Device for measuring surface resistivity of solid insulating material

Abstract

The invention discloses a device for measuring the surface resistivity of a solid insulating material, and belongs to the technical field of insulating material performance testing. The device comprises an upper electrode assembly and a lower electrode assembly which are symmetrically arranged. The upper electrode assembly is formed by combining and fixing a measuring electrode and a high-voltage electrode through an upper electrode jacket; the lower electrode assembly comprises a driving protection electrode and a grounding protection electrode. According to the device, an ideal electric field parallel to the surface of the sample is formed in a measurement area, the mixing of volume current is eliminated, and the purity of the measured current is ensured. In order to realize accurate alignment, the lower electrode jacket is provided with an accommodating cavity, and the side wall of the accommodating cavity is clamped and limited with the upper electrode jacket; meanwhile, the upper and lower electrode jackets are correspondingly provided with positioning magnets to provide auxiliary centering and pressing force. Through the integrated innovative design of electric field shaping and mechanical positioning, the accuracy and repeatability of measurement are guaranteed from the two aspects of principle and operation, and the device is simple in structure, easy and convenient to operate and easy to popularize.

Description

Technical Field

[0001] This invention relates to the field of insulation material performance testing technology, and in particular to a device for measuring the surface resistivity of solid insulation materials. Background Technology

[0002] The resistivity of insulating materials is a core parameter characterizing their electrical insulation performance, directly determining the electric field strength and operating voltage level that the material can withstand in applications such as power equipment and electronic devices. Insulation resistivity typically includes volume resistivity and surface resistivity. Volume resistivity is mainly used to evaluate the insulation characteristics of the material's internal structure (bulk insulation); while surface resistivity has a decisive influence on external insulation performance (such as surface flashover voltage and tracking resistance), and is a key indicator for assessing the rationality of external insulation structure design and operational reliability. Therefore, accurate measurement of the surface resistivity of solid insulating materials is of great significance in material research and development, product quality inspection, and engineering applications.

[0003] Currently, the resistivity of insulating materials is generally measured using a three-electrode system, a standard method designed to separate the volume current and surface current flowing through the sample. A traditional three-electrode structure typically consists of a coaxial ring electrode (measuring electrode and high-voltage electrode) placed on one side of the sample and a ground electrode placed on the other side. However, in practical applications, the following inherent drawbacks have been found when using this structure to measure surface resistivity: First, there is a fundamental error caused by the non-ideal electric field distribution. Ideally, when measuring surface resistivity, the applied voltage should create a uniform tangential electric field parallel to the sample surface between the measuring electrode and the ground electrode, making the measured current purely the surface leakage current. However, in a traditional three-electrode structure, the electric field lines between the high-voltage electrode and the ground electrode are not entirely distributed along the sample surface; instead, there is a significant electric field component perpendicular to the sample surface. This perpendicular electric field component causes a portion of the current to pass through the sample volume, forming a volume current shunt. Therefore, the actual current collected by the measuring electrode is a mixture of surface current and a portion of volume current. The surface resistivity calculated based on this current will be severely distorted and cannot accurately reflect the true surface insulation properties of the material. This is a systematic and fundamental error caused by the electrode structure itself, which is difficult to completely eliminate through subsequent calibration.

[0004] Secondly, there is uncertainty in electrode alignment accuracy during operation. Traditional three-electrode systems typically have separate, independent upper and lower electrode assemblies. When placing the sample and assembling the electrodes, alignment relies entirely on the operator's experience and visual inspection. This can easily lead to misalignment of the upper and lower electrode axes. Such concentricity deviation directly disrupts the symmetry of the electric field, introducing additional electric field distortion, resulting in poor repeatability and high dispersion of measurement results, severely impacting the reliability and comparability of the measurements.

[0005] While some existing technologies attempt to optimize the electric field by adding shielding rings or adjusting electrode dimensions, they fail to fundamentally solve the problem of the inevitable bending of the electric field lines between the high-voltage electrode and the grounding electrode. Other solutions employ complex guide pillars or microscopes for alignment assistance, but these result in complex device structures and cumbersome operation, hindering widespread adoption and standardized measurement.

[0006] Therefore, there is an urgent need for a new type of electrode device that can optimize the electric field distribution in principle and ensure the accuracy of electrode alignment in a simple and reliable manner, so as to achieve accurate, rapid and repeatable measurement of the surface resistivity of solid insulating materials. Summary of the Invention

[0007] This invention proposes a device for measuring the surface resistivity of solid insulating materials, which solves the problems that the geometric distribution structure of traditional electrodes cannot generate an ideal measuring electric field parallel to the sample surface; and the lack of a fast, reliable, and skill-independent mechanical positioning mechanism to ensure the constancy of measurement conditions.

[0008] The core technical solution of this invention lies in the following: By using a symmetrical equipotential electric field shaping structure, the vertical electric field component that causes volume current shunting is eliminated, ensuring that the current collected by the measuring electrode is a pure surface leakage current, thus solving the systematic measurement error inherent in traditional three-electrode structures. The precise positioning structure, combining mechanical clamping and magnetic assistance, eliminates alignment errors, ensuring the consistency of boundary conditions for each measurement and improving the repeatability and reliability of the measurement.

[0009] The specific solution of the present invention is as follows: An apparatus for measuring the surface resistivity of a solid insulating material includes an upper electrode assembly and a lower electrode assembly arranged symmetrically. The upper electrode assembly includes: a measuring electrode, a high-voltage electrode, and an upper electrode sleeve; the high-voltage electrode surrounds the outside of the measuring electrode; a high-voltage electrode terminal is connected to the high-voltage electrode, and a measuring electrode terminal is connected to the measuring electrode; The lower electrode assembly includes: a drive protection electrode, a ground protection electrode, and a lower electrode jacket; the drive protection electrode surrounds the outside of the ground protection electrode; a drive protection electrode terminal is connected to the drive protection electrode, and a ground protection electrode terminal is connected to the ground protection electrode.

[0010] Furthermore, the device includes a support structure, which includes a lower electrode support ring and a lower electrode support plate. The inner diameter of the lower electrode support ring matches the outer diameter of the lower electrode sleeve. The lower electrode support ring and the lower electrode support plate are fixedly connected at a predetermined distance by a connector, thereby clamping and fixing the lower electrode assembly.

[0011] Furthermore, the high-voltage electrode terminal and the drive protection electrode terminal are connected to the same DC high-voltage power supply, the ground protection electrode terminal is grounded, and the measuring electrode terminal is connected to a current measuring instrument.

[0012] Furthermore, the outer diameter of the measuring electrode is D1, the inner diameter of the high-voltage electrode is D2, a DC test voltage U0 is applied, and the current I flowing through the sample surface is measured. s Then the surface resistivity r s for: .

[0013] Furthermore, an upper electrode positioning magnet is provided on the outer wall of the upper electrode jacket; a lower electrode positioning magnet is provided on the outer wall of the lower electrode jacket; the upper electrode assembly and the lower electrode assembly are arranged symmetrically in space, and rapid concentric alignment is achieved through the magnetic attraction between the upper electrode positioning magnet and the lower electrode positioning magnet.

[0014] Furthermore, the upper electrode jacket and the lower electrode jacket are made of polytetrafluoroethylene.

[0015] Furthermore, the lower electrode sleeve is provided with a receiving cavity, the bottom of the receiving cavity abuts against the upper electrode assembly, and the side wall of the receiving cavity is engaged with and limits the upper electrode sleeve.

[0016] Furthermore, the upper electrode jacket and the lower electrode jacket are respectively provided with insulating sleeves, and the high voltage electrode terminal, the measuring electrode terminal, the drive protection electrode terminal, and the grounding protection electrode terminal extend to the outside of the device through the corresponding insulating sleeves.

[0017] Furthermore, an insulating isolation layer is provided between the measuring electrode and the high-voltage electrode, as well as between the driving protection electrode and the grounding protection electrode.

[0018] Furthermore, the device is equipped with a shielded chamber made of metal for electromagnetic shielding, and a temperature and humidity sensor is integrated inside the shielded chamber.

[0019] The present invention has the following technical effects: 1. Eliminate inherent systematic errors and improve measurement accuracy.

[0020] This invention introduces a driving and protective electrode with the same potential as the high-voltage electrode through a symmetrical electrode layout. This structure, in principle, forces the electric field lines in the measurement area to be parallel to the sample surface, effectively eliminating the vertical electric field component present in traditional three-electrode structures. This ensures that the current flowing through the measuring electrode is a pure surface leakage current, rather than a mixture of surface and volume currents. It solves the problem of distorted surface resistivity measurements caused by electric field distortion, obtaining accurate data that truly reflects the insulating properties of the material surface.

[0021] 2. Electrode alignment accuracy and measurement repeatability are fundamentally guaranteed.

[0022] This invention, by creating a receiving cavity in the lower electrode sleeve to form a snap-fit ​​and limiting fit with the upper electrode sleeve, mechanically ensures the concentricity of the upper and lower electrodes. Simultaneously, corresponding positioning magnets provide clamping force and auxiliary guidance. This simplifies the electrode installation operation to a one-step action of "insertion equals alignment, release equals clamping," eliminating the random errors introduced by reliance on operator experience and visual alignment in traditional methods. The highly consistent boundary conditions for each measurement improve the repeatability and comparability of the measurement results.

[0023] 3. The device is easy and efficient to operate, reducing the skill requirements for personnel.

[0024] Thanks to the combined mechanical snap-fit ​​and magnetically assisted positioning scheme, operators do not need to perform any fine-tuning or alignment work. This greatly simplifies the testing process, shortens the time per measurement, and is particularly suitable for rapid testing of batch samples. At the same time, this design reduces reliance on the professional experience and skill level of operators, facilitating the promotion and standardized application of this technology in a wider range of production quality control and laboratory environments.

[0025] 4. Improved device tolerance and strong engineering practicality.

[0026] The electrode structure of this invention achieves high-precision measurement while exhibiting good engineering practicality. The formation of a parallel electric field reduces the stringent requirements for the perfection of the contact interface between the electrode and the sample (such as the dependence on extreme surface smoothness of the electrode), and improves the device's tolerance to minor assembly errors or sample unevenness. Attached Figure Description

[0027] Figure 1 This is a front sectional view of the device in one embodiment of the present invention; Figure 2 This is a top view of the device in one embodiment of the present invention; Figure 3 This is a front sectional view of the device in another embodiment of the present invention; Figure 4This is a schematic diagram showing the spatial relationship between the electrodes and the sample in a traditional three-electrode structure. Figure 5 This is a schematic diagram of the electric field line distribution and electric field intensity vector in one embodiment of the present invention; Figure 6 This is a schematic diagram of the electric field line distribution and electric field intensity vector of a traditional three-electrode structure.

[0028] Explanation of reference numerals in the attached figures: 1-High voltage electrode terminal; 2-Insulating sleeve; 3-Upper electrode outer sleeve; 4-Upper electrode positioning magnet; 5-Stud; 6-Measuring electrode terminal; 7-Measuring electrode; 8-High voltage electrode; 9-Sample; 10-Lower electrode support ring; 11-Nut; 12-Lower electrode support plate; 13-Drive protection electrode terminal; 14-Ground protection electrode terminal; 15-Ground protection electrode; 16-Lower electrode outer sleeve; 17-Drive protection electrode; 18-Lower electrode positioning magnet. Detailed Implementation

[0029] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0030] In this specification, identical components are represented by the same reference numerals. It should be noted that the terms "front," "rear," "left," "right," "upper," and "lower" used in the following description refer to directions in the accompanying drawings, while the terms "bottom surface," "top surface," "inner," and "outer" refer to directions towards or away from a specific component, respectively. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this specification, "multiple" means two or more.

[0031] Example 1 This invention provides a device for measuring the surface resistivity of solid insulating materials, such as... Figure 1 , Figure 2 As shown, the core principle of this device is that it forms a precise division of labor and cooperation system through four electrodes. Its core objective is to guide the current to flow strictly along the surface of the sample 9 and to accurately measure the current.

[0032] High-voltage electrode 8, used to apply the test voltage, is directly connected to a DC high-voltage power supply. The main task of high-voltage electrode 8 is to establish a stable high-potential region over the entire sample 9. High-voltage electrode 8 is the "driving force" for generating surface leakage current, allowing current to flow through the surface of sample 9.

[0033] The driving protection electrode 17 is crucial for achieving "electric field straightening." It is connected to the same power source as the high-voltage electrode 8, thus having the same potential. The driving protection electrode 17 is located directly below the high-voltage electrode 8, in close contact with the upper surface of the sample 9. Since the driving protection electrode 17 and the high-voltage electrode 8 are at the same potential, there is no potential difference between them, and therefore no vertical electric field is generated. The presence of the driving protection electrode 17 is equivalent to establishing a boundary at the same potential as the high-voltage electrode 8 at its edge, forcing electric field lines to emanate horizontally from its inner edge (closer to the measuring electrode 7) and enter the surface region of the sample 9 parallel to it, thereby achieving the effect of "constraining the electric field lines."

[0034] Measuring electrode 7 is the core measuring element, specifically designed to collect "valid" current signals. Measuring electrode 7 is connected to a high-precision ammeter (such as a picoammeter). Because the electric field above measuring electrode 7 is "straightened" and parallel to the surface, almost all the current flowing to measuring electrode 7 is surface leakage current flowing horizontally along the surface of sample 9. The area of ​​measuring electrode 7 is known (determined by its diameter D1), thus the current density can be accurately calculated.

[0035] The grounding protection electrode 15 is used to protect and shield the electrode, ensuring the "purity" of the measurement circuit. The grounding protection electrode 15 can be reliably connected to the ground (zero potential). The grounding protection electrode 15 attracts and conducts away stray currents that may come from inside the sample 9 (volume current) or from the edges, preventing these "noise" currents from mixing into the measuring electrode 7.

[0036] Traditional structures lack a "driving protection electrode 17," and their high-voltage electrode 8 directly faces the sample 9 and the grounding electrode, resulting in a naturally distorted electric field. This causes non-surface currents to be mixed into the current collected by the measuring electrode 7. The driving protection electrode 17 added in this invention actively shapes the electric field shape through the core mechanism of "equipotential constraint," thereby fundamentally solving the problem of measurement inaccuracy.

[0037] In this embodiment, the device includes a symmetrically arranged upper electrode assembly and a lower electrode assembly. The upper electrode assembly includes a measuring electrode 7, a high-voltage electrode 8, and an upper electrode jacket 3. The measuring electrode 7 and the high-voltage electrode 8 have a concentric ring structure, with the high-voltage electrode 8 spaced around the outside of the measuring electrode 7, and an insulating layer is provided between them. The two are combined and fixed by the upper electrode jacket 3, which is made of polytetrafluoroethylene (PTFE) and has good insulation properties and mechanical strength.

[0038] In one possible embodiment, the measuring electrode 7 uses oxygen-free copper as its substrate, and its contact surface with the sample 9 is plated with a 3μm thick hard gold layer. The outer diameter of the measuring electrode 7 is D1. A measuring electrode terminal 6, made of brass and plated with nickel, is connected to its center. The measuring electrode terminal 6 is led out through a PTFE insulating sleeve 2 that passes through the upper electrode jacket 3 to the outside, for connecting a current measuring instrument such as a high-resistance meter or a picoammeter.

[0039] The high-voltage electrode 8 is made of brass with an inner diameter of D2. A high-voltage electrode terminal 1, also made of brass, is connected at the midpoint of the thickness of the high-voltage electrode 8. The high-voltage electrode terminal 1 is led out through another independent PTFE insulating sleeve 2 and connected to a DC high-voltage power supply.

[0040] Four neodymium iron boron (N35) permanent magnets are uniformly embedded at 90° intervals on the circumference of the outer wall thickness of the upper electrode jacket 3 as positioning magnets 4 for the upper electrode.

[0041] The lower electrode assembly is symmetrically arranged in space with the upper electrode assembly. It includes a drive protection electrode 17, a ground protection electrode 15, and a lower electrode sleeve 16. The drive protection electrode 17 and the ground protection electrode 15 are concentric rings, with the drive protection electrode 17 spaced around the outside of the ground protection electrode 15, and an insulating layer between them. They are fixed together by the lower electrode sleeve 16, which is made of polytetrafluoroethylene (PTFE) and has good insulation and mechanical strength. The drive protection electrode 17 corresponds to the high-voltage electrode 8 of the upper electrode assembly, and the ground protection electrode 15 corresponds to the measuring electrode 7 of the upper electrode assembly. The high-voltage electrode terminal 1 and the drive protection electrode terminal 13 are connected to the same DC high-voltage power supply, and the ground protection electrode terminal 14 is grounded. The drive protection electrode 17 and the ground protection electrode 15 are respectively connected to the drive protection electrode terminal 13 and the ground protection electrode terminal 14, both made of brass. Four lower electrode positioning magnets 18 are embedded in the outer wall of the lower electrode jacket 16, which match the upper electrode positioning magnet 4. The upper electrode assembly and the lower electrode assembly achieve rapid concentric alignment through the magnetic attraction between the upper electrode positioning magnet 4 and the lower electrode positioning magnet 18.

[0042] The lower electrode assembly is fixed by a support structure. This support structure includes a lower electrode support ring 10 and a lower electrode support plate 12, both made of polytetrafluoroethylene (PTFE). The inner diameter of the lower electrode support ring 10 is tightly fitted with the outer diameter of the lower electrode outer sleeve 16, ensuring the lower electrode assembly is fixed in position. Four PTFE studs 5 and matching PTFE nuts 11 are used as connectors to securely fasten the lower electrode support ring 10 and the lower electrode support plate 12 at predetermined intervals, thereby firmly clamping the entire lower electrode assembly.

[0043] Furthermore, the device of this invention is externally equipped with a shielded chamber, which is constructed of a metal shell and can house the entire electrode device. The inner wall of the shielded chamber is covered with conductive foam, and the chamber door is equipped with an electromagnetic sealing gasket to form electromagnetic shielding. The shielded chamber integrates a temperature and humidity sensor, a small heater, and a desiccant tray. Before measurement, the environment inside the chamber can be pre-controlled to standard conditions and stabilized for a period of time.

[0044] The electrode structure proposed in this invention ensures that the electric field distribution is parallel to the surface of the sample 9 through the geometric distribution of the electrodes, thus appropriately reducing the requirement for the smoothness of the electrode surface. The symmetrical dual-electrode stacking design of this invention allows the electric field to originate from the "high-voltage electrode 8," but directly below it is not a zero-potential point, but rather a driving protection electrode 17 with the same potential. According to the basic principles of electric fields, electric field lines are not generated between equipotential bodies. Therefore, the electric field cannot pass vertically downwards from the high-voltage electrode 8 through the sample 9; it can only be "squeezed" horizontally out along the inner edge of the driving protection electrode 17 (the boundary of the equipotential body) and flow to the lower potential grounding protection electrode 15. In this way, the electric field is "forced" to form a parallel distribution on the surface of the sample 9.

[0045] In traditional measurements, uneven contact between the electrode and sample 9 can create tiny air gaps, easily triggering localized micro-discharges or capacitive currents. These can all contribute as noise to the measurement signal, severely impacting the measurement of weak currents. This invention uses a geometric structure to make the electric field parallel to the surface, fundamentally reducing the vertical electric field component passing through the "electrode-sample 9" contact interface. Even with tiny air gaps, because the electric field is primarily parallel to the interface, capacitive coupling or discharge interference through these gaps is significantly reduced. Therefore, the system's dependence on achieving "optical-grade" smoothness on the electrode surface to eliminate all air gaps is reduced, improving the device's engineering practicality.

[0046] The measurement method of the device of the present invention is as follows: Wipe the sheet sample 9 (the solid insulating material to be tested) clean with anhydrous ethanol and let it air dry. Lay the sample 9 flat on the upper surface of the drive protection electrode 17 and the ground protection electrode 15 of the lower electrode assembly. Place the upper electrode assembly on top of the sample 9. Relying on the magnetic attraction between the upper electrode positioning magnet 4 and the lower electrode positioning magnet 18, the upper electrode assembly and the lower electrode assembly automatically achieve rapid and accurate concentric alignment.

[0047] Connect the high-voltage electrode terminal 1 and the drive protection electrode terminal 13 to the same DC high-voltage stable power supply (set voltage U0). Reliably ground the ground protection electrode terminal 14. Connect the measuring electrode terminal 6 to a current measuring instrument to measure the surface leakage current Is. Calculate the surface resistivity using the following formula: .

[0048] Example 2 To enhance the positioning reliability and ease of operation of the device, the lower electrode jacket 16 was further optimized. For example... Figure 3 As shown, the lower electrode sleeve 16 is provided with a receiving cavity. The bottom of the receiving cavity abuts against the upper electrode assembly, and the side wall of the receiving cavity is engaged with and limits the upper electrode sleeve 3. The lower electrode sleeve 16 is no longer a simple flat plate or ring-shaped support, but is designed as a structure with a recessed space, which is the receiving cavity.

[0049] The lower electrode sleeve 16 has a stepped structure serving as the bottom of the receiving cavity, with the upper electrode assembly contacting and abutting against the bottom of the cavity. This ensures a defined vertical (Z-axis) termination position between the upper and lower electrode assemblies. The inner wall of the receiving cavity is designed to precisely fit with the outer wall of the upper electrode sleeve 3. This allows for rapid positioning and fixation when the upper electrode assembly is inserted. The fit of the side walls restricts the movement of the upper electrode sleeve 3 (and thus the entire upper electrode assembly) in the horizontal plane (X-axis and Y-axis), ensuring the concentricity of the upper and lower electrodes.

[0050] Comparative Examples To make the differences between the technical solution and beneficial effects of the present invention and the prior art clearer, the electrode structure provided by the present invention is compared and analyzed with the traditional three-electrode structure in combination with simulation calculations.

[0051] like Figure 4 The diagram shows a simplified representation of the spatial relationship between the electrodes and the sample 9 in a traditional three-electrode structure. A traditional three-electrode structure typically consists of an upper measuring electrode 7, a high-voltage electrode 8, and a lower grounding electrode 15. The measuring electrode 7 and the high-voltage electrode 8 are concentric rings, with the high-voltage electrode 8 surrounding the measuring electrode 7. The sample 9 is placed below the measuring electrode 7 and the high-voltage electrode 8, and simultaneously in contact with the lower grounding electrode 15. Each electrode is typically made of metal and mounted on an insulating support frame; there is no forced alignment mechanism between the electrodes.

[0052] The measurement method is as follows: connect the high-voltage electrode 8 to a DC high-voltage power supply, ground the grounding protection electrode 15 to the ground, and connect the measuring electrode 7 to a current measuring instrument. After applying a DC voltage, measure the current flowing through the measuring electrode 7.

[0053] To quantitatively compare the performance differences between the two structures, electric field finite element simulation analysis was performed on the present invention and the traditional three-electrode structure under the same boundary conditions.

[0054] Simulation conditions: Sample 9 thickness 0.3 mm, applied DC voltage: 1 kV.

[0055] Simulation results: Appendix Figure 5 The diagram shows the electric field line distribution and electric field intensity vector diagram when measured using the electrode structure of the present invention (only the right half of the axis of symmetry is shown).

[0056] Appendix Figure 6 The diagram shows the electric field line distribution and electric field intensity vector diagram when using a traditional three-electrode structure for measurement (only the right half of the axis of symmetry is shown).

[0057] Comparison of parallelism of electric field directions: Observation Appendix Figure 5 (In this invention) It can be seen that in the region of the sample 9 surface between the measuring electrode 7 and the driving protection electrode 17, the electric field lines remain essentially horizontal and parallel to each other. The direction of the electric field intensity vector is almost completely parallel to the upper surface of the sample 9. This indicates that the applied voltage mainly generates a tangential electric field along the surface of the sample 9, forcing current to flow along the surface of the sample 9.

[0058] Observation Appendix Figure 6 (Conventional Three-Electrode) As can be seen, in the region on the surface of sample 9 between measuring electrode 7 and high-voltage electrode 8, the electric field lines are noticeably bent. The electric field intensity vector has a significant vertical component on the surface of sample 9. This indicates that the electric field not only drives the surface current but also drives a portion of the current to pass perpendicularly through sample 9.

[0059] In this invention, since the electric field is constrained to be parallel to the surface, the current flowing through the measuring electrode 7 is almost entirely leakage current generated by conduction through the surface of the sample 9, which conforms to the definition of surface resistivity. For a conventional three-electrode system, due to the significant vertical component of the electric field, the current flowing through the measuring electrode 7 actually consists of two parts: a shunt of surface current and a shunt of volume current. Since these two cannot be separated, directly using this current to calculate the surface resistivity using the formula does not yield a true surface resistivity result, leading to distorted measurement values.

[0060] In the embodiments disclosed in this application, the terms "installation," "connection," "linking," and "fixing" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; "linking" can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments disclosed in this invention according to the specific circumstances.

[0061] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A device for measuring the surface resistivity of solid insulating materials, characterized in that, Includes symmetrically arranged upper and lower electrode assemblies; The upper electrode assembly includes: a measuring electrode, a high-voltage electrode, and an upper electrode sleeve; the high-voltage electrode surrounds the outside of the measuring electrode; a high-voltage electrode terminal is connected to the high-voltage electrode, and a measuring electrode terminal is connected to the measuring electrode; The lower electrode assembly includes: a drive protection electrode, a ground protection electrode, and a lower electrode sleeve; the drive protection electrode surrounds the outside of the ground protection electrode; a drive protection electrode terminal is connected to the drive protection electrode, and a ground protection electrode terminal is connected to the ground protection electrode.

2. The device for measuring the surface resistivity of solid insulating materials according to claim 1, characterized in that, The device includes a support structure, which includes a lower electrode support ring and a lower electrode support plate. The inner diameter of the lower electrode support ring matches the outer diameter of the lower electrode sleeve. The lower electrode support ring and the lower electrode support plate are fixedly connected at a preset distance by a connector, thereby clamping and fixing the lower electrode assembly.

3. The apparatus for measuring the surface resistivity of solid insulating materials according to claim 1, characterized in that, The high-voltage electrode terminal and the drive protection electrode terminal are connected to the same DC high-voltage power supply, the ground protection electrode terminal is grounded, and the measuring electrode terminal is connected to a current measuring instrument.

4. The apparatus for measuring the surface resistivity of solid insulating materials according to claim 1, characterized in that, The outer diameter of the measuring electrode is D1, and the inner diameter of the high-voltage electrode is D2. A DC test voltage U0 is applied, and the current I flowing through the sample surface is measured. s Then the surface resistivity r s for: 。 5. The apparatus for measuring the surface resistivity of solid insulating materials according to claim 1, characterized in that, An upper electrode positioning magnet is provided on the outer wall of the upper electrode jacket; a lower electrode positioning magnet is provided on the outer wall of the lower electrode jacket; the upper electrode assembly and the lower electrode assembly are arranged symmetrically in space, and rapid concentric alignment is achieved through the magnetic attraction between the upper electrode positioning magnet and the lower electrode positioning magnet.

6. The apparatus for measuring the surface resistivity of solid insulating materials according to claim 1, characterized in that, The upper electrode jacket and the lower electrode jacket are made of polytetrafluoroethylene.

7. The apparatus for measuring the surface resistivity of solid insulating materials according to claim 1, characterized in that, The lower electrode sleeve is provided with a receiving cavity, the bottom of the receiving cavity abuts against the upper electrode assembly, and the side wall of the receiving cavity is engaged with and limits the upper electrode sleeve.

8. The apparatus for measuring the surface resistivity of solid insulating materials according to claim 1, characterized in that, The upper electrode jacket and the lower electrode jacket are respectively provided with insulating sleeves, and the high voltage electrode terminal, the measuring electrode terminal, the drive protection electrode terminal, and the grounding protection electrode terminal extend to the outside of the device through the corresponding insulating sleeves.

9. The apparatus for measuring the surface resistivity of solid insulating materials according to claim 1, characterized in that, An insulating layer is provided between the measuring electrode and the high-voltage electrode, as well as between the driving protection electrode and the grounding protection electrode.

10. The apparatus for measuring the surface resistivity of solid insulating materials according to claim 1, characterized in that, The device is equipped with an external shielding chamber made of metal for electromagnetic shielding, and the shielding chamber integrates a temperature and humidity sensor.

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