type of protection) Minimum ignition energy, ↑ MIE, ↑ most easily ignited mixture Minimum ignition temperature. Lowest temperature of a hot surface at which a dust layer or dust cloud ( ↑ Godbert-Greenwald apparatus) is ignited. The minimum ignition temperature also depends on the layer thickness; the allowable surface temperature decreases as the layer thickness increases. If the thickness of the dust layer is ≥ 5 mm, the Millikan 272 <?page no="284"?> minimum ignition temperature is specified as the glow temperature [DGUV Information 213-065]. Tables often contain values determined using the BAM furnace ( ↑ Federal Institute for Materials Research and Testing (BAM)) according to [VDI 2263]. [prEN 13237], [ISO/ IEC 80079-20-2] MIQ, short for minimum ignition charge (charge Q). Preferably expressed in units of [nC], is the smallest amount of charge transferred in an electrostatic discharge under specified test conditions that can ignite the ↑ most easily ignited mixture in an explosive atmosphere. It is commonly used to quantify the ignition effectiveness of a discharge emanating from insulating materials ( ↑ brush discharge). ↑ Spark discharges from small charged ↑ capacitances can be evaluated by measuring the transferred charge ( ↑ charge transfer - measurement). Neither brush discharges nor spark discharges are effective for ignition if the transferred charge is less than the MIQ. The term MIQ was first used in German regulations in 2008. Caution! The MIQ is generally applicable to flammable gas mixtures. Dust can be ignited by spark discharges, but this is not to be expected with brush discharges. Exceptions may be ↑ hybrid mixtures. The measurement of the MIQ and its classification into the ↑ MIE and the explosion group ( ↑ MESG) were performed by the German ↑ Physikalisch-Technische Bundesanstalt. The table {Appendix B} gives some values for commonly used flammable gases and vapors that refer to atmospheric conditions when mixed with air. There is no theoretically based way to convert MIE to MIQ, as both are empirically determined values and should not be equated as they contain different units: MIE [Ws], MIQ [As]. [SE Section 3.6.2], [TRGS 727] Mirror charge, ↑ image charge Misting tacker. ↑ Roller coating systems of various configurations are generally used for material webs ( ↑ coating). Web speeds > 1100 m/ min are not uncommon at present, which can lead to the coating material separating and misting. The misting tacker implements the functional principles of electrostatic charging to reduce particle mist ( ↑ useful application). Misting tacker 273 <?page no="285"?> The ↑ charging electrode creates a ↑ field from the pins between S5 and R4 and generates a ↑ DC low-energy plasma in which the particle flow is directed to the earthed rollers. With this solution it is possible, for example, to completely eliminate silicone mist at a speed of 600 m/ min. [Knopf, F. (2012)], [Dilfer, S. (2002)] Mixed polymer. Plastic, consisting of a mixture of different ↑ polymers to optimize required properties, e. g. electrostatic properties. Mixing. A solvent vapor mixture with a gas (e. g. with air) remains intact as long as the density differences of the partners involved are close to each other ( ↑ Brownian molecular motion versus gravity). MM, short for machine model. The original Japanese variant of the human body model ( ↑ HBM) for simulating the disturbances caused by charged persons. The higher body capacitance C P of 200 pF (HBM 100 pF) assumed for a large device (machine) made mainly of metal and the discharge impedance Z of 0 Ω (HBM 1500 Ω ) led to the name MM, because a term had to be found in the Western world to distinguish it from the original HBM. Since, in contrast to the HBM, the body resistance is set to 0 Ω , it is necessary here to specify the parasitic inductance L ( ↑ parasitic elements) of the ↑ ESD test systems due to the low attenuation. The discharge curve has the shape of a decaying sinusoidal oscillation whose maximum current, decay frequency and attenuation curve depend primarily on the parasitic inductances. In industry, the MM is of little importance, since the errors generated by semiconductors are the same as those generated by the actual HBM at 10 - 20 times the charging voltage. Attempts to reproduce semiconductor failures, which could not be reproduced with HBM, with the significantly higher possible current load of the MM failed and led to the realization that a faster increase of the discharge current, as occurs with the charged device model ( ↑ CDM) or the socketed device model ( ↑ SDM), must be the cause of these failures. [ANSI/ ESDA/ JEDEC JS-002] Mobility (also carrier mobility). Quotient of the drift velocity of charge carriers ( ↑ electron, ↑ ion) and the electric field strength. The charge carriers (e. g. the electrons in metals or the ions in gases) do not move in a straight line but in a random zigzag path as a result of continuous collisions with the surrounding atoms. Although the velocity component in the direction of the field is constantly changing, the average value over a longer time interval is constant and proportional to the electric field strength. Model (Latin: modus, modulus). Replica of an event, object, or context that occurs in reality and that is as true to life as possible for the purpose of simulation ( ↑ CDM, ↑ HBM, ↑ MM), illustration (planning and teaching purposes), comprehension (equivalent circuit), or for decorative purposes (miniatures). Mixed polymer 274 <?page no="286"?> Moisture (also called humidity). The electrostatic behavior of materials is mainly determined by the moisture they absorb, their ↑ water activity ( ↑ equilibrium moisture content, ↑ humidity, ↑ material moisture). Mole, short for molecular weight. ↑ SI unit [mol] of the amount of substance n. The mole is a counted number of particles, i. e. a numerical definition based on ↑ Avogadro ’ s number: 1 mol = 6.02214076 × 10 23 / N A . These can be ↑ atoms, ↑ molecules, ↑ ions, ↑ electrons, or other particles or groups in a well-defined composition. Until 2019, the mole was defined as the amount of substance in a system consisting of as many individual particles as there are atoms in 12 g of the carbon nuclide C -12 ( ≙ 6.022 × 10 23 atoms). [DIN 1301-1] Molecular dipole. Term for molecules with a permanent or non-permanent ↑ dipole moment. In the absence of an electric ↑ field, polar molecules (such as H 2 O, HCl, or CH bonds) have a completely random orientation in space (the sum of the dipole moments is zero). When an electric field is applied, the dipole moment is oriented toward the field ( ↑ dielectric). Therefore, polymers in the melt can acquire more or less the properties of an ↑ electret. Under the influence of an alternating electric field, the molecular dipoles are constantly rotated. This leads to frictional heat ( ↑ loss) and thus to heating of the insulating material. Useful application: ↑ microwave oven Molecular force. Collective term for the force acting between atoms and molecules ( ↑ cohesion, ↑ adhesion, except gravitation or chemical bonding). Molecular force causes adhesion and is electrical in origin, with four main types depending on the type of molecule (polar or non-polar): - Molecular force between polar molecules (dipole-dipole interaction), - Molecular force between polar molecules and ions (dipole-ion interaction), - Molecular force due to the induction of a ↑ dipole moment in polarizable molecules, - Dispersion forces due to fluctuations in the charge distribution in the atoms. ( ↑ Van der Waals forces, ↑ non-polar material) Molecule. Group of atoms held together by chemical bonds. The atoms in a molecule can be the same (H 2 , N 2 , O 3 ) or different (CO 2 , H 2 O). Monomer. Basic building components of the plastics industry (e. g. ethene, propene, butene), are produced from crude petroleum (naphtha) by cleavage processes. Catalytic reactions are used to produce chain molecules, i. e. plastics ( ↑ polyaddition, ↑ polycondensation, ↑ polymerization). MOSFET, short for metal oxide semiconductor field effect transistor, ↑ metal oxide FET Most easily ignited mixture. A combustible fuel-air mixture is explosive within its ↑ explosion limits, but the energy required to ignite it in this range depends on its concentration. Ignitability depends largely on the ↑ MIE and the ↑ ignition temperature. The most ignitable mixture is also the most reactive, whose composition is generally close to the so-called stoichiometric ratio λ = 1 ( ↑ stoichiometry). Most easily ignited mixture 275 <?page no="287"?> The reason for the deviation from the stoichiometric ratio in the figure compared to oxygen is the difference in diffusion velocities, i. e. the speed at which random mixing of particles occurs as a result of ↑ Brownian molecular motion. If the diffusion velocity of a gas (e. g. methane) is greater than that of oxygen due to its lower molecular weight, there would be an excess of combustion gas in the combustion zone. The opposite is true for combustion gases (vapors) whose density is greater than that of oxygen. This effect is considered when determining the MIE and ↑ MIQ of gases and vapors. {Appendix B} Motor. In principle, electrostatic motors can be constructed in the same way as electromagnetic three-phase motors: Synchronous motor with rotating pole wheel, or hysteresis rotor; asynchronous motor with induced rotor. ↑ Electrets and ↑ ferroelectrics are used as rotor materials. However, since the electric strength of the air allows only a relatively low ↑ surface charge density of the rotor and stator poles, only low torques can be achieved with electrostatic motors. However, while the electromagnetic motor quickly reaches its limits in terms of miniaturization since the windings cannot be made arbitrarily small, the electrostatic principle proves to be superior for motor dimensions < 1 mm ( ↑ nanotechnology). Another favorable circumstance is that the ↑ breakdown field strength in air increases sharply at distances < 1 mm ( ↑ Paschen ’ s law), allowing higher surface charge densities. [ Jefimenko, O. D. (1971)], [Bähnisch, R. (2003)] Motor 276 <?page no="288"?> Multilayer film, ↑ composite Muon (also known as μ -meson). Unstable, electrically charged elementary particle (lifetime about 2 μ s). It has the same electromagnetic properties as an electron, but its mass is 207 times greater than that of an electron. The rest mass of the muon is m μ = 1.88353109 × 10 -28 kg. Muons have an exceptionally high ability to penetrate matter; slow muons are captured by atomic nuclei and replace electrons in the innermost shell. Energy transitions are possible with these so-called muon atoms, releasing ↑ gamma radiation ( ↑ cosmic radiation). Muon 277 <?page no="289"?> N Nano spinning. A strong electrostatic ↑ field is used to form a ↑ Taylor cone at a capillary nozzle, which merges into the liquid jet. By evaporation or cooling, a thin fiber (< 1000 nm) can be obtained at the counter electrode, which is deposited as a kind of fleece on a plate electrode or as a fiber on a rotating roller. Nanotechnology. Collective term for technological processes in the range up to 100 nm. Electrostatic processes have already found their way into some areas ( ↑ scanning force microscopy, ↑ piezo mechanics). Nanotube, ↑ carbon Natural constant. Invariable physical quantity that emerges from experiments and appears in mathematical formulations of physical laws. The following are important in electrostatics: ↑ elementary charge e 1.602176462 × 10 -19 C electric ↑ field constant ε 0 8.8541878128 × 10 -12 As/ Vm magnetic ↑ field constant μ 0 1.25663706212 × 10 -6 Vs/ Am speed of light in ↑ vacuum c 0 2.99792458 × 10 8 m/ s Planck constant h 6.62606876 × 10 -34 Js Natural earth electrode, ↑ earthing Natural field, ↑ field Natural ventilation, ↑ ventilation NBR, short for nitrile butadiene rubber (synthetic rubber). Polar material with good resistance to oils, greases and hydrocarbons. Flexibility decreases at lower temperatures ( ↑ EPDM). Neck-in, ↑ cast process Negative, ↑ polarity Negative pole, ↑ pole <?page no="290"?> NEMP, short for nuclear electromagnetic pulse. This is caused by extremely strong electric fields that occur briefly when nuclear weapons explode in the upper atmosphere. The very intense ↑ gamma radiation released causes the separation of ↑ electrons in the atmospheric molecules, the formation of ↑ ions and the resulting strong electric fields with a pulse-shaped course. Since NEMP endangers electronic systems over long distances, very complex measures are being taken to protect the electronics of military equipment from ↑ transients. The test is performed by simulation by stretching a sufficiently wide wire mesh across the device to be tested, connected at one end to earth and at the other end to a very powerful surge generator ( ↑ SG). The surge discharge through the wire should produce an extremely strong pulsed field, similar to a NEMP. Net charge, ↑ excess charge Neutral conductor. In Europe it is referred to as “ N ” . Conductor connected to the center or neutral point of the network and capable of contributing to the transmission of electrical energy. [IEC 60050] Neutralization rate. Term used in [IEC 61340-4-7] for ↑ time constant. {Appendix M.6.3} Neutralizer, ↑ ionizer Newton. Derived ↑ SI unit [N] of force F, named after I. ↑ Newton; 1 Newton meter = 1 ↑ Joule. {Appendix M.3.1 and M.6.1.2} Newton, Sir Isaac (1643 - 1727). English mathematician, physicist and astronomer, established three axioms of mechanics and formulated the law of gravitation. NIR spectroscopy, short for near infrared spectroscopy. Uses the wavelength range of 760 - 2500 nm for the simple, fast and non-destructive (< 30 s measuring time) determination of the water content of substances ( ↑ water activity). This measurement method provides accurate and precise analysis of chemical and physical parameters for almost any sample matrix, comparable to reference methods. NIR spectroscopy does not require sample preparation or the use of hazardous chemicals, solvents or reagents. [NIRS DS2500 Analyzer] Nitrile butadiene rubber, ↑ NBR Nitrocellulose. Material converted from purified cotton or wood pulp into brittle collodion wool using nitric acid. Depending on the nitrogen content, “ gun cotton ” (> 13 - 13.4 % N) or “ collodion wool ” (12 - 12.6 % N) is produced. Nitrocellulose is a widely used substance in the chemical industry (e. g. paint production). It is phlegmatized with at least 25 % water or isopropanol and transported in cardboard drums with a plastic bag inside. [Köhler, J. et al. (2008)], ( ↑ celluloid) Noise effect, ↑ cable charging No-load operation. Operating state without power output for machines, only the power required for operation (to cover losses) is consumed. This principle does not seem to apply to electrostatic generators. A ↑ Van de Graaff generator, for example, has its highest power consumption when no current is drawn from it, or it runs faster at constant driving power No-load operation 279 <?page no="291"?> the higher its current output is. This apparent contradiction is explained by the fact that at maximum load ( ↑ short-circuit) it has a potential of zero with reference to its surroundings, i. e. the charge transport takes place at practically the same level. In the unloaded Van de Graaff generator, however, the charge must be transported against an ever-increasing charge potential of the same name (overcoming the repulsive ↑ Coulomb force). As the charge density on its sphere electrode increases, the speed decreases at constant drive power, and a state of equilibrium is finally reached between the supplied charge and the spontaneously emitted charge (maximum voltage). Nominal voltage of a system. Voltage by which a system or a system part is marked. The actual voltage may differ from the nominal voltage within the allowed tolerances. Nonconductor. Insulating materials in electrical engineering, resistors of various materials and ↑ insulators. Non-polar material. It has no permanent spatial charge separation of the molecules (no dipole properties). ● Liquid non-polar materials are e. g. ↑ toluene, benzene or heptane. They are electrostatically chargeable ( ↑ solvent). ● Solid non-polar materials are e. g. ↑ caoutchouc, silicone rubber. When interacting with other materials, they have a significant influence on the generation of ↑ charges ( ↑ Coehn ’ s rule). Nonwoven (also spunbond). Continuous, multidirectional oriented fabric made of thermoplastic or thermoelastic raw materials with appropriate additives, in which continuous fibers (filaments) emerging from a spinneret are drawn off aerodynamically or mechanically, stretched and deposited on a belt and then bonded mechanically, thermally or chemically. For various applications, the spunbonded web is exposed to an electrostatic ↑ field to create an ↑ electret (e. g. for filters to increase separation efficiency). Electrospinning is used to melt a wide variety of suitable materials and combinations of materials (e. g. polymers, metals) and draw them out in a strong electrostatic field to form a flat structure. The same is true for spinning from solution ( ↑ nano spinning). Normal climate (also called standard climate) set to 23 °C at 50 % RH. Since the influence of the ↑ climate is often a decisive factor in electrostatic measurements, the ↑ test climate should also be specified if the standard climate was used, in order to avoid misunderstandings. [ISO 139] (textiles), [ISO 291] (plastics) The [IEC/ TS 60079-32-1] uses different values: 23 ± 2 °C at 25 ± 5 % RH and 40 ± 2 °C at 90 ± 5 % RH for tropical climates and 23 ± 2 °C at 15 ± 5 % RH for arctic climates. Normal condition. Physical conditions for pressure and temperature ( ↑ standard condition). Not chargeable, ↑ chargeability Notified body for explosion prevention. The ↑ ATEX 114 requires an inspection by an independent notified body for equipment and protective systems for ↑ operation as Nominal voltage of a system 280 <?page no="292"?> intended in ↑ Ex-areas. These inspections must include an assessment of the potential hazards due to electrostatic charges. A list of current notified bodies (Europe) can be found in the Official Journal of the European Union 2014/ 34/ EU Equipment and protective systems intended for use in potentially explosive atmospheres. Notified bodies are free to offer their assessment services to any actor located inside or outside the EU. Accordingly, manufacturers of products are free to choose the accredited notified body for their assessment. Nozzle ● Flow channel, with a varying cross-section for the low-loss conversion of pressure energy into kinetic energy. If the flow is an insulating liquid or a particle-laden gas flow, a nozzle can result in a higher charge. ● Outlet orifice, at which a pressurized medium is released. Again, insulating liquids or particle-laden ↑ gases can be charged as they leave the nozzle ( ↑ high-pressure cleaning, ↑ CO 2 fire extinguishing system). NTC thermistor, ↑ thermistor N-type conductivity. Conductivity caused by flow of electrons from a donor. ( ↑ semiconductor) Nuclear electromagnetic pulse, ↑ NEMP Nuclear ionization, ↑ ionizer Nuclear radiation. The ↑ alpha, ↑ beta, ↑ gamma, or neutron radiation emitted by radioactive or excited atomic nuclei, which can be analyzed according to its energy content ( ↑ ionizing radiation) using the nuclear spectrum. Nuclear radiation 281 <?page no="293"?> O Object exhaust system, ↑ exhaust system Obstacle (barrier), ↑ touch protection Occupational exposure limit (OEL). Binding limit values specified in national regulations [TRGS 900] ( ↑ GefStoffV) for the time-weighted average concentration of a substance in the air at the workplace in relation to a specified reference period. The OEL indicates the concentration of a substance up to which no acute or chronic adverse health effects are generally to be expected. It is the shift average of exposure, typically 8 hours per day, 5 days per week, over a working lifetime. Peak exposures during a shift should be dealt with according to national regulations. [IFA Report (5/ 2020)]. Since the OEL is several orders of magnitude lower than the lower ↑ explosion limit (LEL), e. g. for solvents, the question arises whether it is permissible to work in ↑ Ex-zone 1 without respiratory protection. Sometimes it makes sense to convert areas generously designated as Zone 1 to Zone 2. With regard to electrostatic hazards, this still has the advantage that the corresponding protective measures can be omitted. According to the IFA report, a maximum field strength E e ≤ 2.82 × 10 4 V/ m is specified for electrostatic fields. Occupational safety regulations. According to general interpretation, occupational safety regulations include government regulations (laws and ordinances) and the accident prevention regulations of employers ’ liability insurance associations. In Germany, occupational safety regulations are summarized in the ↑ BetrSichV. Offset voltage. Describes, as a function of time, the imbalance of negative and positive ions encountering an insulated conductor in space ( ↑ charging by natural ↑ field). Offset is the deviation of a given value, or a curve of a linearity or stability deviation, from ± zero. [IEC 61340-4-7] Ohm. Derived ↑ SI unit [ Ω ] of the electrical resistance R, named after G. S. ↑ Ohm. {Appendix M.7.1} Ohm, Georg Simon (1789 - 1854). German physicist, worked in the field of physiological acoustics, the interference of polarized light and electricity ( ↑ Ohm ’ s law). Ohmic loss. Because of ohmic ↑ resistance, electrical power in a circuit is converted to heat ( ↑ Joule ’ s law). Ohmic resistance, ↑ resistance Ohmmeter. Term for an instrument used to measure electrical resistance. In the field of electrostatics, a ↑ tera-ohmmeter is generally used (measurement range up to 10 15 Ω with variable ↑ measurement voltage). [SE Section 3] <?page no="294"?> Ohm ’ s law. Law discovered by G. S. ↑ Ohm in 1826, according to which the current flowing through a conductor is proportional to the voltage between the ends of the conductor when the influencing variables (e. g. temperature, pressure) are constant. The ratio of ↑ voltage U to ↑ current I is called the electrical ↑ resistance R: U / I = R = constant. {Appendix M.4 and M.7.1} Oil coating of metal. Various types of sheet metal must be coated with a layer of oil prior to further processing (e. g. deep drawing). Brush or roller applications often produce unsatisfactory results. If the oil is sprayed in an electric field, the oil aerosols align themselves in the electric field and deposit on the surface of the earthed sheet; a very accurate oil application with a deviation of < 5 % is possible. There are also systems where the oil is charged outside of a coating booth and then applied to the earthed metal film web using high speed rotary atomizers. ( ↑ useful application) Oil immersion, ↑ type of protection “ o ” OLED, short for organic light emitting diode. A ↑ thin film device made of organic semiconducting materials, which differs from the ↑ light emitting diode (LED) in that it does not require monocrystalline materials. The current and light densities are lower but allow for low-cost and large-area production (e. g. 250 cm 2 ) with low energy consumption. Roll-to-roll production is possible (e. g. ↑ ITO layer). [Fraunhofer FEP (2017)] One-electrode discharge. ↑ Gas discharges can be classified according to whether one or two electrodes are involved in the process. One-electrode discharges include all gas discharges that occur from charged insulating materials to (earthed) electrodes: ↑ brush discharge, ↑ propagating brush discharge, ↑ super brush discharge, ↑ cone discharge, ↑ thunderstorm lightning. Gas discharges can also occur in the absence of electrodes, e. g. brush discharges between oppositely charged insulators, propagating brush discharges due to insulation breakdown, and thunderstorm lightning between clouds. Since the geometry of the gas discharge cannot be defined for one-electrode discharges or One-electrode discharge 283 <?page no="295"?> discharges without electrodes, it is also not possible to assign a defined ↑ energy to them ( ↑ two-electrode discharge). However, it is possible to approximate the ignition potential of a brush discharge by determining the transferred charge. This can be done with a ↑ coulometer ( ↑ charge transfer - measurement). Open circuit voltage. Characteristic of an active two-pole ( ↑ voltage source). It is the electric voltage between the poles when no current or only a negligible current is flowing ( ↑ short-circuit). Opening spark (sparkover). When an electrical circuit is interrupted (opened), a spark (arc) occurs between the contacts, the duration of which increases with the current and the greater inductance of the circuit. The ignitability of opening sparks for ↑ Ex-atmospheres must be checked when using intrinsically safe circuits ( ↑ electric circuit). Even when using ↑ hose lines, opening sparkovers can occur during disconnection from the system if system parts are not earthed or ↑ stray currents are expected from e. g. ↑ cathodic protection. Such hose lines must have a minimum resistance of 1 k Ω to avoid opening sparks. [TRGS 727 Section 4.9.4] Operating area (electrical). Rooms or places that are essentially used for the operation of electrical systems and which may generally be entered only by ↑ instructed persons. Closed electrical operating sites are used exclusively for the operation of electrical systems and are kept under lock and key. [IEC 60050] Operating current of a circuit. Electric current in a ↑ electric circuit during fault-free operation. [IEC 60050] Operating instruction. The employer must take the necessary precautions when informing employees in accordance with § 81 of the of the Works Constitution Act (German: Betriebsverfassungsgesetz (BetrVG)) and § 14 of the Occupational Health and Safety Act (German: Arbeitsschutzgesetz (ArbSchG)): - Adequate information, in particular on the hazards to which they are exposed by the work equipment in their immediate working environment, even if they do not use this work equipment themselves, and - where appropriate, instructions in a form and language which they can understand for the work equipment used at work. Operating manual. All instructions necessary for the operation and maintenance of process equipment, including, for example, the prevention of electrostatic hazards, are recorded in the operating manual. It contains information on the organization of the plant as well as instructions for the plant personnel on how to act in the event of malfunctions, incidents, and other occurrences. The manufacturer of the machine or system must comply with the relevant regulations, according to which he must supply a safe product. He must describe the intended use in the instructions ( ↑ operation as intended). If an ↑ explosive atmosphere may occur during the intended use, the manufacturer must take appropriate measures to limit the risk to an acceptable level. He must have carried out a ↑ risk assessment for his machine in accordance with ↑ ATEX 2014/ 34, which must be included in the instruction handbook. Open circuit voltage 284 <?page no="296"?> Operating resources (electrical equipment). Objects used for the purpose of generation, conversion, transmission, distribution and application of electrical energy, e. g. machines, transformers, switchgear, measuring devices, protective devices, cables and wirings, power consuming devices. ( ↑ Low Voltage Directive), [IEC 60050] Operating temperature. The maximum temperature reached by operating resources during nominal operation. It can assume different operating temperatures on different parts ( ↑ ignition temperature). Operating voltage. Highest occurring voltage ( ↑ RMS value) on insulated metal parts of electrical equipment. [IEC 61010-1] Operation as intended. Approved operation of an installation by the competent authority in accordance with its design. It includes: - Readiness for operation - Normal operation (operations for which the plant is designed and suitable in the functional condition of the systems) - Abnormal operation (operational processes that take place when plant components or systems malfunction, provided that safety reasons do not prevent continued operation) - Maintenance Operational earthing, ↑ earthing (US: grounding) Operational Safety Regulation, ↑ BetrSichV Ordinance on combustible liquids. Replaced since 2003 by the Operational Safety Regulation ( ↑ BetrSichV) and its technical regulations. Organic glass, ↑ glass Original kilogram. Defined in 1799 as 1 kg = 1 dm 3 of water at 4 °C. In 1899, this definition was replaced by a platinum-iridium cylinder 39 mm high and 39 mm in diameter. Since 2019, the kilogram is defined by Planck ’ s constant. Oscillating quartz (also crystal unit). When an alternating electric voltage is applied, the quartz is stimulated to perform mechanical resonant oscillations by utilizing the piezoelectric effect if the applied alternating field matches its resonant frequency. The frequency, which is between 1 kHz and 1 GHz depending on the length of the crystal, can be maintained very precisely at a constant temperature and is used in many industrial applications (e. g. as a clock generator in telecommunications and electrical engineering). Oscillograph (Latin: oscillare, “ to oscillate ” , Greek: graphein, “ to write ” ). Device for recording oscillations, e. g. characteristic curves (no exact distinction to the ↑ oscilloscope). Oscilloscope (Latin: oscillare, “ to oscillate ” , Greek: skopein, “ to look at ” ). Instrument for visualizing oscillations. In the past, oscilloscopes were used with an ↑ electron-beam tube. Nowadays, digital storage oscilloscopes are almost exclusively used, in which the measurement signals are converted into discrete-time and discrete-amplitude signal sequences using analog-to-digital converters. This allows periodic electrical processes Oscilloscope 285 <?page no="297"?> to be displayed directly and non-electrical processes (e. g. mechanical vibrations, heartbeat, sound) to be displayed after conversion into electrical signals. Osmosis. This describes the passage of liquid molecules through semi-permeable membranes ( ↑ diaphragm) and has an important function for biological systems in nature. Osmosis processes can also be carried out as ↑ electro-osmosis using electric fields. Outer conductor. Conductors that connect power sources to consumer equipment but do not originate from the center or star point. In signal-sensitive systems, outer conductors are often used for ↑ shielding within moving signal lines. If it is an asymmetrical signal system, which is the more common case, the signal-carrying line runs in the center of a concentric cable and a ring-shaped closed mesh runs around the outside, which is connected to ↑ earth or the system ’ s reference potential at the input and output. In symmetrical signal systems, two lines with mirror-image signals run inside the cable and around the outside is a ring-shaped closed mesh connected to earth (or the system ’ s reference potential) at one or both ends of the connection to conduct away interference. [IEC 60050] Outer covering. Refers to the outer covering of a ↑ capacitor that encloses and shields it. In the case of cylindrical ceramic capacitors, the outside covering is the outer metallized surface of the hollow cylinder. The electrical connection of the outer shell is often identified by a marking on the element. When the outer surface is connected to ground, the ↑ stray (built-in) capacitance is reduced. Outer electron, ↑ valence electron Outer shell. Outer electron shell of the atomic model. The electrons present there are responsible for the various forms of chemical bonding ( ↑ valence electron). Overcurrent. Condition in a circuit in which the normal load current is exceeded. A distinction is made between overload and ↑ short-circuit. Circuit breakers (so-called automatic circuit breakers) or fusible resistors are used as overcurrent protection devices. In the electronic field, they have the advantage that their resistance can limit the inrush current (overload protection, ↑ surge arrester). These protective devices are part of preventive fire protection but are not suitable for preventing ↑ personal hazard due to the effects of electric current. Overhead line. The entire installation for the transmission of high voltage current, consisting of supporting points (pylons and their foundations, roof supports, brackets, etc.), above-ground conductors with accessories and earthing. [IEC 60050] Overvoltage ● In electrical networks overvoltage can occur as a result of switching operations, earth faults (internal overvoltage) or resonance phenomena (external overvoltage), which stress the devices far more than their operating voltage ( ↑ thunderstorm lightning, ↑ NEMP, ↑ propagating brush discharge and ↑ super brush discharge). Pulse rise times for electrostatic discharges, for example, are typically < 1 ns. Osmosis 286 <?page no="298"?> ● In electrochemistry this refers to a kinetic phenomenon in which different processes occur at the solid/ liquid contact surface than would be expected from the electrochemical ↑ voltage series. ( ↑ electro kinesis, ↑ charge double layer, ↑ Galvani voltage) Overvoltage category. Classification of parts of an installation or circuit according to standardized limits for overvoltage as a function of the line voltage to earth. Four overvoltage categories are defined for equipment: I with external transformers or plug-in power supply, II with IEC plug, III directly connected, or IV connected to the supply point of the electrical installation. [IEC 60664-1] Overvoltage protector, ↑ surge arrester Oxidizing agents. Substances that oxidize other substances by accepting electrons (electron acceptors). Reducing agents, on the other hand, release electrons. Oxidizing agents include solids (e. g. calcium hypochlorite - Ca(ClO) 2 ), liquids (e. g. hydrogen peroxide - H 2 O 2 ), and gases (e. g. fluorine, oxygen ( ↑ ozone)). ( ↑ ignition source) Oxo polymerization. Chemical ↑ polymerization with the aid of an oxidizing agent, which is used, among other things, to produce polymers with intrinsic ↑ conductivity. Oxygen O 2 . It has a density of 1.429 kg/ m 3 and is slightly heavier than air (1.0). Oxygen itself is not combustible, but it allows and promotes the combustion of combustible substances to a high degree. Air normally contains 21 % oxygen, but the rate of combustion doubles at 24 % oxygen and increases tenfold at 40 % oxygen. On the other hand, combustion does not take place if the oxygen content falls below about 10 % ( ↑ inerting, ↑ limiting oxygen concentration). The ↑ MIE required to ignite a fuel is also strongly influenced by the oxygen content. For example, only about 1/ 100 of the MIE is required for a hydrocarbon-oxygen mixture. During ↑ gas discharges, some of the oxygen is modified into a three-atom molecule called ↑ ozone. Pure oxygen can cause spontaneous combustion if it meets flammable substances such as oil, grease and textiles soiled with these substances. O 2 fittings must therefore be kept free of oil and grease. [DGUV Information 213-073] Oxygen concentration. In breathing air, it should normally be 21 vol. % and not less than 18 vol. %. The change in oxygen concentration results in a change in the ↑ explosionrelated parameters. M. Glor explained the relationship between ↑ MIE and oxygen concentration in 1996. For this purpose, the O 2 concentration is varied at constant ignition source energy and vice versa. Assuming that the ignition sources resulting from electrostatic ↑ gas discharges have relatively low ignition energies (exception: ↑ propagating brush discharge), but the O 2 concentration is determined with an approximately 10 5 times more powerful ignition source, higher oxygen concentrations can be determined for which electrostatic gas discharges do not yet represent ignition hazard. If only low energy ignition sources are to be considered, ↑ inerting (electrostatic) can be achieved for dust and gases or vapors by Oxygen concentration 287 <?page no="299"?> reducing the oxygen content by only a few percent. Special conditions apply to ↑ hybrid mixtures. Oxyhydrogen gas. Mixture of ↑ hydrogen and ↑ oxygen, which forms an ↑ Ex-atmosphere even in small quantities (approx. 4 vol. %) ( ↑ light metal). Ozone (ancient Greek: ozein, “ to smell ” ). A form of oxygen (O 3 ) consisting of triatomic molecules, first described as ozone by C. F. Schönbein in 1839 and discovered in the vicinity of ↑ electrification machines. It is produced wherever the diatomic oxygen molecules are split by the application of energy (e. g. by ↑ gas discharge or ↑ UV radiation). The released oxygen atoms attach themselves to other oxygen molecules, sink to the bottom as O 3 and decompose rapidly at room temperature. It occurs naturally as a gas and protects the ozone layer in the Earth ’ s atmosphere from the sun ’ s UV radiation. As a strong ↑ oxidizing agent, it strongly promotes combustion in high concentrations and is toxic even in low concentrations. The ↑ occupational exposure limit (OEL) for ozone is 0.1 ppm (0.2 mg/ m 3 ). Because of the intense odor, ozone is detected at very low concentrations (about 0.01 ppm). If the exposure lasts longer than about 5 minutes, the gas is no longer perceived. However, it is possible that the gas itself is odorless and only the accompanying nitrogen oxides (NO x ) impart the characteristic odor (conversion of NO 2 + O 2 by UV radiation (daylight) to NO + O 3 ). Ozone is used in a controlled manner for disinfection purposes. Oxyhydrogen gas 288 <?page no="300"?> P Pacemaker, ↑ implant Packaging. Finished product consisting of one or more ↑ packaging means. It is the sum of all components, such as wrapping, closures, labels, and shock protection. To avoid electrostatic ignition hazards, protective measures must be observed when filling and emptying packaging ( ↑ Ex-area, ↑ FIBC, ↑ RIBC, ↑ barrel, ↑ hobbock), high charges can occur, e. g. when removing shrink wrap. For electronic components, directly adjacent packaging and loosely wrapped packaging must provide ↑ ESD protection. Packaging means (and auxiliary packaging means). Used to contain, transport and, where appropriate, store liquid or solid bulk products. Special care must be taken when using packaging means for flammable liquids due to the lower ignition energy compared to solids. Packaging means can present ignition hazards in a variety of ways and are divided into the following categories from an electrostatic standpoint. ● Packaging means made of conductive or dissipative materials can be charged by charged bulk materials through ↑ influence and/ or ↑ charge transfer and must be earthed during ↑ filling process and emptying to prevent discharge sparks. ( ↑ FIBC, ↑ RIBC) ● Packaging means made of chargeable (insulating) materials may already carry a charge resulting from the manufacturing process and/ or be charged during removal from storage or during handling due to separation processes (e. g. cleaning) (consequence: ↑ brush discharges). When filled with chargeable bulk material, they are charged by charge transfer, just like conductive packaging means, but charge dissipation via earthing is not possible. Although this ↑ excess charge can be reduced by adding air ions from the outside, this can lead to high electric field strengths in the wall material that inadmissible brush discharges can be caused during the filling process. When emptying packages made of insulating materials, the possibility of brush discharges must always be expected, regardless of the electrostatic properties of the bulk material. [TRGS 727] Paint / Painting, ↑ lacquer / ↑ coating Pallet container. Preferably ↑ IBC, mounted on a wooden pallet in a reinforcing case, usually made of a metal grid, which can be transported by a forklift truck. During filling and emptying it should be noted that the discharge of electrostatic charges through the pallet may be impaired; additional ↑ earthing is required. Pan. Usually a flat, open-topped container for collecting, for example, drips, overflow or the contents of (burst) containers, which must be designed for the expected quantity for the intended purpose. When handling flammable liquids, pans must always be earthed ( ↑ earthing). Solvent vapors can also collect in a pan, so an ↑ exhaust system must be provided. [TRGS 722, 724 and 727] <?page no="301"?> Paper (Latin: papyrum, Egyptian Greek: papyros). A flat writing material made from the pith of the papyrus tree. Paper made from plant fibers was first used in China in 105 AD. Today, paper is made from chemically or mechanically digested fibers of plant origin, as well as from textileor other fibers. Specially treated paper is used in electrical engineering as an insulating material (e. g. pressboard in oil transformers or in ↑ capacitors). Functional specialty papers are increasingly used (e. g. for shielding electromagnetic radiation [Stocker, T. et al. (2016)]). In the field of electrostatics, paper is generally considered to have dissipative properties, provided it is not coated in any way. Both the paper and the so-called paper coating (e. g. “ art paper ” ) may contain substances that tend to form an ↑ electret during processing (e. g. CaCO 3 with a dielectric constant of ε r = 8.0 or TiO 2 with ε r = 111). Depending on the ink used, paper printed on both sides can behave like a film with isolated conductive areas ( ↑ charge phenomenon). Paper is often used in a solid or loose composite with, for example, aluminum or composites ( ↑ composite). ● Electrical insulation paper. Usually impregnated with synthetic resin, non-porous, without fillers or electrically conductive impurities. ● Kraft paper. Usually, packaging paper made from unbleached sulfate pulp with high static and dynamic strength. Used for paper sacks, shopping bags, etc. ● Pressboard. Board with high density (0.9 - 1.3 g/ cm 3 ), varying thickness, high mechanical strength (e. g. due to the addition of cotton fibers) and smoothness as well as high ↑ permittivity for use in the electrical industry (e. g. oil transformers, capacitors). [TRGS 727 Section 3], [Blechschmidt, J. (2013)] For the measurement of pressboard and other insulating materials, the measurement setup and method are specified in [IEC 60243-1] (Figure). Pressboard is also covered by [IEC 60641-1]. This setup can also be used to test insulating oils. Paper bag. A versatile means of transportation that generally does not present an electrostatic ignition hazard. However, it is often multi-layered with one or more inner layers of film, with an outer layer of kraft ↑ paper that is only partially bonded to other layers (e. g. PE film) and usually shields them from charging. If the layers delaminate, electrostatic ignition hazards may occur. [TRGS 727 Section 6.3.3], [SE Section 7.3.2] Paper test method. Papers must have certain electrostatic or electrical properties for various manufacturing processes (e. g. ↑ coating, ↑ gravure printing, ↑ blocking). For example, resistance measurements alone are not sufficient for ↑ electrostatic print assist. There are currently several general-purpose instruments available for measuring ↑ relaxation time. F. Knopf developed a paper test method for measuring relaxation time using a plate capacitor, which was not widely used: 10 layers of paper are used as the dielectric. After the required climatic conditioning, the plates are closed with a defined contact pressure Paper 290 <?page no="302"?> and the capacitor is charged. An ↑ influence electrostatic field meter equipped with a voltage measuring head records the course of the discharge voltage. From this the maximum charging time and the relaxation time can be calculated {Appendix M.6.2 and M.6.3}. The measuring device was also designed as a climatic chamber, in which an exact relative humidity could be generated over a saturated salt solution (e. g. with lithium chloride 10 % or magnesium chloride 33 % RH) by means of a small fan and a heating plate. [Lüttgens et al. (2017)] Parallel connection. Side-by-side connection of active or passive two poles ( ↑ resistance, ↑ capacitance). When connecting active two poles in parallel, the ↑ open circuit voltages must match. ( ↑ series connection) Calculations according to {Appendix M.6.4.6 and M.7.1.5}. Parallel electrode, ↑ measuring electrode for solids no. 1 Parasitic elements (Greek: parasitikó, “ parasitic ” ). Components and functional elements in electronics often have additional parasitic elements (e. g. parasitic inductances due to resistances or parasitic capacitances of conductive paths) that result from the connection between conductive paths and components during operation. The parasitic elements are located at any point along a discharge path and have a distorting effect on the course of the simulated discharge and thus on the device under test ( ↑ DUT). A distinction is made between trace parasites, active parasites, and passive parasites in the semiconductor. Radiatively coupled elements in antennas are also called parasitic elements. Partial discharge (also known as pre-discharge). A term widely used in high-voltage engineering to describe discharge over part of the insulation distance ( ↑ gas discharge). Partial discharge is divided into: ● Outer partial discharge, between two electrodes in a pin-plate configuration with gas as ↑ dielectric ( ↑ clearance). Partial discharge 291 <?page no="303"?> ● Internal partial discharge, inhomogeneities (e. g. air bubbles or fiber agglomerations) in liquid or solid insulating materials, also known as water or electrical treeing ( ↑ dendrites). ● Sliding discharge, along the contact/ separation surfaces of insulating materials ( ↑ creepage distance). Partial discharges are strongly influenced by secondary factors. ( ↑ influencing factors) Particle (Latin: particula, “ particle ” ), ↑ aerosol, ↑ charging, ↑ coating, ↑ carrier, ↑ molecule, ↑ dust Particle boundary contact. The electrical resistance of insulating materials (polymers) can be reduced by adding conductive particles (e. g. carbon black) to such an extent that electrostatic charges can be safely dissipated. This requires conductive paths, which are created by an appropriate distribution of the conductive particles and their particle boundary contacts ( ↑ pearl string model, ↑ percolation). The ↑ contact resistances between them are reduced at distances < 10 nm by the ↑ tunnel effect to such an extent that an electron current sufficient to dissipate the electrostatic charging occurs. Particle flow. Depending on the viscosity of the coating materials, the separation of the material layers at the nip from roller to roller in ↑ roller coating systems can lead to the generation of a vagabond particle flow, which is entrained by the ↑ air boundary layers present on fast material webs (> 100 m/ min) and leaves them depending on mass and speed. ( ↑ misting tacker) Particle mist, ↑ misting tacker, ↑ dust Particle size. Average diameter of a solid particle as determined by various methods, measured in microor nanometers. As particle size decreases, the specific ↑ charging generally increases. ● The particle size for dust is an ↑ explosion-related parameter. A size > 400 μ m is generally not ignitable. As the size of dust particles decreases, the tendency to explode Particle 292 <?page no="304"?> increases because the ↑ MIE and ↑ MIQ decrease. The ↑ median value of particle size is an influencing factor for the ↑ cone discharge. [TRGS 727 Section 6, A3.6] Pascal. Derived ↑ SI unit [Pa] of pressure p (1 Pa = 1 N/ m 2 ), named after B. Pascal. Paschen, Friedrich (1865 - 1947). German physicist, president of the Physikalisch-Technische Reichsanstalt in Berlin from 1924 to 1933, described the ignition mechanism for gas discharge lines. Paschen ’ s law. F. ↑ Paschen recognized in 1889 that the ignition onset of a gas discharge depends not only on voltage, electrode shape and distance, but also on gas pressure. He established this relationship experimentally: The breakdown voltage U D in a homogeneous field with an electrode spacing d and a pressure p depends only on their product ( ↑ degree of homogenization). The “ Paschen curve ” was later described theoretically by J. S. E. ↑ Townsend. Strictly speaking, this proportionality exists only for electrode distances above about 10 mm. For smaller distances, the breakdown strength increases. The results of Paschen ’ s law are used, for example, in high-pressure gas insulation in confined high-current distribution systems and in electrostatic generators ( ↑ Van de Graaff generator, ↑ Felici generator). [SE Section 5.6] Passive discharge. Use the principle of ↑ corona discharge with the arrangement of single or many very sharp earthed pins. ( ↑ ionizer, ↑ earthing tongue, ↑ material web (discharge of material webs)) The emission of charges (e. g. hair or ship masts) is also a passive discharge ( ↑ breakdown field strength, ↑ St. Elmo ’ s fire). Passive ionizer. ↑ Ionizer connected to ↑ earth electrode. ( ↑ earthing tongue) PE conductor connection. Connection part with a connection to the electrically conductive parts of an electrical device, which establishes the combination with an external PE conductor system. The PE conductor connection is primarily used for safety purposes but is also used for shielding purposes on electronic equipment. Peak value (also maximum value). Which marks the largest magnitude of an alternating electrical quantity during an oscillation period ( ↑ amplitude, ↑ RMS value). Pearl string model. Describes aggregate structures in amorphous polymers and polymer melts. ● Skein model for intertwined static molecular skeins. ● Meander model for folded molecular bundles. [Strobl, G. (2007)] Pearl string model 293 <?page no="305"?> When using carbon black ( ↑ carbon) as a filler to increase conductivity, a tendency towards linear ↑ agglomeration (string of beads) can be observed, which form chains at a minimum concentration and provide continuous conductive paths for the electrical current. ( ↑ carbon fiber) The progression of the electrical resistance of polymers with carbon black content shows noticeable differences in almost all cases, depending on the degree of filling: - At low carbon black contents (below approx. 2 %) the resistivity of the base material is hardly affected. - When the carbon black content is increased slowly, there is a steep drop in resistance by several dimensions in a narrow concentration range. - When the carbon black content is increased further, the resistance stabilizes at a low level. [Maier, R.-D., Schiller, M. (2016)] Pelletron. Machine for generating high voltages up to about 30 MV (at 200 μ A), based on the principle of the ↑ Van de Graaff generator. Instead of the often-fragile rubber band of the Van de Graaff generator, the pelletron uses an endless chain of small conductive parts connected by insulating links, usually made of polyamide, to transport the charge to the consumer. Peltier, Jean Charles Athanase (1785 - 1845). French physicist discovered the thermoelectric ↑ Peltier effect in 1834. Peltier effect. Thermoelectric effect at contact surfaces of semiconductors with different energy levels of the ↑ conduction bands (por n-conducting), at which a temperature difference (approx. 70 K) is generated when current flows or a current flow is generated when temperature differences occur ( ↑ Seebeck effect). Peltier elements based on the Peltier effect can therefore be used for cooling (dew point hygrometers ( ↑ humidity meter)) as well as for heating. For good efficiency, the residual ripple of the direct current used must be as low as possible, since the alternating current component is always converted into Joule ’ s heat. PEN conductor. Symbol PEN (short for protective earth neutral). Electrical conductor that performs the functions of the ↑ protective earthing conductor and the ↑ neutral conductor. [IEC 60050] Penetration depth, ↑ skin depth Penning effect. Reduction of the ignition voltage of a gas discharge by adding another gas with a lower ionization energy. In the case of neon, for example, the ignition voltage can be reduced from 750 to 180 V by adding 0.06 ‰ argon. [Penning, F. M. (1927)], ( ↑ ionization, ↑ impulse excitation) Pelletron 294 <?page no="306"?> Percent by volume. Percentage by volume of a substance in a mixture; abbreviation: vol. % Perceptibility (also tactile sensation). Equipotential bonding of electrostatic charges from or through people is often achieved by touching them with the hand. The currents that flow within milliseconds often go unnoticed. At charge potentials above about 1 kV, sparkovers occur that are not noticeable to humans until about 2 kV. At higher potentials, the felt electrostatic shock becomes increasingly unpleasant and is perceived as painful at about 10 kV. The general opinion is that there is no direct health risk, because the energies converted in the discharge are so low that they neither disturb the heart rhythm nor cause burns ( ↑ personnel charging, ↑ personal hazard, ↑ danger of electric shock). Exceptions are ↑ propagating brush and ↑ super brush discharges. Significant electrostatic discharges can cause shock reactions, which in turn can cause an accident or malfunction. [TRGS 727] Percolation (Latin: percolare, “ to seep through ” ). In polymer systems with the addition of conductive particles (carbon black ( ↑ carbon), ↑ metal fibers), this is understood to mean the formation of a network of electrically conductive filler particles and thus a percolation path. P. Flory and W. H. Stockmayer described gelation processes during polymerization by defining a lattice structure whose nodes are considered randomly occupied or unoccupied. (Flory-Stockmayer-theory), [Stockmayer, W. H. (1944)] Adjacent occupied nodes are considered clusters. The higher the number of occupied nodes, the higher the probability of a continuous cluster through the entire lattice. The attainment of these clusters is referred to as the percolation threshold. In regions of low filler concentration with conductive material, the insulating property of the plastic dominates. From the percolation threshold, the electrical conductivity increases drastically by several orders of magnitude, and further increases do not cause any significant changes in the electrical conductivity of the polymer. ( ↑ pearl string model) Perforation (Latin: perforare, “ to pierce ” ). It is often caused by electrical overload (e. g. ↑ propagating brush discharge) and leads to unwanted damage ( ↑ micropore). The ↑ breakdown of insulating materials caused by high electric field strength is used, for example, in cigarette filters to reduce the concentration of harmful substances in inhaled smoke, or insulating layers on conductive parts of floor coverings, internal coatings of containers and packaging means. For this purpose, pins ( ↑ charging electrode) with direct or alternating high voltage are arranged at a short distance from an earthed plate and the material to be perforated is passed through them. The number of pores is determined by speed, design and current intensity. Strictly speaking, the perforation does not improve the leakage resistance of an insulating layer, but only the charge dissipation at a correspondingly high - but in practice harmless - potential of ↑ charges. Permalloy TM . Belongs to a group of soft magnetic nickel-iron alloys with 72 - 80 % nickel and proportions of copper, molybdenum, cobalt or chromium with very high ↑ permeability μ and low coercivity ( ↑ coercive field strength). Heating this material with 5 % molybdenum under pure hydrogen gas produces supermalloy with even higher permeability. Permalloy 295 <?page no="307"?> Permalloy is already magnetically saturated in the earth ’ s ↑ field and is used to shield low frequency alternating magnetic fields and to make the magnetic cores of signal transmitters, magnetic current sensors, and current transformers. ( ↑ skin depth, ↑ Electromagnetic Compatibility) Permeability (Latin: permeare, “ to pass through ” ). Symbol μ , physical unit [H/ m] or [Vs/ Am], magnetic ↑ field constant: μ 0 = 1.25663706212 × 10 -6 Vs/ Am ( ↑ natural constant), {Appendix M.1} It describes the permeability of matter to magnetic fields and thus the ability to adapt to an external magnetic field (magnetic field strength and ↑ induction in matter-free space). It obligates a voltage jump in [Vs] with a magnetic field induced by a current ( ↑ polarization). Permeability also refers to: - The property of solids to allow liquids or gases to pass through (membrane), - A geotechnical term for determining the permeability of rock and soil, - In physical chemistry and biochemistry, the permeability of cell walls etc., to explain almost all substance transport. Permeability number (also relative permeability). Dimensionless material parameter μ r , indicates how the inductance of a coil, for example, changes through a material core (magnetic ↑ polarization). For air, it is specified as μ r = 1. The permeability number for ferromagnetic materials is not constant but varies with the magnetic field strength from an initial to a maximum permeability, which decreases again with a further increase of the field. The relative permeability μ r corresponds to the relative permittivity ε r . {Appendix M.1.4} The permeability number distinguishes between: - Ferromagnetic materials: Strong permanent magnetization (examples: iron, nickel, cobalt) - Paramagnetic materials: Weakly magnetizable, magnetization is lost without field (examples: aluminum, platinum, oxygen) - Diamagnetic materials: Very weakly and only negatively magnetizable in the presence of the field (examples: copper, water, bismuth) Permittivity (Latin: permittere, “ to allow, to permit ” ). Symbol ε (formerly dielectric constant), unit [F/ m = As / Vm], electric ↑ field constant: ε 0 = 8.8541878128 × 10 -12 As / Vm of matter-free space (vacuum, ↑ natural constant). {Appendix M.1} It describes the polarization property of insulating, polar and non-polar materials and is the proportionality factor between electric field strength and ↑ electric flux density. It provides the relationship between surface charge density and field strength and depends on the density of the material. It can increase or decrease with pressure changes in gases ( ↑ electrostriction, ↑ piezo effect). Permittivity number (also relative permittivity). Symbol ε r , material parameter used to calculate the capacitance ( ↑ dielectric loss). It indicates how the capacitance changes when a dielectric is inserted in place of matter-free space. For air and ↑ vacuum, it is specified as ε r = 1. For materials with unknown properties, it is measured, for example, by Permeability 296 <?page no="308"?> replacing the air in a plate capacitor with the ↑ dielectric to be measured (electric ↑ polarization). In general, permittivity can provide an orientation for determining the sign of the charge of a substance during separation processes ( ↑ triboelectric series). The relative permittivity is influenced by the following factors: field strength and temperature, as well as frequency and anisotropy (directional dependence). {Appendix A and M.1}, [SE Section 3.8.2], [IEC 61620] Personal hazard. Persons are endangered by electrostatic shocks if, according to [TRGS 727], the transferred charge exceeds 50 μ C or the transferred energy exceeds 350 mJ ( ↑ danger of electric shock, ↑ perceptibility). It is generally assumed that a person can be charged up to a maximum of 40 kV by direct charging ( ↑ personnel charging); a maximum of 25 kV can be achieved by their own movement. The energy can be calculated and is 47 mJ for an average person (at C = 150 pF, U = 25 kV), {Appendix M.6}. This is the maximum possible charge for a person with a safety factor of seven. The limit of 50 μ C for the transferred charged corresponds to a capacity of 1500 pF charged to 30 kV (e. g. tank truck). Personal protective equipment (PPE). Equipment intended to be used or worn by employees to protect themselves from hazards. This must comply with the relevant requirements of [TRGS 727 Section 7] and other regulations. Persons working in ↑ Ex-areas must not themselves become electrostatically charged in a hazardous manner. The individual parts of the work wear - from the helmet and its visor to the gloves and safety shoes - must have a dissipation capacity that must be checked regularly ( ↑ clothing). Continuous dissipation must not be interrupted, for example, by protective gloves. To assess possible risks in industrial operations, the person should always be measured on the floor in the danger zone with footwear and, if necessary, gloves. PPE is not allowed to be changed, taken off or put on in Ex-areas of ↑ Ex-zones 0 and 1. In potentially explosive atmospheres, in Ex-zone 0 and, where applicable, in rooms used for medical purposes, clothing must not be electrostatically chargeable ( ↑ chargeability). [IEC 61340-6-1], [Ohsawa, A. et al. (2024)] Collective protective measures have priority over PPE (e. g. ↑ explosion protection, ↑ exhaust system). ● Safety helmets are used to protect the head, e. g. against falling parts, and are predominantly made of highly insulating polymers, so there is a fundamental possibility of hazardous electrostatic charging. However, since electrostatic charging was considered a secondary problem in the risk-benefit analysis compared to the mechanical advantage of high-impact plastics, and since no cases of ignition have been reported in the ↑ use as intended of safety helmets, they are not subject to the restrictions on the dimensions of chargeable surfaces specified in the electrostatic regulations. However, in Ex-zone 0, only helmets made of dissipative material should be used. ● Protective gloves are used to protect the hands during the work process and, like safety footwear, should have adequate low resistance R A < 10 8 Ω in hazardous areas to dissipate charge from objects held in them. They are not charged simply by being worn. Personal protective equipment 297 <?page no="309"?> They must be tested in accordance with [EN 1149-2]. ( ↑ measuring electrode for solids no. 19), [EN 16350] ● Aprons are generally not close-fitting and must therefore be capable of discharging in hazardous areas. They must not be put on, taken off or changed in hazardous areas. ● Safety shoes (formerly known as protective footwear) are used for foot protection and generally also meet the requirement for dissipation of electrostatic ↑ personnel charging. Dissipative footwear has a discharge resistance of R A < 10 5 Ω dissipative footwear must have R A < 10 8 Ω . Shoes worn in ↑ ESD protected areas must not exceed a maximum discharge resistance of 1 or 100 M Ω , depending on the requirements. Shoes should be tested regularly ( ↑ personnel earthing tester). [EN ISO 20345] Personnel charging. Humans are electrically conductive because of the salts, acids and bases in their body fluids. They can therefore store charges even when electrically insulated ( ↑ ionic conduction). The ↑ capacitance typically ranges from 75 pF (20 kg child) to 200 pF. Depending on weight and body size, external charging (e. g. with a Van de Graaff generator at about 200 kV) is limited to a maximum of 35 - 40 kV, as hair and fingertips, for example, spray any charge in the room ( ↑ corona discharge). According to previous findings, the charging of personnel by their own movements could not exceed values of 25 kV ( ↑ personal protective equipment). When touching earthed objects, not only are unpleasant shocks felt ( ↑ perceptibility from about 2 kV), but also ↑ spark discharges are triggered. With an average human body capacitance to earth of about 150 pF, a voltage of 2 kV results in a ↑ spark energy of 0.3 mJ. This means that, for example, gasoline vapor-air mixtures ( ↑ MIE ~ 0.2 mJ) can be ignited below the above-mentioned detectability limit. [IEC 61340-4-5], [TRGS 727 Section 8.2] ● Personnel charging by charge separation ( ↑ charging) occurs during movement, e. g. when walking over insulating floor coverings ( ↑ floor, ↑ walk-in charge), when taking off an article of clothing or when getting up from insulating seats. In any case, an insulated place is required, e. g. by insulating shoes and/ or an insulating floor. [Bauch, H. (2000)] (1) Person steps on electrically neutral floor, (2) charge separation shoes/ floor, (3) spark discharge on earthed part, (4) possible electrostatic shock reaction and/ or device defective, floor remains charged. Personnel charging 298 <?page no="310"?> Personnel earthing, ↑ earthing Personnel earthing tester. Electronic tester with two separate measuring circuits for testing personnel earthing systems such as electrostatic dissipative wrist straps and dissipative footwear. It can be used for access control. The test result is usually reported visually, audible and via signals (e. g. to door openers). Due to possible contamination of shoe soles, a daily test should be performed, especially in hazardous areas. Pesticide (also crop protection products). Electrostatic processes based on the principles of electrostatic ↑ coating have been developed for the application of finely divided solid or liquid pesticides to the foliage of plants. [Maurer, B., Groener, H. (1983)], [Patel, M. K. (2016)] Petroleum (Greek: petros, “ rock, stone ” , Latin: oleum, “ oil ” ). Fraction of crude oil (boiling range 175 - 325°C), electrostatically chargeable, but not explosive at room temperature because its flash point is above 45 °C. ( ↑ CAS number) pH, short for Latin: potentia hydrogenii ( “ strength of hydrogen ” ). Negative decadic logarithm of the hydrogen ion concentration. A measure of the acidic or basic character of a solution as a function of temperature. It has a decisive influence on its ↑ conductivity (e. g. in water). [ISO 80000-9 Annex C] The determination is made either by approximation using indicator papers or by electrometric methods, in which a measuring electrode and a reference electrode are placed together in the liquid. The potential difference between the two electrodes gives the measured value ( ↑ Galvani voltage). Phase shifter. AC currents have a phase that can be shifted by either + 90° or - 90°, depending on the reactance ( ↑ alternating current quantity). At very high frequencies, it is the delay shifts that are caused by detour lines. Phase goniometer. An electrical circuit in which capacitive and inductive reactance ( ↑ alternating current quantity) are connected in such a way that a displacement of ±90° is possible. Phase goniometers can be used to power ionizers to optimize discharge power, e. g. on the front and back sides of a ↑ material web. (Source: www.warmbier.com) Phase goniometer 299 <?page no="311"?> Phlogiston (Greek: phlogistós, “ burnt ” ). 18th century theory in the history of chemistry in which phlogiston was a hypothetical substance used to explain a combustion process, among other things. This theory was refuted by G. C. ↑ Lichtenberg for ↑ electricity and by A. L. Lavoisier for chemistry. Photo (Greek: photós, “ light ” ). This is also the word used to mean “ light ” in combination with other words. Photo semiconductors. Materials that reduce their electrical resistance when exposed to light ( ↑ photoelectric effect), e. g. selenium compounds, zinc oxide, or organic multilayers. As in a ↑ photodiode, absorbed light quanta release electrons from the atomic structure if sufficient energy is available. Free electrons and holes are formed in pairs, resulting in a current when an electric field is applied (electrostatic ↑ copying process). Conventional photo semiconductors for ↑ xerography have a “ dark resistance ” > 10 14 Ω , which drops to 10 7 - 10 9 Ω when exposed to light. [Goldmann, G. (2006)] Photoconductor, ↑ photo semiconductor Photo-dielectric effect. Change in the ↑ permittivity of a material when illuminated ( ↑ photoelectret). Photodiode. ↑ Diode whose ↑ PN junction can be irradiated with light. When a quantum of light enters the PN junction, it can release an electron from its atomic bond ( ↑ photoelectric effect) and thus increase the reverse current of a diode gap. Photoelectret. ↑ Electret made of photoconductive material, e. g. zinc oxide. To form the electret, the photoconductor ( ↑ photo semiconductor) is exposed to an electric field and then darkened again ( ↑ xerography). The latent image is preserved for about 20 h (the beginning of electrostatic photocopying). Photoelectric effect. Causes a quantum-mechanical process in a material in which lightabsorbing ↑ electrons are released from their bound state and cause electric charge transport (photocurrent). Photoelement (also photovoltaic cell). Without an applied bias, any ↑ photodiode can also be operated as a photoelectric element. A space charge separates the carrier pairs released during exposure ( ↑ photoelectric effect). A photoelement with a larger lightsensitive area is also called a “ solar element ” , which is used to convert solar radiation into electrical energy (photovoltaics). Photoionization. Free or bound atoms or molecules can be ionized by ↑ photons (light, UV light, X-rays, or gamma quanta). Photoluminescence. Excitation of ↑ luminescence by irradiation with light or ultraviolet radiation. Photon. Term coined by A. Einstein in 1905 with the symbol γ for the energy quanta of the electromagnetic ↑ field (e. g. light and radiation quanta). Photons are stable, electrically neutral elementary particles without rest mass, moving in the ↑ vacuum at the speed of light c; they are the smallest possible energy quanta of the electromagnetic radiation field. Phlogiston 300 <?page no="312"?> Any interaction between them and matter takes the form of emission or absorption of photons ( ↑ quantum). Physikalisch-Technische Bundesanstalt (PTB) (German National Metrology Institute). As successor of the Physikalisch-Technische Reichsanstalt (PTR), it is the supreme scientific and technical authority and national metrology institute of the Federal Ministry of Economics and Energy (BMWi) with headquarters in Braunschweig and Berlin. It is also a ↑ notified body for explosion protection in the sense of ↑ ATEX 114. Its specialist tasks in the field of explosion protection cover the areas of metrology (metrology for the legally regulated area and for industry) and physical safety engineering. It performs type tests and approvals of systems, equipment and safety devices used in the handling of explosive substances in accordance with legal or professional regulations and ordinances. It conducts research in all areas of explosion protection, e. g. on safety-related parameters, ignition sources such as electrostatics and electrical and mechanical ignition sources, or simulation of flow and combustion processes. Pico-ammeter. A highly sensitive electronic direct current meter, that is often used in electrostatics for measuring ↑ resistance ( ↑ influence electrostatic field meter). Piezo effect (also called piezoelectric effect), (ancient Greek: piezein, “ to press ” ). Discovered in 1880 by the brothers P. J. and P. ↑ Curie on Rochelle salt. When certain crystalline materials are subjected to mechanical stress, an electric voltage can be generated; conversely, such crystals deform when a piezoelectric material is placed in an electric field ( ↑ electrostriction). When a force (pressure or tension) is applied in the direction of the neutral axis of a piezoelectric crystal (e. g. quartz), an electric charge is generated at electrodes perpendicular to the crystal. This is caused by a deformation of the crystal lattice, whereby oppositely charged lattice points are displaced, releasing surface charges proportional to the magnitude of the deformation. If the mechanical stresses are induced by temperature changes, this is called ↑ pyroelectricity. Conversely, the crystal can be excited to elastic motion by applying an electric voltage (reciprocal piezo effect - actuator principle, ↑ piezo mechanics). If the frequency of the excitation by the AC voltage matches the elastic natural frequency of the crystal, resonance occurs, i. e. the crystal emits the AC voltage that excites it. Ceramics and polymers, including polyvinylidene fluoride (PVDF), can be used to exploit the piezo effect if their internal dipoles have been aligned by a strong external DC field ( ↑ electret). The piezo effect can also cause disturbances in highly sensitive current measurements ( ↑ galvanometer, ↑ pico-ammeter) if semicrystalline regions of polymeric insulating materials (e. g. of measurement cables) are moved. The piezo effect is often confusing with triboelectric ↑ cable charging. However, it cannot be avoided by using conductive coatings, but only by avoiding mechanical stress on the cables and/ or by using insulating materials with minimal piezo effect. Various applications of the piezo effect can be found in - Ink jet (both continuous and drop-on-demand), - Ignition devices, e. g. for gas stoves and lighters, - Transducers, e. g. for pulsed pressure increases, Piezo effect 301 <?page no="313"?> - Pulse generators, ultrasonic generators ( ↑ piezo motor), - ↑ Oscillating quartz as a clock generator in quartz clocks, - Ultrasonic sensor and tweeter. A. Patapoutain was awarded the Nobel Prize in Medicine in 2021 for his discovery of human cells, also known as piezo pressure sensors. The pressure sensors of the skin are called piezo1 and those of the inner cells are called piezo2. Piezo mechanics. It is a broad field of application of the ↑ piezo effect around micromanipulation ( ↑ nanotechnology), e. g. in biology, genetic engineering and medicine. Instead of quartz and tourmaline, the preferred materials for piezoelectricity, actuators with high expansion efficiency are required for piezo mechanics. Ceramics made of leadzirconate-titanate (PZT) mixtures are suitable for this purpose and can be produced in almost any desired shape. Piezo motor. For precise linear and rotary motion based on the ↑ piezo effect (actuator principle). Piezoelectric sensor. Used in particular for high-precision force measurement technology or as a small piezoelectric sensor for measuring electrostatic fields. In this case, a piezoelectric forked shutter is arranged in front of a sensor plate ( ↑ EFM). The design of the measuring aperture of piezoelectric sensors has a decisive influence on the measuring ranges recorded. [SE Section 3.13.1] (Source: www.ekasuga.co.jp) Piezoelectric transducers. Available in various shapes (plate, disc, tube) and performance classes, are primarily used to convert ultrasound into applications such as flow measurement, dosing, ↑ loudspeakers, structural monitoring, positioning and medical applications with response times of a few milliseconds. ( ↑ EFM, ↑ coating - ink jet, ↑ piezoelectric sensor) Piezo mechanics 302 <?page no="314"?> Piezoelectricity. All phenomena related to the ↑ piezo effect discovered by the brothers Paul-Jacques and Pierre Curie in 1880. Piezoresistive effect. Describes the change in the electrical resistance of a material due to pressure or tension and dates to the publications of P. W. Bridgman (1932). In principle, this change in resistance occurs in any material. In ↑ semiconductors, the strength of the effect can also be influenced by the orientation of the single crystal and by doping with impurities. Pin electrode, ↑ measuring electrode for solids no. 16 Pinch effect. Contraction of the channel of a ↑ gas discharge as a result of the magnetic field surrounding the current flow. A magnetic field forms around a current-carrying conductor, the field lines of which have the shape of concentric circles and tend to shorten. As the current increases in the initially diffuse gas discharge channel, the magnetic field begins to constrict the current flow into the ↑ plasma. This process represents a compression of the gas combined with its heating. The channel consists of cold or less hot plasma. It is continuously heated by the ohmic power (U × I). This results in the ↑ ignitability of some gas discharges. A pinch effect is not known for ↑ corona discharges, so no ignition potential is attributed to them. When a gas discharge transitions to the plasma state, the electrical resistance of the gas region is greatly reduced and the electric field collapses. This releases an electromagnetic wave whose frequency depends on the length of the gas discharge and its conductors. For ↑ thunderstorm lightning this occurs in the kHz-range ( ↑ spherics), for other gas discharges in the MHz-range ( ↑ spark detection device). Gas compression causes the acoustic effect (bang). Pipe / pipeline. When chargeable liquids flow through pipes, charge separation occurs between the liquid and the inside of the pipe, resulting in opposite polarity ↑ charging. This is also true for gas flows carrying liquid particles. The amount of charge is determined by the electrical resistance of the pipe material and the liquid, as well as the flow velocity and any turbulence. For this reason, electrically conductive piping must always be earthed along its entire length (to avoid ↑ spark discharges). This applies especially to all internal fittings (e. g. ↑ valves, orifices, reducers). For pipes made of electrically insulating materials, charge leakage to the outside and thus high field strengths to adjacent earthed parts must be expected ( ↑ brush discharges, ↑ charge transfer). An insulating inner lining of metal pipes is possible if maximum ↑ layer thicknesses are observed. When solids (powders, granules) are conveyed, the charge can be much higher than when liquids are conveyed. Therefore, due to the possible risk of ↑ propagating brush discharges, insulating and metallic pipes with an insulating lining should not be used for ↑ pneumatic conveying. This applies even if there is no risk of explosion, because the insulating pipe materials can be damaged by propagating brush discharges. [TRGS 727] Electrostatic discharge in pipelines is difficult due to the constantly changing conditions inside the pipe. For bulk materials, discharge can take place at the end of the pipe [Shoyama, M. et al. (2024)]. Pipe / pipeline 303 <?page no="315"?> Plasma (Greek: plasma, “ structure ” ). Term with multiple meanings (blood component, cell component, mineral and state of matter). Known in nature, for example, as aurora borealis and ↑ thunderstorm lightning. As a component of an electric circuit, plasma is generally an electrically conductive, usually very hot gas due to extensive ↑ ionization, which appears electrically neutral to the outside and is associated with luminous phenomena ( ↑ gas discharge, ↑ ignitability). The current transfer takes place on the surfaces of the electrodes involved. It is often referred to as the “ fourth state of matter ” and consists essentially of electrons, charged and partially excited atoms and molecules, and light quanta. The electric field in the plasma causes the movement of charge carriers and thus the transport of current, which results in the magnetic field with a certain frequency. The temperature of the plasma can be deduced from this. Cold plasma is produced when the gas is supplied with only enough energy to “ move ” only the small electrons and not the much larger ions ( ↑ DC low-energy plasma). Cold plasma can also be used to disinfect people and objects. [Müller, P. (2014)], ( ↑ anode fall, ↑ cathode fall) Plasma actuator, ↑ DBD actuator Plasma jet printing, ↑ coating Plastic (polymer). Macromolecular chemical compounds produced by synthesis from lowmolecular substances or by modification of natural products. Synthetic polymers are built from simple molecules (monomers) by ↑ polyreactions ( ↑ polyaddition, ↑ polycondensation, ↑ polymerization). Plastics also include ↑ caoutchouc (rubber), man-made fibers, coating raw materials, and adhesives. From a physical point of view, there are three groups: ↑ thermopolymers, ↑ duromers, and ↑ elastomers. In electrical terms, plastic is generally considered a nonconductor or insulator, but its resistance can be reduced by incorporating conductive foreign substances (e. g. ↑ carbon, ↑ metal fibers) (intrinsic ↑ conductivity). ● Plastic coating. When using conductive objects coated with plastic in ↑ Ex-zones, the requirements of [TRGS 727] must be observed, according to which, among other things, coating thicknesses must have a breakdown voltage of < 4 kV or a volume resistance of < 10 8 Ω ( ↑ area limitation). {Appendix D} ● Plastic sheathing. Sheathing of an ↑ active part (e. g. an electrical cable) with plastic ( ↑ cable designation). Plasticizers. Additives to ↑ plastics that increase plasticity (decrease hardness) at low temperatures. Depending on the type, plasticizers also have electrostatic effects ( ↑ antistatic agents). Plasma 304 <?page no="316"?> Plate capacitor. One of the most important components in electrostatic demonstration experiments, especially an arrangement with plates that can be moved in parallel. It is suitable for investigating the relationship between ↑ charge, ↑ voltage and ↑ capacitance as well as the ↑ permittivity number. {Appendix M.6.4.1} PN junction. Contact point of nand p-conducting material in a semiconductor ( ↑ band model). As a result of thermal motion, charge carriers diffuse across the PN junction and form a space charge barrier that exhibits rectifying behavior. Simple PN junctions are found in ↑ diodes, multilayer junctions in transistors and ↑ thyristors. (Source: Pohl, R. W., CC BY-SA 3.0 <https: / / creativecommons.org/ licenses/ by-sa/ 3.0>, via Wikimedia Commons) The figure shows the visualization of n-conductivity (left: by electrons, green) and pconductivity (right: by defect electrons, brown) in a potassium iodide crystal. The cathode (left) and the anode (right) are platinum pins fused into the crystal. [Pohl, R. W. (1944)] Pneumatic conveying (Greek: pneuma, “ breeze, wind, breath ” ). Transport of small-sized solids (granules, dust) in pipes or ↑ hose lines by means of compressed air or suction. Due to high separation speeds (10 - 100 m/ s) and large contact surfaces (dust), pneumatic conveying results in a high charge between the material being conveyed and the piping. Therefore, there is always a risk of ↑ propagating brush discharges ( ↑ chargeability) in pipes made of insulating materials or with insulating linings. Therefore, combustible dust should only be pneumatically conveyed in electrically conductive and earthed systems. Propagating brush discharges can also cause ↑ breakdowns on electrically insulating linings, resulting in micropores and damage comparable to electrical discharge machining on metal parts ( ↑ gas discharge mark). The material highly charged by pneumatic conveying causes further problems and hazards after separation from the conveying air (e. g. in a ↑ cyclone): Pneumatic conveying 305 <?page no="317"?> - In the ↑ silo: Adhesion to the wall, high volume ↑ charge density of both the still suspended and the already sedimented product, on the surface of which ↑ cone discharges can occur. - In ↑ filters (dust separation): High charge densities on the filter media, which can lead to ↑ brush discharges and ↑ spark discharges on non-earthed metal parts. The charge generated during pneumatic conveying is used for triboelectric powder ↑ coating. Note: At free fall heights > 3 m, velocities of almost 8 m/ s are reached in the downpipe, which are comparable to pneumatic conveying, so the requirements for preventing ignition hazards must also be met here. [Shoyama, M. et al. (2024)], [Schwindt, N. et al. (2017)], [Glor, M. (2001)] Pohl, Robert Wichard (1884 - 1952). German physicist developed physical demonstration techniques and set new standards in physics didactics (electrostatics 1927; mechanics 1930; optics and nuclear physics 1944). Point-charge. Model concept for an idealized, spherically symmetric body with homogeneous charge distribution, which acts on ↑ test charges at a defined distance as if its entire charge were concentrated in one point. [DIN 1324-1], {Appendix M.3.1.2} Point of zero net charge (PZC) (also known as the isoelectric point (pI)). Refers to the ↑ pH value at which a molecule appears electrically neutral to the outside (pH 0 ). Surfaces of solids are generally not neutral because their atoms near the surface cannot be compensated by neighboring molecules as in the interior of the solid; they have a positive or negative excess charge. Since all potentials always strive for equalization, there is ↑ adsorption of ions from the surrounding medium, e. g. ↑ humidity, which compensates for the excess charge of the solid surface. Therefore, under normal ambient conditions, surfaces are always contaminated at the atomic level, which leads to an indefinable ↑ charge and its ↑ charge distribution during separation. ( ↑ zeta potential, ↑ Lewis ’ s acid-base concept, ↑ Brønsted-Lowry definition), [Kosmulski, M. (2009)] Poisson equation. Mathematical equation in the theory of electric field, named after S. D. Poisson. It describes the electric potential in a space with a given charge distribution according to the formula Δ φ = ρ / ε ( Δ : gradient operator, ρ : space charge, ε : permittivity). ( ↑ equipotential lines, ↑ volume charge, ↑ permittivity) Polar liquid, ↑ solvent Polarity. Relationship between pairs of poles that are interdependent but opposite in nature and exert a force on each other ( ↑ electrostatic, ↑ field). Polarity cannot usually be determined in advance due to ↑ charging on contact and separation, because the ↑ soiling of the surfaces means that positive and negative surfaces are always adjacent ( ↑ Lichtenberg figure). Polarity inversion (spontaneous). It is a rarely studied phenomenon of ↑ passive discharge in combination with ↑ ionizers. For fast moving, highly charged ↑ material webs, it can be observed that the passive discharge current between the web and the pins of the ionizer increases almost Pohl 306 <?page no="318"?> exponentially (I = Q web × V web ) when the ↑ breakdown field strength is exceeded. A small distance between the ionizer and the web increases this effect. The ions emitted by the pins of the ionizing electrode reduce the charge on the web. The current flowing in this process creates a dynamic pressure in front of the electrode, and behind the electrode the laminar ↑ air boundary layer is transformed into a turbulent flow. The ions of opposite polarity, which are not required for the discharge, remain in the turbulent boundary layer and can charge the web with opposite polarity after passing the ionizing electrode. A similar and hitherto unexplored phenomenon is observed when liquids are stirred: an increase in the stirring speed causes a change in the polarity of the liquid charge. [Knopf, F. (2017)], [Lugt, H. J. (1983)] Polarization. Generation of two opposite (polar) properties in a previously homogeneous material. ( ↑ coercive field strength) ● Electric polarization. Temporary or permanent ( ↑ electret) alignment of the ↑ molecular dipoles in a ↑ dielectric, i. e. the displacement of elastically bound charges under the ↑ influence of an electric field. Positive elementary particles in the region of the atoms or molecules are deflected in the direction of the field strength, negative ones in the opposite direction. ( ↑ capacitor, ↑ electric flux density) ● Electrochemical polarization. Any directed current in an ↑ electrolyte causes ↑ ions to be deposited on the electrodes. This process causes a counter-voltage that reduces the current flow. When measuring the electrical resistance of liquids, it can cause an increase in resistance and thus an incorrect measurement especially for small resistances. It decreases as the AC voltage is applied with increasing frequency and with a larger electrode surface area (decreasing current density), and also depending on the electrode material and the electrolyte. ● Magnetic polarization. Refers to the orientation ( ↑ magnetization) of elementary magnets in ferromagnetic materials. ( ↑ permeability) ● Optical polarization. In light waves, oscillations occur in all directions perpendicular to the direction of propagation. After passing through a polarizer, the light has only one specific plane of oscillation (polarized light). Polarization force, ↑ dipole force Pole (Greek: polos, “ pivot, axis ” ) ● Electrical engineering: Connection point of a current source (excess of electrons: negative charge (negative pole), lack of electrons: positive charge (positive pole)). ● Physics: Location of highest field line density, e. g. north and south pole in a magnetic field and positive or negative pole in an electric field. ● Geography: Intersection of the earth ’ s axis with the earth ’ s surface (north pole, south pole). ● Mathematics: Point where a function takes the value ∞ . Polyaddition (Greek: polys, “ much ” , Latin: addere, “ to add ” ). Involves the addition of two different types of monomers, each of which has two or more reactive atomic groups. Depending on the functionality of the reactants, polyaddition can lead to linear polymers Polyaddition 307 <?page no="319"?> ( ↑ thermopolymer) or cross-linked plastics ( ↑ duromer). Example: Isocyanate and alcohol form linear polyurethane. In contrast to ↑ polycondensation, ideally no cleavage product is released, and the basic building blocks remain in the polymer molecule. Polycondensation. Usually, two identical or different types of monomers are joined together, each of which has a reactive atomic group at its end. In contrast to ↑ polyaddition, the substitution reaction always produces a cleavage product, e. g. water or ammonia (e. g. acetic acid and ethyl alcohol form ethyl acetate and water, diamine and dicarboxylic acid form polyamide and water). Linear chain molecules (thermospolymers) are formed from bifunctional reactants. Trior polyfunctional reactants form close-meshed spatial network molecules (duromers: e. g. phenol and formaldehyde form phenolic resin and water). Polymer. Macromolecule formed from one or more repeating units (monomers) by ↑ polyreaction. Its structure may result in a chain of molecules that is ball-shaped and intertwined (amorphous polymer). Some polymers also form crystallite-like structures between spherical structures (semicrystalline polymers). Depending on the number of basic components, a distinction is also made between homopolymers (one basic component, e. g. polyethylene, polyvinyl chloride), copolymers (different basic components, e. g. styreneacrylonitrile, also known as SAN) and polymer blends (mixtures of different homoand/ or copolymers to improve or adapt the properties of the polymer). Polymer conductor. Polymers that have been converted from electrical insulators to electrical conductors by special measures. - Extrinsically conductive polymers are created by adding conductive fillers (e. g. carbon black, graphite, ↑ metal fibers), which form a continuous network in the polymers ( ↑ percolation, ↑ pearl string model). The process is variable in terms of polymers and fillers (e. g. ↑ carbon - nanotubes). - Intrinsically conductive polymers are created by ↑ doping certain polymers (polyacetals, polythiopes, polypyrrole, polyaniline), e. g. with a halogen (oxidation, p-doping ( ↑ PN junction)) or an alkali metal (reduction, n-doping). Without doping, the conductivity of these polymers is close to that of semiconductors. These strong oxidizing or reducing agents create delocalized ionic centers in the polymer, for which the respective dopant forms the counterion. The term “ doping ” to increase the conductivity of a polymer is borrowed from semiconductor technology. However, it refers to a partial oxidation or reduction of the polymer and not, as in semiconductor technology, to the incorporation of foreign atoms into semiconductor crystals. This process generates positive or negative charge carriers (polarons, bipolarons) in the molecular chains, which move along the molecular chain when an electric voltage is applied. More regularly the halide ions (e. g. I - ) or alkali metal ions (e. g. Na + ) are arranged, the easier it is for the charges to move along the chain molecules. Polymerization. Monomers with double bonds, usually in carbon, are linked together. Heat and/ or catalysts break the double bond so that other molecules can attach to each molecule via free valences. Polymerization occurs in three stages: - Initiation of the reaction (e. g. by a catalyst) - Growth reaction Polycondensation 308 <?page no="320"?> - Termination reaction (saturation of the free valences, e. g. by formation of a double bond) Polymerization is exothermic, the polymer is always less energetic than the monomers. The number of monomers combined to form a macromolecule is called the degree of polymerization. It is typically between 100 and 100 000. Polyreaction. Macromolecules (polymers) are built from many small molecular building blocks (monomers), such as ethylene, vinyl chloride, and styrene, by polyreaction ( ↑ polyaddition, ↑ polycondensation, or ↑ polymerization). Ponderomotive force. Non-linear force exerted by an electromagnetic field on a macroscopic body, such as the attraction of iron by magnets. ( ↑ electrostriction) Positive, ↑ polarity Positron (positive electron). Elementary particle with the mass of an ↑ electron, but with a positive charge. It is emitted as an “ antielectron ” during radioactive ( β + ) decay and was discovered by C. D. Anderson in 1932 in altitude rays ( ↑ cosmic radiation). Potential (Latin: potentialis, “ acting according to ability ” ). In the original and narrower sense, a scalar, location-dependent physical quantity describing a vortex-free ↑ field, from which the ↑ field strength acting on a ↑ probe (measure of the strength of a force field) follows by ↑ gradient formation. ● The electrostatic potential is the negative gradient of the electric field strength in a static electric field. The reference point for the potential of a charged object is therefore usually the distant, field-free space with a potential of zero. This means that the vectorial ~ E -field always pointed in the direction of the lower potential. Consequently, the field lines always go to the nearest potential equalization (e. g. earth potential). ● The electric potential is the ↑ voltage with respect to a reference point, such as the voltage to earth. A voltage can exist between positive and negative electric potentials, as well as between similar but different electric potentials. ● The difference in magnetic potential between two points in space is the measurable magnetic potential. Potential difference. The difference in electric potential between two points in space is the measurable electric voltage. When two materials with different electron emission energies at the same temperature are brought close to each other in the nm-range ( ↑ charging, ↑ charge equalization), different energy states occur at the common interface. The migration of electrons from the ↑ donor to the ↑ acceptor starts. The number of electrons transferred depends on the potential difference. A state of equilibrium occurs only when the potential difference due to the different exit energies is equal to the difference in charge transferred. ( ↑ charge double layer) Potential measurement. Strictly speaking, potentials can only be measured on electrically conductive objects, e. g. by contact with a ↑ voltmeter, because insulators do not represent ↑ equipotential surfaces and generally do not have a homogeneous charge distribution. ( ↑ EFM with potential matching) Potential measurement 309 <?page no="321"?> Potential surface, ↑ equipotential surface Potting encapsulation, ↑ type of protection “ m ” Powder. Fine grained ↑ bulk material, the particles of which generally do not exceed the dimension of 1 mm. Powder coating. A mixture of different synthetic resin systems and pigments as well as special additives, which are ground to a fine coating powder with a particle size of about 30 - 50 μ m. They are preferably applied using an electrostatic application process ( ↑ coating) and then cross-linked in a curing oven at 150 - 200 °C to form the required painted surface. Powder filling, ↑ type of protection “ q ” Powder transfer system, ↑ PTS Power (electric). Symbol P with the derived ↑ SI unit [W], named after J. ↑ Watt. It describes the energy converted per unit of time. {Appendix M.6.1.3} Power cap, double layer ↑ capacitor Power density. Indicates how much power can be drawn up in how much time. For the electrostatic ignition of a flame, the ↑ MIE is usually specified, but this does not indicate the duration of the discharge. Therefore, to determine the MIE, it is necessary to specify the parameters of the spark discharge into which the electrical energy is converted. Volumetric power density describes the power per volume (liter) [W/ l], gravimetric power density describes the power per mass (weight) [W/ kg]. Precipitation, ↑ separation of substances Pressboard, ↑ paper Pressure decompression. For example, when water steam expands, very high electrostatic charges can be expected even at low initial pressures. Water droplets are formed by condensation and flow out at high speed. The separation of the droplets from the outlet is a separation process ( ↑ charging). The electrostatic discharges that occur are usually an ignition source for explosive gas or vapor-air mixtures. Electrostatic charging must always be expected with pressurized liquids and mists. (Superheated vapor is “ dry ” and should be treated as a gas. Wet vapor contains water droplets (mist)). [TRGS 727 Section 5 and Appendix A1.3] Pressure-resistant, ↑ explosion pressure-resistant design Pressure shock-resistant. Criterion for measures for ↑ explosion prevention. Pressure test. Used to verify the tightness and strength of components and equipment used to transport, store media and/ or serve as reaction vessels. It can only be performed hydrostatically and never with gases ( ↑ leak test). In the case of the latter, there is a risk of bursting due to their compressibility! Pressure venting, ↑ explosion pressure relief Potential surface 310 <?page no="322"?> Pressurized enclosure, ↑ type of protection “ p ” Primary cell (voltaic or ↑ galvanic element). Chemical processes are converted directly into electric voltage. It consists of two electrodes of different materials immersed in a liquid or solid electrolyte. The voltage of the primary cell depends on the difference in electrode potential in the electrochemical voltage series (redox series). Unlike accumulators, primary cells cannot be recharged ( ↑ battery). Primary ionization, ↑ ionization Primary particles. Individual particles in a variety of forms that make up fine-grained, powdered solids. Primeval code. A phenomenon discovered around 1987 by G. Ebner and H. Schürch, according to which seeds germinated in an electrostatic field with water develop completely differently than under normal conditions. It was found that the resulting plants often resembled the original forms. In addition, faster growth, higher yields and better resistance were observed. This phenomenon has since been replicated and verified many times internationally. For example, about 1,250 V/ cm for corn and about 750 V/ cm for wheat have proven to be promising. [Bürgin, L. (2021)], [Dascalescu, L. et al. (1999)] Print assist (electrostatic), ↑ electrostatic print assist (ESA) Printing machine. Coating machine for sheet or web materials. Depending on the processing speed, electrostatic charges are generated by multiple separation processes. Integrated modules, such as ↑ corona pretreatment, can cause additional charging. ( ↑ electrostatic print assist, ↑ ionizer, laminar ↑ air boundary layer, ↑ material web, ↑ misting tacker, ↑ edge strip disposal, ↑ electrostatic ribbon tacking, ↑ blocking, ↑ composite) Probe ● For measuring electric fields: ↑ EFM ● For measuring resistances: ↑ measuring electrode ProdSG, short for German: Produktsicherheitsgesetz (Product Safety Act). Contains regulations on the safety requirements for technical work equipment and consumer products and was amended by the [ ↑ ÜAnlG] in July 2021. Propagating brush discharge. ↑ Gas discharge directly above a charged insulating material at the surface of which a ↑ charge density σ > 26 μ C/ m 2 has been caused by Propagating brush discharge 311 <?page no="323"?> ↑ charge bonding to an earthed object or a bipolar charge. Using the example of a thin, mirror-smooth, high-resistance film (polycarbonate, about 100 μ m thick) - placed on an earthed plate - the process of a propagating brush discharge can be explained: the film is charged ( ↑ corona charging, scheme a). This increases the contact between the film and the plate (Coulomb force). This leads via ↑ influence to a reduction of the field strength in the environment, because the E-field is aligned to the earthed plate ( ↑ image charge). An earthed sphere approaching the film from above (diagram b) initiates a ↑ brush discharge and causes a narrowly limited reduction in the charge density due to preionization ( ↑ leader) via a plasma channel to the earth potential in diagram b (short-circuit). From there, sliding poles spontaneously spread parallel to the surface in a fan-shaped pattern over the entire charged film surface and excite sliding gas discharges ( ↑ pinch effect) in the form of ↑ dendrites ( ↑ fractals) [Müller, L. (2004)]. Experiments have shown that propagating brush discharges no longer occur on an insulator layer at a breakdown voltage < 4 kV or a layer thickness greater than 10 mm. Minimum voltage between the surfaces of an insulating layer for the occurrence of propagating brush discharges according to Maurer et al. [Lüttgens, G., Glor, M. (1989)] Propagating brush discharge 312 <?page no="324"?> As the distance of the film from the earthed surface increases, the energy of the propagating brush discharge decreases to the same extent, transforming into a ↑ super brush discharge, which only allows brush discharges to occur as the distance from the earthed surface increases further. Propagating brush discharge for PVC with ε r = 2.95; film thickness h = 0.18 mm and initial charge σ = 250 nC/ cm 2 , a) surface charge density distribution after discharge, b) corresponding discharge current pulse. [Müller, L. (2004)] The marks visible on the sphere in the photo are reflections of this propagating brush discharge. The plasma channel of the original brush discharge persists during the propagation of the fractal brush discharge until the charge is diverted from the top of the film to earth. During this process, current amplitudes up to 100 A can occur. There is always a residual charge. The plasma channel that forms in the small space between the sphere and the film has a high-power density and emits strong high-frequency ↑ transients that can damage electronic components and devices. ● The expected energy W P [ J] of a propagating brush discharge can be estimated by calculation: W P ¼ A d 2 2 " r " 0 Where A is the area [m 2 ], d is the film thickness [m], σ is the surface charge density [C/ m 2 ], ε 0 is the electric ↑ field constant, and ε r is the ↑ permittivity of the film. ● The extent of a propagating brush discharge can be considerable (in the order of meters). If the corona charging is continued until the electrical permittivity ( ↑ electric strength) of the film is reached, a self-breakthrough will occur, which then also spontaneously transforms into a propagating brush discharge. It is worth noting that no electrode is involved in such a breakdown of the insulation material. The energy released in a propagating brush discharge can reach values of up to 10 J and lead to an ↑ electric shock to persons (danger to life possible) and also to the swirling up of combustible ↑ dust (MIE > 1 mJ), which ignite in this state and thus cause an explosion ( ↑ ignitability of gas discharge). Sedimented dust can basically only burn off and present an explosion hazard only in a whirled-up state. In the 2nd photo, a polycarbonate film Propagating brush discharge 313 <?page no="325"?> (100 μ m) was sprinkled with dust (PAN, particle size about 20 μ m) and charged by corona. The earthed sphere is approached, and the dust is disturbed, causing ignition. ● Propagating brush discharge can occur on electrically conductive pipes or pipe bends with internal insulating lining (shielded system a). When small particles (large specific surface area) strike the insulated lining at high conveying velocities (> 10 m/ s), a continuous ↑ charging of the conveyed material and the lining occurs. The charge on the lining is usually confined by the earthed outer wall of the pipe. If the dielectric strength of the lining is exceeded, a propagating brush discharge occurs with a corresponding ignition hazard and pore formation. In unearthed systems (b) made of self-supporting insulating plastic pipes, these are charged in the same way. Due to the effect of e. g. a positive charge in the pipe, negative charges from the surroundings are attracted and a ↑ bipolar charge layer is also created, which can lead to a propagating brush discharge. Damage to tubes is often attributed to abrasion but is actually the result of numerous pores due to propagating brush discharges. ● The propagating brush discharges that occur during pneumatic dust conveying can be observed on transparent tubing, for example. The photo shows a 30 mm PMMA tube in which the discharge channels are concentrated towards the earthed tube socket. [TRGS 727 Section A.3.4], [IEC/ TS 60079-32-1], [IEC 60079-32-2] Propagating brush discharge 314 <?page no="326"?> Propellant. Pressurized, readily liquefiable gas used to transport e. g. pharmaceuticals, paints, cosmetics. Flowing pure gas does not become electrostatically charged, but it can cause electrostatic ↑ charges as a result of the ↑ aerosols carried at high speed from the spray nozzle. Protection class. Applies to ↑ housing (enclosure) (IP code) - for ↑ shielding against electromagnetic interference, specified in the law on ↑ Electromagnetic Compatibility, - in electrical engineering, an alphanumeric code indicating the degree of protection against contact and against the ingress of foreign bodies and water. [IEC 60529] Protective bonding conductor. Electrical combination of touchable conductive parts and/ or shielding to ensure safe connection to an external protective conductor. [IEC 61010-1] Protective clothing, ↑ personal protective equipment Protective earthing conductor. Electrical conductor with the marking “ PE ” as a protective measure against dangerous body currents in electrical connections. Protective equipment, ↑ personal protective equipment Protective gloves, ↑ personal protective equipment Protective insulation - Protective measure by means of additional ↑ insulation to the basic insulation or by reinforcing the basic insulation. - Additional insulation of the system independent of the operational insulation. [IEC 62606] Protective measures for the prevention of ignition hazards due to electrostatic charging are defined in Germany in Technical Rule 727, which is assigned to the ↑ GefStoffV. [IEC/ TS 60079-32-1] ● Constructive protective measures. These protective measures are required in a plant if explosions cannot be prevented with sufficient certainty. They are intended to limit the effects of an explosion to a harmless level ( ↑ explosion prevention). Proton. Elementary particles with a positive electrical ↑ elementary charge. Together with neutrons, protons form the atomic nucleus, and their number determines the chemical element to which the ↑ atom is assigned. Protons (hydrogen ions) are important for energy storage and the energy conversion of hydrogen (fuel cell). Proton conduction. Transport of electric charges by protons ( ↑ electron conduction). It is possible in solids that are either contaminated with hydrogen (as a special form of ↑ ionic conduction) or in which a hydrogen bond is effective (intrinsic ↑ conductivity, e. g. of polyaniline and polypyrrole). Proton conductors are an important component of fuel cells using porous solids and polymers as electrolytes ( ↑ Brønsted-Lowry definition). [Yoon, M. et al. (2013)] Proton conduction 315 <?page no="327"?> Psychrometer, ↑ humidity meter (aspiration psychrometer), ↑ hygrometer PTB, short for German: ↑ Physikalisch-Technische Bundesanstalt PTC thermistor, ↑ thermistor PTI, short for proof tracking index. Test number for determining the creepage distance ( ↑ comparative tracking index). PTS, short for powder transfer system. Offers a safe solution for feeding one or more reactors or other containers with powders from bags. The system ensures a high level of containment, both for the operator and for the product and environment. (Source: www.dec-group.ch) P-type conductivity, ↑ semiconductor Pump. In the electrostatics, it should be noted that liquids that are not adequately conductive can become dangerously charged by pumps due to the high flow velocities that occur. Appropriate protective measures: ↑ calming section, ↑ charge dissipation. ( ↑ armature), [TRGS 727 Section 4] Puncture, ↑ micropore Pyroelectric infrared sensor (PIR Sensor). A sensor that utilizes the effect of ↑ pyroelectricity, e. g. for infrared and microwave detectors, temperature sensors, and calorimeters. Pyroelectricity. The set of phenomena that occur when crystals are heated or cooled, resulting in internal charge displacement and ↑ polarization at the contact surfaces, whose effects can be measured as charge on the outside. The effect of pyroelectricity is closely related to the ↑ piezo effect. Pyrolysis. Thermochemical decomposition of substances, usually in the absence of oxygen. ( ↑ cracking process, ↑ deflagration, ↑ smoldering gas, ↑ combustion process) PZT ceramics. Piezoceramic materials (lead zirconate titanate), which are used in ↑ piezo mechanics. Psychrometer 316 <?page no="328"?> Q Qualified person for the purposes of [TRBS 1203]. A person who has the necessary specialist knowledge to inspect the work equipment ( ↑ instructed person) as a result of his or her professional training, professional experience and most recent professional activity. Quantum. Smallest possible indivisible unit, e. g. the electric ↑ charge ( ↑ elementary charge) of the magnetic flux or the effect (Planck ’ s quantum of action). Electromagnetic energy is emitted or absorbed in the form of energy quanta. Quantum orbit. ↑ Electrons orbit in the atomic shell on a so-called quantum orbit (radius ~ 10 pm (10 -12 m)). In the uncharged state, the number of orbiting electrons (negative ↑ charge) is always equal to the number of protons in the nucleus (positive charge). The atom appears electrically neutral to the outside world. Quartz glass, ↑ glass Quasi-stationary. Almost infinitely slow change over time. In electrodynamics, for example, such displacement currents can be neglected compared to the line current ( ↑ resistance, impedance ( ↑ alternating current quantity)). This allows to simplify the ↑ Maxwell ’ s equations. Quench tube. Collecting device for cooling the flames and unburned components that escape during an ↑ explosion pressure relief to such an extent and so quickly that the pressure no longer rises to a dangerous level. The effect is based on cooling when passing through narrow gaps ( ↑ quenching distance). Quenching distance. The term is based on the quenching distance for the flame transmission of explosive mixtures ( ↑ MESG), i. e. at voltages below 300 V no ignitable ↑ gas discharges occur. These are based on impact ↑ ionization of the gas molecules by gas ions in the electric field (secondary ionization). The discharge starts when the electric field strength reaches a value of 3 MV/ m under atmospheric conditions. In principle, the process can be induced at lower and lower voltages as the distance between the electrodes is reduced. At voltages below 300 V, the electrode distances become so small (quenching distance) that the short distances are no longer sufficient to accelerate to the energy required for impact ionization. Rembe Q-Rohr ® (Source: www. rembe.de) <?page no="329"?> R Radio-frequency interference (RFI) ● To equipment and systems caused by electromagnetic fields generated by gas discharges ( ↑ Electromagnetic Compatibility), which may originate among other things, from charged surfaces of insulating materials. ( ↑ spark detection device) ● Caused by electrical processes in the atmosphere ( ↑ aurora borealis, ↑ spherics). Radio-frequency interference range. Maximum distance between a radio interference source and the equipment at which interference is to be expected ( ↑ Electromagnetic Compatibility). Radio transmitter. H. ↑ Hertz performed fundamental experiments with a radio transmitter for the generation, emission, and transmission of electromagnetic radiation in 1887. Electromagnetic oscillations are generated by sparks in a ↑ spark gap and emitted by a connected ↑ dipole. Radioactive ionizer, ↑ ionizer Radioactivity. Property of unstable atomic nuclei that spontaneously decay into other atomic nuclei without external influence. This results in the emission of particles such as ↑ alpha (helium-4 nuclei), ↑ beta (electrons) and/ or ↑ gamma radiation ( ↑ electromagnetic radiation). Radius of curvature. The sharpness of the electrode tip determines whether the ↑ gas discharge generated at the tip develops into a ↑ corona discharge or a ↑ brush discharge (ignitable for gases and vapors). Raindrop charging, ↑ Lenard effect Rate of current rise. The quantity of charge (product of current and time) transported in a ↑ gas discharge has a greater disruptive effect (e. g. on electronic devices) the faster it occurs ( ↑ HBM, ↑ CDM), and the current pulse is correspondingly high. As the rate of current rise is essentially reduced with increasing ↑ self-induction of the circuit, it is lower for gas discharges whose currents flow via conductors (e. g. ↑ sparks) than for those that occur without conductors (e. g. ↑ brush discharges, ↑ propagating brush discharges, ↑ thunderstorm lightning). Rate of pressure rise / pressure rise class, ↑ dust explosion class Rayleigh instability. J. W. Rayleigh (1842 - 1919) was the first to publish a comprehensive mathematical derivation according to which an instability of a cylindrical body driven by the capillary force decomposes itself into particles of non-arbitrary spacing in the course of its motion. In the case of Rayleigh instability, a critical value is exceeded at <?page no="330"?> which the ↑ surface tension of the system is reduced. The dissolution of liquid jets into droplets is well known and also applies to nanoscale solid systems where there is a large ratio of surface area to volume. ( ↑ coating - ink jet) Rayleigh limit. Regularity discovered by J. W. Rayleigh, that states that droplets can only carry a certain number of charges depending on their size and surface tension. If the Rayleigh limit is exceeded, the droplets disintegrate, which can occur down to the level of ions, depending on the ambient conditions. ( ↑ atomization, ↑ electrospray ionization) Rayon fiber (viscose). Synthetic fiber obtained from cellulose as a starting material with silk-like properties, characterized by, among other things, a low tendency to electrostatic charging. RCD, short for ↑ residual current device Reactance, ↑ alternating current quantity Reaction. A chemical reaction can be exothermic and cause substances to ignite when heated. This process can begin at room temperature and result in high temperatures due to inadequate heat removal. ( ↑ ignition source, ↑ light metal) Reactive current / reactive voltage, ↑ alternating current quantity Reading accuracy. Reading analog measurements is the process of aligning a needle or calibration mark with a mark on a scale. Reading accuracy depends on the scale ’ s graduation and is defined as the minimum distance that can be read between two distinguishable readings. Reading accuracy is often expressed as a percentage of the final value. Receiving vessel (supply tank). Term is generally used in the chemical industry for containers that usually already contain liquids and into which further solids are to be added. During these processes, several conditions must be met to prevent ignition hazards due to electrostatic discharges, including ↑ earthing, ↑ inerting, ↑ personal protective equipment, ↑ exhaust system. ( ↑ PTS) Recognized rules of technology, ↑ state of the art Recombination. Reversal of ↑ dissociation, i. e. reunification of electrically charged particles ( ↑ ions), resulting in charge neutralization through the interaction of positive and negative charge carriers. Recombination restricts the effectiveness of ↑ ionizers in terms of space and time. Reconditioning (used colloquially for ↑ RIBCs and ↑ barrels). The ↑ ADR defines the terms periodic maintenance, repair and reconditioning for combination IBC (RIBC, ↑ dangerous goods), i. e. the restoration of the original properties for the intended use as packaging permitted under dangerous goods legislation. There are three variants for UN-RIBCs [IEC 61340-4-11]: Reconditioning 319 <?page no="331"?> 1st Periodic maintenance: - Cleaning of the inside (inside of the PE container) and outside (lattice frame, pallet, outside of the PE container) - Visual inspection of the components of a RIBC (pallet, outer grid, inner container and its components (fittings, gaskets, etc.)) - Replacement of fittings and/ or closures and/ or seals and non-UN relevant markings, if necessary - Exclusive use of original components from the original manufacturer - Original specification is binding - Original UN-relevant markings/ labels remain unchanged - Leak test of the inner container, affixing of a test mark. 2nd Repair of the UN-RIBC: Same as “ Regular maintenance of UN-RIBC ” , but in addition: - If necessary, replacement of the inner container with a new and identical inner container from the original manufacturer (= “ rebottling ” ) - If necessary, repair of the cage and/ or pallet to restore the statics of the original design. 3rd Reconditioning of UN-RIBC: Same as “ Repair of UN-RIBC ” , but always including: - Installation of a new approved inner container In addition - Possibility to modify the original specification - Renewal of the UN marking (own UN approval) - Restart of the permitted service life of 5 years. “ RIBC approved for the transport of dangerous goods must be re-tested every 30 months. ” [TRGS 727 Section 4.5.4]. ↑ IBCs with “ UN approval ” may be used for a maximum of 5 years. When reconditioning is no longer possible, these containers are sent for recycling or thermal recovery. RIBCs approved for use in hazardous areas are subject to additional testing and measures. Rectifier, ↑ diode Redundancy (Latin: redundantia, “ abundance ” (repetition)). Technical expenditure, that is not absolutely necessary for the function of a system but is useful for safety-relevant systems. Redundancy also refers to the multiple design ( ↑ diversity) of important technical systems. ● Structural redundancy. Important measurement values, e. g. for monitoring, are determined by several independent measurement systems. If, for example, three measurement systems provide values, only those that are consistently displayed by at least two systems are considered correct (e. g. on a ↑ CO 2 fire extinguishing system). ● Active redundancy. For example, power systems are connected in parallel. Rectifier 320 <?page no="332"?> ● Passive redundancy. There are multiple systems of the same type that will only operate if one system fails (e. g. emergency generator). Reference earth, ↑ earthing Reference equipotential line, ↑ equipotential line Refinement. General term in textile technology for final finishing, to provide the fabric with certain properties after its manufacture ( ↑ finishing). Reflection attenuation, ↑ shielding Refraction. Change in the direction of propagation of waves and ↑ field lines at the interface of two different media. The deflection of a wave (e. g. a light beam) always occurs in the direction of the incident perpendicular as it passes from a medium of lower density (medium 1) to one of higher density (medium 2). On the other hand, an electric field line is deflected away from the incident slit when passing from a medium with low ↑ permittivity to one with higher permittivity. From the continuity of the normal component of the electric displacement density and the tangential component of the electric field strength, the so-called electric refraction law for the deflection of electric field lines follows: tan α / tan β = ε 1 / ε 2 where α and β are the angles formed by the field lines with the normal to the contact surface and ε 1 and ε 2 are the permittivity values of the materials. Accordingly, the law of refraction for magnetic field lines is: tan α / tan β = μ 1 / μ 2 where μ 1 and μ 2 are the permeabilities of the materials. The effect of electric field line refraction is used, among other things, to achieve a uniform reduction in field strength in the insulation of multilayer construction in high-voltage cables. Refueling. Large quantities of flammable liquids with a very low ↑ flash point ( ↑ gasoline) or a high flash point (diesel fuel) are usually filled into the fuel ↑ tanks of vehicles at public ↑ filling stations by non-experts, often under time pressure. This requires actions for water protection and, in the case of gasoline, also for ↑ explosion prevention, which are limited to the prevention of potential ↑ ignition sources. Filling stations prohibit smoking, leaving engines running, and the use of spark-producing electrical equipment. The remaining electrostatic ignition hazards are prevented by two independent methods: Refueling 321 <?page no="333"?> - In the refueling area, the road surface must have a leakage resistance of less than 100 M Ω , so that charging of the vehicle is prevented by the dissipation capacity of the ↑ vehicle tires (carbon black additive), which is sufficient in most cases ( ↑ car). - An additional discharge capability (resistance < 1 M Ω ) is provided between the earthed dispenser and the vehicle via the discharge-capable dispensing hose with dispensing valve. This requires that at least the top of the filler neck is electrically conductive. There are no additional hazards associated with the use of plastic fuel tanks in vehicles. However, the nozzle support on the filler neck and all metal parts must be electrically connected to the vehicle. [TRGS 727 Section 4.10.3] Relative humidity, ↑ humidity Relaxation (Latin: relaxatio, “ to relax ” ). Delayed response of a system or quantity to an external influence or its removal (after-effect), especially the exponentially delayed return of an electrostatically charged medium to its initial or equilibrium state. Relaxation time (also charge decay time). Symbol τ , unit [s], describes the characteristic time span for a system in which an electric charge has discharged to 1/ e (36.8 %). After 2 τ the system is discharged to 13.5 %, after 3 τ to 5.0 %, i. e. almost completely. The relaxation time is used to determine safety-related factors, especially for liquids and powders ( ↑ charging, ↑ bulk material, ↑ granules, ↑ dust). The relaxation time is analogous to the charge decay time of a charged ↑ capacitor. It is the product of the ↑ resistivity and the ↑ permittivity {Appendix M.6.3}. The relaxation time can therefore be used to calculate the maximum allowable leakage resistance for conductive objects (including people). Measurements on liquids must be made at rest and at a defined temperature, since flow and diffusion processes can superimpose the relaxation time. ( ↑ antistatic agents, ↑ bipolar charge layer, discharge ↑ time constant, ↑ charge density, ↑ dwell time). [TRGS 727], [SE Sections 3.7.2 and 7.3.8.1] ● Relaxation time measurement (also charge decay measurement). Method for evaluating the electrostatic properties of materials. [Matschulat, U., Schubert, W. (2023)] The measurement should be performed in a ↑ Faraday cage in the following steps: - The sample (at least 10 × 10 cm 2 ) is clamped in an earthed frame. - The sample is discharged with an active ↑ ionizer. - The sample is charged by corona (5 - 10 kV). - The relaxation time is measured. Relative humidity 322 <?page no="334"?> QUMA Elektronik & Analytik GmbH Preussenstrasse 11-13 42389 Wuppertal GERMANY www.quma.com info@quma.com Fon: +49 (0) 202 7479495 -0 Fax: +49 (0) 202 7479495 -40 QUMAT ® - 628 INSTRUMENT FOR MEASURING RELAXATION OF FOILS AND PAPER A CONTACTLESS MEASURING METHOD • Relaxation measurement •Defined unloading and loading of the sample •Designed and built according to DIN EN 61340-2-1(2016-07) FEATURES • Reproducible and fast measurements • Recording of the charging and discharging curve of the sample • Simple handling • Measuring area 10 x10 cm 2 acc. to DIN/ EN standard • Evaluation and storage of sample data • Results comparison within software possible <?page no="336"?> Note: When measuring paper and similar materials, special attention must be paid to the relative humidity and temperature. For textiles of all types (woven, knitted, non-woven) with and without integrated conductive fibers (surface and core conductive), the ↑ influence field measurement probe should be used. [IEC 61340-2-1], [SE Section 3.15] Remanenz, ↑ hysteresis Remoistening. In manufacturing processes, the ↑ material webs treated with various drying processes often have to be remoistened to avoid detrimental changes such as waviness and an increase in surface area (e. g. paper) due to water absorption. The German engineer F. Knopf simplified the technical solution published by H. Künzig in 1978 by using the principles of separating a web from a roller. The number of contact points is greatly increased by charging of the web with respect to the guide roller. The high level of charging after the web has been separated is used to build up a field between the water nozzles and the web in order to move the aerosols (e. g. water) on the ↑ field lines of a strong electrostatic field (> 100 kV) towards the material web, causing a current to flow between the web and the earthed spray nozzles (see figure ↑ material web). Vagabonding aerosols are thus avoided. ( ↑ atomization, ↑ coating - process no. 3, ↑ humidification, ↑ air boundary layer, ↑ Rayleigh limit), [SE Section 8.2.9], [Künzig, H. (1978)], [Eltex (2017)] Remoistening 323 <?page no="337"?> Repulsion (electrostatic). Electrically charged bodies in the same polarity repel each other ( ↑ Distance Law 3, ↑ Coulomb ’ s law). Repulsion is also used to manipulate very small particles in an inhomogeneous electric field ( ↑ di-electrophoresis). Residual charge. Description of the state of charge, e. g. after a certain discharge time of a previously charged capacitor (discharge ↑ time constant), or when using ↑ ionizers to eliminate charging. A summation of individual residual charges of a harmless level can again lead to dangerously high charges again, e. g. when winding a nearly discharged film web, a high ↑ charge accumulation occurs again on the coil. ( ↑ super brush discharge) Residual current ● Electric current that flows in the event of an insulation fault. [IEC 60050] ● Differential current for residual current devices. The sum of all currents in a network ≠ 0, i. e. part of the current flows out via another path (e. g. earth). [IEC 61008-2-1] Residual current device (RCD). Circuit breakers that switch off when the residual current exceeds a certain value. [IEC 62873-2] Resistance. Symbol R (Z, X: ↑ alternating current quantity), with derived ↑ SI unit [ Ω ]. Quantity that opposes ↑ electron conduction (in solids) or ↑ ionic conduction (in liquids and gases). Each conductor opposes the electric current with a resistance that must be overcome by the electric voltage. Resistance is defined by ↑ Ohm ’ s law {Appendix M.7.1}. Note: The term resistance refers to the specific component, whereas resistivity describes a material property. The electrical resistivity of currently known solids and liquids covers a range of 24 powers of ten. ● Resistance as an electrical component. Fixed or adjustable resistance to reduce the current in a conductor circuit, which serves to divide the voltage in a variety of ways. Inductive resistors are coils, capacitive resistors are plate ↑ capacitors, and variable resistors are e. g. photo resistors ( ↑ capacitance). ● Resistance in electrostatics, ↑ leakage resistance, ↑ volume resistance, ↑ volume resistivity, ↑ surface resistance, ↑ surface resistivity, ↑ input resistance, ↑ strip resistance, ↑ insulation resistance, ↑ internal resistance, ↑ conductivity, ↑ interfacial resistance, ↑ contact resistance, ↑ surge impedance of a line. ● Resistance on insulators. Investigations by U. v. Pidoll have shown that for some mixed polymers or ↑ polymers with conductive additives, a drastic drop in surface resistance to values noticeably below 100 G Ω occurs at measurement voltages of 1000 - 10 000 V. In some cases, resistance drops of six orders of magnitude down to the lower M Ω -range have been observed. Despite a formally too high surface resistance at 1000 V, such materials cannot be experimentally charged electrostatically and can Repulsion (electrostatic) 324 <?page no="338"?> therefore be used in hazardous areas. In most cases, therefore, the simple and arbitrarily accurate measurement of the surface resistance at 10 000 V can be used to assess the electrostatic ↑ chargeability of a material, and the more laborious and inaccurate charging method (e. g. by manual rubbing or tapping with a leather glove) can often be dispensed with. [IEC 60079-32-2], [SE Section 3.5.3.1], [Pidoll, U. v., Chowdhury, K. (2013)] ● Limit values for resistances. The determination and evaluation of the value of the surface resistivity ρ s , above which disturbances or hazards due to electrostatic ↑ charging are to be expected, depends to a large extent on the separation speed, the charge reflux and thus the amount of residual charge ( ↑ chargeability, ↑ interfacial resistance). Resistance coefficient, ↑ temperature coefficient Resistance measurement. A fundamental distinction must be made between resistance measurement in electrical engineering and ↑ electrostatics. The measuring instruments commonly used in electrical engineering do not usually have the measuring ranges and voltages required to measure electrostatic resistance. In the field of electrostatics, resistance measurement is an important method for determining the ↑ chargeability of materials, objects and people, where many ↑ influencing factors must be considered for each measurement. Correct measurements are only possible under defined climatic reference conditions (usually a maximum of 50 % or better 30 % RH) and a sufficiently long conditioning time. Standardized requirements always refer to the referenced products and the specified test conditions. A general transfer to other product groups is not possible. To avoid measurement and interpretation errors, it may be useful to combine physically different test methods in a complementary manner ( ↑ measurement error). For liquids, resistance measurement is called conductivity measurement. The measurement is usually performed according to the current-voltage principle: A direct current source applies a constant measurement voltage in the range of 10 - 1000 V or up to 10 000 V to a large number of ↑ measurement electrodes. The resulting measurement current is measured by a ↑ pico-ammeter and displayed in resistance values. ( ↑ measurement field strength, ↑ surface state, ↑ influence electrostatic field meter), [IEC 62631-3-3] The ↑ Wheatstone bridge can also be used for precision measurements at high resistances. The old principle of ↑ Rothschild resistance measurement is now experiencing a renaissance and has been implemented in ↑ tera-ohmmeters. Different electrode geometries and arrangements give different results with the same sample material. Therefore, the test standard used, and the underlying test conditions must always be specified. To ensure basic statistical reliability, several resistance measures should always be taken, if possible, at different locations on a suitable sample. The prescribed or appropriate measuring electrode must be selected (if specified in a standard). ● For compact solids, ↑ volume resistance R v and/ or ↑ surface resistance R s are used for characterization. Resistance measurement can only be used to the extent that ↑ Ohm ’ s law applies, i. e. the resistance is independent of the measurement voltage and the Resistance measurement 325 <?page no="339"?> measurement time. This is generally true for metals and materials with sufficient dissipation capability. In the case of insulating materials, the current and thus the ↑ charge transport is also dependent on the measurement voltage ( ↑ shell effect). Furthermore, when the measurement field is applied to the measurement current, an internal ↑ charging current can flow, which polarizes the material and/ or charges the capacitance of the measurement electrode. This results in a decrease in the measurement current during the measurement time. If such an insulating sample is short-circuited after the measurement, a corresponding discharge current flows in the opposite direction to the charging current. Therefore, resistance measurements on solid insulators must be performed with DC voltage. Unless otherwise agreed, the resistance is always determined one minute after application of the measuring field, disregarding any polarization phenomena at the electrodes. At high ↑ measurement voltages for determining the surface resistance of antistatic insulating materials (e. g. certain mixed polymers), the resistance typically collapses by several powers of ten. This can be easily recognized at a measurement voltage of 10 000 V. ● For ↑ bulk material (solids), no test methods for resistance measurement have yet been defined; only safety-related statements on electrical resistance are made in technical regulations. Several measurement options are listed under ↑ measuring electrodes (for solids no. 10 - 13). ● For textiles, the electrostatic behavior is tested according to the standard group [EN 1149], [DIN 54345-5] for strips (e. g. filter material) or [IEC 61340-4-9] for special clothing. They are usually classified according to surface and volume resistance with measuring electrode no. 9. If textile materials and products made from them must have electrostatic dissipative properties over a long period of time, resistance measurements with variable electrode spacing are required. (Measuring electrode no. 15 or 2 × no. 6 (point-to-point resistance measurement according to [IEC 61340-4-9].) With a surface resistance measurement, only the corresponding value on the front or back side can be determined. In the case of multi-layer textile structures (e. g. laminates), the inner layers are not measured. Therefore, a continuity resistance measurement must be performed, where the layer with the highest resistance will mainly influence the overall result. If textiles contain ↑ conductive fibers, the measurement may not be suitable or only partially suitable. It does not provide any information about the quantity and distribution of such conductive fibers. In addition, a surface resistance reduced by conductive fibers is not physically equivalent to a homogeneous coating with the same dissipation capability. If conductive fibers are not on the surface of the textile, or if they consist of a core-sheath structure, they cannot be detected by resistance measurement. In this case, suitable additional measurements with a different measuring principle are useful (e. g. charge decay according to [EN 1149-3] ↑ influence field measurement probe). [SE Section 3.14.2] ● For ↑ hose lines, resistance measurements are very complex, especially when they are used in ↑ Ex-areas. They must be designed so that they cannot become dangerously charged. The measurement must be performed at 500 V DC. In practice, a resistance Resistance measurement 326 <?page no="340"?> measurement must be carried out for each hose line supplied and the result documented in a test report or test certificate. It should be recorded: - Longitudinal resistance between hose ends (from fitting to fitting), - Surface resistance of the inside and outside of the hose, - Volume resistance between the inside and outside of the hose. [DGUV Information 213-053], [TRGS 727], [IEC 60079-32-2], [ISO 8031] ● For liquids, orienting electrostatic measurements with so-called dip electrodes are usually sufficient (measuring electrodes no. 2 and 3). The measurement setup is the same as for ↑ volume resistance, where the vessel can be an electrode. The determination of the ↑ conductivity is more problematic than for solids, because the charge transport is mainly done by ↑ ions, whose number and mobility (especially the ↑ temperature) are decisive for the result. The measurement specifications for determining the DC resistivity, the permittivity ε and the dielectric ↑ dissipation factor tan δ are given in [IEC 60247]. The permittivity value is needed to determine the specific conductivity κ [pS/ m] in order to determine the relaxation time τ . The conductivity is only characteristic if the resistance measurement is performed under thermodynamic equilibrium of the liquid. When using DC voltage, ions can be deposited on the electrodes ( ↑ polarization, ↑ electrolysis), resulting in counter-voltages that reduce the current flow. When using measuring electrodes, their ↑ cell constant must always be considered. [IEC 60079-32-2] - For sufficiently conductive liquids where electrolysis phenomena are to be expected, alternating voltage (AC) should be used for resistance measurement. It is advisable to use a tubular capacitor as the measuring cell because the electrode ratios remain constant when determining the thermal behavior. For example, 1.5 V AC at 20 Hz can be used to determine the conductivity at an electrode spacing of 1 mm, 1.5 V AC at 1 - 100 kHz for the permittivity, and 1.5 V AC at 50 Hz for the dissipation factor (measuring electrode no. 4). [Flucon (2021)] - For insulating liquids ( ↑ type of protection “ o ” ), the measurement setup and the method for determining the permittivity are contained in [IEC 61620], in which the conductance ( ↑ alternating current quantity) and the capacitance of a defined measurement setup are determined. It uses 10 - 100 V AC at 0.1 - 1 Hz with a stable “ quasi-square wave voltage ” . ( ↑ paper - pressboard) Resistance noise, ↑ white noise Resistance to earth, ↑ leakage resistance Resistivity. Symbol ρ , unit [ Ω m]. It is a material property that also depends on temperature. (Resistance refers to the concrete object.) Material Resistivity [ Ω m] silver 1.6 × 10 -8 copper 1.7 × 10 -8 tungsten 5.3 × 10 -8 carbon 100 × 10 -8 constantan 4.9 × 10 -7 (20ºC) 5.1 × 10 -7 (600ºC) Resistivity 327 <?page no="341"?> Material Resistivity [ Ω m] distilled water 2 × 10 5 glass 1 × 10 12 aluminum oxide 1 × 10 12 Resolution capacity. The ability of an analyzer to clearly distinguish details of an object that are close together. High-resolution probes are needed to study the charge allocation of charged surfaces, such as photocopiers. These are ↑ influence field measurement probes with apertures of currently about 0.5 mm diameter. This allows details in the charge allocation up to 1 mm in size to be measured. Response current. Fixed value of the current that causes a protective device to respond within a fixed time, called “ agreed time ” . [IEC 60947-2] Return stroke. Term for the counter-discharge that rises from the impact object during ↑ thunderstorm lightning. Reverse direction. Direction of current through a ↑ diode in which only a negligible reverse current flows even with increasing ↑ cut-off voltage. Ribbon cable (twin conductor cable). A double conductor consisting of two wires (waveguides) embedded in parallel in a flexible tape of insulating material to minimize interference from external electromagnetic fields. ( ↑ surge impedance of such a line approx. 300 Ω ). RIBC, short for rigid intermediate bulk containers. It is a large container for the transportation and storage of liquids. RIBCs are made entirely of metal or plastic, as well as plastic inner containers with metal frame constructions and various pallets (wood, PE, steel or combinations of these ( ↑ pallet container)). In general, two versions are used: - Inner container completely encased in dissipative material (e. g. sheet steel: full metal jacket), or - as a design with a metal lattice box ( ↑ area limitation), if the so-called plastic bladder is not made of dissipative plastic. Electrostatic hazards during filling and emptying of metal or dissipative plastic RIBCs can be reliably prevented by earthing. On the other hand, for RIBCs with a plastic liner, earthing the metal liner is a necessary but not always sufficient protective measure. In special cases, further measures must be taken, e. g. internal electrode for earthing the liquid, earthed ↑ filling pipe during filling, etc. [TRGS 727 Section 4.5.4]. Only RIBCs approved for use in ↑ Ex-areas may be used. [IEC 61340-4-11] RIBCs approved for the transport of dangerous goods must be re-tested every 30 months in accordance with TRGS 727 and, unless otherwise specified by the competent authority, the permitted period of use is five years (calculated from the date of manufacture). ( ↑ reconditioning, ↑ ADR, Section 4.1.1.15) Rich mixture. Mixture of combustible gases or vapors in air above the upper ↑ explosion limit. It cannot be made to explode but can burn off with the addition of atmospheric oxygen. Resolution capacity 328 <?page no="342"?> Right-hand screw rule (also known as a corkscrew or three-finger rule). A magnetic field forms around a current-carrying conductor ( ↑ pinch effect), the field lines of which have the shape of concentric circles. The direction of the magnetic field depends on the direction of the current, and the following right-hand screw rule applies: Imagine a screw with a right-hand thread that is screwed into the conductor in the direction of the current, the direction of rotation of the screw indicates the direction of the magnetic field lines. Ring electrode, ↑ measuring electrode for solids no. 9 Ringing. In the case of electrical pulses, higher-frequency decay processes are often superimposed on the actual pulse waveform. When defining pulse shapes for ↑ CDM and ↑ HBM, the maximum allowable ringing is defined to minimize the effects of these decay processes relative to the effects of the main pulse. For example, the HBM pulse is a rapidly rising unipolar pulse that slowly decays. Due to the rapid rise, the pulse oscillates beyond its theoretically highest point, approaches its falling edge again, also oscillates beyond this edge, and repeats this process until it has stabilized on its falling edge. According to [Mil- Std. 883D], the ringing of the HBM pulse must not exceed 15 % of the pulse maximum. In addition, there must be no detectable ringing within 100 ns of the peak. Rise time. Time interval between the moments when the instantaneous value of a pulse ( ↑ ESD) first reaches the 10 % value and then the 90 % value. Risk (Italian: rischio, “ obstacle ” ), ↑ danger or hazard ( ↑ safety). Between “ safety ” and “ hazard ” , the “ limit risk ” represents the greatest justifiable risk of a technical process or condition to be evaluated ( ↑ explosion risk). (Source: www.maschinen-sicherheit.net) For a remaining residual risk, [ISO 3864-2] contains four levels with corresponding signal colors and notes (see figure next page). Risk 329 <?page no="343"?> Risk area (explosion prevention zone), ↑ Ex-zone Risk assessment. With respect to electrostatic charging, risk assessment should be performed by systematic investigation ( ↑ ignition hazard assessment). RMS value. Root-mean-square of a time-varying periodic (physical) quantity. The RMS value of an AC current is as large as that of a DC current of the same ↑ power (thermal effect). The ratio of ↑ peak value to RMS value is √ 2 for sinusoidal values ( ↑ alternating current quantity). Rogowski, Walter Johannes (1881 - 1947). German physicist, studied electrical engineering at the German TH Aachen and later became director of the university ’ s Electrotechnical Institute, known for the ↑ Rogowski coil and the ↑ Rogowski profile. Rogowski coil. Tool for determining the line integral of magnetic induction. The Rogowski coil allows the quantitative investigation of the relationship between current as a cause and magnetic field as an accompanying phenomenon ( ↑ pinch effect). Application: Apparatus for measuring alternating current. Rogowski profile. Profile design (a) at the edges of plate-shaped electrodes whose radius decreases steadily towards the outside. The Rogowski profile follows the ↑ equipotential surface. The exact shape of the rounding therefore depends on the respective plate spacing. It can be calculated, but a cylindrical rounding with a radius r > s is usually sufficient [Hilgarth, G. (1997)]. The Rogowski profile prevents localized increases in field strength, so that spraying of charges can be avoided ( ↑ edge field). The concentration of the field is caused, for example, by sharp edges (c) and thus leads to possible flashovers ( ↑ breakdown, ↑ measurement error). Simulation of three profiles on capacitor plates and their edge fields. The color scale shows the magnitude of the field strength. [Mewes, M. (2018)] Risk area 330 <?page no="344"?> Rolled capacitor, ↑ capacitor Roller bearings. Electrostatically charged rotating bodies can cause damage, particularly in their roller bearings, due to electric breakdown of the lubricating film. At the winding stations of ↑ material webs, ↑ super brush discharges can occur due to ↑ charge accumulation, which turn into ↑ spark discharges in the bearing ( ↑ electrical discharge machining). This results in crater-like damage to the metal surfaces of the rolling elements and the inner and outer rings ( ↑ gas discharge mark). With the help of conductive additives to the lubricating oil or grease, it is possible to achieve trouble-free charge dissipation through the rolling bearings. Roller coating system. Used for full or partial ↑ coating of ↑ material webs. The wide variety of systems causes just as many problems with electrostatic ↑ charging (a selection is shown below). Printing systems Coating systems Doctor blade system Double side coating system Commabar system Reverse commabar system Slot die system Curtain coating system Hotmelt slot die system Case knife system Rotary screen system Dipping system (Foulard) Powder scattering system Reverse roll coating system Micro roller coating system 2-roller coating system 3-roller combi coating system 5-roller coating system Engraved roller system Gravure roller system Gravure indirect system Flexoprinting system Offset lithography system Hot embossing system Nanoimprint system Inkjet system (Source: www.coatema.de) Roller coating system 331 <?page no="345"?> Roller tester ( ↑ measuring electrode for solids no. 5 b). For the ↑ electrostatic print assist in gravure printing, the ↑ impression roller must have certain resistance values. The roller tester must be used to determine the measured values when the impression roller is at operating temperature ( ↑ tera-ohmmeter). Measurements must be taken at a minimum of three points; a 20 % deviation from the average value is acceptable. Rollers. In Ex-areas, only electrically conductive rollers may be used for both ↑ conveyor belts and roller conveyors as well as for small vehicles in order to safely dissipate any charges that may be generated ( ↑ vehicle tires). It must be ensured that the charge is safely discharged via the roller bearings. [TRGS 727 Sections 3.4 and 8.3.6] Röntgen, Wilhelm Conrad (1845 - 1923). German physicist discovered the so-called X-rays in 1895, which were later named after him. He received the first Nobel Prize in physics for this discovery in 1901. Root-mean-square, ↑ RMS value Rotary balance, ↑ Coulomb ’ s balance Rothschild resistance measurement. Originates from a time when it was not possible to measure currents in the pA-range ( ↑ resistance measurement) and is based on the discharge ↑ time constant of a capacitor: A defined capacitor is charged by a measuring voltage source (e. g. 1000 V) and then discharged by the resistance to be measured. The voltage curve is recorded by a ↑ static voltmeter, the time to reach the half value is measured and the resistance is calculated. The Rothschild resistance measurement has a high degree of accuracy but is cumbersome to use in the form described. In contrast to the Rothschild resistance measurement, there are tera-ohmmeters that measure the charging time of a measuring capacitor (in the ms-range) with high accuracy and convert it into resistance values. {Appendix M.6.2} Rotogravure, ↑ gravure printing Rubber, ↑ caoutchouc Rule of technology, ↑ state of the art Roller tester 332 <?page no="346"?> Rust. Porous, loose, easily crumbling layer of bivalent and trivalent iron oxides. Rust is often caused by electrostatic charging of fast flowing ↑ gases, such as compressed air. In combination with ↑ light metals, rust is a significant hazard in the presence of mechanically generated sparks ( ↑ aluminothermic reaction). White rust is a form of corrosion on zinc and galvanized materials. Rust 333 <?page no="347"?> S Sack (also bag), ↑ packaging, ↑ liner Safe gap, ↑ MESG Safety. The feeling of not being at risk, which is subjectively perceived as certainty about the reliability of protective equipment and objectively represented by the absence of hazard. The distinction between safety and hazard is represented by ↑ risk. Safety extra-low voltage (SELV). Protective measure in which unearthed circuits with rated voltages ≤ 50 V AC or ≤ 120 V DC are operated. They must be safely separated from circuits with higher voltages. If earthing is required to dissipate electrostatic charges, this may be accomplished by a protective resistor R of approximately 1 M Ω without impairing the quality of this protective measure. [IEC 61140] Safety helmet, ↑ personal protective equipment Safety instruction, ↑ operating instruction Safety lamp. A lamp that cannot ignite an ↑ Ex-atmosphere. Encapsulation is mainly used as a protective measure. ( ↑ Davy) Safety-related parameters, ↑ explosion-related parameters, {Appendix B} Safety shoes, ↑ personal protective equipment Safety signs. Are a marking at the workplace that quickly and easily draw attention to objects and conditions that can cause hazards. In the field of electrostatics, safety signs are often used to indicate earthing, e. g. of a drum during refilling ( ↑ warning sign). Safety storage cabinet. Must meet the requirements of the regulations applicable to the location where it is installed. For the storage of flammable liquids, [EN 14470-1] applies. If, for example, the interior is declared as Ex-zone 1, all conductive objects must be earthed, which can be done via the shelf, for example, if it is not covered due to misunderstood cleanliness requirements. Saturated vapor. Dry vapor that becomes visible only when it escapes into the atmosphere and condenses. ( ↑ wet vapor) Saturation quantity of the air, ↑ humidity Saturation vapor pressure. State at which the vapor and condensate phases of, for example, a flammable liquid is in thermodynamic equilibrium. It takes some time to reach saturation vapor pressure, so it is not referred to as vapor pressure. Sawtooth curve. Periodically recurring phenomenon of self-discharge. Sawtooth curves occur, for example, when the 2 kV voltage gauge head for the ↑ influence electrostatic field <?page no="348"?> meter is used, when the measured voltage breaks through the air gap between the field plate of the probe and the meter (at about 4 kV). This may damage the meter. Scanning force microscopy (SFM). Method for measuring surface charges: An oscillating cantilever is excited by the ↑ piezo effect above the sample at its resonance frequency (20 - 300 kHz). Its free end facing the sample has a very fine pin (pyramid or cone 3 - 4 μ m high, base area 9 - 16 μ m, pin radius 5 - 25 nm). When approaching the sample surface up to about 100 nm, interaction forces of various types ( ↑ Van der Waals forces, electrostatic attraction or repulsion, dispersion forces, etc.) lead to a change in the resonant frequency of the cantilever or, if the excitation frequency is fixed, to a decrease in the oscillation amplitude. A control circuit ensures that this amplitude damping is kept constant as the surface is scanned. As a result, the distance to the surface remains constant and threedimensional height information can be obtained from the control signal. The quality of the image ranges from the representation of atoms arranged in the crystal to fields of view of about 100 × 100 μ m 2 . A variant of this technique as an analytical instrument uses metallized cantilevers and pins and attaches the insulating sample to a counter electrode. If a circuit is closed between the vibrating pin via the varying air gap capacitor and the sample capacitance to the flat counter electrode, alternating currents can be measured ( ↑ Kelvin voltmeter). A variation of the local surface charge leads to a varying influence of the ↑ image charge in the metallized measurement tip. Due to the distance dependence of this effect, AC currents in the pA-range can be measured at a frequency corresponding to the oscillation frequency of the cantilever. No external power supply is required. The measurable charge contrast depends on the ↑ electron emission energy and the Fermi level of the contacting materials, as well as on the electrical conductivity and dipole properties. [Krivcov, A. et al. (2019)] Related methods allow the spatially resolved representation of DC field potentials, the polarity of ↑ ferroelectrics or the potential distribution across microelectronic devices, even synchronized with the operating clock of e. g. processors (several MHz). Schering bridge. A special measurement bridge named after H. E. M. Schering (1880 - 1959) for determining a ↑ capacitance and its ↑ dissipation factor. The Schering bridge is mainly used as a high voltage bridge to determine the frequency dependence of ↑ dielectric losses. ( ↑ bridge network) Schwenkhagen, Hans Fritz Carl (1900 - 1958). German electrical engineer and university lecturer developed the operating principle of the ↑ influence electrostatic field meter ( ↑ EFM) in 1930 while working in industry. Screen printing (also known as serigraphy or silkscreen). A through-printing process in which the ink is transferred to the substrate, usually with a plastic squeegee, through a fine-mesh fabric (usually a plastic screen). The non-image areas of the mesh are covered to form the printing plate. This creates charges that can reduce print quality. SDM, short for socketed device model. It is a rarely used ↑ model that simulates the discharge of an electrostatically charged device by contacting the device with a test socket in the test system ( ↑ HBM). SDM 335 <?page no="349"?> SDM was developed as a more effective test option for ↑ CDM. In contrast, SDM testing can also be performed in an ↑ ESD tester, which is also suitable for HBM and ↑ MM with only a few modifications. With the SDM, a certain part of the ESD tester is always connected to the ↑ DUT via the test socket, which are charged together and also discharged to ground. This forces a higher amount of charge through the DUT during SDM. In this respect, the test is harder than CDM. On the other hand, due to the additional parasitic capacitance of the ESD tester, the rise time of the discharge is longer than with CDM, and the test is therefore softer than with CDM. Accordingly, both effects together result in an approximation of the test severity of CDM and SDM. In this context the SDM is an alternative to the CDM and is used where the very complex CDM tests cannot be performed due to the time required. When SDM tests fall below critical failure thresholds, a CDM test can be used to further investigate the sensitivity of the DUT in specific cases. [ANSI/ ESD S5.3.1] Seal, ↑ gasket Second. ↑ SI base unit [s] for the time t. It is 9 192 631 770 times the period of the radiation corresponding to the transition between the two hyperfine structure levels of the ground state of atoms of the nuclide 133 Cs. [DIN 1301-1] Secondary cell. Represents an ↑ accumulator and, unlike the ↑ primary cell, can be discharged and recharged. ( ↑ lithium-ion accumulator), [IEC 62485-1] Secondary electron. Released when electrons strike a material ( ↑ gas discharge). The yield of this so-called secondary electron emission depends on the irradiated material and the energy of the primary electrons and can be up to a factor of 20. This effect is used, for example, in secondary electron multipliers, where multiplier sections (dynodes) can be connected in series to achieve amplification factors of 10 8 . Secondary ionization, ↑ ionization Sedimentation (of dust, including metal). A constant hazard in manufacturing areas. It can cause a fire if ignited by an external ignition source. This creates a whirl, which can form an explosive ↑ dust-air mixture. Whirling can also be caused by vibration and ventilation/ air drafts. Regular removal of deposits is therefore an important safety measure in ↑ explosion prevention. Seebeck, Thomas Johann (1770 - 1831). German physicist discovered the thermoelectric ↑ Seebeck effect in 1821. Seebeck effect. Depending on the combination of materials, a temperature-dependent ↑ thermoelectric voltage is generated at the contact point of two different conductors in an electrical circuit when heated. The Seebeck effect is the inverse of the ↑ Peltier effect and is used technically to measure temperature and to generate electricity directly from heat. A current application of the Seebeck effect is to thermoelectrically convert the heat loss at the exhaust muffler in premium car combustion engines into direct current, e. g. to replace an “ alternator ” . Seal 336 <?page no="350"?> Selenium drum. In electrostatic copiers, a selenium-coated drum serves as a ↑ photo semiconductor for recording and transferring the latent ↑ charge image ( ↑ xerography). Self-conductive plastic, ↑ conductivity Self-discharge. The ↑ time constant for self-discharge of a charged material ( ↑ relaxation time) is the product of its ↑ volume resistivity ρ v and its ↑ permittivity ε , which is the product of the electric field constant ε 0 and the relative permittivity ε r {Appendix M.1}. Although self-discharge is independent of the size and shape of the charged material, e. g. the liquid in a tank, its calculation should be used only as a guide. For example, the question of the ↑ dwell time after which the charge on the surface of a liquid has dropped to harmless values (e. g. for sampling) can only be answered reliably by measurement. [TRGS 727] ● Self-discharge under reduced air pressure is a special form of ↑ ionization. According to ↑ Paschen ’ s law, the electric breakdown strength of a gas is largely proportional to its pressure. Therefore, under reduced air pressure (10 - 50 mbar), highly charged plastic surfaces will cause ionization of the surrounding gas even without the involvement of ↑ electrodes, thereby discharging themselves. This effect is exploited during ↑ vacuum deposition to eliminate interfering charges by discharging the charged plastics by allowing them to remain in a pre-vacuum for a short time before introducing them into the high vacuum. Self-induction. Causes an ↑ induced voltage in a current-carrying conductor when the current strength changes, which, according to ↑ Lenz ’ s law, is directed in such a way that it counteracts the change in current overtime ( ↑ resistance). ● The self-induction voltage generated in the supply lines when an inductive circuit is closed is polarized in such a way that it slows down the steep rise in current. This damping effect can already be detected in supply lines, e. g. on switching sparks. If ↑ gas discharges occur without leads (i. e. free of self-induction), e. g. with ↑ brush, ↑ propagating brush and ↑ thunderstorm lightning-like discharges, this attenuation is missing; the current pulses are correspondingly high and can cause faults in electronic devices ( ↑ ESD), among other things. ● When opening, on the other hand, the coil magnetic field is reduced. This leads to a self-induction voltage, which is polarized in such a way that the coil current tries to continue flowing in the same direction, thus delaying the reduction of the magnetic field. This can lead to arcs at the opening contact, which can also interfere with electronic devices as so-called ↑ bursts. Self-induction 337 <?page no="351"?> Semiconductor. Solids whose electrical resistance lies between that of metals and insulation materials ( ↑ nonconductor), and which are divided into: ● Intrinsic semiconductors, which become semiconducting when energy is applied. The ↑ electron in the conduction band and the ↑ defect electron in the valence band become mobile. ( ↑ band model) ● Doped semiconductors ( ↑ doping). Foreign atoms in small concentrations can change resistivity by dimensions. An electron of the impurity atom becomes freely mobile by adding very little energy. In the presence of donors, the negatively charged electrons and in the presence of acceptors, the positive defect electrons are responsible for the conductivity (impurity semiconductor). [Wedler, G., Freund, H.-J. (2018)] Semiconductor counter. Detector for ↑ gamma radiation. The effect that electromagnetic radiation generates free charge carriers in ↑ semiconductors is utilized. Semiconductor counters are well suited for the spectroscopy of gamma radiation due to their highresolution capacity. Semiconductor diode. Electronic component with at least one ↑ PN junction acting as a rectifier. The blocking layer width between the nand p-conducting material is increased if the positive pole is connected to the n-conductor and the negative pole to the p-conductor when a voltage is applied ( ↑ variable-capacitance diode). This polarity direction is called blocking direction and has a high DC resistance (blocking direction M Ω to G Ω ). When the polarity is reversed, the blocking layer width of the PN junction is reduced to such an extent that a forward current is generated (forward bias m Ω to Ω ). As the characteristics of semiconductor diodes have steep edges in the forward and blocking direction, they can also be used for voltage or current limiting ( ↑ surge arrester). Separation of substances. By utilizing the principles of ↑ charge displacement, ↑ influence, ↑ Coulomb force and the conditions of ↑ charge double layer and different conductivities ( ↑ surface resistance, ↑ permittivity), substances can be separated, deposited or moved towards an electrode in an electrostatic field. This requires that the particles have a distinctly different ↑ triboelectric series and are sufficiently dry. [Dascalescu, L. et al. (2017)] It should be noted that polarity and charge level can be significantly influenced by targeted contamination of the surfaces with ↑ charge control agents (e. g. urea), plasma or electron beam treatment. Semiconductor 338 <?page no="352"?> One of the most common principles is the corona roller separator, in which the electrically conductive and insulating particles to be separated can be charged on a conductive cylinder and thus separated. The main problem with electrostatic separation processes is achieving reproducible charging by friction between the particles to be separated and the wall material. Repeated runs lead to an enrichment effect and thus to better separation results. The dielectric constant of the materials to be separated can also be altered by suitable substances, so that even very similar materials such as ABS and PS {Appendix C} can be separated reliably and with over 99 % purity. ● Filtering technology (precipitation) is a very broad field: - A ↑ DC low-energy plasma can be used to remove liquid and particulate components from a gas stream, such as the crankcase of an internal combustion engine, over a short distance. In contrast to electro filtration, more than 1.5 times the breakdown voltage - related to the distance between the electrodes - is applied. [SE Section 8.2.13] - Electro filtration has a high efficiency (up to 99.5 %) and is therefore mainly used for exhaust gas and exhaust air purification due to the low pressure drop. Relatively long separation sections are required, and the operating voltage must be well below half the breakdown voltage to avoid unwanted breakdowns. In this technology, electrically charged ↑ aerosols and/ or dust particles are deflected from their trajectory by electric fields ( ↑ deflection) and brought to separation. To be highly effective, the particles to be separated must be sufficiently charged by ↑ corona charging (up to about 70 kV DC), which generates gas ↑ ions. When a gas ion encounters a suspended particle, its charge is distributed more or less rapidly over its surface, depending on its conductivity. Separation of substances 339 <?page no="353"?> The figure shows a separator through which the particle-laden gas stream passes. In its axis are thin metal wires that are brought to such a high negative potential by a high voltage source that corona charging occurs. At the same time, an electric field is created that is directed toward the wall of the separator, which directs the negatively charged particles of the gas stream toward the positively charged wall (collecting electrode). The particles remain there if their resistivity ρ v is within the following unfavorable ranges ρ v ≤ 100 Ω m: The particles are discharged at the collecting electrode and immediately repelled (as they are now charged in the same direction). ρ v ≥ 1 G Ω m: The particles form a charged layer on the collecting electrode until a breakdown ( ↑ back-spraying) occurs, causing the dust layer to detach locally. Since electrostatic precipitators are mainly used for flue gas cleaning, it should be noted that the particles to be precipitated are subject to a strong ↑ temperature influence and the resulting change in conductivity. ( ↑ charging electrode, ↑ Coulomb ’ s law, ↑ electro aerosol, ↑ filter, ↑ charge detection, ↑ useful application) Separation process. Separation of materials of the same or different material composition or their ↑ crushing. Depending on the number of contact points, more or less “ fragments ” (in the nm-range) of the respective other material partner will remain on the surfaces involved. Since the cleavage planes of the fragmented surface particles are preferably located near mechanical defects, but the latter are a preferred location for ↑ trap electrons, charge transfer occurs. Ions dragged along during the separation process also cause ↑ charge transport and thus ↑ charging. Separation speed. In addition to the influence of the ↑ surface resistance, the speed at which the contacting substances are separated is mainly responsible for the evaluation of ↑ chargeability. If the separation speed is high enough, even substances that are generally considered to have dissipation capability can be charged, e. g. water when sprayed at a nozzle under high pressure ( ↑ high-pressure cleaning). [Baumann, F. (2023)] Separator. Widely used term for the separation of substances, e. g. centrifuge or semipermeable separation in a ↑ capacitor. ( ↑ separation of substances) Series connection. Combination of active or passive two-terminal networks in a series as one current path ( ↑ resistance, ↑ capacitance). When active two-terminal networks are connected in series, the internal resistances and the short-circuit currents change. ( ↑ parallel connection) Calculation according to {Appendix M.6.4.6 and M.7.1.5}. SFM, short for ↑ scanning force microscopy Separation process 340 <?page no="354"?> SG, short for surge generator. It is primarily used to simulate thunderstorm lightning and is also used in research into ↑ NEMPs. The SG can be found in many different forms in high-voltage laboratories, where it is used to test the high-voltage resistance of electrical devices by artificially generating flashovers. In principle, an SG consists of several capacitors that are charged in parallel and then connected in series (voltage multiplication). The capacitors discharge and a defined voltage with a maximum value of up to several megavolt is generated, to which the object to be tested is exposed via a spark gap. (A pulse from an SG is generally fatal to humans in the event of direct contact! ( ↑ danger of electric shock)). [IEC 61000-4-5] Shell effect (sheath effect). In the case of ↑ plastics whose electrical resistance is to be reduced by finely distributed conductive additives (e. g. carbon black ( ↑ carbon), steel fibers), a decrease in the concentration of conductive particles can often be observed in the surface layers near the surface. This is caused by the tendency of the molten polymer to envelop the conductive particles ( ↑ wettability, ↑ surface tension) and results in the electrical resistance on the solidified surface of the finished part being significantly higher than inside the material. After removing this μ m-scale shell layer, it may be possible to achieve the desired low resistivity values. This shell effect has little effect on the antistatic properties of a plastic part but can cause erroneous measurements if the test voltage is too low ( ↑ surface resistance). Since experience has shown that these sheath layers are already penetrated at voltages of around 1000 V, there is generally no ignition risk. To detect the shell effect, measuring devices can be used that automatically increase the measuring voltage in small steps up to 1000 V and measure the voltage and resistance during breakdown. [SE Section 3.5.3], [Brunner, J. (2019)] Shielding. In electrically conductive substances (e. g. also in polymers with added conductive carbon black ( ↑ carbon)), the shielding effect for ↑ electromagnetic radiation is mainly caused by ↑ eddy current losses, i. e. the ↑ absorption increases with increasing conductivity. Hysteresis losses occur in ferromagnetic materials (e. g. also in polymers with added steel fibers) and also in ferroelectric materials (e. g. also in polymers with added barium titanate); a broad hysteresis curve means high absorption. The absorbed radiation energy is either converted to heat in the absorber (heat of absorption) or used to excite atoms or molecules. The figure shows the absorption of electromagnetic radiation by a shielding wall element (reflection attenuation), but without considering the refraction effect. Shielding 341 <?page no="355"?> ● Shielding when measuring high-resistance systems (resistance > G Ω ), parasitic potentials can occur in the measurement circuit due to electric or magnetic fields from the environment and falsify the measurement result. Electric fields, e. g. from charged persons, act by ↑ influence. If magnetic fields occur in the measurement circuit, a parasitic potential is generated by ↑ induction. Protection against external electric fields can be achieved by electrically conductive shielding ( ↑ Faraday cage). The influence of magnetic fields is reduced by small cross sections of the measuring circuit for magnetic field lines or by soft magnetic shielding materials ( ↑ Permalloy TM ). ● The shielding effect is used in the ICM-2 measuring device of the Saxon Textile Research Institute e. V., Chemnitz (STFI) to determine the electrostatic dissipation properties of protective clothing textiles or similar flat structures. [EN 1149-3], [SE Section 3.14.2] Shock, ↑ electric shock Short-circuit. Conductive connection between conductors (active parts) that are necessarily live in relation to each other due to a fault or deliberately caused short-circuit, when there is no useful resistance in the fault circuit ( ↑ conductor short circuit). In the electrostatic discharges that form plasma, the supply of electrical energy is converted into light and heat in a short-circuit and the current flow is reduced to zero. These discharges are usually one-time events due to the lack of further energy supply. [IEC 60050] ● Short-circuit current, characteristic of an active two-pole ( ↑ current source). It is the electric current between the poles when there is no or negligible resistance. ● Short-circuit current strength enables the internal resistance of a ↑ voltage source to be determined, which is the quotient of ↑ open circuit voltage and the short-circuit current strength. Shrink process, ↑ cast process Shunt. An electrical component connected in parallel with an electrical conductor (circuit) in order to divert a partial current from this part. It is often used, for example, to extend the measuring range of ammeters and is therefore also referred to as a parallel resistor or current measuring resistor. A series resistor is used to extend the measuring range of a voltmeter. The parallel connection of a capacitance is used, for example, to stabilize the voltage or to filter frequencies. Shock 342 <?page no="356"?> SI / SI base units / derived SI units, short for French: Systéme International d ’ Unités. The name and the abbreviation ‘ SI ’ were defined at the 11th General Conference on Weights and Measures (CGPM) in 1960. The meter, kilogram, second system of units (MKS system) was generated from a large number of units of the CGS system (centimeter, gram, second) - in particular due to the inconsistency between the systems of electrostatics and electromagnetic units of measurement and the lack of coordination between the various disciplines. New definitions have been in effect since May 20, 2019, and all SI units refer to the defined values of the seven selected ↑ natural constants (SI base units). For static electricity, the new definitions of the base units have hardly any impact, as we still have to make do with deviations in the two-digit percentage range when taking measurements. The derived SI units are coherent products, i. e. products, quotients or power products of SI base units formed with the numerical factor 1. { ↑ Appendix M}, (www.bipm.org) Siemens. Derived ↑ SI unit [S] of the electrical ↑ conductivity κ , named after W. v. ↑ Siemens; reciprocal of the unit of ↑ resistance: 1 S = 1/ Ω = s 3 A 2 / m 2 kg. In the Englishspeaking world, the backward spelling of Ohm “↑ mho ” is preferred instead of Siemens. {Appendix M.7.2} Siemens, Werner von (1816 - 1892). German engineer and entrepreneur made fundamental inventions in the field of electrical engineering and was the founder of electrical power engineering. Sieve analysis. Method for determining the particle size distribution of a fine-grained ↑ bulk material by sieving with superimposed sieves of different mesh sizes (prerequisite for determining the ↑ MIE). [DIN 66165-1 and 66165-2], [ISO 3310-1, 3310-2 and 3310-3] Sieving. It is not known to be a particularly critical process from an electrostatic point of view, provided that all conductive parts of the equipment are earthed. As a rule, only small containers are filled by sieving, usually in slow processes, so that higher charges are not to be expected. [TRGS 727 Section A1.4] gives a specific charge of 10 -5 to 10 -3 μ C/ kg. Silica gel. Glass-hard grains of silicon dioxide that can absorb up to 20 % of their weight in water vapor due to their large internal surface area. Silica gel can be regenerated by heating and is usually colored with a moisture indicator (cobalt compounds). Blue coloration indicates a dry state, pink coloration indicates wet state. Silica gel is used to keep the inside of moisture-sensitive equipment dry. Silicate glass, ↑ glass Silicone caoutchouc, ↑ caoutchouc Silicone oil. Has excellent electrical insulation properties due to its high ↑ volume resistivity (up to 1 P Ω m). Its charge is correspondingly high as it flows through ↑ hoses, which can increase to such an extent with highly viscous silicone oil that ↑ propagating brush discharges occur during filling. Silo (Spanish: silo, “ grain pit ” ). Large container for the storage of bulk material, which can be considered a rigid ↑ packaging means ( ↑ IBC) with respect to electrostatic charges. Due to its size, the following types of discharge must also be considered: Silo 343 <?page no="357"?> - ↑ Cone discharges, which can form on the surface of the bulk material, ( ↑ super brush discharge), - ↑ thunderstorm lightning-like discharges, which are considered possible in the dust cloud above the bulk material. For the latter, investigations have shown that they do not occur even with very large dust loads with a volume < 100 m 3 or up to 3 m in diameter and any height. In larger silos, there is no risk of ignition if the electric field strength is less than 500 kV/ m over the entire area. The level of electrostatic charge in a silo also depends on the type of bulk material feed; it is particularly high in ↑ pneumatic conveyors. Separation in an attached ↑ cyclone can reduce the product charge by up to 90 % due to the increasing ↑ charge density ( ↑ charge transfer). [TRGS 727] Sink (current sink, consumer, counterpart to the ↑ current source). To test electrostatic discharges ( ↑ ESD) against electronic components, a simple circuit is usually formed in which the electrostatic discharge energy is first stored as a voltage in a capacitor C. The stored energy is then discharged via a circuit consisting of an active resistor R and an inductive reactance X L to a sink, which may be an electronic component to be tested. The discharge is usually defined by the current waveform, although the stored electrical energy is often an important parameter as well. ( ↑ DUT) Skin depth (also penetration depth) ● It indicates how far electromagnetic radiation can penetrate a material before it is attenuated to 37 % of its original amplitude. This is particularly important for ↑ shielding, since only shielding with a material thickness sufficiently large compared to the skin depth of the electromagnetic radiation to be shielded is fully effective. The skin depth is determined by the ↑ permeability, which is a material dependent property via the relative permeability number. The lower the frequency of a layer hitting a shield, the deeper it penetrates. Therefore, at very low frequencies, shielding may not be possible or may only be possible with materials that have a very high relative permeability ( ↑ Permalloy TM , ↑ skin effect). ● The skin depth of AC current is linearly dependent on frequency: the higher the frequency, the lower the skin depth. For a copper cable with a resistivity of 0.0174 Ω mm 2 / m, the skin depth is 9.38 mm at 50 Hz, 9.38 μ m at 50 MHz, and 93.8 nm at 500 GHz (skin effect). The lower the skin depth, the higher the reflection, e. g. of radar beams. Skin effect. An effect that is linearly dependent on the frequency of the alternating current, in which the current flow is displaced to the surface (skin) as a result of ↑ selfinduction in the homogeneous conductor, because the magnetic field surrounding each conductor generates a counter voltage that is greatest in the center of the conductor (e. g. in the ↑ lightning rod). ( ↑ skin depth, ↑ shielding) The skin effect has practical application in induction stoves. Sink 344 <?page no="358"?> Sliding brush discharge. Generally referred to as ↑ propagating brush discharge. Sliding discharge. Which can occur on ↑ creepage distances. Slippage. Generally, the lag between two links of a transmission caused by poor synchronization or friction. Slippage occurs, for example, when the speed of ↑ material webs is greater than the peripheral speed of a web guide roller in the system. It is the source of high electrostatic charges, especially when guide rollers are in contact with a very small wrap angle, or transport rollers are stiff so that the contact partner “ slips ” . Smoke detector, ↑ ionization fire detector Smoldering fire. Flameless oxidation, e. g. of a deposited combustible dust. It can be triggered by self-heating or when the ↑ glow temperature of dust deposits is reached. A smoldering fire can ignite dust that has been whirled up. Smoldering gas (also pyrolysis gas). Gas produced by incomplete ↑ combustion processes, by endothermic or exothermic decomposition, by ↑ deflagration, by ↑ pyrolysis or by thermally loaded dust deposits (dust deposits generally have a heat-insulating effect and can smolder, for example, on hot surfaces ( ↑ ignition source)). Smoldering gas can cause pressure build-up and/ or form explosive mixtures with air. It should be noted that the ↑ MIE values of smoldering gas are generally much lower than those of the flammable substances from which it is formed. It can be ignited by even weak electrostatic ↑ gas discharges that would not have posed a hazard to solids (e. g. dust pile in a silo). Snow particles. Are generated especially when carbon dioxide flows out of a fire extinguisher due to the rapid expansion of the gas, combined with strong electrostatic charging due to sublimation and aerosol formation. ( ↑ heat of compression, ↑ CO 2 fire extinguishing system) Socketed device model, ↑ SDM Soil resistance (also known as earth resistance or spreading resistance). The electrical resistance of soil depends on its structure and moisture content. It can only be accurately determined for a given site by measurement. The following empirical values for the resistivity of soil types can be used as a guide: Soil resistance 345 <?page no="359"?> Clay approx. 100 Ω m Wet sand, gravel approx. 300 Ω m Dry sand, gravel approx. 1 k Ω m Stone approx. 3 k Ω m In the case of electrostatic discharge, the resistance of all types of soil is sufficient, so that testing can be omitted. ( ↑ cathodic protection), [IEEE 80-2013], [NFPA 70] Soiling ( ↑ contamination). The accumulation of solid, liquid or gaseous (ionized gases) contaminants can have an unexpectedly large effect on the electrostatic behavior of materials. It can lead to a reduction or increase in ↑ electric strength or ↑ surface resistance [IEC 61010-1]. ● Conductive soiling can act as an ↑ antistatic agent on the surface. Dirt adhering to the surface can reduce the contact area on contact and thus reduce the ↑ charging. Currentlimiting resistors on ↑ ionizers can be connected in parallel by the contamination, cancelling their effect, so that ignitable flashes can occur on the generally highly charged ↑ material webs. ● Insulating soiling can reduce or negate the effect of ionizers. With passive ionizers such as ↑ discharge brushes, the discharge current can cause individual filaments to glow and lead to ignition. Pollution of discharge brushes thus becomes an acute fire hazard. ● Insulating liquids, even small amounts of undissolved contaminants (e. g. condensation in gasoline) can cause significant liquid charge in insulating liquids due to the contact surfaces created. ● Flowing ↑ gases can only lead to electrostatic charges due to the liquid or solid impurities ( ↑ aerosols) they carry. [TRGS 727] Solid. When solids ( ↑ bulk material, ↑ granules, ↑ dust) are fed into tanks containing flammable liquids, the explosion prevention measures must be observed. [TRGS 727 Section 6.3.3], [SE Section 7.3.7] Solidification point. Temperature at which a state of equilibrium exists between the solid and liquid phases, or at which a liquid changes to the solid state of matter. Solidification potential. Generated by charge separation when ↑ crystallization occurs at the ↑ solidification point. Solvent. The most common solvent is water. To assess electrostatic hazards, it is necessary to know the conductivity of the solvent ( ↑ charging). They can be classified as: ● Non-polar liquids, such as carbon disulfide, heptane, tetrachloromethane, toluene, benzene, xylene, have low electrical conductivity, are electrostatically chargeable and cannot be mixed with water. ● Polar liquids, such as water, ethylene glycol, ethanol, ethyl acetate, etc., have medium to high electrical conductivity and are therefore generally not considered electrostatically flammable. [TRGS 727 Section 4], {Appendix B} Soiling 346 <?page no="360"?> Solvent vapor. Mixture of the gas phase of a ↑ solvent above the ↑ flash point with air. Depending on the temperature, solvent vapor is usually heavier than air and therefore sinks to the ground (bottom ↑ exhaust system). This can be demonstrated with the setup shown (e. g. with cloth soaked in alcohol). [SE Section 6.10.4] Sorption. Generic term for ↑ absorption, ↑ adsorption and ↑ desorption. Sorption isotherm. Curve resulting from the graphical representation of the dependence of the moisture content of a substance on the relative ↑ humidity of the surrounding atmosphere at constant temperature. The sorption isotherm thus indicates the state of equilibrium between the hygroscopic substance and the humid ambient air ( ↑ water activity). When a moist substance is dried with dry air, this occurs along the desorption isotherm; when it is humidified with moist air, along the adsorption isotherm. Together, the two sorption isotherms form a ↑ hysteresis. Sorting (electrostatic), ↑ separation of substances Source. Singular point with a ↑ charge in the electric ↑ field. Location where the field lines begin ( ↑ point-charge). Space charge. Symbol ρ , unit [C/ m 3 ]. Spatially distributed electric charge formed by charge carriers (mainly of one charge sign), at the edge of which an electric field strength occurs ( ↑ cloud dipole). This can lead to the influence of adjacent conductive parts, resulting in corresponding radii of curvature, ↑ corona or ↑ brush discharges. Space charges can cause electrostatic ignition hazards, e. g. during the filling of reactors or silos with fine-particle bulk materials, during ↑ high-pressure cleaning of large containers, or during the generation of ↑ water curtains. In nature, under a cloudless sky, a field of about 400 V/ m prevails when clouds are present, which is in the kV-range. {Appendix M.3.1.4} Space charge 347 <?page no="361"?> Spark (Gothic: fonk, “ fire ” ) ● Electrical spark, such as occurs when a switch is operated in a high-voltage circuit, is a ↑ plasma interspersed with glowing particles of the contact materials. ● Electrostatic spark is defined as a ↑ gas discharge ( ↑ spark discharge). [TRGS 727 Section A3.1], [SE Section 2.5] ● Mechanical spark, solid particle heated to incandescent temperature and propelled by the application of mechanical energy during friction and separation. In terms of igniting an explosive atmosphere, mechanical sparks that cool as they travel have low ↑ ignitability (e. g. from alloyed steel). However, if they continue to heat up by oxidation with the oxygen in the air and possibly even burst ( ↑ flint), they pose an ignition hazard ( ↑ ignition source). Spark chamber. Electrostatic device for detecting ↑ nuclear radiation. The spark chamber consists, for example, of several metal plates arranged in parallel with potential differences of several 1000 V to each other. Ionizing radiation causes ↑ ionization along its path between the plates, resulting in sparks. The spark track can be recorded. Spark detection device. All ↑ gas discharges in which the ↑ pinch effect occur emit highfrequency signals with a wide range ( ↑ ESD). These signals can be used to detect gas discharges. The emitted high-frequency oscillations can be received by a spark detection device in the long and short-wave range. The main spectrum is in the range of 2 - 40 kHz. Weak high-frequency signals up to the high MHz-range can be detected but cannot be detected with such an indicator. The spark detection device cannot be compared to a charge meter, such as a handheld ↑ coulometer, which must detect the energy of a spark W = ½ C × U 2 . Spark discharge. Occupies a special position among electrostatic ↑ gas discharges: - It is a discharge between two electrodes. - The converted electrical ↑ energy can be calculated. The spark discharge from a charged ↑ capacitor is shown schematically. Discharge begins when the field strength between the two electrodes exceeds the ↑ breakdown field strength of the atmosphere, with the discharge channel extending the entire length between the electrodes. There is always a ↑ pinch effect with heating of the surrounding gas and resulting ↑ ignitability for flammable mixtures ( ↑ MIE). The spark gap becomes conductive due to the ↑ plasma and a short current flow. The energy converted in a spark discharge initially represents the gross amount of the calculated value, because the losses occurring in the leads are not included. If the capacitor contains a ↑ dielectric, it must be expected that some of the charge will remain there as residual polarization and will not be converted in the spark discharge. Spark 348 <?page no="362"?> Spark energy. Energy that can be calculated for a ↑ spark discharge from the ↑ capacitance or the charge of a ↑ capacitor and the applied voltage. It should be noted that only the gross energy can be determined in this way, i. e. the residual charge remaining in the capacitor and the losses in the cables and electrodes are not considered ( ↑ MIE). {Appendix M.6.1} Spark erosion, ↑ electrical discharge machining Spark gap. The distance between two electrodes bridged by a ↑ spark in a gas discharge. Since the length of the spark gap is determined only by the voltage between the electrodes and their shape under constant gas conditions (gas type and gas pressure), it can be used to measure the voltage in a ↑ spherical spark gap. Spark ignition. ↑ Sparks can ignite flammable mixtures depending on the electrical energy converted in them ( ↑ spark discharge). Spark inductor. High-voltage transformer (open iron core with coaxially arranged coils) operated by pulsed direct current (mostly electromechanical circuit breakers). The secondary voltage (dimension 100 kV) is highly asymmetrical, resulting in a pronounced polarity. In the past, spark inductors were often used to operate ↑ gas discharge tubes. ( ↑ Wagner ’ s hammer) Spark quenching. Reduction of the opening spark at electrical contacts by connecting a ↑ capacitor in parallel, which then stores part of the electrical energy. When the contact is closed again, the capacitor is discharged again. Spark quenching can also be achieved by wiring with ↑ diodes ( ↑ junction capacitance). Sparkover at a fiber bridge, ↑ fiber bridge sparkover SPD, short for surge protection device, ↑ surge arrester Specific charging. A term often used in connection with the triboelectric charging tendency ( ↑ frictional charging) of substances, but which does not do justice to the term “ specific ” . The magnitude and sign of the charge generated during the separation process depend not only on the properties of the material being tested, but also on the properties of the material against which it is being tested. In addition, the nature of stress during the separation ↑ charging process also has a significant influence on the amount of charge. As a result, neither a definition nor a standardized test method for specific charging is possible. ( ↑ influencing factors) Specific earth resistivity ρ E , ↑ soil resistance Specific earth resistivity 349 <?page no="363"?> Specific surface (according to [ISO 9277]). The surface area of a solid (e. g. powder) in relation to its mass in [m 2 / g]. It can be determined, for example, by ↑ adsorption of gases. Activated carbon, for example, has a specific surface area of up to 2000 m 2 / g. Specimen. A body with negligible (low) response to the field into which it is introduced. The effects of the field variables on the specimen are to be determined. Ideally, the test object itself does not affect the force field and is point-like. ( ↑ point-charge) Sphere electrode, ↑ measuring electrode special application Spherical spark gap. Relatively simple method of measuring high DC, surge, and AC voltages with an accuracy of about 5 %. Voltage measurements with the spherical spark gap are based on the defined relationship between the ↑ breakdown voltage in air and the ↑ clearance. The measurement method is described in [IEC 60052], where the voltage values from 2 - 200 kV are assigned to the gap widths in a table, considering the corresponding sphere diameters. Spherics. Atmospheric impulse radiation, caused mainly by lightning discharges. They emit electromagnetic waves in a broad frequency band whose wavelength is mainly determined by the length of the lightning channel acting as an antenna. Corresponding to lightning lengths in the km-range, the frequency band of spherics is in the range of 5 - 10 kHz. Due to their long wavelength, spherics can be detected over long distances (megameters) with appropriate low-frequency receivers and are used in meteorology for thunderstorm forecasting, thunderstorm statistics, and for the ↑ lightning detection system. Spike discharge, ↑ corona discharge Spill containment basin. ↑ Floor pan, which is primarily used for water protection and to contain the contents of storage tanks in the event of a spill. If flammable liquids with a low ↑ flash point are stored, the earth leakage resistance of the interior of the spill containment basin must be < 100 M Ω . Splash guard. In Ex-areas of Zone 1, the splash guard is subject to the ↑ area limitation or must be dissipation-capable and earthed if this is exceeded. Split core type current transformer. Special design of the ↑ current transformer whose iron core can be opened like a pair of clamps. This allows a current-carrying conductor to be enclosed and its AC or pulsed current to be determined without contact. Spray charging, ↑ coating, ↑ spraying Spray painting. A process in which the combination of coating material and gas (e. g. compressed air) generates high electrostatic charges. Persons performing spray painting must be earthed (usually through the spray gun). The person ’ s ↑ leakage resistance - even through gloves - must be < 10 8 Ω ( ↑ personal protective equipment). ( ↑ coating) Spraying of liquids (e. g. in ↑ high-pressure cleaning and ↑ tank cleaning) and solid particles (e. g. ↑ CO 2 fire extinguishing systems). It is sometimes an underestimated source Specific surface 350 <?page no="364"?> of dangerously high electrostatic charges. The entire system must be considered when evaluating potential charges: ● Piping: Due to the ↑ Debye length, which depends on the electrical conductivity of the liquid, charge separation ( ↑ charging) occurs as the liquid flows through. The Debye length describes the thickness of the diffuse layer of ions of one polarity. The ions of opposite polarity are attached to the tube wall by adsorption. Liquids with high electrical conductivity have a low Debye length. The adhesion conditions on the tube wall result in low velocities in the diffuse layer region and low charge separation. Liquids with low electrical conductivity undergo charge separation due to the larger Debye length. [Wedler, G., Freund, H.-J. (2018)] ● Outlet nozzle: The Helmholtz double layer that forms when the nozzle surface comes into contact with the liquid is broken ( ↑ charge double layer). Part of the charge remains on the nozzle (e. g. conduction to earth in the case of metal nozzles! ), while the opposite charge is carried away with the medium. High separation speeds and low electrical conductivity of the liquid and/ or high electrical resistance of the nozzle reduce the charge backflow and favor charge separation [Lüttgens et al. (2020)]. High separation speeds during high pressure atomization are sufficient to generate high space charge densities by charge separation of demineralized water at the conductively earthed outlet nozzle [Baumann, F. (2023)]. ● Liquid jet: Droplet disintegration due to hydrodynamic instability or upon impact of the droplets leads to charge separation, preferably in liquids with high electrical conductivity such as water ( ↑ Lenard effect, ↑ Rayleigh limit, ↑ atomization). The ↑ volume charges generated during spraying can lead to ignitable ↑ gas discharges. [TRGS 727] Spreading resistance of an earth electrode. Resistance of the earth measured between an earth electrode and a reference electrode. [IEC 60050] Spring-tongue electrode, ↑ measuring electrode for solids no. 3 Spunbond, ↑ nonwoven Square ohm. Occasionally used as a unit [ Ω □ ] of the ↑ surface resistivity ρ s instead of Ohm [ Ω ]. The specification in square ohms indicates that the measured value has been converted to a ↑ measuring electrode with a square measuring surface. {Appendix M.7.1.3} St. Elmo ’ s fire. Named after St. Erasmus (Italian slang: “ Santo Elmo ” ) is one of the mysterious phenomena of ↑ thunderstorm electricity. St. Elmo ’ s fire can be observed in the dark on pointed, exposed objects (e. g. ship masts, summit crosses, pins on the wingtips of an airplane) when thunderclouds pass through. During a thunderstorm, the air-electric ↑ field on these objects can increase to breakdown field strength and then lead to a ↑ corona discharge. However, efforts to safely discharge thunderclouds in this way have not been successful. In fact, during a thunderstorm, reverse charges are emitted from the branches and leaves of trees, as well as from the hair of humans and animals due to the tip effect ( ↑ back-spraying). This affects the air-electric field and creates a space-charge field that alters the original thunderstorm field (see figure next page). St. Elmo ’ s fire 351 <?page no="365"?> Standard condition. State of a solid, liquid, or gaseous substance under certain physical conditions. The technical standard condition is characterized by the standard atmospheric pressure (p 0 = 101.325 kPa at 20°C), also known as the ↑ atmospheric condition, and temperature (T 0 = 273.15 K = 0°C). Standard gap width, ↑ MESG Standardization (Latin: norma, “ guideline, rule, angle ” ). Uniform definition of a rational order in technology and business, where each standard is intended to represent an optimal solution. Standardization sets benchmarks for quality and safety, facilitates design and production, and contributes to understanding in science and technology. ( ↑ DIN standard) - ↑ ISO - International Organization for Standardization - ↑ IEC - International Electrotechnical Commission - CEN - Comitée Européen de Normalisation - CENELEC - ↑ Comitée Européen de Normalisation Electrotechnique - ITU - International Telecommunication Union - ETSI - European Telecommunications Standards Institute - ↑ DKE - Deutsche Kommission Elektrotechnik Elektronik Informationstechnik in DIN und VDE - ↑ DIN - Deutsches Institut für Normung e. V. - ↑ VDE - Verband der Elektrotechnik Elektronik Informationstechnik e. V. Standard condition 352 <?page no="366"?> Standards of electrostatics. In the electrostatics series of standards, the main number is 61340, which may then be specified in up to two subtitles (e. g. 61340-4-2: Electrostatics - Part 4-2: Standard test methods for specific applications - Test methods for clothing). In Germany, the IEC standards are adopted and therefore have the same numbering. In general, only older standards and standards developed by other organizations have different numberings (e. g. [NFPA 77]). Start field strength (or critical field strength). Field strength value from which there is an exponential increase in the number of free electrons at the onset of a ↑ gas discharge ( ↑ Townsend discharge). State of matter. Describes the state forms of a substance caused by pressure and temperature: solid - liquid - gaseous ( ↑ sublimation). When the state of matter changes, considerable energies are always released or absorbed. In electrostatic terms, the transitions of a substance from one state of matter to another can lead to electric charging and changes in conductivity. State of the art. Must always be considered in the context of the generally accepted rules of technology and the state of the art in science and research. The assessment of where, for example, a process or technical solution is to be classified can be based on the extent to which it has proved itself in practice and the extent to which it is recognized. It presents the technical possibilities based on reliable scientific and technical knowledge. In particular, the state of the art should be determined based on comparable processes, equipment or operating methods that have proven themselves in practice. It is used in regulations, ordinances and codes of practice and considers “ economic justifiability ” . In patent law, the state of the art refers to processes and devices that have already been published. It can also be defined as the best performance available on the market. ● According to case law, the accepted rules of technology are generally accepted if they represent the prevailing view among the majority of experts. The rule must be a. generally accepted in the scientific community; and b. put into practice, tested and proven. Both levels must represent the prevailing view of experts. Legislators or regulators refer to the accepted rules of technology to ensure that laws and regulations are not overtaken by technological developments, but always consider the current prevailing opinion of experts. The accepted rules of technology are of great importance for the assessment of criminal or civil liability: those who comply with them have the initial appearance of not having acted negligently. ( ↑ DIN standard) ● The state of the art in science and research represents a dynamic state of knowledge that is still evolving and needs to be verified from a technical and safety perspective. [Karsten, U. B., Lawicki, T. (2012)] State of the art 353 <?page no="367"?> Static conductivity. Conductivities and relaxation times of some liquids are in [IEC/ TS 60079-32-1] and {Appendix B}. ( ↑ conductivity) Liquid Conductivity [S/ m] Relaxation time [s] Low conductivity highly purified paraffins 10 -14 2000 lubricating oils 10 -14 to 10 -9 0.02 to 2000 typical paraffins 10 -13 to 10 -11 2 to 200 purified aromatic compounds (toluene, xylene etc.) 10 -13 to 10 -11 2 to 200 kerosene (petroleum) 10 -13 to 5×10 -11 0.4 to 200 fuel depending on sulfur content * 10 -13 to 10 -10 0.2 to 200 white oils 10 -13 to 10 -10 0.2 to 200 ethers 10 -13 to 10 -10 0.2 to 200 gas oil 10 -12 to 10 -10 0.2 to 20 aromatic brand solvent mixtures 10 -12 to 10 -9 0.02 to 20 proprietary aromatic solvent mixtures 5 × 10 -12 to 5 × 10 -11 0.4 to 4 natural gas condensate without corrosion inhibitor 10 -11 to 10 -10 0.2 to 2 Medium conductivity fuels and oils containing dissipative additives 5×10 -11 to 10 -9 0.02 to 0.04 heavy (black) fuel oils 5 × 10 -11 to 10 -7 2 × 10 -4 to 0.4 esters 10 -10 to 10 -6 2 × 10 -5 to 0.2 High conductivity crude oil ≥ 10 -9 ≤ 0.02 natural gas condensate with corrosion inhibitor ≥ 10 -9 ≤ 0.02 alcohols 10 -6 to 10 -4 2 × 10 -7 to 2×10 -5 ketones 10 - 7 to 10 - 4 2 × 10 -7 to 2×10 -4 water (not distilled) ≥ 10 -4 ≤ 2 × 10 -7 pure water 5 × 10 -6 10 -6 (Source: [TRGS 727 Annex F]) * Particularly high charging occurs when using fuels whose sulfurcontaining components have been replaced, e. g. at conductivities < 50 pS/ m and simultaneous sulfur content < 50 ppm. Static electricity. Paraphrase of the term “ electrostatic charges ” to emphasize the distinction from dynamic electricity ( ↑ electrostatics - system comparison). Static voltmeter. Mechanical ↑ electrometer used to measure voltages in the electrostatic sector ( ↑ electroscope, ↑ filament electrometer). The static voltmeter is increasingly being replaced by electronic electrometers. Even ↑ EFMs with a voltage-measuring attachment can be used as static voltmeters. ( ↑ voltmeter) Static conductivity 354 <?page no="368"?> Staudinger, Hermann (1881 - 1965). German chemist, Nobel Prize winner, discovered the macromolecular structure of plastics in 1920. Steam, ↑ vapor Steam electrification machine. Based on the observation that the ↑ aerosols carried along by the flow of expanded ↑ vapor cause charging, attempts were made as early as the 18th century to generate electricity directly from flowing vapor. Steam was produced in a fired boiler, insulated on glass feet, and this steam flowed through a metal rake, also insulated, where it caused charging. However, the efficiency was much lower than in the other ↑ electrification machines. ( ↑ pressure decompression) Steel fiber addition. It is a reliable way to make electrically insulating materials conductive. This effect is exploited in the textile sector by adding very thin staple fibers of stainless steel during the spinning process ( ↑ metal fiber). The decisive criterion is that sufficient dissipation capacity is guaranteed over long distances (e. g. for the dissipation of unwanted charges on filter bags). A conductive network can also be achieved by adding steel fibers to injection molded plastic parts, which has the advantage over powdered conductive fillers (carbon black) of a lower added quantity ( ↑ carbon fiber, ↑ conductive fiber). [TRGS 727], group [EN 1149] Step voltage. Part of the earthing voltage that can be bridged by a person taking a step of 1 m, with the current path running from foot to foot through the human body. The voltage depends on the shoes, the ground and its moisture (soil, concrete, asphalt, gravel, etc.). A voltage funnel is created around the earthing of high-voltage power lines lying on the earth, and also in the event of a lightning strike, where the step voltage can be an indirect danger. The diameter of the funnel depends on local conditions. Depending on the magnitude of the step voltage, a person or animal in the vicinity of the point of impact will bridge a voltage U S , causing a dangerous current to flow through the body via the feet and legs ( ↑ danger of electric shock). The limits for U S2 to U S1 for humans are voltages ≤ 50 V AC and ≤ 120 V DC. [IEC/ TS 60479-1] Sterilization. Use of gas ionization, in particular for neutralizing odours by forming ozone at the ionizing electrode. Stickiness ( ↑ adhesion). Bonding forces between solids of the same or different types. Stimulated state. State of a (micro)physical system (e. g. molecule, atom) with a higher energy than its energetic ground state. Upon emission of ↑ photons, the return to the ground state occurs within a very short time ( ↑ gas discharge). Stimulated state 355 <?page no="369"?> Stoichiometry (Greek: stoicheion, “ basic substance ” , “ element ” ). The study of the quantitative composition of chemical combinations. A stoichiometric ratio of 1 (mixing ratio λ = 1) means that the components added to a chemical reaction dissolve into new combinations without residue. The ignition energy requirement for a combustible mixture passes through a minimum at a stoichiometric ratio of 1 ( ↑ MIE). Storage of hazardous substances. Must be in an appropriate quantity, which should generally not exceed a daily/ shift requirement. ● Active storage. Storage of substances in portable containers that are emptied or filled discontinuously in the place of storage, e. g. as a removal or collection container. The properties of the stored substances determine the regulations to be complied with (e. g. ↑ earthing). ● Passive storage. Storage of substances in filled tightly closed containers that are completely emptied after opening ( ↑ storage classes). ● Storage of flammable liquids. The ↑ BetrSichV applies in combination with the “ Technical Rules ” of [TRGS 509, 721 to 725 and 727]. Storage classes. Hazardous substances are classified into different storage classes according to [TRGS 510], considering their product-specific properties and hazard potential regarding preventive measures (e. g. fire and explosion prevention). The storage classes are based on the regulations of the Hazardous Substances Act and their classification is based on the Hazardous Substances Ordinance ( ↑ GefStoffV). Stray capacitance. For ↑ capacitors, the ↑ capacitance can be calculated from the size and spacing of the conductive surfaces. For large distances between capacitor surfaces (small capacitances), partial capacitances to earth and to other unearthed conductors must be considered and added to the original capacitance as stray capacitance. ( ↑ capacitance measurement, ↑ measurement error) Stray current. Stray earth current that may flow in electrical systems or parts thereof, e. g. - as a return current in power generation systems (e. g. overhead power lines and rails, underground cables), - as a result of an earth fault or ↑ short-circuit (fault in the electrical installation), - due to external magnetic induction with high currents (induction furnaces), - by lightning (e. g. IEC 62305). If stray currents can occur, they must be limited. For example, only ↑ hose lines with a resistance of ≥ 10 3 Ω should be used in these areas to avoid sparking during disconnection. ( ↑ cathodic protection, ↑ ignition source), [ISO 80079-36] Streamer, ↑ thunderstorm lightning Strip resistance. Symbol R ST , unit [ Ω ]. Used to measure the resistance of a strip (50 × 350 mm 2 ) of textile fabric ( ↑ measuring electrode for solids no. 15). [TRGS 727 Section 2] Stoichiometry 356 <?page no="370"?> Sublimation (Latin: sublimare, “ to raise ” ). This describes the direct transition of a substance from the solid ↑ state of matter to the gaseous state (or vice versa) without passing through the intermediate liquid state. The heat absorbed or released in this process is always equal to the sum of the heat of fusion and the heat of vaporization. Sublimation nucleus. Insoluble ↑ condensation nuclei in the atmosphere on which water steam forms ice particles directly, i. e. without prior fog formation, at low temperatures and high humidity ( ↑ cloud dipole). Suction voltage method, ↑ ionizer test Super brush discharge. Strong ↑ gas discharge due to the accumulation of individual charges of the same name on insulating materials, which is only possible if the repelling ↑ Coulomb force of the individual charges is overcome by a “ constraint ” (gravity), e. g. in a silo, when form-fitting plastic trays are stacked, or in the presence of a distant earthed conductor behind the insulating material. The entire charge is released in a ↑ one-electrode discharge ( ↑ ignitability) when a conductive electrode (which can be a person) is approached. ● The best way to detect this is to record the current flow of the discharge oscillographically; conventional hand-held ↑ coulometers have too small a measuring range. A super brush discharge can be generated experimentally with the following setup. Five thin-walled plastic tubes of the same material, charged in the same direction by rubbing, e. g. with a lambskin, repel each other when placed on top of each other between two insulating forks. The Coulomb force causes the tubes to float on top of each other. While only the maximum surface charge density (26 μ C/ m 2 ) can be achieved on the individual tubes, the gravitational or mechanical force causes a much stronger ↑ brush discharge. When a super brush discharge is triggered, the tubes in the forks fall on each other, resulting in the ↑ pinch effect, i. e. heating of the surrounding gas and the resulting ignitability of flammable mixtures. ● Super brush discharge often occurs when processing webs. The webs are charged e. g. when running over rollers and are rolled up again with their charges on the coil. This leads to ↑ charge accumulation on the coil due to the mechanical overcoming of the repelling Coulomb force. Since the coil is generally non-conductive, the charge cannot be dissipated via the winding shaft. The accumulated charge on the coil rises sharply and spontaneously leads to a super brush discharge, which turns into a ↑ propagating brush discharge and, under certain circumstances, into a ↑ spark discharge ( ↑ electrical discharge machining) in the area of the shaft bearing (Photo). If a person or a Super brush discharge 357 <?page no="371"?> conductive, earthed part approaches the highly charged film wrap, a super brush discharge also occurs. [Schubert, W., Ohsawa, A. (2024)] (Source: Durst Phototechnik AG) SuperCap (super capacitor), double layer ↑ capacitor Support basket. Conductive support cages of filter systems must be permanently earthed, especially when insulating ↑ filter materials are used. Surface. In general, a boundary surface that separates a body or a closed piece of space from the rest of the space or from some other medium. ( ↑ contact surface) Surface charge. This describes to the ↑ surface charge density ( ↑ charging, ↑ excess charge) that forms on the surface of a ↑ dielectric. Surface charge is particularly noticeable on moving ↑ material webs or during ejection of plastic parts and can be felt by operators ( ↑ body current). It can charge insulated metal parts by influence and thus lead to ↑ spark discharges to persons or to ignition when handling solvents. [SE Section 7.5.18] Surface charge density (also areic charge). Symbol σ , unit [C/ m 2 ], quotient of charge and surface area of a charged object. The highest value of the electric charge density on a surface that can be achieved under ↑ atmospheric conditions is σ max = 26 μ C/ m 2 and is referred to as the maximum surface charge density. This results in the maximum ↑ breakdown field strength E of air with E = σ max / ε 0 ~ 3 MV/ m. Only from ~ 3000 V/ mm (> 170 million electrons/ mm 2 ) electrons leave a surface. With only one more charge carrier at the pin or edge ( ↑ Rogowski profile), impact ↑ ionization begins, which lifts electrons out of their outer orbits when they collide with other particles. The surrounding area begins to glow blue; the atmosphere is ionized, the electrons are available for ↑ charge transport, and the air becomes conductive. {Appendix M.3.2} The surface charge density in the example (film e. g. polycarbonate) is reached when no more charge can be added (A) due to the constant ↑ Coulomb force. As soon as a charge of opposite polarity (e. g. an influenced earthed metal plate or a ↑ bipolar charged layer) is applied to the underside, the repulsive Coulomb force between the charged particles decreases, creating space for further charge (B). This creates “ space ” for the surface charge SuperCap 358 <?page no="372"?> density to increase until the dielectric strength of the film is exceeded (C). ( ↑ permittivity, ↑ propagating brush discharge) Surface coating, ↑ coating Surface current. Differentiated into direct and alternating current: ● Direct current always flows in the volume of a conductor and, in the case of other substances, where the least resistive conduction path is present, usually in the volume near the surface ( ↑ shell effect, ↑ leakage current). ● For alternating current, the ↑ skin depth is frequency dependent ( ↑ skin effect). Surface energy. Essential criterion for ↑ coating and ↑ wettability of surfaces. Correctly, the term surface energy should be extended to “ interfacial energy ” . However, this describes the free energy of an “ ideal ” liquid or solid surface against an “ ideal ” vacuum and is therefore only relevant in very rare cases. Therefore, surface energy is used to summarize the relative energy values of solid/ solid, solid/ liquid, liquid/ liquid, solid/ gas, or liquid/ gas contact surfaces. It characterizes the property of a material system and can be used to explain “ polar ” and “ non-polar ” behavior. This classification is important for the possibility of coating it with different materials. The surface energy describes the energy/ area: e. g. 38 mN/ m = 38 mJ/ m 2 = 38 × 10 -3 Nm/ m 2 . The unit of measurement [ ↑ dyn] is often used incorrectly. Surface phenomena, ↑ charging, ↑ charging phenomena on material webs Surface potential. Value of the electrostatic ↑ charging of a surface, which can be measured with an ↑ EFM in [V/ m]. The value is important for evaluating the resulting ignition effectiveness. [IEC/ TS 60079-32-1 Section 6.3.4] Surface resistance. Symbol R S , unit [ Ω ]. An important parameter for determining the electrostatic properties ( ↑ dissipation capability) and behavior ( ↑ resistance) of a material and thus its classification. The surface resistance cannot be exactly determined physically, because the DC measurement also records areas of the sample close to the surface ( ↑ shell effect, ↑ surface current). It therefore has the character of a comparative quantity for which the electrode arrangement and the measurement conditions must be specified. A statement about the ↑ skin depth of the current paths (as a function of the ↑ measurement Surface resistance 359 <?page no="373"?> voltage) in layers near the surface is not made but is possible to a limited extent for a circuit with a protective electrode ( ↑ measuring electrode for solids no. 9, ↑ measurement error). German regulations often use a measured value for surface resistance that refers to an electrode geometry (measuring electrode for solids no. 2) with a distance of 10 mm and a length of 100 mm. It is smaller than the resistivity by a factor of 10. This geometry was chosen to minimize the influence of the ↑ edge field when applying the measurement voltage. Surface resistivity. Symbol ρ s in [ Ω □ ] (also Ω square or Ω 2 ). Refers to a square area (electrode length = electrode spacing). The size of the square is irrelevant. It is sometimes referred to as a “ square ohm ” . Surface resistivity allows comparison of materials whose surface resistivity values have been determined according to different test standards. ● Surface resistivity values (measured after conditioning at 23 °C and 50 % RH) are listed for some plastics. {Appendix C} [SE Section 3.5], {Appendix M.7.1.3} Surface reverse current. Resulting from the ↑ breakdown field strength being exceeded when two partners are separated and flowing back to the conductive and earthed partner or to the partner with a significantly higher electrical capacitance. ( ↑ material web, ↑ surface reverse current density) This depends on the ↑ interfacial resistance of both materials ( ↑ surface resistance), the number of contact points (surface roughness, contact pressure) and the separation speed. The figure shows a possible measurement setup: bare metal conductive roller in an insulated bearing (> 10 14 Ω ) and a current collector (carbon brush) to the measuring device (preferably an oscilloscope) with a parallel connected measuring resistor (R = 10 6 Ω ). [Gabel, M., Schön, G., (1970)] Surface reverse current density. Symbol j R [A/ cm]. Describes the reduction of the surface charge density σ L after the separation line, which flows per unit time along the more or less conductive surface of the material web through the unit length laid perpendicular to the current density. It is essentially driven by the field strength parallel to the paper surface. The surface reverse current density generates the reverse current [A], which can be measured on an insulated conductive roller, e. g. together with a resistance and a µ-ammeter. ( ↑ surface charge, ↑ surface charge density, ↑ surface reverse current) The mechanical separation of a material web from a roll with at least dissipation capability must be divided into four phases ( ↑ charge separation), (Diagram): Surface resistivity 360 <?page no="374"?> Charging process on a roller (shown heavily distorted) σ : surface charge density σ = f(x), W: metal roller, F: field generated by σ , x 0 : separation line, c: x 0 < x < x m , d: x > x m - Phase 1 describes the charge exchange in region a, depending on the geometric arrangement (contact surface), in which the average surface charge density σ k is generated ( ↑ charging, ↑ donor, ↑ acceptor). - Phase 2 in region b is characterized by ↑ surface reverse current ( ↑ tunnel effect) combined with exceeding the ↑ breakdown field strength. This combination of carriers, mainly electrons and a few ions, is called reverse current plasma (cold low-energy plasma). This region is only a few millimeters in size (< 1 cm). ( ↑ DC low-energy plasma, ↑ dark discharge) - Phase 3 in region c describes the surface reverse current density j R , which depends on the surface conductivities of the partners involved, as well as the surface charge density σ 0 and the degree of ionization of the air. - Phase 4 in region d (x m ), the ↑ charge transport is constant over the surface charge density σ m . Here, σ m = f (R v) (R: surface resistance of the material web, v: web velocity). The total current I flowing with the material web in the described system corresponds to the charge transported with the web, which can be calculated as: σ m = I / b v (b: web width). Surface reverse current density 361 <?page no="375"?> The photo shows a typical situation of the web path in a gravure press. Exceeding the breakdown field strength can be seen as a glow discharge (blue line at the separation line of the transparent material web from the semiconducting ↑ impression roller when the ↑ electrostatic print assist is switched on). It is part of the surface reverse current I R and usually cannot lead to ignition ( ↑ MESG). [Gabel, M., Schön, G. (1970)], [Schubert, W., Ohsawa, A. (2024)], [Knopf, F. (2024)] Surface state. Additional energy states for electrons occurring on free semiconductor surfaces due to periodic lattice potential changes or oxide layers. The surface state can affect the contact resistance between the attached electrode and the sample during ↑ resistance measurements. Therefore, the ↑ measurement field strength should always be selected much higher than the potentials resulting from the surface state. Surface temperature. Which indicates the risk of ignition emanating from the surface of a heated object. Ignitability depends on the nature and concentration of the substance in a mixture with air, as well as the surface and shape of the hot part. The maximum allowable surface temperature is the highest temperature that can be reached by a system part or the surface of an electrical equipment during operation under the most unfavorable conditions (but within recognized tolerances), at which a surrounding ↑ Ex-atmosphere simply cannot be ignited ( ↑ hot surface, ↑ glass apparatus). The maximum surface temperatures are defined in ↑ temperature classes. [TRGS 727], [SE Section 4] Surface tension. Force at the solid/ liquid or liquid/ gas phase boundary that causes the smallest possible surface area (spherical shape) to form at their contact surfaces. In the case of liquids, the surface appears to behave like pre-stressed, thin, elastic skin. Surface tension is caused by intermolecular cohesive forces that cancel each other out within the liquid, but not at the surface. Electric charges can counteract these cohesive forces; the liquid surface is enlarged ( ↑ wettability) or torn open ( ↑ atomization). ( ↑ charge double layer, ↑ contact angle) Surface treatment, ↑ corona pretreatment Surface volume resistance. Antiquated term from the DIN 53 482 standard (withdrawn in 1996), which defined a ↑ volume resistance without specifying the size of the contact surface. Surfactants. Are substances with surface-active properties. They consist of a ↑ hydrophobic and a ↑ hydrophilic part and are suitable as ↑ antistatic agents if their hydrophobic part can be anchored in the material to be coated. The outward-facing hydrophilic moiety can then bind moisture and reduce ↑ surface resistance. They are classified as anionic surfactants, with the hydrophobic group on the anion, or cationic surfactants, with Surface state 362 <?page no="376"?> the hydrophobic group on the cation (e. g. quaternary ammonium salts as additives to increase the conductivity of liquids). ( ↑ avivage) Surge arrester (also surge diverter, overvoltage protector). Protective device that serves as operating resources in the power supply network to limit hazardous ↑ overvoltage. These elements behave with high resistance up to a certain voltage that is still harmless in the respective situation and do not yet represent a load. However, if the applied voltage exceeds a limit value, these elements become low-resistance and dissipate the energy associated with the increased voltage (to earth). If the overvoltage is fast, irregular pulses ( ↑ transient), measures for ↑ transient protection are required. For example, encapsulated spark gaps are used as a protective element for very high currents, e. g. for ↑ EMP events. Other components include ↑ lightning arresters, ↑ varistors (for sensitive devices), ↑ TVS diodes or ↑ Zener diodes. However, overvoltage protection also refers to switching structures ( ↑ diodes) in electronic devices that prevent the occurrence of overvoltage, e. g. as a result of electrostatic charges ( ↑ ESD protection). Overvoltage protection is also part of internal ↑ lightning protection, as overvoltage in the electrical power supply is not only caused by switching operations ( ↑ burst), but also by ↑ lightning strikes. Surge generator, ↑ SG Surge impedance of a line. The electrical surge impedance Z W [ Ω ] is the characteristic value of a line that indicates the ohmic resistance with which a line must be terminated in order for ↑ adaptation to occur. It is the quotient of the instantaneous values of voltage and current at each point of a line where alternating electric fields propagate. ( ↑ resistance) Surge protection device (SPD), ↑ surge arrester Surge voltage. It is pulsed high voltage that acts as a disturbance or test variable on components, devices or systems ( ↑ ESD test generator, ↑ SG). Susceptance, ↑ alternating current quantity Susceptibility (Latin: suscipere, “ to absorb ” ) refers to - the ratio of the ↑ magnetization or ↑ polarization of a material in a magnetic or electric ↑ field to the corresponding magnetic or electric field strength ( ↑ permeability, ↑ permittivity), - the sensitivity of electronic devices to simulated disturbances ( ↑ ESD, ↑ burst, ↑ SG) in the context of EMC tests ( ↑ Electromagnetic Compatibility). {Appendix M.1.3} Suspension (Latin: suspendere, “ to suspend ” ). Dispersed distribution ( ↑ dispersion) of very small but non-molecular solid particles in a medium (gas or liquid). Usually, the liquid is the cohesive medium (phase). If it is electrostatically insulating, it must be noted that the suspended particles and their interface effects (separation ↑ charging) cause much higher charges than in pure liquids. ( ↑ aerosol), [TRGS 727] Suspension 363 <?page no="377"?> Synchrocyclotron. Special form of the ↑ cyclotron, in which the orbital frequency of the accelerating voltage decreases with increasing mass of the accelerated ions; there is an exact adaptation to the velocity of the particles to accelerate. Synchrotron (Greek: syn, “ together ” , chronos, “ time ” , electron). Orbital accelerator for charged particles developed from the ↑ cyclotron, in which acceleration is achieved by electric fields and orbital guidance by magnetic fields. Synthetic caoutchouc, ↑ caoutchouc Synthetic material, ↑ plastic Synchrocyclotron 364 <?page no="378"?> T Tank (Hindi: tankh, “ water container ” ). Storage or transport container for liquids or gases. When filled with flammable liquids, measures against the hazards of electrostatic charges are essential ( ↑ calming section, ↑ charging), since the field emanating from a charged liquid can cause ↑ brush discharges on conductive equipment in the gas space. Electrical conductivity is always required for materials used in larger tanks. However, thin linings of insulation material are allowed under certain conditions ( ↑ layer thickness). Fuel tanks (up to about 100 l) made of chargeable plastics are common in vehicles. In general, they do not pose an electrostatic ignition risk for ↑ gasoline because they always contain a ↑ rich mixture. It is only during the first refueling (after the vehicle has been manufactured or repaired) that the charge caused by the incoming gasoline can become an ignition hazard ( ↑ gasoline vapor). A simple protective measure has proven to be a conductive wire placed in the ↑ filling pipe and electrically connected to the vehicle body, which causes a ↑ corona discharge ( ↑ earthing). [TRGS 727] ● Floating roof tank. Compared to tanks with a fixed roof, these have the advantage that no explosive mixture can form in them because the roof floats directly on the liquid. It should be noted that the seal between the floating roof and the tank shell may be electrically insulating and therefore the roof plate must also be earthed, particularly for reasons of ↑ lightning protection. ● Demountable tank with a capacity > 450 l, which by its design is not intended to transport goods without handling and which can normally only be removed when empty ( ↑ ADR). Tank cleaning. Conductive (polar) liquids, e. g. water, can become electrostatically charged when sprayed ( ↑ Lenard effect, ↑ high-pressure cleaning). The charge is increased by a second immiscible phase, e. g. emulsified oil components. During the cleaning of the approx. 20 000 m 3 central tanks of supertankers with sprayed, circulated seawater at a pressure of 1 MPa (nozzle diameter 4 cm), serious explosions occurred on three ships of this type within one month in 1969. The empty tanks to be cleaned were enriched with a ↑ Ex-atmosphere due to crude oil residues. In subsequent investigations, room potentials of up to 40 kV were measured during spraying. For the ignition mechanism, it was assumed that the initially very small droplets ( ↑ atomization, ↑ Rayleigh limit) reassembled into coherent water slugs charged by ↑ influence, acting as insulated conductors ↑ spark discharges to metal fixtures. Since the enormous size of the spray cloud was considered critical for these ignitions, such tank cleanings may only be performed after ↑ inerting. [ISGOTT (2020)], [Steen, H. (2000)] When cleaning tanks up to a size of about 10 m 3 with liquid ejectors, no ignition hazard is to be expected, provided that no excessively high pressure is applied. [TRGS 727], [Baumann, F. (2023)], [Van de Weerd, J. M. (1971)], [Lindbauer, R. L. (1975)] Taylor cone. G. I. Taylor was the first to describe the phenomenon of a liquid forming a cone as it exits a capillary tube, which transforms into a filamentary structure when it <?page no="379"?> enters a sufficiently strong electric field ( ↑ nano spinning, ↑ electrospray ionization). This occurs because of the hydromechanical forces in the liquid in combination with the electric field, gravity, external gas pressure and ↑ surface tension. The filamentary structure then dissolves because of the ↑ Rayleigh instability. In practice, the Taylor cone is used to generate monodisperse ↑ aerosols or ions (e. g. for mass spectroscopy). [Taylor, G. I. (1964)] Technical ventilation, ↑ ventilation Telescoping. At the end of many manufacturing processes, the product is rewound. Freshly produced films, but also other materials, tend to telescope during rewinding, i. e. the material web moves sideways, so that the coil can hardly be used in further process steps. To prevent this, the web can be fixed electrostatically on an earthed roller with a ↑ charging electrode before winding ( ↑ useful application). [SE Section 8] Temperature (Latin: temperatura, “ proper mixture ” , “ nature ” ). Symbol T with the ↑ SI base unit [K] ( ↑ Kelvin), is a state variable that is a measure of the average kinetic energy of the particles of a system in disordered thermal motion. At absolute zero, defined as 0 K, atoms and molecules no longer move. This is where the scale of absolute temperature, also known as thermodynamic temperature, begins because it is equal to the energy of particle motion. Temperature differences are measured in Kelvin. Another common unit of temperature is the degree ↑ Celsius [°C], where absolute zero is - 273.15 °C (= - 459.67 °F, ↑ Fahrenheit). Temperature can have a direct effect on the electrostatic properties of a material, but it can also have an indirect effect by changing the relative ↑ humidity. An example is water, whose resistance in the frozen state can increase by several orders of magnitude depending on the water hardness (number of dissolved salts). Anyone can verify this with a simple experiment. Technical ventilation 366 <?page no="380"?> Temperature class. System for classifying electrical equipment according to its maximum surface temperature with respect to the surrounding atmosphere of flammable gases and vapors in the Ex-area. When determining this temperature, a safety margin from the lowest ignition temperature of the substances grouped in the temperature class is considered to compensate for variations due to manufacturing tolerances. The operating conditions (e. g. conveying hot media) as well as heat radiation from sources without direct connection (e. g. hot pipes or spotlights) must be considered. ( ↑ flammable liquid, ↑ ignition temperature) Class Ignition temperature [°C] Maximum surface temperature [°C] Example T1 > 450 450 Hydrogen T2 > 300 to ≤ 450 300 Ethylene T3 > 200 to ≤ 300 200 Gasoline T4 > 135 to ≤ 200 135 Ethyl ether T5 > 100 to ≤ 135 100 n/ a T6 > 85 to ≤ 100 85 Carbon disulphide [IEC 60079-0] Temperature coefficient. Proportionality factor for the change in a physical quantity as a function of ↑ temperature (electrical ↑ resistance, length, volume, etc.). The temperature coefficient indicates the change in resistance in [ Ω ] as a function of the change in temperature in ↑ Kelvin [K]: ● Metals. When heated, the atoms vibrate more strongly around their position in the ↑ crystal lattice. This hinders the movement of the free electrons, and the resistance of these substances increases as the temperature rises (PTC ↑ thermistor). ● Non-metals, semiconductors. The stronger vibrations of the atoms lead to the generation of more free charge carriers. The resistance of these materials decreases with increasing temperature (NTC ↑ thermistor). ● Insulating materials with conductive fillers. Increased ↑ tunnel effects due to thermal fluctuations cause a reduction in resistance. ● Liquids and gases. Here, charge transport is mainly by ↑ ionic conduction, which is also strongly dependent on the disordered thermal motion of the particles. Temperature influence. The electrical resistance ( ↑ conductivity) of materials is more or less affected by ↑ temperature ( ↑ temperature coefficient). Therefore, a temperature specification is required for all resistivity values that are not related to room temperature. For polymers, an approximate guide to the effect of temperature is that for a 40 K increase in temperature, the resistance decreases by approximately one dimension and vice versa. This can be used during processing, e. g. the higher the temperature, the lower the charge during injection molding. Tempering. General term for thermal post-treatment (heating, slow cooling) of a material to eliminate thermal stresses created during rapid cooling or to change the structure (microstructure) of a solid (e. g. to improve conductivity). For example, the electrical Tempering 367 <?page no="381"?> resistance of plastics made conductive by adding carbon black ( ↑ carbon) can be influenced by annealing. Tera-ohmmeter. Measuring device that works according to the ↑ current-voltage measurement method and can measure resistances of at least 10 12 Ω . It should have measuring voltages of at least 1000 V ( ↑ influence electrostatic field meter, ↑ measurement field strength, ↑ resistance measurement). The TOM 610 ® (Figure) has the possibility to measure the ↑ breakdown resistance. To do this, the measurement voltage is increased from 10 V to 100 V and then in 50 V steps to 1000 V. This allows the ↑ breakdown voltage and the measured resistance to be recorded. [Brunner, J. (2019)] Termination impedance. Prevents reflections at the end of an open RF line from feeding back into the line. For example, shielded RF lines with an impedance of 50 Ω should be terminated with a characteristic impedance of 50 Ω so that the reflection factor is zero. Test charge. An electrically charged test ↑ specimen used to measure the force effect and to determine the field magnitudes of electric and magnetic fields. Test climate. The ↑ surface resistance, which is crucial for evaluating the electrostatic chargeability of materials, is mainly influenced by the ↑ humidity ( ↑ water activity). Therefore, these measurements must be performed in a defined test climate after appropriate conditioning. The usual conditions are 23 °C and 50 % RH or 23 °C and 30 % RH, depending on the expected resistance [TRGS 727]. The conditioning requirements are specified in the test standards. ( ↑ measurement error) Test gas. Gas or gas mixtures with special manufacturer tolerance, analysis accuracy and purity for checking and adjusting the sensitivity of ↑ gas warning devices and for calibrating their sensors. Test mark, ↑ GS mark Test mixture, ↑ explosive test mixture Test rig. General term for the simulation of production processes to determine electrostatic parameters and, for example, the suitability of ↑ ionizers. In a test rig for material webs, the web path over a varied arrangement of guide rollers in combination with an unwinding and rewinding system is always preferable to a circulating web. [SE Section 5.2.1.3] Test sample. Part or material sample for the determination of e. g. electrical parameters. Rectangular plates with dimensions of at least 60 × 150 mm 2 or larger are required for measuring the ↑ surface resistance of enclosures or parts of enclosures made of insulating material for electrical equipment in hazardous areas. [IEC 60079-0] (Source: www.kleinwaechtergmbh.de) Tera-ohmmeter 368 <?page no="382"?> Test standard. The standards in which the test procedures are defined. Thermionic effect. Based on thermal ↑ electron emission, it enables the direct conversion of thermal energy into electrical energy. In tests, voltages of about 1 V have been achieved at working temperatures of 1800 °C (efficiency of about 10 %). Thermistor (Greek: thermos, “ warm ” ; Latin: resistor, “ resistance ” ). Electrical component consisting of mixtures of sintered metal oxides and oxidized mixed crystals whose resistance is strongly dependent on temperature. A thermistor can change its resistance due to two influences: - From the outside, due to the ambient temperature (externally heated thermistor), then preferably used for temperature detection - From the inside by the heat generated by a current flowing through it (self-heated thermistor) There are two different types of thermistors: ● NTC thermistor (negative temperature coefficient thermistor). An electrical conductor whose resistance decreases with increasing temperature (negative ↑ temperature coefficient). This includes any type of ↑ ionic conduction. As electronic components, they consist of mixtures of metal oxides and oxidized mixed crystals that are sintered with the addition of binders and used, for example, to limit inrush currents. Thermistor 369 <?page no="383"?> (Source: [Springer, G. (1996)]) ● PTC thermistor (positive temperature coefficient thermistor). An electrical conductor whose resistance increases with increasing ↑ temperature. In addition to all metals, PTC thermistors include ferrous ceramics with additives of metal oxides and metal salts, which have a significantly higher positive temperature coefficient than metals. A commonly used material is barium titanate (BaTiO 3 , ↑ permittivity ε r ≈ 1200). R E : Final resistance, R N : Resistance at ϑ N , R min : Minimum resistance, ϑ A : Initial temperature, ϑ N : Nominal temperature, ϑ E : Final temperature (Source: [Springer, G. (1996)]) Thermite reaction, ↑ aluminothermic reaction Thermoelectret. The Japanese scientist M. Euguchi developed the first thermoelectrets around 1919, whose internal polarity lasted for several years. ( ↑ electret) Thermoelectric effect. General term for ↑ Peltier and ↑ Seebeck effect. Thermite reaction 370 <?page no="384"?> Thermoelectric voltage. Two wires of different metals or metal alloys soldered or welded together at one end form a thermocouple. This provides an electric voltage when there is a temperature difference between the junction (measurement point) and the other ends (reference point) ( ↑ Peltier and ↑ Seebeck effect). Thermopolymer (also thermoplastic). Polymer materials that can be formed, welded and melted within a certain temperature range. Thin film technology. For electrostatics, the measurement methods for determining the relative ↑ humidity using the capacitance change due to water absorption are important. Thin film technology makes it possible to produce capacitors with hygroscopic dielectrics and water vapor-permeable electrodes. Such large-area electrodes provide accurate measurement results in rapid succession. ( ↑ humidity sensor) Thomson, Sir William, later Lord ↑ Kelvin of Largs Thomson bridge. Extension of the ↑ bridge network of Ch. ↑ Wheatstone for measuring extremely small DC resistances (down to 1 μΩ ). Thomson effect. Similar to the ↑ Peltier or ↑ Seebeck effect, describes the heat transport in a current-carrying conductor between two points of different temperatures. The Thomson effect is usually superimposed by the heating of the conductor due to its electrical resistance. (The Thomson effect should not be confused with the ↑ Joule-Thomson effect). Thread electrometer. Powerless voltage meter ( ↑ electrometer). An elastically clamped metal thread is deflected by the voltage to be measured in the electric field of a plate ↑ capacitor according to the relationship Q = U × C. The deflection can be read, for example, on a transparent scale. When the measuring voltage is applied, a ↑ charging current flows to charge the intrinsic capacitance of the thread electrometer. After that, self-consumption is determined only by the insulation of the device. ( ↑ electroscope) Three-phase current. It is generated by connecting three alternating voltages that are 120° out of phase (also called three-phase alternating current). Three-phase current is the most common type of power supply and is used in Europe with an effective voltage of 400 V (phase to phase) and 230 V (phase to neutral). In electrostatics, three-phase current is used, for example, in the ↑ electric curtain. Throttle valve. Often installed in piping. In ↑ Ex-areas, always ensure that the throttle valve remains electrically dissipative when using insulating ↑ gasket. (This applies to all ↑ armatures.), [SE Section 7.5.16] Thunder. Sonic phenomenon of ↑ thunderstorm lightning condensed into ↑ plasma by strong magnetic fields, which triggers shock waves of heated air. Thunder is perceived as a Thunder 371 <?page no="385"?> sharp bang up to a distance of about 300 m from the point of impact of the lightning, which changes into the typical thunder roll only at greater distances due to the echo effect. [SE Section 4.2.4] Thunderstorm electricity. Direct conversion of thermal energy (strong vertical air currents) into electrical energy, which is stored in so-called ↑ cloud dipoles. Accordingly, thunderstorms occur much more frequently over tropical land areas than in temperate zones. The charge equalization takes place in a ↑ thunderstorm lightning, in which - despite its spectacular appearance - electrical energy equivalent to a few euros at best is converted. Thunderstorm lightning. A typical thunderstorm cell is a giant electrostatic generator with water droplets and ice crystals as charge carriers. Small droplets/ hailstones are transported upwards in the updraft (up to 100 km/ h) and are predominantly positively charged. Larger ones are transported downwards in the downdraft and are predominantly negatively charged. (Source: VDE e. V.) Thunderstorm lightning can be observed within a cloud, between different clouds, and between clouds and earth. Only about 10 % of thunderstorm lightning strikes between clouds and the earth, as shown in the following schematic: Thunderstorm electricity 372 <?page no="386"?> After a previous gas discharge in the cloud, a pre-discharge L (called “ leader ” ) develops, which spreads downwards in steps. As the pre-discharge progresses, the field strength between the pre-discharge and the earth or the pin of an earthed object increases accordingly. This results in an upward counter-discharge (C) of opposite polarity to the predischarge. Due to the slow onset of ionization in the discharge channel, the velocity of the upward counter-discharge is still relatively low for the first 100 m. However, the ↑ pinch effect and the resulting plasma accelerate the discharge process to about 10 8 m/ s. During this initial phase, the counter-discharge seeks the pin of the descending pre-discharge, and at a field strength of about 500 kV/ m, a flashover occurs between the two. This completes the circuit between the cloud and the target on the earth. Only now does the actual lightning discharge S (called “ streamer ” ) begin. Currents in the range of 100 kA flow in times of about 100 μ s. This is what causes the damage and ↑ transients of thunderstorm lightning. The strong magnetic fields caused by the high currents condense the lightning channel into a plasma and lead to spectacular lightning phenomena and thundering sounds. Even if the lightning strike occurs at a distance and leaves no visible scorch marks, the high induction currents in the body pose a danger to humans and animals. Based on lightning current measurements, more than 70 % of cloud-to-earth lightning strikes consist of several (up to ten) individual discharges with time intervals between 10 and 200 ms. ● The effects of thunderstorm lightning can be divided into direct and indirect effects: - The heating Δ T of the materials through which the lightning current flows is a direct effect, which is essentially determined by their electrical resistance. With typical values for a lightning strike of 100 μ s and 100 kA, the energy converted into heat with a material resistance of 1 Ω is about 10 kWh. Since there is no heat dissipation during the short flash duration, all the energy is available for heating. As a result of the steep rise and fall of the current, current displacement occurs on the surface of the body struck by the lightning ( ↑ skin effect), leading to significantly greater heating of regions near the surface (risk of ignition of flammable materials). If the material contains moisture (e. g. trees), spontaneous evaporation may occur, leading to an increase in pressure and subsequent bursting of the body. When lightning strikes a conductive surface, such as the roof of a steel silo, the current is concentrated on a small area and heats it rapidly. The result can be annealing colors after cooling, melting spots, or even holes caused by molten metal that can cause ignition if it drips on combustible material. - Mechanical effects can be caused by the high current increase and the resulting compression to plasma (strong magnetic fields) on conductive objects. The resulting radial acoustic pressure wave leads to movements (e. g. on overhead lines) and deformations (e. g. on truss constructions and downspouts of gutters) on flat and hollow bodies. The latter are deformed into a double-layered sheet metal strip. On the other hand, when lightning strikes insulating surfaces, there is no heating due to current flow, but holes can be caused by high voltage failures (e. g. in a roof tile). Thunderstorm lightning 373 <?page no="387"?> - The indirect far-field effects include lightning phenomena (plasma) and thunder (shock waves of heated air), which is perceived as a sharp bang up to about 300 m from the point of impact and changes to the typical rolling thunder only at a greater distance due to the echo effect, as well as the transient effects of the lightning impulse (electromagnetic radiation ( ↑ spherics), electromagnetic pulses ( ↑ LEMP)). - Indirect near-field effects (within a radius of approx. 100 m) are: - Induction voltages in electrical wiring systems, which lead to short-term overvoltage that can damage inadequately shielded electrical and electronic devices (endangering antenna systems and power supply networks). - Influence charges on conductive objects insulated from earth, which are caused by rapid changes in field strength (up to 10 13 V/ m × s). They charge to high potential and can cause damage, e. g. electric breakdowns. To test the risk to antenna systems and power supply networks, thunderstorm lightning is simulated with an overvoltage generator ( ↑ SG) ( ↑ surge arrester). [IEC 62305-4] Note: When a thunderstorm lightning strikes the properly functioning ↑ lightning protection system of a house, there is a risk of inductive coupling into the electronic devices inside. The magnetic field generated by the lightning current around the lightning conductor can induce voltages in the conductors of the devices that can cause damage (e. g. microprocessors). The general recommendation to pull out the mains plug to protect against thunderstorm lightning is not sufficient in this case. For the evaluation of lightning damage, it is extremely important for loss insurers to determine the time and place of the lightning strike as accurately as possible. ● Lightning detection, in Europe ↑ lightning detection system ● Protection against lightning, ↑ lightning protection Thunderstorm lightning-like discharges. Can occur, for example, in dust and ash clouds. Volcanic eruptions generate stormy updrafts to great heights, in which friction and separation processes between volcanic ash and ice crystals also lead to charging. These relationships have been studied and confirmed, for example, during the volcanic eruption of Eyjafjallajökull (Iceland, March/ April 2010). The eruption of Mount Vesuvius (Pompeii, August 79 AD) was already described by G. Plinius Secundus in Epistulae Book 6 as a discharge similar to lightning. Experiments by P. Boschung show that such discharges do not occur in technical systems with a volume < 60 m 3 , or a linear dimension < 3 m. Theoretical considerations suggest that lightning-like discharges can occur in larger silos or containers at field strengths > 500 kV/ m ( ↑ cone discharge). [Boschung, P. et al. (1977)], [TRGS 727 Section A 3.5] Thyristor. Device with at least four successive semiconductor zones of alternating conduction. When a control pulse is applied to the inner zones (gates), the thyristor acts as a switched ↑ diode for high load currents ( ↑ PN junction, ↑ band model). Thunderstorm lightning-like discharges 374 <?page no="388"?> Time constant. Time interval resulting from the product of ↑ resistance and ↑ capacitance {Appendix M.6.3.1}. In practice, 5 τ is used to reach the respective end state ( ↑ relaxation time). ● The charging time constant is an exponentially increasing physical quantity up to the e-th part (1 τ ). The time τ is specified when the capacitor voltage has reached approximately 63 % of the charging voltage. The longer the charging time of a capacitor, the greater the charging resistance and capacitance. ● The discharge time constant is a physical quantity that decreases exponentially to the e-th part ( - 1 τ ). It is determined by the rate of discharge of a capacitance (accumulation of charges in different materials) across a resistance to approximately 37 % (e -1 ) of the original charge voltage. Time-of-flight effect. A phenomenon that occurs in electron and ion radiation when the time of flight of the particles in a high frequency alternating electric field corresponds to the period of oscillation. It is used, for example, in space-charge-wave tubes ( ↑ klystron). Tires, ↑ vehicle tires TLP, short for transmission line pulser. A test system that works on the principle of total reflection of signals at the mismatched end of a line (test generator for semiconductor devices). Instead of approaching the damage threshold as with ↑ CDM, ↑ HBM, ↑ MM and ↑ SDM, the TLP observes the response of the input structure of the semiconductor device by applying a series of extremely fast, rising, low-energy pulses (rise time in the range of 100 ps) and optimizes it by appropriate modifications so that an incoming ESD pulse is dissipated in the best possible way. ( ↑ DUT), (see figure next page) TLP 375 <?page no="389"?> (Source: www.we-online.com) Toluene. Electrostatically chargeable and flammable liquid with a ↑ flash point of 5 °C. Because toluene vapors have a stoichiometric ratio of 1 ( λ = 1) to atmospheric oxygen at 20 °C, it has reached its ↑ MIE at room temperature and is disproportionately involved in electrostatically ignited fires and explosions. Toner. Fine black or colored powder (particle size approx. 20 μ m) with a low melting point. In combination with ↑ charge control agents, toners can be electrostatically charged in a defined manner in order to adhere to oppositely charged substrate surfaces (latent electrical ↑ charge image). After being transferred to the substrate, toners are melted by thermal radiation (thermally fixed, ↑ laser printer, ↑ xerography, ↑ magnetography). To improve print quality, even finer toners (1 - 2 μ m) were developed, which are embedded as electrically charged toner particles in a non-conductive liquid (HP Indigo technology) due to the hazard of lung penetration. Tornado (cyclone or waterspout). A relatively small whirlwind (about 200 m in diameter) that occurs in connection with thunderstorms with wind speeds of up to about 140 m/ s, triggered by high temperature differences (the strongest storms on Earth). Heated air on the ground rises at speeds of up to 40 m/ s, begins to rotate increasingly under the influence of the Coriolis force, and transports a lot of swirled material upwards like in a hose ( ↑ cloud dipole). Touch protection (electrical) ● Protection against contact for enclosures of electrical operating resources, the requirements for which are defined in [IEC 60529] (IP code, International Protection Code). The first digit of the IP code defines protection against foreign bodies and contact, the second digit defines protection against water, and the third digit defines access to hazardous active parts. Other code numbers are possible. ● Touch protection for active discharge bars ( ↑ ionizers) and charging electrodes must be connected in such a way that the possible current is limited to 500 µA (AC) and 2 mA (DC) for generally accessible discharge pins to which high voltage is applied, so that no personal injury can occur. The tolerance of the components (e. g. resistor) must be observed. [IEC 61140], [BS IEC 60479-2] Toluene 376 <?page no="390"?> Touch voltage. Voltage that can occur between simultaneously touchable parts during an insulation fault. The effect of the touch voltage can be significantly influenced by the impedance of the person touching the parts. For humans, the limits are 50 V for AC and 120 V for DC. For children ’ s toys and in the animal and agricultural sectors, the limits are 52 V AC and 60 V DC. The touch voltage may only be measured with measuring instruments whose internal resistance corresponds to that of a human being (approx. 1 k Ω ) or an animal (approx. 500 Ω ). ( ↑ danger of electric shock), [IEC 60364-4-41] Townsend, Sir John Sealy Edward (1868 - 1957). British physicist developed in 1897 the drop method for the direct determination of the ↑ elementary charge in the ↑ levitation experiment ( ↑ Millikan experiment) and studied ionization processes in gases ( ↑ Townsend discharge), thus confirming the laws established experimentally by F. ↑ Paschen. Townsend discharge. Describes the processes of an independent ↑ gas discharge between two electrodes (usually pin and plate). When a certain ignition voltage (start field strength, ↑ corona inception voltage) is reached, the number of free electrons begins to increase exponentially as a result of collisions (impact ↑ ionization) of ions with neutral gas molecules ( ↑ avalanche effect). These measurements can be reproduced with the setup shown. At a sufficiently large distance, the ignition voltage U depends not only on the ↑ field strength E, but also on the radius of curvature r of the pin (U = r × E). ( ↑ Trichel pulses), [Hilgarth, G. (1997)] Trade supervision. Monitoring of the implementation of state regulations and ordinances on occupational safety and health in commercial enterprises carried out by trade supervisory authorities. Transferred charge, ↑ charge transfer Transformer (also power transformer) (Latin: transformare, “ to transform ” ). An electrical device that transforms an alternating current voltage into a higher or lower voltage of the same frequency. Transformers usually consist of two or more coils with a defined number of wire windings around a ferrite (or iron) core, forming a magnetic circuit. The operating principle is based on electromagnetic ↑ induction. Transformer 377 <?page no="391"?> Transient (also electrical fast transient (EFT)). An unpredictable, non-periodic, shortterm (nanoto micro-seconds) voltage pulse that propagates as a “ traveling wave ” in an electrical network or can affect electronic circuits as a disturbance pulse. Caused by electrostatic discharge, thunderstorm lightning, switching operations, nuclear explosion ( ↑ LEMP, ↑ NEMP, ↑ propagating brush discharge, ↑ super brush discharge). Transient protection. Protective elements, circuits or structures that keep harmful transient pulses away from electrical or electronic components or equipment ( ↑ EMP, ↑ LEMP, ↑ NEMP). These must be capable of dissipating the energy of the expected ↑ transients ( ↑ lightning arresters, ↑ surge arresters). The generation of voltages must be kept below a level that is not destructive to the equipment being protected, e. g. by connecting a ↑ varistor, ↑ Zener or ↑ TVS diode in parallel. In particular, devices and systems that need to be protected against the effects of ↑ thunderstorm lightning require up to three different protection elements, usually with additional delay elements or delay lines, are required to gradually reduce the energy and voltage to a safe level. In integrated devices, we no longer speak of protection circuits or elements, but of protection structures, whose protection functions are integrated into the semiconductor structure. Transient voltage suppressor, ↑ TVS diode Transmission belt. V-belt or flat belt, which is used to drive rotating parts. As a result of the continuous separation between the drive belt and the pulley, electrostatic charges can be so high that there is a danger of ignition in an explosive atmosphere in the surrounding area ( ↑ belt electricity). The level of charge is caused by the electrical properties of the belt and pulley materials and increases with belt speed, belt tension and the width of the contact surface. Drive belts should therefore not be used in ↑ Ex-zone 0. For safe operation in Zone 1, limit values are specified for the speed and electrical resistance of drive belts and their pulleys. [TRGS 727 Section 3.5] Transmission line pulser, ↑ TLP Transport container. May be rigid ( ↑ RIBC) or flexible ( ↑ FIBC). If they are conductive or electrostatic dissipative, they must be earthed during filling and emptying, but not during transport. Transport roller, ↑ guide roller Trap. An adhesion point, especially in semiconductors, that can trap electrons or defect electrons in certain quantum states and thus remove them from the conduction mechanism. Trap electron. Solid insulators can generally only be charged on their surfaces ( ↑ charging). This is because charge carriers ( ↑ electrons) are quickly trapped as they attempt to migrate through the insulating material. ( ↑ crushing) Treeing. A term used in particular in high-voltage technology for the tree-like propagation of an insulation fault due to ↑ partial discharge ( ↑ dendrites, ↑ fractals). Water treeing occurs when water is trapped in small cavities (e. g. in cable insulation). Transient 378 <?page no="392"?> Triboelectric charging, ↑ frictional charging Triboelectric powder coating, ↑ coating Triboelectric series. Since electron transitions are mainly responsible for ↑ charging, the level and sign of the charge can be derived from the differences in ↑ electron emission energy. This allows a triboelectric spectrum to be set up in which materials ( ↑ donors) are always positively charged compared to those lower down ( ↑ acceptors) (table). In general, electron conducting substances (e. g. ↑ metal) are classified as donors. In addition, A. ↑ Coehn found that substances with donor properties always have a higher ↑ permittivity than substances with acceptor behavior. The reliability of a triboelectric series should not be overestimated, as ion transitions and other influences can play a role in the separation charging in addition to the electron transitions ( ↑ charge double layer). This has led to different triboelectric spectra being determined, which are not consistent with each other. Triboelectricity. A term for the fact that contact and motion processes lead to ↑ charging ( ↑ frictional charging, ↑ coating). Triboluminescence, ↑ luminescence Trichel pulses. First detected by G. W. Trichel in 1938, are pulses in the ↑ corona discharge between the pin and the plate that vary in strength depending on the sign. They have a pulse duration in the ns-range and the frequency can be up to 10 5 pulses/ s. The Trichel pulses occur in the vicinity of the pin: A: Precursors of the corona discharge as low-current ↑ dark discharges due to the escape of electrons as a result of the ↑ tunnel effect ( ↑ field emission). B: Short-wave radiation (e. g. from radioactive substances) causes ↑ ionization of the gas and can release electrons from the electrode surface. C: As the potential difference increases, short, dependent and irregular pulse discharges occur. These can be visually detected as a dotted area and correspond approximately to the initial voltage of the discharge. Trichel pulses 379 <?page no="393"?> D: As the potential between the pin and the plate increases, periodic, selfsustaining pulse discharges occur. E: As the pulse frequency increases, the current fluctuations are smoothed out to a continuous discharge. F, G: When the ↑ breakdown voltage is reached, the discharge changes to a ↑ spark discharge. [Gravendeel, B. (1987)], [Dilfer, S. (2002)] Tripod electrode, ↑ measuring electrode for solids no. 7 Tunnel effect. Describes quantum mechanical charge transport between adjacent conductive materials that are separated by insulating materials over minimal distances. It is important for systems made of insulating materials (e. g. polymers) that are to be made electrically conductive by adding conductive filler particles (e. g. carbon black ( ↑ carbon)). If the distances between the conductive particles are greater than 10 nm, the total resistance is determined by the high resistivity of the insulating material. If the distances between the conductive particles are reduced, electrons can be transported by quantum mechanical tunneling processes under the influence of the electric measuring field. Conductivity caused in this way improves with increasing temperature, as thermal fluctuations lead to an increasing tunneling probability ( ↑ temperature coefficient). TVS diode, short for transient voltage suppressors. A limiting diode for fast voltage pulses, such as those occurring in electrostatic ↑ gas discharges. In principle, it is a fast ↑ Zener diode that can discharge over-voltages of both polarities of the same voltage and is used, among other things, to protect sensitive electronic measuring equipment from electrostatic discharges. Two-electrode discharge. In electrostatics, the ↑ spark discharge is the only form of twoelectrode discharge whose geometry can be used to calculate the converted ↑ energy, unlike the ↑ one-electrode discharge. Two-filament voltmeter. A non-powered voltmeter consisting of two metal filaments that are clamped in parallel to one and other in a metal housing in a highly insulated manner. The voltage to be measured is applied to the filaments and the case, the former moving away from the latter according to the potential difference. The measurement is made after magnification with a microscope or by projection ( ↑ filament electrometer). Type approval. Antiquated term for ↑ type examination certificate. Type examination certificate. Issued by authorized national or international test centers ( ↑ notified body). This certifies that the equipment conforms to the required design specifications. A type-examination certificate is required if the product is subject to an EU directive that requires a type-examination. ( ↑ ATEX) Tripod electrode 380 <?page no="394"?> Type of protection (ignition protection type for explosive atmospheres). Systematization of general measures taken for electrical equipment and systems to prevent ignition of an ambient ↑ Ex-atmosphere. They comply with the basic safety requirements of the ↑ ATEX Directive ( ↑ equipment protection level (EPL)): “ d ” - Flameproof enclosure. The escape of an explosion that may occur inside an enclosure must be prevented by flameproof enclosure in combination with flameproof enclosure openings ( ↑ MESG). The surface temperature must be below that of the surrounding explosive atmosphere when a possible fault occurs. Flameproof enclosure is also suitable for equipment of ↑ equipment category II 2G and II 3G if ignition sources occur during normal operation. “ p ” - Pressurized enclosure. The ingress of an ↑ Ex-atmosphere into an enclosure of electrical equipment is prevented by the presence of an inert gas inside the enclosure at a pressure greater than that of the surrounding atmosphere. The overpressure is maintained with or without purge of the inert gas. “ q ” - Powder filling. Filling the enclosure of electrical equipment with a fine-grained filling material ensures that an arc generated in the enclosure will not ignite an explosive atmosphere surrounding the enclosure when used as intended. Ignition by flames or ignition by elevated temperatures on the surface of the enclosure must not occur. Quartz sand or glass particles are commonly used. “ o ” - Oil immersion (liquid encapsulation). Electrical equipment or parts thereof are made safe by enclosing them in a nonflammable liquid (e. g. oil) so that an explosive atmosphere above or outside the enclosure cannot be ignited. ( ↑ fiber bridge sparkover) “ e ” - Increased safety. Additional measures are being taken to prevent, with an increased degree of safety, the possibility of impermissibly high temperatures and the generation of sparks and arcs inside or on external parts of electrical equipment where these do not occur in normal operation. “ i ” - Intrinsic safety. Equipment contains only intrinsically safe circuits ( ↑ electric circuits) in which no thermal effects (e. g. opening or closing sparks) have energy values approaching the MIE of the surrounding explosive atmosphere. “ p ” , “ v ” - Pressurization. Pressurized/ externally ventilated space. Spaces located in an Ex-atmosphere or in an Ex-area with a combustible dust atmosphere are protected by pressurization or forced ventilation, or both. Also enclosed is a space in a non-hazardous area that has an internal release point of an incendiary substance. “ n ” - Vapor safety (also fume safety). The ingress of gases is prevented by the design of the enclosure. (nA - Non sparking device, nC - Encapsulated device, nL - Energy limited apparatus, nL - Associated energy-limited apparatus, nR - Restricted-breathing enclosure) “ m ” - Potting encapsulation. Equipment or parts thereof that can ignite an explosive atmosphere must be embedded in a sufficiently resistant potting compound. “ t ” - Dust protection by enclosure. Type of protection also applicable to non-electrical equipment where the enclosure is so tight that no combustible dust can penetrate, and the surface temperature of the enclosure is limited. [IEC 60079-14] must be observed. “ h ” - Non-electrical explosion protection. The basic standard ( ↑ ATEX 114) defines the requirements for the design, construction, testing and marking of non-electrical equipment intended for use in potentially explosive atmospheres. It also applies to Type of protection 381 <?page no="395"?> components, protective systems, devices, and assemblies of these products that have their own potential ignition sources. This standard serves as the basis for placing these devices on the market. “ c ” , “ b ” , “ k ” - Non-electrical type of protection. Additional requirements for nonelectrical explosion protection are specified for the design and construction of equipment intended for use in potentially explosive atmospheres and already protected by type of protection “ c ” (constructional safety), “ b ” (ignition source monitoring) and “ k ” (immersion in liquid). ● The devices are generally marked with the prefix “ Ex ” and the letter “ G ” for gases/ vapors or “ D ” for dust. (+ application possible, - application not possible): EPL a EPL b EPL c Level of protection Very high High Extended d Flameproof enclosure (G) da db dc [IEC 60079-1] p Pressurization (G, D) - pxb, pyb pzc [IEC 60079-2], [IEC 60079-13] q Powder filling (G) - q + [IEC 60079-5] o Oil immersion - ob oc [IEC 60079-6] e Increased safety (G) - eb ec [IEC 60079-7] i Intrinsic safety (G, D) ia ib ic [ABNT IEC/ TS 60079-39] n Vapor safety (G) - - nc, nr [IEC 60079-15] m Potting encapsulation (G, D) ma mb mc [IEC 60079-18] t Dust protection by enclosure (D) ta tb tc [IEC 60079-31] s Special protection sa sb sc [IEC 60079-33] h Basics, non-electrical equipment (G, D) + + + [ISO 80079-36], [IEC 60079-0] c b k Constructional safety Control of ignition source Liquid immersion ca ba ka cb bb kb cc bc kc [ISO 80079-37] Type of protection 382 <?page no="396"?> U ÜAnlG, short for German: Gesetz zur Anpassung des Produktsicherheitsgesetzes [ ↑ ProdSG] und zur Neuordnung des Rechts der überwachungsbedürftigen Anlagen vom 27.07.2021 (Act on the adaptation of the Product Safety Act and on the reorganization of the law on systems requiring monitoring of 27.07.2021) Ultrasound. Generally defined as one of 13 ↑ ignition sources. The energy emitted by the transducer is absorbed by the liquids or solids being treated and, as a result of internal movements (e. g. friction), heating can occur to above their ignition temperature. Detailed regulations can be found in [TRGS 723]. Under-level filling, ↑ filling pipe Unipolar charge (also monopolar). Charge of only one sign on a charged insulator ( ↑ charge distribution). Used for other ranges of electrical engineering: High-voltage direct current transmission, asymmetrical signal transmission, generation of an electric voltage using ↑ Lorentz force, field-effect transistor. Upper explosion limit (UEL), ↑ explosion limit Use as intended. Statements about the safety of a device or operating resources always cover only the area of its intended use. Example: According to its approval, a drum can only be used to hold, store and transport certain products. For example, it is not permitted to be used as a support or as a substitute for a ladder. Useful application (electrostatic). To bring electric charges of a defined height, with the correct sign, in a targeted manner, as homogeneously as possible, to a specific location for a specific time, to exploit the effects of the ↑ Coulomb force. The useful application can be found in many areas of industry. The principle of ↑ charge displacement is used, where a current flow is initiated between a ↑ charging electrode (it can also be the plate of a capacitor) and a counter potential ( ↑ counter electrode). For applications, e. g. on ↑ material webs (laminating, ↑ electret production), it makes sense to place the charging electrode opposite an “ edge ” to concentrate the current flow. The surface can be electrostatically <?page no="397"?> conductive or insulating. In any case, it must be ensured that the charge applied to it cannot flow to earth potential during the intended processing time. ( ↑ chargeability, ↑ adhesion, ↑ blocking, ↑ remoistening, ↑ cast process, ↑ in-mold labeling, ↑ separation of substances, ↑ air boundary layer, ↑ xerography, ↑ laser printer, ↑ primeval code, ↑ perforation), [SE Section 8] The use of pulsed electric fields has been successfully applied to the production of ↑ food since about 2010. UTC, short for Universal Time Coordinated. Since 1972 the new name for Greenwich Mean Time (formerly GMT), has served as the world time to which all time zones refer. UV radiation. The invisible, high-energy portion of optical radiation ( ↑ electromagnetic radiation) that is not perceived by humans, with wavelengths λ in the range 100 - 400 nm, adjacent to the “ blue end ” of the visible spectrum. It is a weakly ↑ ionizing radiation, e. g. produced by atmospheric ↑ gas discharges ( ↑ Lenard effect). It is divided into: UV-A: 400 - 315 nm UV-B: 315 - 280 nm UV-C: 280 - 100 nm It has both biological properties (including germicidal and carcinogenic) and physical effects. For example, UV radiation from the sun can cause chemical reactions such as hydrogen chloride (HCl, also known as chlorine oxyhydrogen): HCl has been passed through a highquality borosilicate glass that is 100 % transmissive to UV-A and 60 % transmissive to UV-B. Under certain circumstances, sunlight can also cause explosions ( ↑ ignition source no. 9). [SE Section 7.7.4] UTC 384 <?page no="398"?> V Vacuum. Enclosed space on Earth with a pressure significantly lower than that of the atmosphere (average 101.325 kPa ( ≈ 1 bar) at sea level). It contains fewer particles available to transport matter or energy. The best vacuum is in interstellar space. Some ↑ natural constants are related to vacuum. For example, the speed of light in a vacuum is 299 729 458 m/ s ( ≈ 300 000 km/ s). The ↑ permittivity ε r is 1 in a vacuum and 1.00059 at normal pressure in air. However, this small deviation from vacuum is accepted in engineering. ( ↑ mean free path, ↑ Avogadro ’ s number, ↑ Paschen ’ s law) Vacuum range Pressure range Rough vacuum 1000 to 10 -1 Pa (1 to 10 -3 mbar) Fine vacuum 10 -1 to 10 -3 Pa (10 -3 to 10 -5 mbar) High vacuum 10 -3 to 10 -7 Pa (10 -6 to 10 -9 mbar) Ultra-high vacuum < 10 -7 Pa (< 10 -9 mbar) Vacuum cleaner. Pneumatic or electric vacuum cleaners are not unproblematic for industrial use if they are used in ↑ Ex-areas or if they are used to vacuum combustible dust from the floor (e. g. wood dust). All necessary measures must be taken to avoid ↑ sparks and ↑ propagating brush discharges (earthing of all metal parts, dissipative filter inserts, electrically conductive hoses, ↑ filter material). Vacuum cleaners must only be used for their intended purpose (extraction of dust layers) and not to collect spilled products. Valence band (Latin: valentia, “ strength, valence ” ). Energy range of the bound electrons in the ↑ band model. The number of ↑ valence electrons determine the chemical properties of the atom. Valence electrons. The electrons of an ↑ atom available for chemical reactions from the incompletely covered outer electron orbits. Valence electrons determine the various forms of chemical bonding and the chemical and physical properties of atoms or their bonding states. (Noble gases do not have valence electrons.) Validation (Latin: validus, “ effective ” ). Method of evaluating components, products, processes and projects to ensure that they conform to the specified requirements. [ISO 9000] Valve. Controllable throttle or shut-off device in ↑ pipe/ pipeline ( ↑ armature). Since a greater or lesser portion of the valve surface is always exposed to the flow, electrostatic charges often occur. Therefore, in ↑ Ex-areas all metal valve parts (e. g. ball and pipe section) must be earthed to prevent ↑ spark discharge. Valves with insulating coatings are problematic. Contamination can create conductive islands that are insulated from earth, or high ↑ charge densities can occur that trigger ↑ propagating brush discharges. (see figure next page) <?page no="399"?> Van de Graaff, Robert Jemison (1901 - 1967). American physicist, inventor of the ↑ Van de Graaff generator for generating high DC voltages (up to over 100 kV). Van de Graaff generator. An electrostatic machine designed by R. J. ↑ Van de Graaff to generate high voltages (up to over 100 kV), mainly for experimental purposes. The basic principle of electrostatic generators ( ↑ Felici generator, ↑ pelletron) is that mechanical work is applied against the electric field (overcoming the repulsive ↑ Coulomb force), thus increasing the voltage. The ↑ charge separation effect of the tape at the lower pulley is used to transport charge to electrode (2) with the elastomeric tape and to accumulate charge on the insulated sphere at the top. The earthed pin (1) causes the belt to discharge. When the Van de Graaff generator is placed in a pressure vessel, voltages >> 1 MV can be generated. ( ↑ gas discharge tube) Van der Waals, Johannes Diderick (1837 - 1923). Dutch physicist, discoverer of the laws of attraction between molecules. Van der Waals forces. Term for intermolecular forces ( ↑ molecular force) based on electrostatic interactions. The range is small < 10 -7 m [Ambrosetti, A. et al. (2016)]. ( ↑ adsorption) When two atoms or molecules come close to each other, the following situations can occur: - Dipole-dipole interaction: polar molecules attract each other. - Dipole-ion interaction: polar molecules and ions attract each other. - Dipole moment in polarizable molecules: ↑ influence creates a rectified dipole moment, resulting in an attractive force between the two particles. Vapor (steam) (The term “ steam ” is usually used for water.). Gaseous phase of a substance that is in contact and in thermodynamic equilibrium with the solid or liquid phase of the same substance ( ↑ combustible substance (flammable vapor)). Most vapors are invisible. In the case of a cloud of white “ water steam ” , it is not the vapor itself that is visible, but its fraction that has already condensed into small water droplets ( ↑ aerosols, ↑ wet vapor, ↑ fog). When vapor is expanded, no electrostatic charge should be expected, Van de Graaff 386 <?page no="400"?> since flowing ↑ gases are not charged. However, high charging can occur if some of the vapor condenses due to cooling during flashing and these aerosols undergo separation charging. ( ↑ atomization, ↑ steam electrification machine) Vapor-air mixture. Based on water, this can cause ↑ inerting (displacement of atmospheric oxygen). Explosive vapor-air mixtures are formed from ↑ flammable liquids when the ↑ flash point in air is exceeded. Vapor pressure curve. A certain vapor concentration is formed over any liquid surface according to its vapor pressure and temperature. The figure shows a vapor pressure curve for ethanol with the mixing ranges entered therein. According to this, the explosive capability exists only within the explosion range limited by the lower explosion temperature (at 12°C) and the upper explosion temperature (at 37°C). [SE Section 1.2.2] Vapor recovery system, ↑ gas swing adsorption Variable capacitor, ↑ capacitor Variable-capacitance diode (also varicap). The barrier layers in ↑ semiconductor diodes can also be used as capacitors. Since the blocking layer width can be controlled by an external DC voltage, the ↑ junction capacitance can also be changed. The junction capacitance can be varied up to about 600 pF, with the capacitance decreasing almost inertia-free as the cut-off voltage increases. Variable-capacitance diodes are used for capacitive tuning of resonant circuits, but their ↑ capacitor quality is not sufficient for use in electrostatic measurement. Variable-capacitance diode 387 <?page no="401"?> Varistor (Latin: varius, “ different ” , Latin: resisto, “ resistance ” ) (also known as VDR - voltage dependent resistor). Is used to protect components and systems from overvoltage, e. g. as a result of electrostatic charging ( ↑ arrester). Varistors usually consist of sintered metal oxide grains (usually zinc oxide) with different conductivities, whose contact surfaces form a network of series and parallel circuits and in which the resistance decreases as the voltage increases. Varistors are always connected in parallel with overvoltage-sensitive components or devices. Because they are available with holding voltages as low as a few volt, they can also be used to protect the inputs of measurement devices, such as ↑ electrometers and ↑ oscilloscopes. Varistors are generally used in combination with other components in protective circuits. When high-energy transient pulses are expected, varistors alone are generally not sufficient to dissipate the energy and must be combined with, for example, ↑ lightning arresters. VbF, short for German: Verordnung über brennbare Flüssigkeiten (Ordinance on combustible liquids). Since 2003 it has been replaced by Operational safety regulation ( ↑ BetrSichV) and its technical regulations. [VbF] VDE, short for German: Verband Deutscher Elektrotechniker e. V. (Association for Electrical, Electronic & Information Technologies). Founded in 1893, based in Frankfurt/ Main. It is the publisher of the VDE regulations, which are prepared by the ↑ DKE, which is supported by the VDE. VDE regulations and VDE guidelines are also DIN standards. The VDE maintains an approved neutral testing center for electrical equipment and components, which allows manufacturers to affix a test mark with the VDE logo. VDI, short for German: Verein Deutscher Ingenieure ( ↑ Association of German Engineers) of all disciplines VDR, ↑ varistor Vector. A quantity in space of a given length, direction, and directionality. A vector has a beginning and an end point. In a coordinate system it is described in terms of length and angle. The length is also called the magnitude of the vector. A vector whose start and end points coincide is called a zero vector; it has no direction. A vector of length 1 that is parallel to a vector of the same direction is called an “ associated unit vector ” and is denoted by a superscript 0. In the electrostatics, the vector of the electric ↑ field strength has a starting point, but it ends at infinity. Whereby the electric field strength has a negative gradient ( ↑ potential). ( ↑ electric flux density, ↑ field lines, ↑ homogenization) Vector arithmetic. Since vectors must consider not only the magnitude but also the direction (the angle), these arithmetic operations differ considerably from the arithmetic rules for numbers (scalars). Addition and subtraction correspond to the geometric composition of distances in space ( ↑ field lines, ↑ EFM, ↑ excess charge). Varistor 388 <?page no="402"?> Vehicle charging. Vehicles behave electrically like ↑ capacitors as soon as they are insulated from earth by their tires and/ or the floor covering. Their capacitances range from about 100 pF (small transport vehicles) to several 1000 pF (tanker trucks). They can be charged, for example, during loading or unloading (filling or emptying), but also during rolling due to ↑ influence. This can lead to discharge sparks; therefore, the ↑ leakage resistance of small vehicles must not exceed 100 M Ω and large vehicles must not exceed 1 M Ω in ↑ Ex-areas ( ↑ refueling, ↑ earthing, ↑ earth monitoring). Contamination of the ↑ vehicle tires (e. g. with road salt in winter) can have a significant impact on vehicle charging. Vehicle tank. Preferably made of polyethylene. Shortly after the first refueling, the tank contains a ↑ rich mixture, which is why an explosion will not occur and the tank can therefore be filled by “ anyone ” ( ↑ gasoline, ↑ gasoline vapor, ↑ refueling). A fire can only occur in the upper part of the fuel filler neck. [SE Sections 1.4 and 7.5.8] Vehicle tires. Should have dissipation capability to prevent ↑ vehicle charging (during fueling and driving). In the past, this was achieved by adding carbon black ( ↑ carbon). This has been replaced by the addition of highly dispersed silica (e. g. ↑ Aerosil ® ), which means that charge dissipation is no longer readily available. As a solution, a small conductive strip is usually arranged in the middle of the tread, which establishes an electrical connection to the under-protector and, via this, contact with the rim. In Ex-areas, the value of the ↑ leakage resistance for vehicle tires (e. g. for forklift trucks) must not exceed 100 M Ω . [TRGS 727] Ventilation. should prevent or limit the formation of hazardous ↑ Ex-atmospheres. If the type of air guidance ensures that there is no risk of explosion at any time or place, e. g. due to electrostatic charging, appropriate protective measures may not be required. This can only be achieved if it is possible to estimate the maximum quantity of flammable gases and vapors that can escape and if the location of the source and the dispersion conditions are sufficiently known. Dust and vapors must be extracted at the point of generation ( ↑ exhaust system - object). Hazardous dust deposits must be safely prevented. In above-ground spaces, the construction and weather conditions normally result in natural ventilation where air is exchanged at least once an hour (air exchange rate n = 1/ h). In basement spaces, an air exchange rate of 0.4/ h can be used as a guide. Higher air exchange rates and a more targeted air flow can be achieved with technical ventilation, the effectiveness of which must be monitored. [TRGS 721 to 723 and 725] Venturi principle. Named after the Italian physicist G. B. Venturi (1746 - 1822), in which a pipe is constricted to such an extent that the dynamic pressure rises sharply, and the flow velocity increases inversely proportionally. When a pipe is connected at its narrowest point, a vacuum is created in the pipe, which can suck in liquids or fluidized solids, thin continuous strips and gases and transport them into the nozzle (powder ↑ coating), ↑ edge strip disposal, ↑ jet pump). The Venturi principle is also used to measure flow rates by measuring the differential pressure between p W and p E (see figure next page). Venturi principle 389 <?page no="403"?> (Source: de-academic.com) Verification (of calibration) (late Latin: aequare, “ to make equal ” , “ to compare ” ). Quality testing and marking of measuring instruments reserved for legal metrology (verification office). In Germany, it is governed by the Measurement and Verification Act (MessEG) in combination with the Measurement and Verification Ordinance (BGBl. 2014). Among other things, verification is mandatory for pricing applications, e. g. fuel at gas pumps, letter scales for postage, and meters for electrical energy consumption. Violin bow effect. It is also used to explain the phenomenon that similar substances can become electrostatically charged in opposite directions when separated. After much study, P. S. H. Henry came up with an explanation called “ asymmetric friction ” : When two substances rub against each other, the surfaces (sizes) involved are by no means always the same. An extreme example of this is when a violin bow rubs against a violin string. The string is rubbed at a point, the bow along a line. Although both parts are made of the same material, collagens (long-fiber, high-molecular scleroproteins), the catgut string is always positively charged compared to the horsehair bow, which is negatively charged. Henry explained that when the violin bow is struck across the string, the string is subjected to a higher specific charge and therefore heats up more at the point of friction than the bow, whose charge is spread over its entire friction length. The string is thus heated to a higher temperature than the bow, always in relation to the rubbed areas, with the result that it releases electrons to the bow ( ↑ electron emission energy). This explains the positive charge of the string and the negative charge of the bow. With a little experimental skill, it is possible to demonstrate this effect of asymmetric friction on other similarly chargeable materials. [Henry, P. S. H. (1953)] Viscosity (Latin: viscum, “ mistletoe, bird ’ s glue ” ). Force acting through internal friction between molecules or atoms, exhibited by gases and liquids. Ductile solids also exhibit viscosity. As temperature increases, viscosity decreases in liquids and increases in gases. The viscosity of some electrically insulating liquids can be influenced by electric ↑ polarization, e. g. by applying an electric field ( ↑ electrorheological fluid). Volt. Derived ↑ SI unit [V] of the electric ↑ voltage U, named after A. ↑ Volta. 1 V is defined as the electric voltage between two points of a homogeneous and uniformly tempered Verification (of calibration) 390 <?page no="404"?> metallic conductor in which a power of 1 Ω is converted at a constant current of 1 A between these points. {Appendix M.4} Volta, Allessandro Graf (1745 - 1827). Italian physicist invented the ↑ electroscope (straw electroscope, precursor of the ↑ gold leaf electroscope) and the ↑ plate capacitor. He described the contact electricity between different metals and realized that two metals and an ↑ electrolyte were necessary for the generation of galvanic electricity ( ↑ Voltaic pile). The first suggestions for the construction of an ↑ influence electrifying machine can be traced back to him. Voltage (electric) (also tension). Symbol U with the derived ↑ SI unit [V], named after A. ↑ Volta. It is defined by the ↑ charge Q and the energy W and is equal to 1 V when the electric charge of 1 C is separated or transported with the energy of 1 Nm. (1 V = 1 kgm 2 / s 3 A) As a result of different ↑ potentials, the voltage is the cause of the current flow in a circuit and its value represents the work done when a charge is moved in the electric ↑ field ( ↑ high voltage, ↑ low voltage, ↑ Voltaic potential, ↑ Galvani voltage, ↑ Lenard effect). {Appendix M.4} Voltage balance, ↑ Kirchhoff ’ s balance Voltage divider. Used for adaptation of the voltage requirement of a load (e. g. dimming a lamp, speed control of a DC motor) and is a series connection of at least two resistors. In ↑ measurement technology, it is also used to measure ↑ high voltages with voltmeters in the V-range. Voltage dividers for alternating current can also be implemented using inductive or capacitive reactance resistors ( ↑ alternating current quantity). Example of a high-voltage measurement using a voltage divider: The belt generator B supplies a high voltage of e. g. 100 kV. With a ratio of the resistances R v / R p = 100 / 1, a voltage of 1 kV is present at the static voltmeter V. If a resistance value of 100 G Ω is selected for R v , the belt generator is loaded with 1 μ A. If it could deliver a maximum current of 10 μ A, the voltage divider would consume 10 % of its power and the measurement error would be correspondingly large. {Appendix M.7.1} Voltage drop. Occurs in any conductor carrying current, so that the original voltage is no longer available at the current consumer. According to ↑ Ohm ’ s law, the greater the current and resistance, the greater the voltage drop. Voltage drop can also be considered for only one part of a circuit. Voltage level. Electric voltages are typically in the mVto MV-range. Typical units are: - Millivolt: ↑ thermoelectric voltage, ↑ contact potential - Volt: ↑ primary cell, electrical engineering (power supply) - Kilovolt: ↑ gas discharge tubes, electrostatic processes ( ↑ useful application) - Megavolt: ↑ thunderstorm lightning, ↑ accelerators Voltage level 391 <?page no="405"?> Voltage limiter. A device whose resistance decreases with increasing voltage ( ↑ varistor). Voltage measuring head, ↑ influence electrostatic field meter Voltage series ● The electrochemical series arranges chemical elements and combinations according to their electrical or electrochemical potential and thus allows them to calculate the voltage for the pairing of different elements and combinations ( ↑ Lewis ’ s acid-base concept). ● The ↑ triboelectric series was postulated by A. ↑ Coehn. Voltage source. Active two-terminal network for supplying a defined voltage. A voltage source converts non-electrical energy into electrical energy or forms electrical energy (power supply unit). The performance of a voltage source is mainly determined by its ↑ internal resistance ( ↑ adaptation). In ↑ no-load operation, the voltage source is unloaded, no current is flowing, and it has its highest possible voltage, the ↑ open circuit voltage. In a short-circuit, a current flow that is only determined by the internal resistance of the voltage source. The latter is calculated from the quotient of the open circuit voltage and the short-circuit current. In contrast to electrotechnical voltage sources, electrostatic voltage sources generally have such a high internal resistance that they are not damaged in the event of a short-circuit ( ↑ electrostatic - system comparison). Voltaic pile. The first usable source of electricity was invented by A. ↑ Volta in 1800 by connecting individual galvanic elements ( ↑ primary cell) in series to generate high voltage. He placed a cloth disk moistened with diluted sulfuric acid on a zinc plate and a copper plate on top. He made a large number of these galvanic elements and stacked them so that the zinc plate of the next element was on top of the copper plate of the previous element. This ↑ series connection results in the addition of the voltages of the individual elements. Experiments with Volta ’ s pile accelerated the study of electricity and led, among other things, to the discovery of ↑ electrolysis. Voltaic potential (also Voltaic effect at contact potential). Defines the external electrical surface potential due to excess charges of opposite polarity at phase boundaries ( ↑ charge double layer) when they are separated. This external potential difference and the internal electric potentials result in the ↑ Galvani voltage. Depending on the position of the material partners in the electrochemical series, corrosion (e. g. material partner Cu/ Zn) occurs on contact due to the galvanic potential as a result of the electric current flow. [Westphal, W. H. (1970)] Voltameter (not to be confused with ↑ voltmeter). From today ’ s perspective, is a historical device for measuring quantities of electricity ( ↑ coulometer). It is based on the electrolytic precipitation caused by the electric current. Examples of voltameters: Voltage limiter 392 <?page no="406"?> ● Oxyhydrogen voltameter for measuring the amount of oxyhydrogen produced by electrolysis of aqueous solutions (the amount of charge of 1 C produces 0.174 ml of oxyhydrogen under normal conditions). ● Silver voltameter used to measure the amount of metal deposited from a silver nitrate solution (the amount of charge of 1 C deposits 1.118 mg of silver). ● Copper voltameter which measures the amount of metal deposited from a copper sulfate solution (the amount of charge of 1 C deposits 0.329 mg of copper). Volt-ampere. Unit [VA] of electrical power P, equal to ↑ Watt [W]. Volt-amperes are preferably used to denote apparent power in alternating current (to distinguish it from active power in [W]). Voltmeter. General term for a device used to measure electric voltages. To avoid errors in electrostatic measurements, the internal resistance of a voltmeter must be so high that the voltage source is not noticeably loaded. In the field of electrostatics, this condition is met by ↑ static voltmeters and ↑ spherical spark gaps. ( ↑ influence electrostatic field meter, ↑ contact voltmeter) Volume. According to [TRGS 727] und [IEC/ TS 60079-32-1], different volumes are limited for different material statuses, e. g.: - Use of insulating containers for ↑ Ex-zone 1 to a maximum of 5 l. - Processing of flammable liquids in plastic containers > 5 l is not allowed without additional explosion protection measures. Volume charge. Spatially distributed electric charge in a defined volume, formed by charge carriers (predominantly of one charge sign). ( ↑ space charge) Volume charge density, ↑ charge density Volume conductivity. Term for homogeneous conductivity in a body ( ↑ resistance, ↑ volume resistance). Volume resistance. Symbol R V , unit [ Ω ]. It is used in material classification as an important parameter for determining the electrostatic properties ( ↑ dissipation capability) and its electrostatic behavior ( ↑ resistance). When determining the volume resistance, a DC voltage is applied to two ↑ measuring electrodes (DC resistance). Possible polarization phenomena at the electrodes are neglected ( ↑ resistance measurement). If the expected volume resistance is > 10 9 Ω m, a guard ring circuit must be used for the measurement ( ↑ measurement error). Volume resistivity. Symbol ρ v , unit [ Ω m] (occasionally also [ Ω cm]). Is the electrical resistance between two opposite electrodes, each with an area of 1 m 2 at a distance of 1 m (cube of 1 m 3 ) (DC resistivity). In practice, it is the volume resistance related to a cubic unit volume ( ↑ measurement voltage, ↑ measuring electrode). {Appendix M.7.1 and M.7.1.4}, [SE Section 3.5.5] Volume resistivity 393 <?page no="407"?> W Wagner ’ s hammer (induction coil). Magnetic self-interrupter designed by J. P. Wagner in 1836, which takes its energy from the circuit to be interrupted. The most common application is a bell. Today, Wagner ’ s hammer has been largely replaced by electronic circuits. The illustration shows a Wagner ’ s hammer as a high voltage generator with a variable spark gap as an overvoltage limiter. Waiting time (also delay time for measurements). Time between the application of a ↑ measurement voltage and the reading of the measured value on a measurement circuit. For ↑ resistance measurement with DC voltage, a stable measurement result can be obtained after the waiting time ( ↑ charging current). Unless otherwise specified, the measurement result on insulating materials is read 1 minute after the measurement voltage is applied, because experience has shown that the constant state is reached then for materials with a ↑ volume resistivity ρ v < 100 G Ω m. For materials with higher resistivity, the decrease in measurement current may last for several minutes, hours, or days. If the time dependence of the resistance is to be characterized for such materials, correspondingly longer application times of the measurement voltage are required. Walk-in charge. To evaluate the charging behavior of a ↑ floor or floor covering, it is generally sufficient to measure its leakage resistance. For a more differentiated evaluation of the electrostatic behavior when walking on the floor, a test method has been developed that involves footwear in combination with a person. The person performing the test must walk on a defined test surface in a precisely defined manner. The voltage to earth generated on the person is used for evaluation. <?page no="408"?> More than 30 years ago, there was already a mechanized walking test according to the now withdrawn standard [DIN 54345-3], in which a specially designed roller moves over the material to be tested. Here, too, the voltage induced against earth during the process at a “ person capacity ” is evaluated. In both methods, the charge curve is plotted on a voltagetime graph and used to evaluate the electrostatic properties of the tested pavement. ( ↑ measuring electrode for solids no. 20, ↑ personnel charging), [IEC 61340-2-3], [IEC 61340- 4-5] Walking test, ↑ walk-in charge Warning sign. Part of an organizational measure to avert a hazard. If, for example, an ignition risk due to electrostatic charges from housing or parts of housing made of plastic cannot be avoided by the design of the operating resources (e. g. by limiting the dimensions of chargeable surfaces), a warning sign must indicate the safety measures to be applied during operation. Example: The transparent plastic covers of linear luminaires can - if charged - pose an ignition risk for ↑ Ex-atmospheres. The warning sign “ Only clean with a damp cloth ” warns the user not to charge the plastic by wiping it dry. The warning sign can be part of a ↑ type examination certificate and must therefore not be removed. [IEC 60079-0], [TRGS 727] Waste. Product or material that is discarded or no longer needed at the end of a process. Explosive and flammable wastes are of major electrostatic concern. Flammable or hazardous waste should be handled with similar electrostatic precautions as non-waste materials [IEC/ TS 60079-32-1]. Requirements are made regarding the size of containers ( ↑ container size) for open discharge. Containers with a capacity of more than 5 l must be made of conductive substance and earthed. According to other regulations, liquid waste must be stored in closed containers protected against overpressure. The ↑ gas swing adsorption shall be used to reduce emissions during container filling, or displacement air shall be exhausted. In addition, open transfer points should be equipped with exhaust systems. The displaced gas from the containers and the extracted air shall be fed into solvent recovery or post-combustion. Water activity. Moisture absorption from the air ( ↑ equilibrium moisture content) reduces the electrical resistance of insulating materials to a greater or lesser extent depending on their water absorption capacity. The influence of ↑ humidity on the ↑ surface resistivity ρ s is shown in figure. Due to the low hygroscopicity of ↑ polymers (e. g. PE, PP, PTFE), no significant reduction in their ↑ chargeability is to be expected for this group of materials as a Water activity 395 <?page no="409"?> result of higher humidity. On the other hand, the surface resistance of polyamides, for example, is noticeably reduced by higher humidity. The term water activity is also used for the amount of water available for microbial and biochemical reactions in food. Water aerosols, ↑ remoistening, ↑ atomization Water content. Which indicates the amount of water in mass % present in a substance (gas, liquid, solid). For a given product, there is a direct relationship between the ↑ water activity and the water content, the ↑ sorption isotherm. It can be presented graphically or in tabular form. Relating the existing water vapor pressure of gas mixtures to the highest possible water vapor pressure gives the relative ↑ humidity (RH), which is expressed in %. Water curtain. It can be used by firefighters to safely suppress water-soluble gases (e. g. chlorine) released during an accident. It should be noted that ↑ spraying water under high pressure can lead to electrostatic charges, resulting in ↑ space charge clouds with a corresponding ignition hazard. Water droplet generator, ↑ Kelvin generator Water film. When water flows over an insulating material surface, the decisive factor for the generation of charging is whether a film of water forms behind the flowing water ( ↑ hydrophilic surface) or whether an unwetted insulating material remains ( ↑ hydrophobic surface, e. g. oil or wax view). If a water film forms, the flowing water molecules separate from the molecules adhering to the hydrophilic surface and the charges can equalize immediately. If a water film does not form, ↑ charging occurs directly against the hydrophobic surface and, accordingly, charges are carried along by the occurring water and the water becomes an insulated electrical conductor with a ↑ capacitance corresponding to its size, which can dissipate in a ↑ spark discharge. Water steam. Water in the gaseous state ( ↑ humidity). Waterfall electricity, ↑ Lenard effect Watt. Derived ↑ SI unit [W] of electrical power P ( ↑ volt-ampere), named after J. ↑ Watt, which is defined as a direct current of 1 A at a direct voltage of 1 V (1 W = 1 J/ s = 1 VA = 1 kg m 2 s -3 ). {Appendix M.6.1.2} Watt, James (1736 - 1819). English engineer and inventor. Among other things, he invented the steam engine and, together with M. Boulton, developed it into a universally applicable machine that contributed significantly to the industrial revolution. Watt-hour. Incoherent, derived ↑ SI unit [Wh] named after J. ↑ Watt as a common measure of energy (1 Wh = 3600 Ws = 3.6 kJ). Watt-second. Derived ↑ SI unit [Ws] named after J. ↑ Watt for energy and work W. It is internationally equated with ↑ Joule [ J] (1 Ws = 1 J). Waxes. General term for a group of hydrocarbon mixtures that soften and become liquid at temperatures of around 40 °C and above. They are used in a variety of applications (including as adhesives in the production of composites (e. g. butter wrappers)). They are Water aerosols 396 <?page no="410"?> generally ↑ insulating materials that are well suited for the production and demonstration of ↑ electrets ( ↑ carnauba wax). Web tension profile. When unwinding or transporting ↑ material webs over ↑ guide rollers, a run-off edge occurs as a result of adherence forces of the web to each other or to the guide roller. The different distribution of the pull-off forces is also responsible for the load distribution on the web surface. An optical measuring device has been developed at the Fraunhofer IVV for recording the force ratios, in which the electrostatic ↑ charging of the web against a guide roller is used to create constant conditions ( ↑ useful application). The measured values should be used to gain knowledge about processing, especially for packaging films. [SE Section 8.2.12], [Ludat, N. et al. (2018)] Weighing. Used to determine the unknown mass of an object, either by comparison with a known mass or by the effect of gravity on the mass. In precision weighing (less than 1 mg), interference from electrical fields must always be considered. Both the object and the environment (e. g. plastic windshield) can be electrostatically charged, and field forces can cause a measurement error. Simple discharge measures, such as ↑ ionizers, often provide a remedy. Welding electrode. A metal rod coated with various materials. Depending on the application, the coating consists of calcium carbonate, titanium dioxide (rutile) and organic substances and combinations thereof and serves in particular to ionize and stabilize the arc and to shield the molten metal from nitrogen and oxygen (embrittlement, pore formation) by means of shielding gases. Wet separation, ↑ separation of substances Wet vapor. Mixture of liquid and vapor of the same substance. If more heat is added to the wet vapor, the temperature remains constant until all the liquid has evaporated Wet vapor 397 <?page no="411"?> ( ↑ saturated vapor); only then does the temperature rise (superheated vapor). In electrostatics, charging must always be expected in flowing wet vapor due to the entrained ↑ aerosols ( ↑ gas flow). Wettability. Condition in which the solid/ gaseous interface is replaced by the solid/ liquid interface. Wettability causes a liquid to adhere more or less intensively to the surface of a solid, e. g. to the walls of a vessel. A liquid is said to be wettable if it stands higher on the wall than in the center of a vessel, its ↑ contact angle is < 90°. Correspondingly, a contact angle > 90° describes the fact that a liquid is poorly wettable and therefore stands lower on the vessel wall than in the center. The ↑ adhesion of the solid and/ or the ↑ cohesion in the liquid are the main determinants of wettability ( ↑ surface tension). In general, the surfaces of insulating materials have low wettability and can therefore electrostatically charge even conductive liquids (e. g. water) flowing along them ( ↑ container cleaning). A widely used process to improve wettability ( ↑ surface energy) is ↑ corona pretreatment. It is mainly used to improve the adhesion of applied layers (e. g. printing on polyethylene films). The adhesive forces on the surfaces of insulating materials are also influenced by the charge states present there. For example, latent electrostatic charge patterns ( ↑ xerography) can be visualized via their adhesion effects using ↑ liquid toner. Wetting agent. A substance that causes a reduction in the ↑ surface tension (interfacial tension) of liquids to achieve better ↑ wettability of the materials in contact with them ( ↑ antistatic agents, ↑ surfactants). Wheatstone, Sir Charles (1802 - 1875). English physicist and inventor invented the needle telegraph, the bridge network named after him and, independently of W. v. ↑ Siemens, the dynamo-electric principle. Wheatstone bridge. Four-arm circuit for ↑ resistance measurement, invented by S. H. Christie and named after Ch. ↑ Wheatstone, based on ↑ Kirchhoff ’ s rules. In contrast to the direct methods (current/ voltage measurement method), the Wheatstone bridge is a comparison method ( ↑ bridge network) in which the resistance of the ↑ DUT in one branch of the bridge is compared with a known resistance in the other branch of the bridge by zero balancing. The Wheatstone bridge requires more effort but results in higher accuracy. When used with AC voltage, it can also be used to determine reactance ’ s. ( ↑ alternating current quantity, ↑ inductance, ↑ capacitance, ↑ capacitance measuring bridge) White noise. A disturbance signal with constant power density across all frequencies, named after H. Nyquist (1899 - 1976). It is named for the sonic impression that can be heard when white noise is amplified enough to be heard through a connected loudspeaker. It serves as a mathematical model to describe the slight change in electrical circuits and resistances caused by the thermal movement of electrons, resulting in a so-called noise voltage. According to Nyquist, the average noise power of Wettability 398 <?page no="412"?> white noise depends on the temperature and the range used. It sets an upper limit for measuring high resistances. (device: psophometer) Wide-range electrode, ↑ ionizer Wiedemann-Franz-Lorenz law. A physical law empirically established by G. H. Wiedemann, R. Franz (1853), and L. Lorenz (1872), according to which the thermal and electrical conductivity of metals in particular are almost proportional to the absolute ↑ temperature, i. e. good conductors of electricity are also good conductors of heat and vice versa. Wien bridge. A circuit named after M. K. W. Wien (1866 - 1936), which is based on the principle of the ↑ Wheatstone bridge, whereby in addition to the active resistances, capacitances are connected in parallel in one branch of the bridge and in series in the other. In this way, impedance measurements can be made. ( ↑ bridge network) Wilcke, Johan Carl (1732 - 1796). Swedish physicist described the phenomenon of the ↑ electrophorus in 1762 and interpreted the process of ↑ influence as dielectric polarization in 1777. Wimshurst machine. ↑ Influence electrifying machine developed by J. Wimshurst (1832 - 1903), which has symbolized the concept of electrostatics since the 19th century. An analogy can be drawn between the principle of the Wimshurst machine and the dynamoelectric principle of W. v. Siemens. Both machines are “ excited ” by remanence (residual charge or residual magnetism) and convert mechanical energy into electrical energy. Both can be used as motors and generators. Wind, ↑ ion wind Winding / Unwinding ● When winding ↑ material webs, the charges coming from the processing machine are accumulated in the roll (e. g. field strengths of 1 MV/ m have been measured). ( ↑ super brush discharge) In addition, ↑ telescoping often occurs, i. e. the web moves sideways. ● When unwinding material webs, separation of the existing contact can also lead to high electrostatic charges may occur. [TRGS 727 Section 3.3], [Schubert, W., Ohsawa, A. (2024)] Wiring system. The entirety of cables, lines and busbars and their fastening as well as their mechanical protection. [IEC 60050] Wood. As a cellulosic material, wood - like the ↑ paper made from it - has a relatively low electrical resistance in electrostatic terms but is classified as an insulating material in electrical terms. Its resistance is strongly influenced by moisture ( ↑ water activity). Electrostatic charging is generally not a problem when using wood due to its dissipative properties. Any charge on a ↑ packaging means can be safely discharged to earth by direct Wood 399 <?page no="413"?> contact with a dry wooden stick (usually > 100 M Ω ), as this does not generate a spark. The dissipative property of wood can be neutralized by thin insulating layers of varnish (e. g. on seating furniture). Work, ↑ energy Work clearance permit. If work is to be performed in hazardous areas (e. g. explosion hazard, radiation hazard), the company must specify the appropriate measures to prevent hazards in writing on a work clearance permit before the work begins. This may be necessary, for example, if electrostatic measurements are to be performed in an ↑ Ex-area ( ↑ Ex-zone, ↑ clearance measurement). Work equipment. Tools, devices, machines, or installations must be designed in such a way that a dangerous electrostatic charge is avoided or limited. If this is not possible, they must be equipped with devices to dissipate such charges ( ↑ BetrSichV). Work wear, ↑ personal protective equipment Workplace ordinance (German: Arbeitsstättenverordnung [ArbStättV]). As amended on 19.6.2020, it serves to ensure the safety and health protection of employees when setting up and operating workplaces. It is addressed to the employer, who must ensure that the workplace does not cause any hazards to employees and that any remaining hazards are kept to a minimum. There is no reference to electrostatics in the ArbStättV. Companies operating internationally must therefore comply with the relevant national regulations and standards for workplaces and ensure that they meet the requirements of each country in which they operate. This usually requires careful research and adaptation to local regulations and standards. Workstation platform. In electrostatically sensitive device ( ↑ ESDS) protection zones, the workstation platform must be connected to the ↑ earth. It should have a surface resistance between 100 k Ω and 1 G Ω . Wrap-around effect. In the electrostatic ↑ coating process, more or less of the coating material reaches the backside of the object through the electric field. [Mamidi, V. R. (2013)], [Bueno, M. R. et al. (2024)], [Mehta, D. et al. (2023)] Wrist earthing, ↑ earthing - personnel earthing Work 400 <?page no="414"?> X Xerography (Greek: xeros, “ dry ” , graphein, “ to write ” ). A copying process introduced by Ch. Carlson in 1937 and now widely used based on electrostatic principles. A ↑ photo semiconductor placed on a conductive, earthed surface is charged by a ↑ corotron ( ↑ corona charging). Since photo semiconductors are insulators in the unexposed state, charges on them cannot flow off. Light reflected by the text to be copied is projected onto the surface of the charged semiconductor and causes conductivity at the exposed points. This generates a latent, electrical ↑ charge image, i. e. the charge is retained at the projection points of dark parts of the image (letters), while it flows off in the light areas in between. ( ↑ copying process) The image is developed by applying a low melting point powder ( ↑ toner) to the surface, which is equipped with ↑ charge control agent and charged by ↑ carriers. The powder particles are attracted and held only by the charged surface elements and slide off the exposed areas. The toner is transferred from the photo semiconductor to the substrate (e. g. paper) and adhered there by electrostatic and ↑ Van der Waals forces. The powder on the substrate is fixed to the inked areas by heat treatment. Modern systems work according to the principle shown here, where the image is written into the photo semiconductor using either a ↑ laser or an LED. [Goldmann, G. (2006)] X-rays. Extremely short wavelength electromagnetic radiation ranging from the shortest ↑ UV to the ↑ gamma radiation range. They penetrate materials according to their mass, making differences in density visible. X-rays are produced as so-called breaking radiation by the scattering of fast charged particles (practically only ↑ electrons) from atomic nuclei ( ↑ photons). <?page no="415"?> Y Y. This letter identifies an electrical cable with a PVC ↑ plastic jacket. For example, NYM-J 3 × 1.5: “ N ” : VDE standard cable, “ Y ” : PVC insulation, “ M ” : jacketed cable, “ J ” : protective earthing conductor present, “ 3 × 1.5 ” : Three wires with a cross-section of 1.5 mm 2 each. <?page no="416"?> Z Zener, Clarence Melvin (1905 - 1993). U. S. physicist explained the transition of electrons from the ↑ conduction to the ↑ valence band in quantum mechanical terms ( ↑ tunnel effect). Zener diode. ↑ Diode named after C. M. ↑ Zener that is permanently reverse-biased and is usually a semiconductor with a ↑ PN junction. During the transition from the reverse to the breakdown region, a small increase in voltage causes a large increase in current, resulting in the release of ↑ valence electrons, which become free floating charge carriers (transition of electrons from the ↑ valence to the ↑ conduction band). As a result of the high ↑ cut-off voltage, the free electrons in the semiconductor crystal are also accelerated to such an extent that they also release valence electrons when they collide with atoms ( ↑ avalanche effect). Zener diodes are used for voltage stabilization, voltage limiting, voltage reference, etc. Zener voltage. Voltage of a ↑ Zener diode at which the blocking range ends, and the breakdown begins. Zero drift. A phenomenon that is particularly important for ↑ influence electrostatic field meters. Even slight contamination and differences in contact potential between the rotating vane and the influence electrodes will cause a zero shift. For this reason, both surfaces are made of the same largely corrosion-free material (preferably gold-plated in the same batch). Zero indicator, ↑ EFM Zero method. Principle for high-precision measurement procedures in which the measured variable is adjusted against a variable, known variable, until the difference is zero. Traditionally, the zero method is used for ↑ bridge networks. When it is important to eliminate the ↑ field distortion caused by the probe in ↑ field strength measurements, the zero method is also suitable. The potential of the probe is changed by a compensation circuit until the displayed field strength is zero. The potential of the probe then corresponds to the potential of the charged object or the ↑ equipotential line on which it is located ( ↑ EFM, ↑ potential measurement). Zero potential. Which is important for evaluating the field situation. If, for example, the floor and barrel are earthed, they are at zero potential. A person with dissipation capability shoes standing on an insulating step will become charged when emptying a metal bucket. The field strength between the bucket and the part of the system to be filled can become so high that a ↑ spark discharge occurs there. [SE Section 2.11.2], (see figure next page) <?page no="417"?> Zeta potential. An outward potential of particles ( ↑ charge double layer) responsible for their ↑ electro kinesis. In ↑ electrophoresis it is calculated from the migration speed in the DC field and its ↑ permittivity. Zinc oxide, ↑ photo semiconductor Zone, ↑ Ex-zone Zeta potential 404 <?page no="418"?> M Mathematic toolbox To make it easier to work with the mathematic toolbox, the ↑ SI units, symbols, and ↑ decadic multiples relevant to electrostatics are mentioned first. This is followed by a selection of formulas needed for calculations. SI base units Base quantity Symbol Name Unit length (radius, distance) l (x, r, d) meter m mass m kilogram kg time t second s electric current I ampere A thermodynamic temperature T Kelvin K amount of substance n mole mol luminous intensity I V candela cd Derived SI units Coherent products, quotients or power products of the SI base units, i. e. those with a numerical factor of 1. Derived quantity Symbol Name Unit Relationship electrical capacitance C farad F 1 F = 1 C/ V = 1 As/ V = kg -1 m -2 s 4 A 2 force F Newton N 1 N = 1 J/ m = m kg s -2 frequency f Hertz Hz 1 Hz = 1/ s = s -1 inductance L Henry H 1 H = 1 J/ A 2 = kg m 2 s -2 A -2 power P Watt W 1 W = 1 J/ s = 1 V A = kg m 2 s -3 electrical conductivity κ Siemens/ meter S/ m 1 S/ m = 1/ Ω m electric charge Q Coulomb C 1 C = 1 A s electrical resistance R Ohm Ω 1 Ω = 1 V/ A = kg m 2 s -3 A -2 resistivity ρ Ohm meter Ω m 1 Ω m = 10 6 Ω mm 2 / m electric voltage (electrical potential) U volt V 1 V = 1 J/ C = 1 W/ A = kg m 2 s -3 A -1 electric (electrostatic) field strength E volt/ meter V/ m 1 V/ m = 1 N/ C energy (work) W Joule J 1 J = 1 N m = 1 W s = 1 CV = kg m 2 s -2 Celsius temperature ϑ , t degree Celsius °C 0 °C = 273.15 K angular frequency ω 1/ second 1/ s 1/ s = 1 Hz pressure p Pascal Pa 1 Pa = 1 N/ m 2 = kg/ ms 2 electric flux density ~ D 1 As/ m 2 = 1 C/ m 2 <?page no="419"?> Symbol Name A area C capacitance D flux density E electrostatic field strength F force, Faraday constant I electric current L inductance P electric power Q electric charge R electrical resistance R e leakage resistance R v volume resistance R s surface resistance T temperature (in Kelvin) U electric voltage V volume W energy (work) e elementary charge (base of natural logarithms) f frequency l length m mass r radius (distance) s distance t time α (Alpha) temperature coefficient Δ (Delta) change (difference) ε (Epsilon) permittivity ( ε o = electric filed constant) κ (Kappa) electrical conductivity η (Eta) efficiency ϑ (Theta) temperature μ (My) permeability ( μ o = magnetic field constant) π (Pi) constant = 3.141592 … ρ (Rho) volume charge, resistivity ρ s (Rho) surface resistivity ρ v (Rho) volume resistivity σ (Sigma) surface charge density τ (Tau) time constant ϕ (Phi) potential (Galvani voltage) Χ (Chi) electrochemical surface potential Ψ (Psi) external electric potential (Voltaic potential) ω (Omega) angular frequency 406 M Mathematic toolbox <?page no="420"?> Decadic multiples are indicated by prefixes. It is important to note that these are only used in increments of a thousand in a single calculation. Power of 10 SI prefix Symbol Numeric value 10 24 yotta Y 1 000 000 000 000 000 000 000 000 10 21 zetta Z 1 000 000 000 000 000 000 000 10 18 exa E 1 000 000 000 000 000 000 10 15 peta P 1 000 000 000 000 000 10 12 tera T 1 000 000 000 000 10 9 giga G 1 000 000 000 10 6 mega M 1 000 000 10 3 kilo k 1 000 10 2 hecto h 100 10 1 deca da 10 10 -1 deci d 0.1 10 -2 centi c 0.01 10 -3 milli m 0.001 10 -6 micro µ 0.000 001 10 -9 nano n 0.000 000 001 10 -12 pico p 0.000 000 000 001 10 -15 femto f 0.000 000 000 000 001 10 -18 atto a 0.000 000 000 000 000 0 001 10 -21 zepto z 0.000 000 000 000 000 000 001 10 -24 yocto y 0.000 000 000 000 000 000 000 001 M.1 Field constants M.1.1 Permittivity ε Unit: farad/ meter [F/ m] " ¼ " 0 " r ε 0 absolute permittivity (8.854 pF/ m = 8.854 × 10 -12 As/ Vm) ε r relative permittivity, value of material (dielectric loss index) Note: ● permittivity of vacuum ε r = 1 ● permittivity of air amounts to ε r = 1.00059 (The modest deviation from 1 (< 1 %) in technical aspects allows to use the results of vacuum.) ● ε 0 allows to relate charge density to field strength ● permittivity number of various materials: see {Appendix A} M.1 Field constants 407 <?page no="421"?> M.1.2 Permittivity number of a material ε r Permittivity in a capacitor is determined by the following relationship: " r ¼ C r C 0 C r capacitance with material C 0 capacitance without material M.1.3 Electric susceptibility χ e e ¼ " r 1 ε r relative permittivity, value of material Note: In engineering terms, the electric susceptibility of air is set to zero. M.1.4 Permeability μ Unit: Henry/ meter [H/ m] or [Vs/ Am] ¼ B H ¼ 0 r B magnetic flux density H magnetic field strength μ 0 permeability of vacuum (1.25663706212 × 10 -6 Vs/ Am) μ r relative permeability Note: The field constants permittivity and permeability are linked via the speed of light c = 299 792 458 m/ s and thus form the basis for electromagnetic waves ( ↑ electromagnetic radiation). The electric field strength E and the magnetic flux density B are at right angles to each other in the propagation direction v. " 0 ¼ 1 0 c 2 0 ¼ 1 " 0 c 2 M.2 Force F, ~ F Unit: Newton [N] ~ F ¼ Q ~ E Q charge [C] ~ E vector of field strength E field strength [V/ m] 408 M Mathematic toolbox <?page no="422"?> Example: The power effective on an electron in an electric field at a field strength of 100 V/ m amounts to: ~ F ¼ e ~ E ¼ 1 : 6022 10 19 C 100 V m ¼ 160 : 22 10 19 N The direction of the power is given by the vector of the field strength. M.3 Charge Q Unit: Coulomb [C] or [As] Q ¼ C U C capacitance [F] U voltage [V] Example: A 100 pF-capacitor is to be charged 1 kV. The required charge is calculated as follows 100 × 10 -12 F × 10 3 V = 0.1 μ C. Note: The charge of the series connection of capacitors (Q S ) { ↑ M.6.4.6.2} is equal to the product of C S tot and the applied voltage U and is composed of the charges Q S of C 1 and Q S of C 2 . M.3.1 Coulomb ’ s law F ¼ 1 4 " 0 Q 1 Q 2 d 2 F force [N] Q 1 , Q 2 charge [C] d distance [m] π circle number (3.141592 … ) ε 0 absolute permittivity (8.854 pF/ m) M.3.1.1 Attraction of two point-charges F ¼ 1 4 " Q 1 Q 2 d 2 ε permittivity [F/ m] π circle number (3.141592 … ) Q 1 , Q 2 charge [C] d distance of point charges in meters [m] Note: Coulomb ’ s law states that the force between two point-charges is inversely proportional to the product of the charges directly and the square of their distance. The direction of the M.3 Charge Q 409 <?page no="423"?> force coincides with the line connecting the two charges. Charges of the same sign repel each other, while charges of different signs attract each other (Figure: ↑ field - force effects). M.3.1.2 Field of point charge ~ E ¼ Q P 4 " 0 r 2 ~ E field strength radially from/ to point charge [V/ m] Q P point charge [C] π circle number (3.141592 … ) ε o absolute permittivity (8.854 pF/ m) r distance from the charge Q P [m] Example: If the positive point charge Q P = 3 × 10 -9 C is in vacuum / air, the field strength E = 26.963 V/ m (3 × 10 -9 / 4 π × 8.854 × 10 -12 ) is generated at a distance of one meter. The field strength (the vector) is directed radially away from the point charge { ↑ M.1}. M.3.1.3 Specific charge Q spec Unit: Coulomb/ kilogram [C/ kg] Q spec ¼ Q m Q object charge [C] m object mass [kg] M.3.1.4 Volume charge density ρ Unit: Coulomb/ cubic meter [C/ m 3 ] ¼ Q V Q charge in volume V [C] V volume [m 3 ] M.3.2 Surface charge density σ Unit: Coulomb/ square meter [C/ m 2 ] C m 2 ¼ dQ dA ¼ d C U ð Þ dA ¼ ½ As ½ V ½ V ½ m 2 max C m 2 ¼ 2 : 6 10 5 As m 2 Q ¼ Z dA 410 M Mathematic toolbox <?page no="424"?> Q charge [C] dQ charge of the surface element dA [C] A area with charge Q [m 2 ] dA surface element with charge dQ [m 2 ] C capacitance [F], [As/ V] U voltage [V] M.3.3 Breakdown field strength E Unit: volt/ meter [V/ m] E ¼ " 0 ¼ 2 : 6 10 5 As Vm 8 : 85 10 12 m 2 As ¼ 2 : 93 10 6 V m 3 MV = m σ surface charge density [C/ m 2 ] ε o absolute permittivity (8.854 pF/ m) M.4 Voltage U Unit: volt [V] U ¼ I R I current [A] R resistance [ Ω ] M.5 Homogeneous field between planar plates Unit: volt [V] U ¼ E s U voltage between the plates [V] E field strength in the direction to the negative plate [V/ m] s plate spacing [m] Example: A voltage of 100 V is applied to two plates (gap: air, distance: 10 mm). The field strength is calculated as 100 V / 0.01 m = 10 kV/ m. M.6 Capacitance C Unit: farad [F], relation: 1F = C/ V = As/ V = kg -1 m -2 s 4 A 2 M.6 Capacitance C 411 <?page no="425"?> M.6.1 Energy W stored in capacitor Unit: Watt second [Ws] W ¼ 1 2 C U 2 W ¼ 1 2 Q U C capacitance [F] U voltage [V] Q charge [As] Example: What is the stored energy in a capacitor of 100 pF at 1000 V? 0.5 × 100 × 10 -12 F × (10 3 V) 2 = 50 µJ Note: The energy stored in the capacitor is also used to define the ignition sensitivity of a substance, the minimum ignition energy (MIE). The ignition capability of a gas discharge is characterized by the minimum ignition charge (MIC). MIE and MIC can be related by multiplying the latter by the optimum voltage during the ignition test. M.6.1.1 Minimum ignition energy W MIE W MIE ¼ 1 2 Q I U opt Q I charge to ignition [As] U opt optimal ignition voltage [V] M.6.1.2 Correlation energy - power Energy W: 1 Watt second [Ws] = 1 Joule [ J] = 1 Newton meter [Nm] Power P: 1 Watt [W] = 1 Joule/ second [J/ s] = 1 Newton meter/ second [Nm/ s] Note: Conversion of Joule to calorie and vice versa: 1 J = 0.23884589663; 1 cal = 4.1868 J M.6.1.3 Electric power P P ¼ U I P ¼ I 2 R P ¼ U 2 R U voltage [V] I current [A] R resistance [ Ω ] Example: A voltage of 100 V is applied to a resistor of 1 M Ω . What is the power converted? 100 2 V 2 / 1 × 10 6 Ω = 10 mW 412 M Mathematic toolbox <?page no="426"?> M.6.2 Charging voltage U c ( t ) and discharging voltage U d ( t ) at the capacitor U c t ð Þ ¼ U 0 1 e t R C U d t ð Þ ¼ U 0 e t R C HWZ ¼ R C ln 2 ð Þ U c (t) charging voltage in function of time t [s] U d (t) discharging voltage in function of time t [s] U 0 initial voltage (voltage at the time t 0 [s]) HWZ half-life time (50 %) R charge/ discharge resistance [ Ω ] C capacitance [F] ln(2) 0.693 … M.6.3 Time constant τ (Also called “ relaxation time ” , “ charging time constant ” or “ discharge time constant ” .) Unit: second [s] ¼ " v ¼ C R E ε permittivity [F/ m] ρ v volume resistivity [ Ω m] R E leakage resistance [ Ω ] C capacitance [F] Note: In [IEC 61340-4-7], under A5 Neutralization rate, it is stated: “ If the conductivity does not change, the relative rate of charge neutralization is constant, and the charge will decay exponentially with a time constant τ equal to the permittivity of the air e 0 divided by the conductivity λ . ” ¼ e 0 The value e 0 for air is incorrect and should be replaced with ε (permittivity) for air. This describes self-discharge through the surrounding air. M.6.3.1 Time constant τ (in RC combination) ¼ R C R charge/ discharge resistance [ Ω ] C capacitance [F] M.6 Capacitance C 413 <?page no="427"?> Time t Charging voltage U c Discharging voltage U d HWZ 0.5 × U 0 0.5 × U 0 0 0 U 0 τ 0.63 × U 0 0.37 × U 0 2.3 × τ 0.9 × U 0 0.1 × U 0 4.6 × τ 0.99 × U 0 0.01 × U 0 ∞ U 0 0 Example: A capacitance (charged object) is discharged in 3 s across a resistance of R = 100 M Ω so that the residual voltage is 1/ 10 of the initial value. What is its capacitance? 2.3 × 3 s / 1 × 10 8 Ω = 69 nF According to the table, after time = 2.3 τ the discharge voltage has dropped to 1/ 10 of the initial value. M.6.4 Configuration of some capacities M.6.4.1 Plate - plate (same size) C Pl ¼ " A s C Pl capacitance of plate capacitor [F] ε permittivity [F/ m] A area of plate [m 2 ] s distance of plate [m] Example: What is the capacitance between two plane-parallel circular electrodes with a diameter of 50 mm and a distance of 1 mm between them? ε × 25 2 × π × mm 2 / 1 mm = 17.85 pF M.6.4.2 Sphere across a conductive area C SA ¼ 4 " r 1 þ r 2d C SA sphere capacitance across a conductive area [F] ε permittivity [F/ m] r radius of sphere [m] d distance between center of sphere and area [m] Example: What is the capacitance between a sphere with a diameter of 0.2 m at a distance of 0.3 m over an infinite surface? 4 π × ε × 0.1(1 + 0.1 / 0.6) = 12.98 pF 414 M Mathematic toolbox <?page no="428"?> M.6.4.3 Conductive sphere in space C SS ¼ 4 " r C SS capacitance of the sphere in space [F] ε permittivity of medium in space [F/ m] r radius of sphere [m] Example: What is the capacitance of a sphere with a diameter of 0.2 m in space? 4 π × ε × 0.1 = 11.13 pF M.6.4.4 Cylinder (wire) over surface C WS ¼ 2 " l ln 2s r C WS capacitance of the wire [F] ε permittivity [F/ m] l length of wire (l >> r) [m] s distance from center of wire to surface [m] r radius of wire [m] Example: What is the capacitance between a wire 0.8 mm in diameter and 2 m long, stretched 3 mm above a surface? 2 π × ε × 2 / ln(2 × 3 / 0.4) = 41.1 pF M.6.4.5 Coaxial cable / cylinder capacitance (Cable consisting of a middle conductor, dielectric material, and a conductive shield) C CC ¼ 2 " l ln r o r i C cc capacitance of the coaxial cable [F] ε permittivity of dielectric material [F/ m] l length of cable [m] r o outer radius of dielectric [m] r i inner radius of dielectric [m] M.6.4.6 Circuits of capacitances M.6.4.6.1 Parallel connection (shunt) of single capacitors C P tot ¼ C 1 þ C 2 þ C 3 þ . . . C P tot total shunt capacitance [F] C 1 , C 2 , C 3 , … single capacitors M.6 Capacitance C 415 <?page no="429"?> M.6.4.6.2 Series connection of single capacitors 1 C S tot ¼ 1 C 1 þ 1 C 2 þ 1 C 3 þ . . . C S tot total series capacitance [F] C 1 , C 2 , C 3 , … single capacitors M.6.4.6.3 Series connection of two single capacitors C S tot ¼ C 1 C 2 C 1 þ C 2 C S tot total series capacitance [F] C 1 , C 2 single capacitors Example: What is the capacitance of the series connection of a 10 pF-capacitor and a 20 pFcapacitor? 10 × 20 / 30 = 6.67 pF M.6.4.7 Impedance of a capacitance R C Unit: Ohm [ Ω ] R C ¼ 1 ! C ω circular frequency (2 π × f ) [1/ s] C capacitance [F] Example: What is the resistance (reactance) of a 100 pF-capacitor at 50 Hz-alternating current? ½ π × 50 × 100 × 10 -12 = 31.83 M Ω M.7 Resistance - conductivity M.7.1 Resistances Unit: Ohm [ Ω ] M.7.1.1 Resistance R of a material R ¼ U I R ¼ P I 2 R ¼ U 2 P U voltage on the resistor [V] I current through the resistor [A] P power transfer in the resistor [W] 416 M Mathematic toolbox <?page no="430"?> Example: When the resistance is measured with a test voltage of 100 V, a current of 10 nA flows. The resistance is calculated as follows: 100 V / 10 nA = 10 G Ω M.7.1.2 Leakage resistance R L (object or material) R L ¼ U V I E U v voltage between electrode on object and earth [V] I E current from object to earth (earth leakage current) [A] Example: An earth leakage current of 5 nA flows from a conductive object when a voltage of 500 V is applied. The discharge resistance can be calculated as follows: 500 V / 5 × 10 -9 A = 100 G Ω M.7.1.3 Surface resistance R S (object or material) R S ¼ U I U DC voltage between two attached electrodes (preferably 10, 100 or 500 V) I measuring current at the surface [A] Example: If a current of 10 nA flows across a measuring electrode when a voltage of 100 V is applied, the surface resistance is calculated as: 100 V / 10 ×10 -9 A = 10 G Ω . Note: The surface resistivity ρ s is the measured value obtained when the electrode spacing = electrode length (squared). M.7.1.4 Volume resistivity ρ v (object or material) (measured with a guard ring electrode, ↑ measurement error) Unit: Ohm meter [ Ω m] V ¼ R V A s V ¼ U I R V volume resistance of material [ Ω ] A usable area of applied electrode circular: π × (d+g) 2 / 4 rectangular: (a+g) × (b+g) s current conducting path in the material [m] d diameter of guarded electrodes [m] a, b length, width of guarded rectangular electrode [m] g gap width between measuring surface and guard ring [m] U voltage (DC) [V], between two opposite electrodes with the area [m 2 ] I measurement current [A] through the object, distance [m] M.7 Resistance - conductivity 417 <?page no="431"?> M.7.1.5 Circuits of resistors M.7.1.5.1 Parallel connection (shunt) of single resistors 1 R P tot ¼ 1 R 1 þ 1 R 2 þ 1 R 3 þ . . . R P tot total resistance with shunt connection [ Ω ] R 1 , R 2 , R 3 , … single resistors M.7.1.5.2 Parallel connection (shunt) of two single resistors R P tot ¼ R 1 R 2 R 1 þ R 2 R P tot total resistance with shunt connection [ Ω ] R 1 , R 2 single resistors Example: The total resistance from the parallel connection of a 20 k Ω resistor and a 10 k Ω resistor is calculated as follows: 20 × 10 3 × 10 × 10 3 / 30 × 10 3 = 6.67 k Ω M.7.1.5.3 Series connection of single resistors R S tot ¼ R 1 þ R 2 þ R 3 þ . . . R S tot total resistance with series connection [ Ω ] R 1 , R 2 , R 3 , … single resistors Example: If a resistance of 10 M Ω and a resistance of 20 M Ω is in series connection, a resistance (total) of 30 M Ω (10 × 10 6 + 20 × 10 6 ) results. M.7.1.5.4 Series connection of impedances In contrast to the DC circuit, other calculations must be made for the AC circuit. For impedance Z, the resistance R (active resistance), the reactance X (reactive resistance), the inductance X L (inductive reactance), the condensance X C (capacitive reactance) and the angular frequency ω { ↑ M.6.4.7} must therefore be considered. Z ¼ ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi R 2 þ X L X C ð Þ 2 q ¼ ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi R 2 þ ! L 1 ! C 2 s ¼ ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi R 2 þ X 2 p For the admittance Y (apparent conductance) the calculation is: Y ¼ ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 1 R 2 þ 1 X L 1 X c 2 s 418 M Mathematic toolbox <?page no="432"?> M.7.1.5.5 Parallel connection (shunt) of impedances Note: Refer to the text for M.7.1.5.4. 1 z ¼ ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 1 R 2 þ 1 X C 1 X L 2 s ¼ ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 1 R 2 þ ! C 1 ! L 2 s ¼ ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 1 R 2 þ 1 X 2 r M.7.2 Conductivity κ (The term is preferably used for liquids.) Unit: Siemens/ meter [S/ m] ¼ 1 v ρ v volume resistivity [ Ω m] Example: If a resistance of 5 × 10 9 Ω is measured on a liquid sample with an ohmmeter, the conductivity can be expressed as 1 / 5 × 10 9 Ω = 0.2 × 10 -9 S/ m. M.7.2.1 Conductivity unit cu (The term [cu] is the preferred unit of conductivity in the petroleum industry.) 1 cu = 1 pS/ m Note: It is called a “ unit ” , but it is not a unit in the system of units. M.7.2.2 Conductance G (applied electrical engineering) Conductance G allows a simple calculation of the resistance of a conducting wire. G ¼ l R A 2 l conductor length [m] R resistance [ Ω ] A conductor cross-section [mm 2 ] Material Conductivity [m/ Ω mm 2 ] aluminum 34 iron 10 copper 56 constantan 2 Example: An aluminum wire has a length of 36 m and a cross section of 0.75 mm 2 . The electric resistance of this wire is: 36 m / 34 m/ Ω mm 2 × 0.75 mm 2 = 1.41 Ω M.7 Resistance - conductivity 419 <?page no="433"?> Appendix A Permittivity numbers ε r of selected materials. Further values can be found in the DKvalues App from Endress+Hauser GmbH&Co.KG. Material ε r aluminum oxide 6 … 9 barium titanate 1200 CA (cellulose acetate) 3.5 … 4.5 CAB (acetobutyrate) film 3.8 … 4.1 EP (epoxy resin) 3.2 … 4.3 glass 3.5 … 9 mica 6 … 8 calcium carbonate 8 mineral oil (for transformers) 2 … 2.5 PA (polyamide) 3.5 … 4.5 paper (for insulation) dry 2 … 2.5 paper (for insulation) oil-impregnated 3 … 4 PC (polycarbonate) 2.8 … 3.0 PE (polyethylene) 23 … 24 PETP (polyethylene terephthalate) 3.2 … 4.4 PMMA (polymethyl methacrylate) 3.1 … 4.5 POM (polyacetal) 4 PP (polypropylene) 2.3 … 2.5 PS (polystyrene) 2.5 PTFE (polytetrafluoroethylene) 2.0 … 2.1 PVC (polyvinyl chloride) 3.8 … 4.3 SI (silicone rubber) 2.5 … 5 silicon oxide 3.9 tantalum pentoxide 26 titanium dioxide 111 UF (urea-formaldehyde) 6 … 7 UP (polyester casting resin) 3 … 7 <?page no="434"?> Appendix B Flammable gases and vapors data ● TRGS 727 Prevention of ignition hazards due to electrostatic charging, 07/ 2016 ● Nabert/ Schön, Safety-related key figures of flammable gases and vapors, 2nd edition, Deutscher Eichverlag Braunschweig, Reprint 1970 ● Technical Recommendations for Requirements for Avoiding Electrostatic Hazards in Industry Appendix D, Material Data [ JNIOSH TR 42 (2007)] ● Dräger Gases List 2018 (Edition November 2017), Dräger Safety AG & Co. KGaA, Lübeck (D) ● Honeywell Gas Guide 2013, Honeywell Analytics, Life Safety Distribution AG, Hegnau (CH) Since these sources provide different information for individual items, the values in the table mainly correspond to the CAS Registry of GESTIS-Stoffenmanager ® , the Hazardous Substance Information System of the German Social Accident Insurance (as of November 2018). Values not available there are based on information from the database www. chemsafe.ptb.de. The values given refer to atmospheric conditions when mixed with air. <?page no="435"?> Appendix C Surface resistance value of common plastics Abbr. Description n ρ s [10 n Ω ] [1] n ρ v [10 n Ω m] [1] Permittivity ε r [2] Water absorption [%] (ASTMD570) [3] Breakdown strength [kV/ mm] [1] Duroplast - D Thermoplast - T Elastomer - E ABS acrylonitrile-butadiene-styrene copolymer 14 … 15 12 … 15 2.8 … 2.9 0.2 … 0.45 34 T ASA acrylic ester-styrene-acrylonitrile terpolymer 14 … 15 12 T CA cellulose acetate, type 432 11 … 13 10 … 12 3.5 … 4.5 6 T CP cellulose propionate 1.2 … 2.8 CAB cellulose acetobutyrate, type 413 12 … 13 11 … 12 3.8 … 4.5 0.9 … 3.2 T EP epoxy resin 12 … 14 11 … 12 3.2 … 4.3 0.05 … 0.2 D EPDM ethylene-propylene-diene caoutchouc E ETFE ethylene-tetrafluoroethylene copolymer > 14 16 2.55 0.03 (T) EVA ethyl-vinyl acetate 13 … 14 13 … 14 0.05 … 0.13 T FEP perfluorinated (ethylene-propylene plastic) 16 … 17 < 0.1 (T) MF melamine-formaldehyde resin, type 152 8 … 10 7 … 9 0.1 … 0.6 D PA 6 polyamide 10 … 13 8 … 15 3.5 … 4.5 1.3 … 1.9 20 2) T PA 6.6 polyamide 13 15 3.8 1.5 25 2) T 422 Appendix C <?page no="436"?> Abbr. Description n ρ s [10 n Ω ] [1] n ρ v [10 n Ω m] [1] Permittivity ε r [2] Water absorption [%] (ASTMD570) [3] Breakdown strength [kV/ mm] [1] Duroplast - D Thermoplast - T Elastomer - E PB polybutene 13 … 14 2.3 … 2.5 < 0.02 T PC polycarbonate 15 … 17 13 … 14 2.8 … 3.0 0.16 35 T PEEK polyetheretherketone 16 16 3.2 20 2) T PE-HD polyethylene, high density 14 … 16 13 … 15 2.35 17 1) T PE- HMW polyethylene, high molecular weight, high molar mass 13 18 2.3 17 1) T PE- UHMW PE ultra-high molar mass 14 > 15 2.3 45 1) T PEI Polyetherimide 13 17 3.15 60 T PE-LD PE low density 14 … 15 14 T PES polyetherslufon 14 16 3.5 0.43 25 2) T PET polyethylene terephthalate 13 … 16 11 … 16 3.2 … 4.4 0.30 22 2) PF phenol formaldehyde resin, type 31 8 … 10 5 … 9 0.3 … 1.2 D PI polyimide 14 … 15 0.32 D PMMA polymethyl methacrylate, acrylic glass 14 12 … 15 3.1 … 4.5 0.1 … 0.4 20 … 25 T PMP poly-4-methylpentene-1 13 2.1 0.01 T POM polyoxymethylene (polyacetal) 13 … 14 12 … 15 3.5 … 4.0 25 2) T PP polypropylene 14 … 15 14 2.2 … 2.6 0.01 … 0.03 T PP-H polypropylene; homopolymer 14 15 2.3 70 1) T PPO polyphenylene oxide 17 17 2.6 50 1) T PPS polyphenylene sulfide 16 16 3.05 0.02 23 T PS polystyrene 14 … 15 13 … 16 2.5 … 2.8 0.03 … 0.1 40 1) T PSU polysulfone 14 13 … 16 3.14 0.02 30 2) T PTFE polytetrafluoroethylene 16 … 17 14 … 18 2.0 … 2.1 0 20 (T) Appendix C 423 <?page no="437"?> Abbr. Description n ρ s [10 n Ω ] [1] n ρ v [10 n Ω m] [1] Permittivity ε r [2] Water absorption [%] (ASTMD570) [3] Breakdown strength [kV/ mm] [1] Duroplast - D Thermoplast - T Elastomer - E PUR polyurethane 11 … 13 8 … 10 0.1 … 0.9 E D T PVAC polyvinyl acetate T PVC-P polyvinyl chloride (soft PVC) 10 … 13 7 … 14 3.6 … 7.5 0.04 … 0.4 20 … 25 T PVC-U polyvinyl chloride (hard PVC) 13 … 14 12 … 15 3.3 0.15 … 0.75 20 … 40 T PVDF polyvinylidene fluoride 14 … 15 11 … 14 8 … 9 21 2) T SAN styrene-acrylonitrile 14 … 15 14 … 16 3.0 0.2 … 0.3 18 T SBR styrene butadiene rubber 14 12 E UF urea-formaldehyde 6 … 7 0.4 … 0.8 D UP unsaturated polyester resin (casting resin) 11 … 12 10 … 11 3 … 7 D Literature: X 1) 0.2-mm film [1]-[IEC 60243-1], [2]-[IEC 61189- 2-719], [3]-[Dominhaus, H. (1992)] X 2) 1-mm plate 424 Appendix C <?page no="438"?> Appendix D Restrictions on insulating solid materials and isolated conductive or dissipative parts in hazardous areas for equipment within the scope of IEC 60079-0 and IEC/ TS 60079-32-1. Group I Group II Group III EPL Ma, Mb Mining Subgroup EPL Ga Zone 0 EPL Gb Zone 1 EPL Gc Zone 2 EPL Da Zone 20 EPL Db Zone 21 EPL Dc Zone 22 A) Restriction on size of insulating solid materials in hazardous areas Limitation of surface areas (Note 1) [IEC 60079-0] ≤ 10 000 mm 2 A ≤ 5 000 mm 2 ≤ 10 000 mm 2 ≤ 10 000 mm 2 No limits B ≤ 2 500 mm 2 ≤ 10 000 mm 2 ≤ 10 000 mm 2 C ≤ 400 mm 2 ≤ 2 000 mm 2 ≤ 2 000 mm 2 B) Maximum diameter or width of bars, rods, thin pipes, cables (Note 2) [IEC 60079-0] ≤ 30 mm A ≤ 3 mm ≤ 30 mm ≤ 30 mm No limits B ≤ 3 mm ≤ 30 mm ≤ 30 mm C ≤ 1 mm ≤ 20 mm ≤ 20 mm C) Limitation of thickness of non-metallic layer (insulating coatings) to avoid any incendive discharge (Note 3) [IEC 60079-0] ≤ 2 mm A ≤ 2 mm No limits B ≤ 2 mm C ≤ 0.2 mm Appendix D 425 <?page no="439"?> Group I Group II Group III EPL Ma, Mb Mining Subgroup EPL Ga Zone 0 EPL Gb Zone 1 EPL Gc Zone 2 EPL Da Zone 20 EPL Db Zone 21 EPL Dc Zone 22 D) Maximum acceptable transferred charge (Note 4) [IEC/ TS 60079- 32-1] ≤ 60 nC A ≤ 25 nC ≤ 60 nC ≤ 60 nC ≤ 60 nC a ≤ 200 nC a ≤ 200 nC a B ≤ 10 nC ≤ 25 nC ≤ 25 nC C No measurable discharge ≤ 10 nC ≤ 10 nC a Values only valid for spark discharges from unearthed conductive or dissipative parts. E) Maximum allowed isolated capacitance in Zones with explosive atmosphere (Note 5) [IEC/ TS 60079- 32-1] ≤ 10 pF A ≤ 3 pF ≤ 6 pF No requirements if charging processes capable of generating hazardous potentials are unlikely to occur during normal operation including maintenance and cleaning ≤ 6 pF (MIE < 10 mJ) ≤ 10 pF (MIE > 10 mJ) No requirements if charging processes capable of generating hazardous potentials are unlikely to occur during normal operation including maintenance and cleaning B ≤ 3 pF ≤ 3 pF C No isolated conductive objects allowed ≤ 3 pF 426 Appendix D <?page no="440"?> Note 1: ● Synthetic fabrics used in cloths for cleaning or wiping can develop sufficient static electric charge to produce discharges capable of igniting solvent vapours. Typically, charge generation increases with the speed and vigour of the wiping action. The material being cleaned or wiped, if insulating, also can accumulate sufficient charge to produce an incendive discharge. Cotton or synthetic fabric treated with a static dissipative compound may be required if static electric charge generation needs to be controlled, especially if flammable insulating solvents are being used for cleaning or wiping. ● The presence of contamination (e. g. grease or moisture) may affect the potential ignition hazard when using insulating materials. ● Conductive solids, objects or liquids may form hazardous isolated conductive islands if present on charged insulating surfaces. Note 2: ● The width criterion applies to thin pipes, cable sheaths, and other insulating materials having small widths or diameters. ● Equipment marked IIB is suitable for applications requiring group IIA equipment. Similarly, equipment marked IIC is suitable for applications requiring group IIA or group IIB equipment. ● These border limits are also used e. g. in [IEC 60079-0], [CLC/ TR 50404], [TRGS 727], [ JNIOSH TR 42], and [BS 5958]. ● The subdivisions are based on the maximum experimental safe gap (MESG) or the minimum ignition current ratio (MIC ratio) of the explosive gas atmosphere in which the equipment may be installed (see [IEC 60079-20-1]). More details can be found in [IEC/ TS 60079-32-1 Annex C.6 and D.3]. ● The limits in line A) and B) are not absolute values that prevent incendive discharges, they merely reduce it to a generally accepted low level. ● The present state of knowledge indicates that there is no ignition risk due to brush discharges in the case of sensitive dust providing that there are no flammable gases or vapours (see [IEC/ TS 60079-32-1 Annex A.3.4]). However, charge generation processes stronger than manual rubbing may create incendive propagating brush discharges under certain circumstances (see [IEC/ TS 60079-32-1 Section 6.3.4.2]). Note 3: ● One of main reasons for the thickness limitation is that the maximum thickness of nonmetallic layer is intended to permit dissipation of charge through the insulation to earth, by this means the static charge is not able to build up to incendive levels. ● An internal printed circuit board may be considered to be an extended flat conductive surface, though this need not be applied in small hand-held equipment unless the equipment is likely to be subjected to a prolific charge generating mechanism (such as might occur in pneumatic transfer of powders or charge spraying in a powder coating process). Charging through normal handling of hand-held equipment is not considered Appendix D 427 <?page no="441"?> to lead to a prolific charge generating mechanism and therefore would not lead to a situation where a propagating brush discharge might occur. ● A single flat conductive surface not exceeding 500 mm 2 is not considered to be an extended flat surface. [IEC 60079-0 Section 7.4.3] Note 4: ● The limits for Zone 1 and Zone 21 ensure that incendive discharges should not occur during normal operation. The limits for Zones 0 and 20 are further reduced to account for abnormal situations and the high level of safety required for these zones. ● For the explanation of EPL see [IEC 60079-0]. ● All the values contain a certain safety margin. Recent work indicates that the value hitherto used for IIB contains a lower safety margin than all other values. To equalize all safety margins the values for IIB have been reduced from 30 nC to 25 nC. 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BImSchG (Bundes-Immissionsschutzgesetz) Gesetz zum Schutz vor schädlichen Umwelteinwirkungen durch Luftverunreinigungen, Geräusche, Erschütterungen und ähnliche Vorgänge, v. 17.05.2013 (BGBl. I S. 1274; 2021 I S. 123), zuletzt durch Artikel 1 des Gesetzes v. 24.09.2021 (BGBl. I S. 4458) geändert. 12. BImSchV 12. Verordnung zur Durchführung des Bundes-Immissionsschutzgesetzes - Störfall- Verordnung i. d. F. der Bekanntmachung v. 15.03.2017 (BGBl. I S. 483), zuletzt durch Art. 107 der Verordnung v. 19.06.2020 (BGBl. I S 1328) geändert. 26. BImSchV 26. Verordnung zur Durchführung des Bundes-Immissionsschutzgesetzes (Verordnung über elektromagnetische Felder), neugefasst durch Bek. v. 14.08.2013. DDR-Gesetzblatt 148 (1952) Bekanntmachung der Arbeitsschutzbestimmung 282 - Anlagen zur Lederentfettung durch Benzin - v. 14.10.1952. EMVG Elektromagnetische-Verträglichkeit-Gesetz v. 14.12.2016 (BGBl. I S. 2879), geändert durch Artikel 3, Absatz 1 des Gesetzes v. 27.06.2017 (BGBl. I S. 1947). EU 2013/ 35 Directive 2013/ 35/ EU of the European Parliament and of the Council of 26 June 2013 on the minimum health and safety requirements regarding the exposure of workers to the risks arising from physical agents (electromagnetic fields) (20th individual Directive within the meaning of Article 16 (1) of Directive 89/ 391/ EEC) and repealing Directive 2004/ 40/ EC. EU 2014/ 30 Directive 2014/ 30/ EU of the European Parliament and of the Council of 26 February 2014 on the harmonization of the laws of the Member States relating to electromagnetic compatibility (recast). EU 2014/ 35 Directive 2014/ 35/ EU of the European Parliament and of the Council of 26 February 2014 on the harmonization of the laws of the Member States relating to the making available on the market of electrical equipment designed for use within certain voltage limits (recast). GbV (Gefahrgutbeauftragtenverordnung) Verordnung über die Bestellung von Gefahrgutbeauftragten in Unternehmen; neugefasst durch B. v. 11.03.2019 BGBl. I S. 304; zuletzt geändert durch Artikel 3 V. v. 26.03.2021 BGBl. I S. 475. GefStoffV (Gefahrstoffverordnung) Verordnung zum Schutz vor Gefahrstoffen, v. 26.11.2010 (BGBl. I S. 1643, 1644), zuletzt durch Artikel 2 der Verordnung v. 21.07.2021 (BGBl. I S. 3115) geändert. GGBefG (Gefahrgutbeförderungsgesetz) Gesetz über die Beförderung gefährlicher Güter, v. 06.08.1975 (BGBl. I S. 2121), neugefasst durch Bek. v. 07.07.2009 I 1774, 3975, zuletzt durch Artikel 13 des Gesetzes v. 12.12.2019 (BGBl. I S. 2510) geändert. Laws and Regulations 435 <?page no="449"?> GPSG (Geräte- und Produktsicherheitsgesetz) Gesetz über technische Arbeitsmittel und Verbraucherprodukte, Artikel 1 des Gesetzes v. 06.01.2004 (BGBl. I S. 2, ber. S. 219), in Kraft getreten am 01.05.2004, außer Kraft getreten aufgrund Gesetzes v. 08.11.2011 (BGBl. I S. 2178) m. W. v. 01.12.2011. ProdSG (Produktsicherheitsgesetz) Gesetz über die Bereitstellung von Produkten auf dem Markt, v. 27.07.2021 (BGBl. I S. 3146, 3147), durch Artikel 2 des Gesetzes v. 27.07.2021 (BGBl. I S. 3146) geändert. Ersetzt V 8053-8 v. 08.11.2011 I 2178, 2179; 2012 I 131 (ProdSG 2011). 11. ProdSV 11. Verordnung zum Produktsicherheitsgesetz - Explosionsschutzprodukteverordnung v. 06.01.2016, (BGBl. Nr. 2 v. 15.01.2016 S. 39). REACH EC Regulation (EC) No 1907/ 2006 of the European Parliament and of the Council of 18 December 2006 concerning the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH), establishing a European Chemicals Agency, amending Directive 1999/ 45/ EC and repealing Council Regulation (EEC) No 793/ 93 and Commission Regulation (EC) No 1488/ 94 as well as Council Directive 76/ 769/ EEC and Commission Directives 91/ 155/ EEC, 93/ 67/ EEC, 93/ 105/ EC and 2000/ 21/ EC. SprengG (Sprengstoffgesetz) Gesetz über explosionsgefährliche Stoffe i. d. F. v. 10.09.2002 (BGBl. I S. 3518), zuletzt durch Artikel 4 Absatz 67 des Gesetzes v. 07.08.2013 (BGBl. I S. 3154) geändert. StrlSchV (Strahlenschutzverordnung) Verordnung zum Schutz vor der schädlichen Wirkung ionisierender Strahlung v. 29.11.2018 (BGBl. I S. 2034, 2036), zuletzt durch Artikel 1 der Verordnung v. 20.11.2020 (BGBl. I S. 2502) geändert. ÜAnlG Gesetz zur Anpassung des Produktsicherheitsgesetz [ProdSichG] und zur Neuordnung des Rechts der überwachungsbedürftigen Anlagen v. 27.07.2021. VbF Verordnung über brennbare Flüssigkeiten in der Fassung der Bekanntmachung v. 13.12.1996 (BGBl. I S. 1937; 1997, S. 447), zuletzt durch Artikel 11 der Verordnung v. 02.06.2016 (BGBl. I S. 1257) geändert. Rules and Information Note: DGUV: Deutsche Gesetzliche Unfall-Versicherung - German Statutory Accident Insurance. TRBS: Technische Regel für Betriebssicherheit - Technical Rule for Operational Safety. TRGI: Technische Regel für Gasinstallationen - Technical Rule for Gas Installations. TRGS: Technische Regel für Gefahrstoffe - Technical Rule for Hazardous Substances. DGUV Grundsatz 313-002 Auswahl, Ausbildung und Beauftragung von Fachkundigen zum Freimessen nach DGUV Regel 113-004 - Selection, training and deployment of clearance measurement experts according to DGUV Regel 113-004. DGUV Information 205-026 Sicherheit und Gesundheitsschutz beim Einsatz von Feuerlöschanlagen mit Löschgasen (05/ 2018) - Safety and health when using gaseous extinguishing systems. DGUV Information 209-072 Wasserstoffsicherheit in Werkstätten (03/ 2021) - Hydrogen safety in workshops. DGUV Information 209-090 Tätigkeiten mit Magnesium (06/ 2018) - Activities with magnesium. DGUV Information 213-053 Schlauchleitungen, Sicherer Einsatz, Merkblatt T 002 - Hose lines, safe use, fact sheet T 002. 436 Bibliography <?page no="450"?> DGUV Information 213-057 Gaswarneinrichtungen und -geräte für den Explosionsschutz, Einsatz und Betrieb, Merkblatt T 023 - Gas warning devices and appliances for explosion protection, use and operation, fact sheet T 023. DGUV Information 213-065 Sicherheitstechnische Kenngrößen, Ermitteln und bewerten, Merkblatt R 003 - Determination and evaluation of safety parameters, fact sheet R 003. DGUV Information 213-073 Sauerstoff (09/ 2018) - Oxygen. DGUV Information 214-911 Safe operations of helicopters during aerial work (2020-09). DGUV Regel 100-500 Betreiben von Arbeitsmitteln (aktualisiert 11/ 2024) - Operation of work equipment. DGUV Regel 109-001 Schleifen, Bürsten und Polieren von Aluminium, 02/ 2021 - Grinding, brushing and polishing of aluminum. DGUV Regel 113-004 Behälter, Silos und enge Räume; Teil 1: Arbeiten in Behältern, Silos und engen Räumen - Containers, silos and confined spaces, Part 1. TRBS 1203 Zur Prüfung befähigter Personen. Ausgabe: März 2019, GMBl 2019, S. 262 [Nr. 13 - 16] (23.05.2019) - For qualified person verification. TRGI 2018 DVGW Arbeitsblatt G 600 (Hrsg. DVGW; Deutscher Verein des Gas- und Wasserfaches) - DVGW works heet G 600. TRGS 407 Tätigkeiten mit Gasen - Gefährdungsbeurteilung, Februar 2016, GMBl 2016, S. 328 - 364 [Nr. 12 - 17] v. 26.04.2016, geändert und ergänzt: GMBl 2016, S. 880 [Nr. 44] v. 26.10.2016 - Working with gases - risk assessment. TRGS 509 Lagern von flüssigen und festen Gefahrstoffen in ortsfesten Behältern sowie Füll- und Entleerstellen für ortbewegliche Behälter, Ausgabe: September 2014, GMBl 2014, S. 1346 - 1400 [Nr. 66 - 67] v. 19.11.2014, ergänzt u. berichtigt GMBl 2017, S. 229 [Nr. 12] v. 06.04.2017 - Storage of liquid and solid hazardous substances in stationary containers and filling and emptying stations for mobile containers. TRGS 510 Lagerung von Gefahrstoffen in ortsbeweglichen Behältern, GMBl 2021, S. 178 - 216 [Nr. 9 - 10] v. 16.02.2021 - Storage of hazardous substances in portable containers. TRGS 720 Gefährliche explosionsfähige Gemische - Allgemeines, Ausgabe: Juli 2020 GMBl 2020, S. 419 - 426 [Nr. 21] v. 24.07.2020, berichtigt: GMBl 2021, S. 399 [Nr. 17 - 19] v. 16.03.2021 - Hazardous explosive mixtures - general. TRGS 721 Gefährliche explosionsfähige Gemische - Beurteilung der Explosionsgefährdung, Ausgabe: Oktober 2020, GMBl 2020, S. 807 - 814 [Nr. 38] v. 02.10.2020, berichtigt GMBl 2020, S. 1116 [Nr. 51] v. 21.12.2020 - Hazardous explosive mixtures - Evaluation of explosion hazards. TRGS 722 Vermeidung oder Einschränkung gefährlicher explosionsfähiger Atmosphäre, Ausgabe: Februar 2021, GMBl 2021, S. 399 - 415 [Nr. 17 - 19] v. 16.03.2021, (inhaltsgleich: TRBS 2152 Teil 2) - Avoidance or limitation of hazardous explosive atmospheres. TRGS 723 Gefährliche explosionsfähige Gemische - Vermeidung der Entzündung gefährlicher explosionsfähiger Gemische, Ausgabe: Juli 2019, GMBl 2019, S. 638 - 656 [Nr. 33 - 34], v. 26.08.2019, geändert: GMBl 2020, S. 815 [Nr. 38] v. 02.10.2020 - Hazardous explosive mixtures - Avoiding the ignition of hazardous explosive mixtures. TRGS 724 Gefährliche explosionsfähige Gemische - Maßnahmen des konstruktiven Explosionsschutzes, welche die Auswirkung einer Explosion auf ein unbedenkliches Maß beschränken, Ausgabe: Juli 2019, GMBl 2019, S. 656 - 664 [Nr. 33 - 34] v. 26.08.2019 - Hazardous explosive mixtures - constructive explosion prevention measures that limit the effects of an explosion to a harmless level. TRGS 725 Gefährliche explosionsfähige Atmosphäre - Mess-, Steuer- und Regeleinrichtungen im Rahmen von Explosionsschutzmaßnahmen, Ausgabe: Januar 2016, GMBl 2016, S. 238-256 [Nr. 12 - 17] v. 26.04.2016, zuletzt geändert und ergänzt: GMBl 2018, S. 194 [Nr. 7 - 11] v. 03.04.2018 - Hazardous explosive atmospheres - measuring, control and regulating equipment as part of explosion protective measures. Rules and Information 437 <?page no="451"?> TRGS 727 Vermeidung von Zündgefahren infolge elektrostatischer Aufladungen, Ausgabe: Januar 2016, GMBl 2016, S. 256 - 314 [Nr. 12 - 17] v. 26.04.2016, berichtigt: GMBl 2016, S. 623 [Nr. 31] v. 29.07.2016 - Prevention of ignition hazards due to electrostatic charging. TRGS 900 Arbeitsplatzgrenzwerte (AGW), Ausgabe: Januar 2006, BArBl. Heft 1/ 2006, S. 41 - 55, Zuletzt geändert und ergänzt: GMBl 2021, S. 580 [Nr. 25] v. 23.04.2021 - Occupational exposure limits (OEL). Standards (Status 2024) Standards and similar documents are always sorted by number. DIN VDE 0292: 2021 System for cable designation; German version HD 361 S4: 2021. NFPA 10: 2022 Standard for Portable Fire Extinguishers, National Fire Protection Association ® . EN 1081: 2021 Resilient, laminate and modular multilayer floor coverings - Determination of the electrical resistance; German version EN 1081: 2018+A1: 2020. ISO 10965: 2011 Textile floor coverings - Determination of electrical resistance. EN 1127-1: 2019 Explosive atmospheres - Explosion prevention and protection - Part 1: Basic concepts and methodology; German version EN 1127-1: 2019. EN 1149-1: 2006 Protective clothing - Electrostatic properties - Part 1: Test method for measurement of surface resistivity; German version EN 1149-1: 2006. EN 1149-2: 1997 Protective clothing - Electrostatic properties - Part 2: Test method for measurement of the electrical resistance through a material (vertical resistance); German version EN 1149-2: 1997. EN 1149-3: 2004 Protective clothing - Electrostatic properties - Part 3: Test methods for measurement of charge decay; German version EN 1149-3: 2004. EN 1149-5: 2018 Protective clothing - Electrostatic properties - Part 5: Material performance and design requirements; German version EN 1149-5: 2018. EN 12115: 2021 Rubber and thermoplastics hoses and hose assemblies for liquid or gaseous chemicals - Specification; German version EN 12115: 2021. EN ISO 12696: 2022 Cathodic protection of steel in concrete; German version EN ISO 12696: 2022. EN 12921 Machines for surface cleaning and pre-treatment of industrial items using liquids or vapors. EN 12954: 2020 General principles of cathodic protection of buried or immersed onshore metallic structures; German version EN 12954: 2019. DIN 1301-1: 2010 Units - Part 1: Unit names, unit symbols. prEN 13237: 2022 Potentially explosive atmospheres - Terms and definitions for equipment and protective systems intended for use in potentially explosive atmospheres; German and English version prEN 13237: 2022. DIN 1324-1: 2017 Electromagnetic field - Part 1: State quantities. SN EN 13821: 2003 Potentially explosive atmospheres - Explosion prevention and protection - Determination of minimum ignition energy of dust/ air mixtures. ISO 139: 2005 Textiles - Standard atmospheres for conditioning and testing (ISO 139: 2005 + Amd.1: 2011); German version EN ISO 139: 2005 + A1: 2011. EN 14034-2: 2011 Determination of explosion characteristics of dust clouds - Part 2: Determination of the maximum rate of explosion pressure rise (dp/ dt) max of dust clouds; German version EN 14034- 2: 2006+A1: 2011. EN 14034-3: 2011 Determination of explosion characteristics of dust clouds - Part 3: Determination of the lower explosion limit LEL of dust clouds; German version EN 14034-3: 2006+A1: 2011. 438 Bibliography <?page no="452"?> EN 14470-1: 2023 Fire safety storage cabinets - Part 1: Safety storage cabinets for flammable liquids; German version EN 14470-1: 2023. prEN ISO 14738: 2020 Safety of machinery - Anthropometric requirements for the design of workstations for industries and services (ISO/ DIS 14738: 2020); German and English version prEN ISO 14738: 2020. ISO 1629: 2013 Rubber and latices - Nomenclature. EN 16350: 2014 Protective gloves - Electrostatic properties; German version EN 16350: 2014. AS/ NZS 1768: 2021 Lightning protection (Australian/ New Zealand Standard). EN ISO 179-1: 2023 Plastics - Determination of Charpy impact properties - Part 1: Noninstrumented impact test; German version EN ISO 179-1: 2023. EN ISO 20345: 2024 Personal protective equipment - Safety footwear (ISO 20345: 2021 + Amd 1: 2024); German version EN ISO 20345: 2022 + A1: 2024. ISO 21898: 2024 Packaging - Flexible intermediate bulk containers (FIBCs) for non-dangerous goods (ISO 21898: 2024); German version EN ISO 21898: 2024. VDI 2263: 2018 Dust fires and dust explosions - Hazards - assessment - safety measures ISO 291: 2008 Plastics - Standard atmospheres for conditioning and testing (ISO 291: 2008); German version EN ISO 291: 2008. EN 3-7: 2007 Portable fire extinguishers - Part 7: Characteristics, performance requirements and test methods; German version EN 3-7: 2004+A1: 2007. ISO 3310-1: 2016 Test sieves - Technical requirements and testing - Part 1: Test sieves of metal wire cloth. ISO 3310-2: 2013 Test sieves - Technical requirements and testing - Part 2: Test sieves of perforated metal plate. ISO 3310-3: 1990 Test sieves; technical requirements and testing; part 3: test sieves of electroformed sheets. ISO 3864-2: 2016 Graphical symbols - Safety colours and safety signs - Part 2: Design principles for product safety labels. EN 50110-1: 2023 Operation of electrical installations - Part 1: General requirements; German version DIN EN 50110-1: 2024. CLC/ TR 50404: 2003 Electrostatics - Code of practice for the avoidance of hazards due to static electricity. DIN 51412-1: 2005 Testing of petroleum products - Determination of the electrical conductivity - Part 1: Laboratory method. DIN 51480-1: 2011 Electrorheological suspensions - Requirements, testing and application - Part 1: Basics and field strength independent properties. DIN 51794: 2003 Testing of mineral oil hydrocarbons - Determination of ignition temperature. DIN 53486: 1975 VDE-specifications for electrical tests of insulating materials; evaluation of the electrostatical behaviour (WITHDRAWN). DIN 54345-3: 1985 Testing of textiles; electrostatic behaviour; determination of electrostatic charge of textile floor coverings by machine (WITHDRAWN). DIN 54345-5: 1985 Testing of textiles; electrostatic behaviour; determination of electrical restistance of strips of textile fabrics. BS 5958-1: 1991 Code of practice for Control of undesirable static electricity - Part 1: General considerations. BS 5958-2: 1991 Code of practice for Control of undesirable static electricity - Part 2: Recommendations for particular industrial situations. IEC 60050 International Electrotechnical Vocabulary (IEV), https: / / electropedia.org/ Standards (Status 2024) 439 <?page no="453"?> IEC 60052: 2002 Voltage measurements by means of standard air gaps; German version EN 60052: 2002 IEC 60079-0: 2017 Explosive atmospheres - Part 0: Equipment - General requirements; German version EN IEC 60079-0: 2018. IEC 60079-1: 2014 Explosive atmospheres - Part 1: Equipment protection by flameproof enclosures “ d ” ; German version EN 60079-1: 2014. IEC 60079-2: 2018 Explosive atmospheres - Part 2: Equipment protection by pressurized enclosure “ p ” (IEC 31/ 1401/ CD: 2018); Text in German and English. IEC 60079-5: 2015 Explosive atmospheres - Part 5: Equipment protection by powder filling “ q ” ; German version EN 60079-5: 2015. IEC 60079-6: 2015 Explosive atmospheres - Part 6: Equipment protection by liquid immersion “ o ” ; German version EN 60079-6: 2015. IEC 60079-7: 2015 Explosive atmospheres - Part 7: Equipment protection by increased safety “ e ” ; German version EN 60079-7: 2015. IEC 60079-10-1: 2021 Explosive atmospheres - Part 10-1: Classification of areas - Explosive gas atmospheres (IEC 60079-10-1: 2020 + COR1: 2021); German version EN IEC 60079-10-1: 2021. IEC 60079-11: 2021 Explosive atmospheres - Part 11: Equipment protection by intrinsic safety “ i ” (IEC 31G/ 327/ CDV: 2020); German and English version prEN 60079-11: 2020. IEC 60079-13: 2017 Explosive atmospheres - Part 13: Equipment protection by pressurized room “ p ” and artificially ventilated room “ v ” ; German version EN 60079-13: 2017. IEC 60079-14: 2019 Explosive atmospheres - Part 14: Electrical installations design, selection and erection (IEC 31J/ 301/ CD: 2019); Text in German and English. IEC 60079-15: 2019 Explosive atmospheres - Part 15: Equipment protection by type of protection “ n ” (IEC 60079-15: 2017); German version EN IEC 60079-15: 2019. IEC 60079-18: 2014 Explosive atmospheres - Part 18: Equipment protection by encapsulation “ m ” ; German version EN 60079-18: 2015. SN EN 60079-20-1: 2010 Explosive atmospheres - Part 20-1: Material characteristics for gas and vapour classification - Test methods and data. IEC 60079-31: 2016 Explosive atmospheres - Part 31: Equipment dust ignition protection by enclosure “ t ” (IEC 31/ 1248/ CD: 2016). IEC/ TS 60079-32-1: 2020 Explosive atmospheres Part 32-1: Electrostatic hazards, guidance (Technical Specification). IEC 60079-32-2: 2015 Explosive atmospheres - Part 32-2: Electrostatics hazards - Tests; German version EN 60079-32-2: 2015. IEC 60079-33: 2012 Explosive atmospheres - Part 33: Equipment protection by special protection “ s ” (IEC 33/ 927/ CDV). ABNT IEC/ TS 60079-39: 2019 Explosive atmospheres Part 39: Intrinsically safe systems with electronically controlled spark duration limitation. IEC 60112: 2024 Method for the determination of the proof and the comparative tracking indices of solid insulating materials (IEC 112/ 643/ CDV: 2024); German and English version prEN IEC 60112: 2024. IEC 60156: 2023 Insulating liquids - Determination of the breakdown voltage at power frequency - Test method (IEC 10/ 1201/ CDV: 2023); German and English version prEN IEC 60156: 2023. IEC 60204-1: 2019 Safety of machinery - Electrical equipment of machines - Part 1: General requirements (IEC 44/ 873A/ CD: 2020); German version EN 60204-1: 2018. IEC 60228: 2023 Conductors of insulated cables; German version EN IEC 60228: 2024. IEC 60243-1: 2013 Electric strength of insulating materials - Test methods - Part 1: Tests at power frequencies; German version EN 60243-1: 2013. 440 Bibliography <?page no="454"?> IEC 60243-2: 2013 Electric strength of insulating materials - Test methods - Part 2: Additional requirements for tests using direct voltage; German version EN 60243-2: 2014. IEC 60247: 2004 Insulating liquids - Measurement of relative permittivity, dielectric dissipation factor (tan δ ) and d. c. resistivity; German version EN 60247: 2004. IEC 60364-4-41: 2017 (UNE-HD 60364-4-41) Low-voltage electrical installations - Part 4-41: Protection for safety - Protection against electric shock, (IEC 60364-4-41: 2005, modified + A1: 2017, modified); German implementation of HD 60364-4-41: 2017 + A11: 2017. IEC/ TS 60479-1: 2005 Effects of current on human beings and livestock - Part 1: General aspects (IEC/ TS 60479-1: 2005 + Corrigendum October 2006). BS IEC 60479-2: 2019 Effects of current on human beings and livestock - Part 2: Special aspects. IEC/ TR 60479-5: 2024 Effects of current on human beings and livestock - Part 5: Touch voltage threshold values for physiological effects; ED2-CD: 2024. IEC 60529: 2013 Degrees of protection provided by enclosures (IP Code) (IEC 60529: 1989 + A1: 1999 + A2: 2013); German version EN 60529: 1991 + A1: 2000 + A2: 2013. IEC 60641-1: 2007 Specification for pressboard and presspaper for electrical purposes - Part 1: Definitions and general requirements; German version EN 60641-1: 2008. IEC 60664-1: 2020 Insulation coordination for equipment within low-voltage supply systems - Part 1: Principles, requirements and tests; German version EN IEC 60664-1: 2020. IEC 60749-26: 2018 Semiconductor devices - Mechanical and climatic test methods - Part 26: Electrostatic discharge (ESD) sensitivity testing - Human body model (HBM); German version EN IEC 60749-26: 2018. IEC 60749-27: 2012 Semiconductor devices - Mechanical and climatic test methods - Part 27: Electrostatic discharge (ESD) sensitivity testing - Machine model (MM) (IEC 60749-27: 2006 + A1: 2012); German version EN 60749-27: 2006 + A1: 2012. IEC 60749-28: 2022 Semiconductor devices - Mechanical and climatic test methods - Part 28: Electrostatic discharge (ESD) sensitivity testing - Charged device model (CDM) - device level (IEC 60749-28: 2022); German version EN IEC 60749-28: 2022. IEC 60749-29: 2011 Semiconductor devices - Mechanical and climatic test methods - Part 29: Latchup test; German version EN 60749-29: 2011. IEC 60947-1: 2021 Low-voltage switchgear and controlgear - Part 1: General rules; German version EN IEC 60947-1: 2021. IEC 60947-2: 2022 Low-voltage switchgear and controlgear - Part 2: Circuit-breakers (IEC 121A/ 482/ CDV: 2022); German and English version prEN IEC 60947-2: 2022. IEC 61000-3-3: 2013 Electromagnetic compatibility (EMC) - Part 3-3: Limits - Limitation of voltage changes, voltage fluctuations and flicker in public low-voltage supply systems, for equipment with rated current ≤ 16 A per phase and not subject to conditional connection (IEC 61000-3-3: 2013 + A1: 2017 + A2: 2021 + A2: 2021/ COR1: 2022); German version EN 61000-3-3: 2013 + A1: 2019 + A2: 2021 + A2: 2021/ AC: 2022. IEC 61000-4-1: 2006 Electromagnetic compatibility (EMC) - Part 4-1: Testing and measurement techniques - Overview of IEC 61000-4 series; German version EN 61000-4-1: 2007. IEC 61000-4-2: 2008 Electromagnetic compatibility (EMC) - Part 4-2: Testing and measurement techniques - Electrostatic discharge immunity test; German version EN 61000-4-2: 2009. IEC 61000-4-4: 2012 Electromagnetic compatibility (EMC) - Part 4-4: Testing and measurement techniques - Electrical fast transient/ burst immunity test; German version EN 61000-4-4: 2012- IEC 61000-4-5: 2014 Electromagnetic compatibility (EMC) - Part 4-5: Testing and measurement techniques - Surge immunity test (IEC 61000-4-5: 2014 + A1: 2017); German version EN 61000-4- 5: 2014 + A1: 2017. IEC 61008-1: 2017 Residual current operated circuit-breakers without integral overcurrent protection for household and similar uses (RCCBs) - Part 1: General rules (IEC 61008-1: 2010, modified + Standards (Status 2024) 441 <?page no="455"?> A1: 2012, modified + A1: 2012/ COR1: 2016 + A2: 2013, modified + A2: 2013/ Cor.: 2014); German version EN 61008-1: 2012 + A1: 2014 + A1: 2014/ AC: 2016 + A2: 2014 + A11: 2015 + A12: 2017. IEC 61008-2-1: 2020 Residual current operated circuit-breakers without integral overcurrent protection for household and similar uses (RCCB ’ s) - Part 2-1: RCCBs according to 4.1.1 (IEC 23E/ 1219/ CD: 2020); Text in German and English. IEC 61010-1: 2022 Safety requirements for electrical equipment for measurement, control, and laboratory use - Part 1: General requirements (IEC 66/ 769/ CD: 2022); Text in German and English (UL 840). IEC 61140: 2016 Protection against electric shock - Common aspects for installation and equipment; German version EN 61140: 2016. IEC 61189-2: 2006 Test methods for electrical materials, printed boards and other interconnection structures and assemblies - Part 2: Test methods for materials for interconnection structures; German version EN 61189-2: 2006. IEC/ TR 61340-1: 2020 Electrostatics - Part 1: Electrostatic phenomena - Principles and measurements (IEC TR 61340-1: 2012 + COR1: 2013 + COR2: 2017 + AMD1: 2020). IEC 61340-2-1: 2022 Electrostatics - Part 2-1: Measurement methods - Ability of materials and products to dissipate static electric charge (IEC 61340-2-1: 2015 + AMD1: 2022); German version EN 61340-2-1: 2015 + A1: 2022. IEC 61340-2-3: 2016 Electrostatics - Part 2-3: Methods of test for determining the resistance and resistivity of solid materials used to avoid electrostatic charge accumulation; German version EN 61340-2-3: 2016. IEC 61340-3-2: 2006 Electrostatics - Part 3-2: Methods for simulation of electrostatic effects - Machine model (MM) electrostatic discharge test waveforms; German version EN 61340-3-2: 2007. IEC 61340-4-1: 2015 Electrostatics - Part 4-1: Standard test methods for specific applications - Electrical resistance of floor coverings and installed floors (IEC 61340-4-1: 2003 + A1: 2015); German version EN 61340-4-1: 2004 + A1: 2015. IEC 61340-4-4: 2018 Electrostatics - Part 4-4: Standard test methods for specific applications - Electrostatic classification of flexible intermediate bulk containers (FIBC); German version EN IEC 61340-4-4: 2018. IEC 61340-4-5: 2018 Electrostatics - Part 4-5: Standard test methods for specific applications - Methods for characterizing the electrostatic protection of footwear and flooring in combination with a person; German version EN IEC 61340-4-5: 2018. IEC 61340-4-7: 2021 Electrostatics - Part 4-7: Standard test methods for specific applications - Ionization (IEC 101/ 629/ CD: 2021); Text in German and English. IEC 61340-4-9: 2021 Electrostatics - Part 4-9: Standard test methods for specific applications - Garments (IEC 101/ 626/ CD: 2021); Text in German and English. IEC 61340-4-11: 2023 Electrostatics - Part 4-11: Standard test methods for specific applications - Testing of electrostatic properties of composite IBC (IEC 101/ 698/ CDV: 2023); German and English version prEN IEC 61340-4-11: 2023. IEC 61340-5-1: 2023 Electrostatics - Part 5-1: Protection of electronic devices from electrostatic phenomena - General requirements (IEC 101/ 679/ CDV: 2023); German and English version prEN IEC 61340-5-1: 2023. IEC 61340-6-1: 2018 Electrostatics - Part 6-1: Electrostatic control for healthcare - General requirements for facilities; German version EN IEC 61340-6-1: 2018. IEC 61386-21: 2021 Conduit systems for cable management - Part 21: Particular requirements - Rigid conduit systems; German version EN IEC 61386-21: 2021 + A11: 2021. IEC 61620: 1998 Insulating liquids - Determination of the dielectric dissipation factor by measurement of the conductance and capacitance - Test method; German version EN 61620: 1999. 442 Bibliography <?page no="456"?> IEC 62305-1: 2021 Protection against lightning - Part 1: General principles (IEC 81/ 644/ CD: 2021); Text in German and English. IEC 62305-4: 2021 Protection against lightning - Part 4: Electrical and electronic systems within structures (IEC 81/ 643A/ CD: 2021); Text in German and English. IEC 62485-1: 2015 Safety requirements for secondary batteries and battery installations - Part 1: General safety information; German version EN IEC 62485-1: 2018. IEC 62606: 2013 General requirements for arc fault detection devices (IEC 62606: 2013, modified); German version EN 62606: 2013. IEC 62631-3-1: 2023 Dielectric and resistive properties of solid insulating materials - Part 3-1: Determination of resistive properties (DC methods) - Volume resistance and volume resistivity - General method; German version EN IEC 62631-3-1: 2023. IEC 62631-3-2: 2023 Dielectric and resistive properties of solid insulating materials - Part 3-2: Determination of resistive properties (DC methods) - Surface resistance and surface resistivity; German version EN IEC 62631-3-2: 2023. IEC 62631-3-3: 2015 Dielectric and resistive properties of solid insulating materials - Part 3-3: Determination of resistive properties (DC methods) - Insulation resistance; German version EN 62631-3-3: 2016. IEC 62873-2: 2016 (BS IEC 62873-2), Residual current operated circuit-breakers for household and similar use. Residual current devices (RCDs). Vocabulary. NFPA 651 Standard for the Machining and Finishing of Aluminum and the Production and Handling of Aluminum Powders (WITHDRAWN), National Fire Protection Association ® . DIN 66165-1: 2022 Particle size analysis - Sieving analysis - Part 1: Fundamentals. DIN 66165-2: 2016 Particle size analysis - Sieving analysis - Part 2: Procedure. NFPA 70: 2023 National Electrical Code ® (NEC) is the benchmark for safe electrical design, installation, and inspection to protect people and property from electrical hazards, National Fire Protection Association ® . NFPA 70E: 2024 Standard for Electrical Safety in the Workplace ® , National Fire Protection Association ® . ISO 7010: 2019 Graphical symbols - Safety colours and safety signs - Registered safety signs; German version EN ISO 7010: 2020. NFPA 77: 2024 Recommended Practice on Static Electricity, National Fire Protection Association ® . NFPA 780: 2023 Standard for the Installation of Lightning Protection Systems, National Fire Protection Association ® . IEEE 80-2013 “ IEEE Guide for Safety in AC Substation Grounding, ” in IEEE Std 80-2013 (Revision of IEEE Std 80-2000/ Incorporates IEEE Std 80-2013/ Cor 1-2015), vol., no., pp. 1-226, 15 May 2015, doi: 10.1109/ IEEESTD.2015.7109078. ISO 80000-9: 2019 Quantities and units - Part 9: Physical chemistry and molecular physics; German version EN ISO 80000-9: 2019. IEC 80079-20-1: 2018 Explosive atmospheres - Part 20-1: Material characteristics for gas and vapour classification - Test methods and data (ISO/ IEC 80079-20-1: 2017, including Cor 1: 2018); German version EN ISO/ IEC 80079-20-1: 2019. ISO/ IEC 80079-20-2: 2016 Explosive atmospheres - Part 20-2: Material characteristics - Combustible dusts test methods, German version EN ISO/ IEC 80079-20-2: 2016. ISO 80079-36: 2016 Explosive atmospheres - Part 36: Non-electrical equipment for explosive atmospheres - Basic method and requirements; German version EN ISO 80079-36: 2016. ISO 80079-37: 2016 Explosive atmospheres - Part 37: Non-electrical equipment for explosive atmospheres - non-electrical type of protection constructional safety “ c ” , control of ignition sources “ b ” , liquid immersion “ k ” ; German version EN ISO 80079-37: 2016. Standards (Status 2024) 443 <?page no="457"?> ISO 80079-38: 2016 Explosive atmospheres - Part 38: Equipment and components in explosive atmospheres in underground mines; German version EN ISO/ IEC 80079-38: 2016. ISO 8031: 2020 Rubber and plastics hoses and hose assemblies - Determination of electrical resistance and conductivity; German version EN ISO 8031: 2020. ISO 8044: 2020 Corrosion of metals and alloys - Vocabulary; Trilingual version EN ISO 8044: 2020. Mil-Std 833D (1996) Military Standard 833D Department of Defense, Testmethod Standard Microcircuits (Method 3015,7), USA. DIN 8580: 2022 Manufacturing processes - Terms and definitions, division. ISO 9000: 2015 Quality management systems - Fundamentals and vocabulary; German and English version EN ISO 9000: 2015. ISO 9277: 2022 Determination of the specific surface area of solids by gas adsorption - BET method. ASTM D2155-18 Standard Test Method for Determination of Fire Resistance of Aircraft Hydraulic Fluids by Autoignition Temperature, reapproved: 2024. ASTM E2019-03 (2019) Standard Test Method for Minimum Ignition Energy of a Dust Cloud in Air. ASTM E582-21 Standard Test Method for Minimum Ignition Energy and Quenching Distance in Gaseous Mixtures (2021). ASTM F150-06 (2018) Standard Test Method for Electrical Resistance of Conductive and Static Dissipative Resilient Flooring. ANSI/ ESDA/ JEDEC JS-002: 2018 Joint Standard for Electrostatic Discharge Sensivity Testing - Charged device Model (CDM) Device Level (Japan). ANSI/ ESD S5.3.1: 2009 Electrostatic Discharge Sensitivity Testing - Charged Device Model (CDM) - Component Level. ANSI/ ESD STM15.1: 2019 Methods for the Resistance Testing of Gloves and Finger Cots. JNIOSH TR 42 (2007) Recommendations for requirements for avoiding electrostatic hazards in industry 2007. 444 Bibliography <?page no="458"?> The best result. With Eltex. Whether charging, discharging or grounding - the targeted use of electrostatics means safe processes. And Eltex knows what matters. With individual, industry-specific solutions for your company that you can rely on for the long term. Our eltEXPERTS will also find an efficient and sustainable discharge solution for your requirements using modular Eltex components. 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