Handheld device for detecting electrostatic discharge

Abstract

The present invention relates to a handheld device for detecting electrostatic discharge, comprising an evaluation unit and a cable antenna (1;1') made from a coaxial cable, wherein the cable antenna is formed in a coil shape having n windings (2;2') with n≧2, each winding (2;2') is wound around a winding axis, each winding has a diameter of less than 30 cm, and the windings of the cable antenna are preferably separated from each other by at least one spacer.

Description

Technical Field

[0001] Generally, the present invention relates to the technical field of detecting an electrostatic field within a measurement object, such as a container like a chemical reactor. In particular, the present invention relates to a handheld device for detecting electrostatic discharges within such a reactor, in which, due to the handling of low-conductivity liquids and / or suspensions, electrostatic charges, and thus electrostatic discharges ("ESD"), can often occur. The present invention also relates to the use of such a handheld device.

Background Art

[0002] Conventionally, as a reactor for performing, for example, the production of chemical substances, a steel hollow container has generally been selected. During the production of such chemical substances, where low-conductivity liquids and / or suspensions are often processed, for example, by stirring, electrostatic charges are generated, and as a result, electrostatic discharges often occur. However, due to the fact that the processes for the production of chemical substances can generate flammable gases, i.e., an explosive atmosphere within the headspace of each chemical reactor used can occur, any kind of ignition of such an explosive atmosphere should be avoided. For example, an electrostatic discharge can be an ignition source for an explosive atmosphere, leading to an explosion, which can have serious consequences not only for the chemical production and the employees but also for the container itself, such as disruptive discharges that penetrate the enamel of the steel hollow wall of the container.

[0003] To avoid such problems, several industrial solutions have been proposed in the past, primarily aimed at avoiding the generation of a flammable atmosphere, which essentially means charging the liquid or powder into an inert atmosphere, or avoiding the generation of any kind of ignition source, i.e., avoiding the presence of elements and conditions that could generate an ignition source. However, such solutions cannot be implemented in the process of chemical manufacturing, or can only be implemented with considerable effort, due to the requirements of the liquid used and the respective containers, such as their material properties. Therefore, there is a need for measurement techniques that can be used to assess the probability of ignition sources occurring in the form of potential electrostatic ignition in such containers, and to determine explosion protection measures.

[0004] Considering the above, U.S. Patent No. 3,753,102 proposes a measurement system for measuring the charge of turbulent material flowing through a pipe in order to identify the risk of explosion within the material. The fluctuations in the charge of the turbulent material flowing through electrodes are measured by an AC voltmeter, and the AC component induced by the change in the electric field is directly conducted to a DC voltmeter via an AC amplifier and rectifier. U.S. Patent No. 5,151,659 discloses a similar measurement system in which the induced charge is directly measured at a rapidly vibrating electrode placed in a protective opening in front of the surface where the charge is measured. However, with respect to the proposed solutions in these cases, the measurement methods cannot be used to determine electrostatic discharge in a chemical reactor because their integrity may be compromised. Furthermore, the measurement results are susceptible to interference due to the sensitivity of each measurement method.

[0005] As a further measure, it has been proposed to inert the inside of the reactor to completely avoid the occurrence of electrostatic discharge during operation in order to prevent ignition of an explosive atmosphere. However, the requirements for electrically inertifying such a reactor are complex and costly. As an alternative solution, it has been proposed to replace commonly used steel enamel vessels with steel enamel vessels in which platinum fibers are provided within the enamel layer. It is assumed that, due to the lower volume resistivity of such a coating, the material stirred in the reactor should not be as charged, or the inner wall of the reactor should be able to discharge any generated static charge more easily. However, these desired effects must first be tested and / or confirmed in order to avoid any undesirable effects or results. For such tests, in the relevant technical field, for example, Alexis Pey and Martin Glor, "Charging powders in vessels with flammable vapor atmospheres. An industrial approach" (Journal of Electrostatics, Volume 117, 2022, 103695, ISSN 0304-3886), have proposed detecting tuft discharges using a loop antenna with a diameter of at least 700 mm, which is installed in the vessel before the material to be agitated is filled into the vessel. Here, the aforementioned diameter size is the minimum diameter size required to accurately detect any electrostatic discharge in the vessel. However, the manufacture of chemicals is not always carried out in large vessels such as those with a volume of 100 liters to 1000 liters, but can also be carried out in small vessels such as those with a volume of less than 30 liters, so the proposed loop antenna cannot be used in such small vessels. Furthermore, the proposed loop antenna is difficult to transport due to its large size.

[0006] Therefore, the object of the present invention is to provide a solution for measuring the frequency of electrostatic discharges, with a focus on reducing the requirements for deactivating the reactor, and thereby confirming the usefulness of a new design for small-volume reactors for chemical production with respect to explosion prevention. [Overview of the project]

[0007] The present invention addresses the above problem of evaluating the usefulness of novel vessel designs for chemical manufacturing reactors, particularly with respect to avoiding electrostatic discharge. According to a first aspect of the present invention, a handheld device for detecting electrostatic discharge is proposed, comprising an evaluation unit and a cable antenna, the cable antenna, which may also be provided in the form of a probe, is formed in a coil shape by windings of n turns, where n≧2, and each winding is wound around a winding axis. Here, the winding axis may be a common winding axis, i.e., one winding axis common to all windings. Alternatively, the windings may include multiple different winding axes that are arranged parallel to each other but not coaxially. Furthermore, the diameter of each winding of the coiled cable antenna of the handheld device is less than 30 cm, and the windings of the cable antenna are spaced apart from each other, such spacing may be achieved by at least one spacer. By using a coiled antenna, the use of a large-diameter antenna can be avoided in order to maintain a small size of the device, and therefore a handheld size. Therefore, the diameter, or more precisely the circumference of the cable antenna, can be compensated for by the number of turns in the winding, also called turns. Thus, by applying more turns, a smaller diameter of the cable antenna can be achieved while maintaining reliable detection of electrostatic discharge. The more turns in the winding, the higher the sensitivity of the discharge detection, i.e., the larger the amplitude of the measured signal.

[0008] According to certain embodiments, the number of turns n of the winding of the cable antenna of the handheld device of the present invention conforms to n > 2, and the number of turns n of the winding can conform to 3 ≤ n ≤ 11. In this regard, it is noted that the number of turns can affect the detectable representation of the measurement result. More specifically, a winding with more turns in the cable antenna of the handheld device of the present invention can result in a significant extension of the discharge duration displayed on the meter or display when comparing the detection of the same discharge type. Here, the discharge may be represented as oscillations with decreasing positive and negative amplitudes. The more turns there are, the more the amplitude reduction can be observed, which is why the discharge duration visible on the meter increases. Also, by using a cable antenna with a large number of turns, electrostatic discharge can be reliably detected even with a small winding diameter. Therefore, the cable antenna of the handheld device of the present invention can be used multifunctionally, particularly in all kinds of small reactor vessels, i.e., depending on the number of turns of the winding. Furthermore, the measurement sensitivity of the cable antenna of the handheld device of the present invention can be increased as the number of windings increases. In this case, since background noise is generally present with such measurement techniques, a compromise must be made between the degree of sensitivity and the avoidance of background noise capture by the evaluation unit of the form used, with respect to the selected number of windings. Another advantage of the miniaturization of the handheld device of the present invention is improved portability due to the miniaturization of the cable antenna.

[0009] According to a specific embodiment of the handheld device of the present invention, the diameter of each winding of the cable antenna of the handheld device is approximately 5 cm, and the diameters of adjacent windings of the cable antenna of the handheld device of the present invention may differ from each other. Therefore, the diameters of the cable antenna windings do not need to be the same as each other; they may be smaller or larger than each other, that is, the diameter of one winding may be smaller or larger than the diameter of an adjacent winding. Furthermore, all windings of the cable antenna of the handheld device of the present invention may have matching winding shapes, and the winding shapes of the cable antenna are selected from a group of shapes consisting of circular, elliptical, triangular, or square, that is, the winding shapes of the cable antenna may be circular, elliptical, triangular, square, polygonal, or any combination of the shapes listed above. Therefore, the windings of the cable antenna of the handheld device of the present invention do not need to be circular, and may have other shapes or combinations of shapes as described above. Hereinafter, it is noted that the structural shape of the cable antenna of the handheld device of the present invention may affect the presentation of measurement results.

[0010] According to a further specific embodiment of the handheld device of the present invention, each spacer is sized to provide a distance between windings that, if present, substantially corresponds to the outer diameter of the cable, i.e., the outer diameter of the cable. This means that each spacer is sized to provide a distance between windings that is similar to or identical to the outer diameter of the cable of the cable antenna, and the distance "similar" to the outer diameter of the cable is within ±20% of the diameter size, or within ±10% of the diameter size. Alternatively or additionally, each spacer of the handheld device of the present invention is made of an insulating material, such as a plastic material such as polyvinyl chloride, polypropylene, or polytetrafluoroethylene, and one specific material such an electrically insulating plastic material may be Teflon®. Thus, with or without spacers, each winding is electrically insulated from adjacent windings by either spacers or air.

[0011] According to a further specific embodiment of the handheld device of the present invention, the windings of the cable antenna may be separated from each other by at least two spacers, the two spacers may be configured to be positioned opposite each other, i.e., the two spacers in such a configuration are positioned on opposite sides of the antenna winding structure. This can achieve a uniform distribution of spacers across the diameter of the cable antenna. Alternatively, the windings of the cable antenna of the handheld device of the present invention may be separated from each other by at least three spacers, the spacers may be configured to be positioned at equal distances from each other, i.e., the spacers are positioned such that each spacer provides the same distance to each of its adjacent spacers. Here again, a uniform distribution of spacers across the diameter of the cable antenna can be achieved. Alternatively, the distance between windings may be achieved by providing spacer material along the entire cable antenna, i.e., insulating spacer material fills all the gaps between adjacent windings, thereby achieving a constant distance between windings. Thus, any configuration of spacers or provision of spacer material is satisfied as long as the distance between adjacent windings can be maintained in an insulating state.

[0012] According to a further specific embodiment of the handheld device of the present invention, the cable antenna is made from a coaxial cable, i.e., an electrical cable of the type consisting of an inner conductor surrounded by a concentric conductive outer shell, wherein the inner conductor and the conductive outer shell are separated by an insulating material, such as a dielectric material. When the cable antenna of the handheld device of the present invention is made from a coaxial cable, the inner conductor may contain silver. For example, the inner conductor may be made from silver, or any other suitable type such as copper may be silver-plated as the inner core. For example, due to the good conductivity of such a coaxial cable using a silver or silver-plated inner conductor instead of an inner conductor made from pure copper, only low measurement losses occur within the coaxial cable, thereby improving the measurement sensitivity of such a cable antenna. In addition, a coaxial cable having the aforementioned structure with a silver inner conductor or silver-plated inner conductor exhibits improved durability and can withstand higher mechanical loads due to the improved mechanical strength of the inner conductor. In addition, the conductive outer shell may be made from a rigid or inflexible material such as iron sheet material to increase mechanical strength, thereby eliminating the need for spacers to achieve a stable distance between adjacent windings. When using flexible material for the conductive outer shell of a cable, using one or more spacers is advantageous in maintaining an insulating distance between adjacent windings.

[0013] According to a further specific embodiment of the handheld device of the present invention, the evaluation unit may comprise one or more of an oscilloscope, a display, a wireless communication module such as a Bluetooth connectivity module, and a network analyzer. Generally, any of these potential components of the handheld device of the present invention are connectable to a cable antenna and therefore detachable, or generally quite small, so that the handheld device offers good portability and a good size for use in the hand.

[0014] According to a further specific embodiment of the handheld device of the present invention, the handheld device may be configured for measurements in containers having a small internal volume, and the handheld device may be configured for measurements in containers having an internal volume of less than 30 liters. However, it should be noted here that the length / diameter ratio, rather than volume, is the determining factor, as the diameter of the container needs to be increased accordingly when taking into account internal technical structures such as flow breakers, agitators, etc. According to a further specific embodiment of the handheld device of the present invention, the handheld device may be configured specifically for measurements in reactors for chemical production, including all respective safety measures, and chemical production may involve processing suspensions with low conductivity, i.e., κ < 50 pS / m, which would result in a risk of high electrostatic discharge. However, measurements in reactors for chemical production are not limited to processing suspensions with low conductivity, and suspensions with medium conductivity, 50 pS / m < K ≤ 10,000 pS / m, and suspensions with high conductivity, 10,000 pS / m ≤ K, may also be processed and therefore measured. Furthermore, even if the device of the present invention is a handheld device, it can be used in a temporarily fixed manner, i.e., in a stationary use where the handheld device is used with a container such as a reactor. Generally, when used with a container such as a reactor, the cable antenna is the part of the device configured to be located inside the reactor, for example, protruding through an opening from the outside to the inside of the reactor, while the evaluation unit, etc., is left outside the reactor. This also applies to stationary use where the cable antenna is configured to be fixedly located within the reactor volume, while the evaluation unit is configured to be located outside the reactor shell. In addition to reactors, the handheld device of the present invention can be configured for measurements inside other types of containers or vessels, such as silos, which may contain explosive atmospheres and where electrostatic discharge may occur, for example, in chemical manufacturing or tank filling operations. Alternatively or additionally, the device can also be used with respect to the overall flow of fluids and powders, or around charging processes, such as the movement of conveyor belts or plastic films, where explosive atmospheres may occur.

[0015] According to a second aspect of the present invention, the use of the handheld device described above is provided for detecting electrostatic discharge in an environment including an explosive atmosphere, such as around a charging process in a place where an explosive atmosphere may be generated, for example, a conveyor belt or plastic film is in motion. Thus, the handheld device of the present invention can be used multifunctionally in any atmosphere in which an explosive atmosphere and electrostatic charge may be generated in combination, even in small or hard-to-reach spaces.

[0016] In addition, according to a third aspect of the present invention, the use of the handheld device described above is provided for detecting electrostatic discharge in containers having a volume of less than 30 liters, such as reactors for chemical manufacturing. Generally, the handheld device of the present invention can be used to evaluate types of electrostatic discharge, such as brush discharge, spark discharge, or corona discharge, as well as the probability of occurrence and ignition potential of electrostatic discharge. Specifically, the handheld device of the present invention can be used to evaluate the ignition potential of electrostatic discharge in reactors of different types, i.e., different in terms of their layout, material properties, etc. According to a particular embodiment of such use of the handheld device of the present invention, the detection of electrostatic discharge may be performed on demand, usually when a charge generation process is assumed during operation and its relevance to the possibility of ignition must be investigated in order to derive explosion protection measures. Alternatively, the detection of electrostatic discharge may be performed continuously at a sampling rate of, for example, 2 μs. Here, a sampling rate of 2 μs is suitable for detecting, for example, brush discharges, while the duration of different electrostatic discharges, such as spark discharges, is longer, i.e., up to 0.5 ms, and consequently, a higher sampling rate is required for detecting this particular type of discharge. In general, the sampling rate of the handheld device of the present invention depends on the number of turns of the winding. For example, with an 11-turn winding, a coarser sampling rate may be sufficient.

[0017] The devices described above may be controlled by a control unit, and any kind of operation or monitoring of the devices and their components may also be controlled by such a control unit. The term “control unit” as used herein encompasses any physical or virtual processing device, such as a CPU, which can also control an entire workstation, including one or more devices, so that a workflow and steps of the workflow can be performed. A control unit may, for example, carry different types of application software and provide instructions to a device or a particular component thereof. A control unit may receive information from a data management unit about which steps need to be performed. Furthermore, a control unit may be integrated with a data management unit, may be contained in a server computer, and / or may be part of a single device, or distributed across multiple devices in each processing system. A control unit may be embodied, for example, as a programmable logic controller that runs a computer-readable program with instructions for performing actions. Herein, a user interface may be further provided to receive such commands from the user, and the term “user interface” as used herein encompasses any appropriate application software and / or hardware for interaction between the operator and the machine, including but not limited to graphical user interfaces for receiving commands from the operator as input and providing feedback and conveying information thereto. Furthermore, the system / device may expose several user interfaces to serve various types of users / operators.

[0018] Where used herein and in the appended claims, the singular forms “a,” “an,” and “the” include the plural unless the context explicitly indicates otherwise. Similarly, the words “comprise,” “contain,” and “encompass” are interpreted inclusively, not exclusively, that is, “include but not limited to.” Likewise, the word “or” is intended to include “and” unless the context explicitly indicates otherwise. The terms “plurality,” “multiple,” or “multitude” refer to two or more integer multiples, i.e., 2 or > 2, and the terms “single” or “sole” refer to one, i.e., = 1. Furthermore, the term “at least one” should also be understood as one or more, i.e., 1 or > 1, which are also integer multiples. Thus, words using singular or plural forms also include plural and singular forms, respectively. Furthermore, when the terms “herein,” “above,” “previously,” and “below,” and any similar terms are used herein, they refer to the entire Specified Specified Specified Specified, and not to any particular part thereof.

[0019] Furthermore, certain terms are used for convenience and are not intended to limit the invention. The terms “right,” “left,” “up,” “down,” “under,” and “above” refer to directions in the figures. The terms include those explicitly mentioned, their derivatives, and terms with similar meanings. In addition, spatially relative terms such as “beneath,” “below,” “lower,” “above,” “upper,” “proximal,” and “distal” may be used to describe the relationship of one element or feature shown in the figures to another element or feature. These spatially relative terms are intended to encompass various positions and orientations of the device in use or operation, in addition to the positions and orientations shown in the figures. For example, if the device in the figure is inverted, an element described as “below” or “below” another element or feature would be considered “above” or “over” the other element or feature. Therefore, the exemplary term “downward” may encompass both upward and downward positions and orientations. The device may be in other orientations (90-degree rotation or other orientations), and the spatially relative descriptors used herein may be interpreted accordingly. Similarly, descriptions of movement along various axes and movement about various axes include the positions and orientations of various specific devices.

[0020] To avoid repetition in the figures and descriptions of various aspects and exemplary embodiments, it should be understood that many features are common to many aspects and embodiments. The descriptions of specific embodiments of this disclosure are not intended to be exhaustive or to limit this disclosure to the exact form disclosed. Specific embodiments and examples of this disclosure are described herein for illustrative purposes, but various equivalent modifications are possible within the scope of this disclosure, as will be recognized by those skilled in the art. Certain elements of the embodiments described above may be combined with or used in place of elements of other embodiments. Furthermore, while advantages related to specific embodiments of this disclosure have been described in the context of those embodiments, other embodiments may also exhibit such advantages, and it is not necessary to demonstrate such advantages so that all embodiments are included within the scope of this disclosure as defined by the appended claims. Where an aspect is omitted from the description or figures, it does not mean that that aspect is missing from embodiments that incorporate that aspect. Rather, that aspect may be omitted for the purpose of clarity and to avoid redundant descriptions. In this context, the following applies to the remainder of this description: To make the drawings easier to understand, if a drawing contains reference numerals not described in the directly relevant part of the specification, a preceding or succeeding part of the specification should be referenced. Furthermore, for clarity, if not all features of a part are referenced in a section of a drawing, refer to another section of the same drawing. Similar numerals in two or more drawings represent the same or similar elements.

[0021] The following embodiments are intended to illustrate various specific embodiments of the present invention. Therefore, the specific modifications discussed below should not be construed as limitations on the scope of the invention. It will be apparent to those skilled in the art that various equivalents, modifications, and alterations can be made without departing from the scope of the invention, and therefore, such equivalent embodiments should be understood to be included herein. Furthermore, the features of the claimed apparatus can be used for the claimed applications, and vice versa. Further aspects and advantages of the present invention will become apparent from the following description of the specific embodiments shown in the figures. [Brief explanation of the drawing]

[0022] [Figure 1] A conceptual diagram of a cable antenna for a handheld device according to one embodiment of the present invention. [Figure 2] Conceptual diagram of a cable antenna for a handheld device according to an alternative embodiment of the present invention. [Modes for carrying out the invention]

[0023] Figure 1 shows a conceptual diagram of a cable antenna 1 of a handheld device according to one embodiment of the present invention, the cable antenna 1 comprising an 11-turn winding 2. Each winding 2 has a similar circular shape and a common diameter φ CThe length is less than 30 cm and has a common winding axis. In the embodiment shown in Figure 1, the stability provided by the mechanical properties of the cable antenna 1 is sufficient to maintain a constant distance 3 between two adjacent windings 2 without the need for spacers. As can be seen from Figure 1, the distance 3 is the same as or approximately the same as the outer diameter of the cable antenna 1. The cable antenna 1 is implemented by a coaxial cable having a conductive outer shell 21 as an outer component, which encloses an insulating material, with an inner conductor 22 concentrated and embedded as the inner core of the coaxial cable. The proximal end 23 of the cable antenna 1 is connected to an evaluation unit (not shown) of a handheld device of an embodiment of the invention described herein. The distal portion of the cable antenna 1, including its distal end 24, advances toward the proximal portion of the cable antenna 1, including the proximal end 23, and the distal portion of the cable antenna 1, after completing the winding advance, extends toward the proximal portion of the cable antenna 1, parallel to, or at least adjacent to, the winding axis of the winding 2. Here, the distal portion of the cable antenna 1 is positioned at a distance from the winding to avoid any contact with the conductive outer shell 21 of the cable antenna 1 in the winding region. At this time, at the distal end 24 of the cable antenna 1, the inner conductor 22 protrudes from the conductive outer shell 21 and the insulating material, and connects to the conductive outer shell 21 at a position close to the proximal end 23 of the cable antenna 1.

[0024] Figure 2 shows a conceptual diagram of a cable antenna 1' for a handheld device according to an alternative embodiment of the present invention, the cable antenna 1' comprising an 11-turn winding 2'. Each winding 2' has a similar square shape and a common diameter φ Sis less than 30 cm and has a common winding shaft. In the embodiment shown in FIG. 2, the stability provided by the mechanical properties of the cable antenna 1' is sufficient to maintain the distance 3' between two adjacent windings 2' without requiring a spacer. As can be seen from FIG. 2, the distance 3' is the same as or approximately the same as the outer diameter of the cable antenna 1'. The cable antenna 1' is implemented by a coaxial cable having a conductive outer shell 21' surrounding an insulating material, in which an inner conductor 22' is centrally embedded as the inner core of the coaxial cable. The proximal end 23' of the cable antenna 1' is connected to an evaluation unit (not shown) of a handheld device of an alternative embodiment described herein of the present invention. The distal portion of the cable antenna 1' including its distal end 24' proceeds towards the proximal portion of the cable antenna 1' including its proximal end 23', and the distal portion of the cable antenna 1' extends parallel to or at least adjacent to the winding axis of the winding 2' in a direction towards the proximal portion of the cable antenna 1' after the winding progression. Here, the distal portion of the cable antenna 1' is arranged and configured at a distance from the winding to avoid any contact with the conductive outer shell 21' of the cable antenna 1' in the winding region. At this time, at the distal end 24' of the cable antenna 1', the inner conductor 22' protrudes from the conductive outer shell 21' and the insulating material and connects to the conductive outer shell 21' at a position close to the proximal end 23' of the cable antenna 1'.

[0025] Although the present invention has been described in connection with its specific embodiments, it should be understood that this description is for the purpose of illustration only. Accordingly, the present invention is intended to be limited only by the scope of the claims appended hereto.

Explanation of Reference Numerals

[0026] 1 Cable antenna, square 1’ Cable antenna, circular 2 Winding 2’ Winding 21 Conductive outer shell having an inner insulating material 21’ Conductive outer shell having an inner insulating material 22 Internal conductor 22' Internal conductor 3. Distance between adjacent windings 3' Distance between adjacent windings φ C Diameter of a square cable antenna φ S Diameter of a circular cable antenna

Claims

1. A handheld device for detecting electrostatic discharge, Evaluation unit and A cable antenna (1;1') made from a coaxial cable is provided, The cable antenna (1;1') is formed in a coil shape by windings (2;2') with n turns, where n ≥ 2. Each winding (2; 2') is wound around the winding axis, Diameter of each winding (2;2') Ｃ ;φ Ｓ ) is less than 30 cm, A handheld device in which the windings (2;2') of the cable antenna (1;1') are separated from each other by at least one spacer.

2. The number of turns n of the winding (2;2') is n > 2, preferably 3 ≤ n ≤ 11. The aforementioned winding shaft is a common winding shaft, Diameter of each winding (2;2') Ｃ ;φ Ｓ ) is approximately 5 cm, and / or The diameter (φ) of adjacent windings (2;2') Ｃ ;φ Ｓ The handheld device according to claim 1, wherein the two are different from each other.

3. All windings (2;2') have a shape that matches each other, and / or The handheld device according to claim 1 or 2, wherein the winding shape of the cable antenna (1; 1') is selected from the group consisting of circular, elliptical, triangular, square, polygonal, and combinations thereof.

4. Each spacer provides a distance between the windings (2;2') similar to the outer cable diameter of the cable antenna (1;1'), and / or The handheld device according to any one of claims 1 to 3, wherein each spacer is made of an insulating material, preferably a plastic material, more preferably polyvinyl chloride, polypropylene, or polytetrafluoroethylene.

5. The windings (2;2') of the cable antenna (1;1') are separated from each other by at least two spacers, the two spacers preferably arranged opposite each other, or The handheld device according to any one of claims 1 to 4, wherein the windings (2;2') of the cable antenna (1;1') are separated from each other by at least three spacers, the spacers preferably arranged at equal distances.

6. The handheld device according to any one of claims 1 to 5, wherein the cable antenna (1; 1') is made from a coaxial cable having an internal conductor containing silver.

7. The aforementioned evaluation unit is oscilloscope, display, Wireless communication module, and / or A handheld device according to any one of claims 1 to 6, comprising a network analyzer.

8. The handheld device according to any one of claims 1 to 7, wherein the handheld device is configured for use in a stationary state together with a container.

9. A handheld device according to any one of claims 1 to 8, which is adapted for use with a container having a small internal volume, more preferably a container having an internal volume of less than 30 liters.

10. The handheld device according to any one of claims 1 to 9, wherein the handheld device is adapted for measurements in a reactor for chemical production, and the chemical production preferably involves processing a suspension of low conductivity.

11. Use of the handheld device according to any one of claims 1 to 10 for detecting electrostatic discharge in an environment containing an explosive atmosphere.

12. Use of the handheld device according to any one of claims 1 to 10 for detecting electrostatic discharge in a container having a volume of less than 30 liters, preferably in a reactor for chemical production.

13. The use of the handheld device according to claim 11 or 12, wherein the handheld device is used to evaluate the type of electrostatic discharge and the probability of occurrence and ignition of the electrostatic discharge.

14. The use of the handheld device according to any one of claims 11 to 13, wherein the detection of the electrostatic discharge is performed on request.

15. The use of the handheld device according to any one of claims 11 to 14, wherein the detection of the electrostatic discharge is preferably performed continuously at a sampling rate of 2 μs.

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