Capacitive voltage divider

Abstract

The utility model discloses a capacitive voltage divider in the technical field of electrostatic measurement, which comprises a high-voltage arm capacitor, the high-voltage arm capacitor comprises a plurality of capacitors connected in series, and the high-voltage arm capacitor is a hollow cylinder; the low-voltage arm capacitor is arranged in the high-voltage arm capacitor, and the low-voltage arm capacitor comprises at least two low-voltage capacitors which are connected in parallel and have different capacitance values; the high-voltage arm capacitor is connected with the low-voltage arm capacitors through the change-over switch, and the high-voltage arm capacitor can be connected with different low-voltage capacitors through state switching of the change-over switch. According to the utility model, the technical problem that the measurement result is inaccurate due to the fact that the capacitive voltage divider is influenced by stray inductance during human body potential measurement can be solved.

Description

Technical Field

[0001] The utility model belongs to the technical field of electrostatic measurement and relates to a capacitive voltage divider. Background Art

[0002] The capacitive voltage divider can attenuate the high voltage pulse signal into a low voltage signal without distortion. It has the advantages of large voltage division ratio, fast response time and good insulation performance.

[0003] The design of the existing capacitor voltage divider focuses on the performance and structure of the capacitor, such as the impact of temperature, axis offset, plate size, etc. on the capacitance value, and the impact of test conditions and environment on the capacitance and the voltage divider ratio has not been studied. Especially in the field of human body potential testing, since the resistance of the inductor changes with the test frequency, the wiring cable will be affected by the stray inductance at high frequencies, which will affect the voltage divider ratio and make the measurement results inaccurate. Utility Model Content

[0004] The utility model aims to overcome the deficiencies in the prior art and provide a capacitive voltage divider to solve the technical problem that when measuring human body potential, the capacitive voltage divider is affected by stray inductance, resulting in inaccurate measurement results.

[0005] In order to solve the above technical problems, the utility model provides a capacitive voltage divider, comprising:

[0006] A high-voltage arm capacitor, the high-voltage arm capacitor comprises a plurality of capacitors connected in series, and the high-voltage arm capacitor is a hollow cylinder;

[0007] A low-voltage arm capacitor, wherein the low-voltage arm capacitor is arranged inside the high-voltage arm capacitor, and the low-voltage arm capacitor includes at least two low-voltage capacitors connected in parallel and having different capacitance values;

[0008] A switching switch, the high-voltage arm capacitor is connected to the low-voltage arm capacitor through the switching switch, and the state switching of the switching switch can connect the high-voltage arm capacitor to different low-voltage capacitors.

[0009] Furthermore, the inner and outer plates of the high-voltage arm capacitor are both made of aluminum.

[0010] Furthermore, the edge of the electrode plate uses polytetrafluoroethylene as a supporting material.

[0011] Furthermore, the high voltage arm capacitor and the low voltage arm capacitor have the same temperature coefficient.

[0012] Furthermore, the size of the hollow cylinder is designed according to the national standard GB / T 16252-1996 "Adult Hand Size" to match the human hand.

[0013] Furthermore, the high voltage arm capacitance value is lower than 10 pF.

[0014] Furthermore, a grounding device is connected to the grounding terminal of the low-voltage arm capacitor.

[0015] Furthermore, it also includes a signal processing module for converting a voltage signal into a digital signal, and the signal processing module is connected to the non-grounded side of the low-voltage arm capacitor.

[0016] Furthermore, the signal processing module includes a temperature sensor for measuring ambient temperature.

[0017] Compared with the prior art, the utility model has the following beneficial effects:

[0018] By placing the low-voltage arm capacitor inside the coaxial high-voltage arm capacitor, the length of the wiring cable is shortened, the influence of the cable stray inductance is reduced, and the influence on the voltage divider ratio of the voltage divider is further weakened, thereby improving the accuracy of the measurement result;

[0019] The low-voltage arm capacitor includes at least two low-voltage capacitors connected in parallel. The switching switch is used to switch the connection relationship between the high-voltage arm capacitor and the low-voltage capacitor, which meets the requirements of the test instrument for a wide voltage test range and low-voltage test accuracy. The capacitance of the low-voltage capacitor can be freely adjusted according to actual needs, thereby adjusting the voltage divider ratio of the capacitor voltage divider. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of a capacitive voltage divider provided in an embodiment of the present application.

[0021] Figure 2 It is a schematic diagram of a theoretical voltage divider ratio of a capacitive voltage divider at different frequencies provided in an embodiment of the present application.

[0022] Figure 3 It is a schematic diagram of an actual voltage divider ratio of a capacitive voltage divider at different frequencies provided in an embodiment of the present application.

[0023] Figure 4 A schematic diagram comparing an actual voltage division ratio and a theoretical voltage division ratio of a capacitive voltage divider provided in an embodiment of the present application at a test level of ±1 kV.

[0024] Figure 5 A schematic diagram comparing an actual voltage division ratio and a theoretical voltage division ratio of a capacitive voltage divider provided in an embodiment of the present application at a test level of ±6 kV.

[0025] In the figure: 1. High-voltage arm capacitor; 2. Low-voltage arm capacitor; 3. Switch; 4. Signal processing module; 5. Grounding device. DETAILED DESCRIPTION

[0026] The utility model is further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the utility model, and cannot be used to limit the protection scope of the utility model.

[0027] In the description of the present utility model, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present utility model. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present utility model, unless otherwise specified, "multiple" means two or more.

[0028] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0029] like Figure 1 As shown, the utility model provides a capacitive voltage divider, including a high-voltage arm capacitor 1: the high-voltage arm capacitor 1 includes a plurality of capacitors connected in series, which are hollow cylinders, and are shaped as a small cylinder coaxial with the large cylinder dug out from a large cylinder. These capacitors have independent housings and lead-out terminals, which are connected in series and encapsulated in the insulating housing of the high-voltage arm capacitor 1; the inner and outer plates of the high-voltage arm capacitor 1 are made of aluminum. Compared with iron, aluminum has high strength, light weight, and is convenient for transportation. In addition, aluminum has strong corrosion resistance and good thermal conductivity. The existing market generally uses aluminum inner and outer plates of capacitors, and polytetrafluoroethylene is used as a supporting material at the edge of the plate; polytetrafluoroethylene: commonly known as "plastic king", is a high molecular polymer obtained by polymerization of tetrafluoroethylene as a monomer, with a chemical formula of (C2F4)n, excellent heat resistance and cold resistance, can be used for a long time at -180 to 260°C, and has the characteristics of acid and alkali resistance and resistance to various organic solvents. At the same time, polytetrafluoroethylene has the characteristics of high temperature resistance and can adapt to the application environment of this embodiment;

[0030] A low-voltage arm capacitor 2, wherein the low-voltage arm capacitor 2 is arranged inside the high-voltage arm capacitor 1. Placing the low-voltage arm capacitor 2 inside the high-voltage arm capacitor 1 can shorten the length of the wiring cable to the greatest extent, thereby reducing the influence of stray inductance on the voltage division ratio. The stray inductance refers to the equivalent inductance presented by the cable inductance between the high-voltage arm capacitor 1 and the low-voltage arm capacitor 2, and the conductors in the circuit, such as: connecting wires, component leads, component bodies, etc.;

[0031] The high-voltage arm capacitor 1 and the low-voltage arm capacitor 2 are electrically connected. In this embodiment, a cable connection as short as possible is used to shorten the influence of stray inductance. The grounding end of the low-voltage arm capacitor 2 is connected to a grounding device 5. Grounding the low-voltage arm capacitor 2 is a conventional setting in the field of voltage dividers and will not be repeated in this embodiment.

[0032] Furthermore, it also includes a switching switch 3, the high-voltage arm capacitor 1 is connected to the low-voltage arm capacitor 2 through the switching switch 3, and the state switching of the switching switch 3 can connect the high-voltage arm capacitor 1 to different low-voltage capacitors. The capacitive voltage divider realizes the test range of the adjustable voltage by controlling the switching of the switching switch 3. In this embodiment, the test gear is divided into ±1kV and ±6kV by switching the connection between the high-voltage arm capacitor 1 and two low-voltage capacitors with different capacitance values, which is manifested as the voltage divider ratio is set to 1:1000 and 1:2200, and the instrument's requirements for a wide voltage test range and low voltage test accuracy are tested accordingly.

[0033] The high-voltage arm capacitor 1 and the low-voltage arm capacitor 2 have the same temperature coefficient, which can make the voltage divider ratio relatively stable in a temperature-changing scenario.

[0034] The size of the hollow cylinder is designed according to the national standard GB / T 16252-1996 "Adult Hand Size". The hollow cylinder used in this embodiment matches the human hand, adopts a cylindrical coaxial shape, and has no restrictions on the size of the outer conductor and the inner conductor. The area involved is as small as possible, thereby reducing the test error caused by changes in human body capacitance when testing human body voltage.

[0035] It also includes a signal processing module 4 for converting a voltage signal into a digital signal, and the signal processing module 4 is connected to the non-grounded side of the low-voltage arm capacitor 2. In this embodiment, the voltage signal after voltage division is converted into a digital signal by an AD conversion unit of the signal processing module 4; preferably, the signal processing module 4 includes a temperature sensor for measuring the ambient temperature, and a temperature compensation algorithm for real-time compensation of the voltage division ratio can be integrated in the signal processing module 4, further weakening the influence of temperature on the measurement result, wherein about the temperature compensation algorithm:

[0036] Temperature compensation algorithm is an important technical means, which can be used to improve the accuracy and stability of temperature measurement. In practical applications, according to specific needs and conditions, appropriate compensation methods and parameter calibration strategies are selected to effectively improve the reliability and accuracy of temperature measurement. The research and application of temperature compensation algorithms will continue to promote the development of temperature measurement technology and provide more reliable temperature data for applications in various fields. There are many specific implementation methods of temperature compensation algorithms, among which the most common methods are linear compensation and nonlinear compensation. Temperature compensation algorithms belong to existing mature technologies. In this application, they only play a role in weakening the influence of temperature on the measurement results, and will not be repeated in this embodiment.

[0037] The dimensions of the high-voltage arm capacitor 1 used in this embodiment are: the radius of the outer plate , Inner plate radius , plate length L = 113mm, plate thickness , the thickness of PTFE as support material , according to the parallel plate capacitance formula The simulated capacitance value can be deduced to be C=9.986pF, which is lower than 10 pF and can meet the design requirements. A 6kV high voltage is applied to the outer conductor and the inner conductor voltage is set to 0V. Figure 2 and Figure 3 is the error between the actual voltage divider ratio and the theoretical value at different frequencies, Figure 4 and Figure 5 The figure is a schematic diagram of the actual and theoretical voltage divider ratios of the voltage divider under different test gears. When the test frequency is less than 1kHz, the errors of the voltage divider ratio at the 1kV and 6kV gears are 0.12% and 1.03% respectively. When the test frequency is 50Hz, the errors can be kept below 1% and 2% respectively, meeting the design requirements.

[0038] Working principle: By placing the low-voltage arm capacitor 2 in the coaxial high-voltage arm capacitor 1, the low-voltage arm capacitor includes at least two low-voltage capacitors in parallel, and the switching switch 3 is used to switch the connection relationship between the high-voltage arm capacitor 1 and the low-voltage capacitor, which meets the requirements of the test instrument for a wide voltage test range and low-voltage test accuracy. The capacitance of the low-voltage capacitor can be freely adjusted according to actual needs to adjust the voltage divider ratio of the capacitive voltage divider. By shortening the length of the wiring cable between the low-voltage arm capacitor 2 and the high-voltage arm capacitor 1, the influence of the cable stray inductance is reduced, and the influence on the voltage divider ratio of the voltage divider is further weakened, thereby improving the accuracy of the measurement result.

[0039] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A capacitive voltage divider, characterized in that: include: A high-voltage arm capacitor (1), the high-voltage arm capacitor (1) comprising a plurality of capacitors connected in series, the high-voltage arm capacitor (1) being a hollow cylinder; A low-voltage arm capacitor (2), the low-voltage arm capacitor (2) being arranged inside the high-voltage arm capacitor (1), the low-voltage arm capacitor (2) comprising at least two low-voltage capacitors connected in parallel and having different capacitance values; A switching switch (3), wherein the high-voltage arm capacitor (1) is connected to the low-voltage arm capacitor (2) via the switching switch (3), and the state switching of the switching switch (3) can enable the high-voltage arm capacitor (1) to be connected to different low-voltage capacitors.

2. The capacitive voltage divider according to claim 1, characterized in that: The inner and outer plates of the high-voltage arm capacitor (1) are both made of aluminum.

3. The capacitive voltage divider according to claim 2, characterized in that: The edge of the electrode plate adopts polytetrafluoroethylene as a supporting material.

4. The capacitive voltage divider according to claim 1, characterized in that: The high-voltage arm capacitor (1) and the low-voltage arm capacitor (2) have the same temperature coefficient.

5. The capacitive voltage divider according to claim 1, characterized in that: The size of the hollow cylinder is designed according to the national standard GB / T 16252-1996 "Adult Hand Size" to match the human hand.

6. The capacitive voltage divider according to claim 5, characterized in that: The high voltage arm capacitor (1) has a value lower than 10 pF.

7. The capacitive voltage divider according to claim 1, characterized in that: The grounding end of the low-voltage arm capacitor (2) is connected to a grounding device (5).

8. The capacitive voltage divider according to claim 1, characterized in that: It also includes a signal processing module (4) for converting a voltage signal into a digital signal, wherein the signal processing module (4) is connected to the non-grounded side of the low-voltage arm capacitor (2).

9. The capacitive voltage divider according to claim 8, characterized in that: The signal processing module (4) comprises a temperature sensor for measuring the ambient temperature.

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