Non-contact power frequency ac voltage measurement method and measurement device

Abstract

This invention pertains to non-contact AC voltage measurement equipment, comprising a non-contact method and a non-contact device for measuring power frequency AC voltage. The device includes a first non-contact capacitive sensor and a second non-contact capacitive sensor. By designing a non-contact method and device for measuring power frequency AC (live wire to neutral wire) line voltage, not only is the insulation layer of the protected power line not damaged, but the operator can also safely and easily obtain the voltage of the line being measured, greatly improving work safety and efficiency.

Description

Technical Field

[0001] This application relates to non-contact AC voltage measuring equipment, and particularly to a non-contact power frequency AC voltage measuring method and a non-contact power frequency AC voltage measuring device. Background Technology

[0002] Currently, in conventional power frequency AC voltage measurements, the measuring equipment is directly connected to the power line for power supply and measurement. However, to protect electrical safety, exposed power lines in modern electrical environments are often protected with insulating layers or plastic casings. In this case, traditional contact measurements either require breaking through the insulation layer to make contact or piercing through the insulation layer to make contact with the power line. Regardless of whether the measurement is made by breaking through or piercing, the insulation layer of the protected power system will be damaged, thus creating a potential electrical safety hazard. Summary of the Invention

[0003] In view of at least one of the above technical problems, this application provides a non-contact power frequency AC voltage measurement method, a non-contact power frequency AC voltage measurement device, and a program algorithm for the non-contact power frequency AC voltage measurement device, which realizes the measurement of non-contact power frequency AC voltage and solves the problem.

[0004] A non-contact method for measuring power frequency AC voltage, characterized by comprising the following steps:

[0005] S1. Clip the first non-contact capacitive sensor and the second non-contact capacitive sensor onto the outer sheath of the AC voltage line, with the first non-contact capacitive sensor as the voltage sensing terminal and the second non-contact capacitive sensor as the reference ground, to form a complete circuit.

[0006] S2. There is leakage current in the insulation layer between the metal conductor and the first non-contact capacitive sensor, and the micro current is collected by the current signal sampler;

[0007] S3. The micro-current signal I / V collected by the current signal sampler is converted to obtain the converted AC voltage signal. The AC voltage signal is then processed and differentially compared with the sensing line voltage of the first non-contact capacitive sensor.

[0008] Preferably, step S3 includes the following sub-steps:

[0009] S31. The acquired micro-current signal is converted from an I / V signal to obtain a converted AC voltage signal. The AC voltage signal is shaped and filtered to restore the voltage signal of the power frequency line. This signal is an AC signal of the same frequency and phase but different amplitude after attenuation of the power supply in the power frequency line. Subsequently, the power frequency line voltage signal is sent to the first A / D converter for analog-to-digital conversion. The converted digital signal is sent to the MCU for calculation and processing to determine the currently acquired voltage and frequency values.

[0010] After S32.MCU calculates the current voltage and frequency values, it performs digital-to-analog conversion through the first D / A converter to restore the voltage and frequency signals collected by the first A / D converter. The voltage and frequency signals converted by the first D / A converter are then smoothed through the AC filtering stage to obtain the internal output AC drive signal.

[0011] The S33.AC drive signal is amplified by the power amplifier to boost the transformer voltage. At this time, the primary / secondary ratio parameter of the transformer is designed to be consistent with the attenuation factor of the first non-contact capacitive sensor. The secondary output signal of the transformer and the sensing line voltage of the first non-contact capacitive sensor are amplified by the differential current amplifier.

[0012] S34. After being amplified by the differential current amplifier, the current is converted into an I / V signal to obtain a recognizable voltage signal. Subsequently, the recognizable voltage signal is sent to the second A / D converter for analog-to-digital conversion, and then the converted digital signal is sent to the MCU for calculation and processing.

[0013] S35. Determine whether the value calculated by the MCU is equal to zero. If it is equal to zero, it means that the internal reconstruction voltage is equal to the external induced voltage. If it is not equal to zero, the first D / A converter needs to be integrated until it is equal to zero. The integration is completed, and the output of the first D / A converter after integration is maintained.

[0014] S36. After processing in step S35, the current value of the differential amplifier is made equal to zero. At this time, the secondary output signal of the transformer is attenuated by the attenuator until it is attenuated to a voltage signal that can supply power to the signal processing circuit.

[0015] S37. The attenuated voltage signal is sent to the AC signal processor for filtering and RMS conversion to obtain a standard DC voltage signal. This signal is proportional to the internal analog power frequency voltage output. The proportional DC voltage signal is sent to the third A / D converter for analog-to-digital conversion. The converted digital signal is sent to the MCU for processing, calculation and display.

[0016] Preferably, in step S1, the first non-contact capacitive sensor includes a live wire voltage reconstruction electrode V2 and a live wire voltage sensing electrode A1, with a parasitic capacitance C1 formed between the live wire voltage sensing electrode A1 and the live wire voltage V1, and a parasitic capacitance C2 formed between the live wire voltage reconstruction electrode V2 and the live wire voltage V1. The second non-contact capacitive sensor includes a neutral wire voltage reconstruction electrode V4 and a neutral wire voltage sensing electrode A2, with a parasitic capacitance C3 formed between the neutral wire voltage sensing electrode A2 and the neutral wire voltage V3, and a parasitic capacitance C4 formed between the neutral wire voltage reconstruction electrode V4 and the neutral wire voltage V3.

[0017] Preferably, in step S31, the micro-current signal is converted into an AC voltage signal by an I / V conversion circuit. The I / V conversion circuit includes an operational amplifier chip U1. Pin 2 of the operational amplifier chip U1 is connected to the live wire voltage sensing electrode A1 through a resistor R1. A resistor R2 is connected between pins 2 and 6 of the operational amplifier chip U1. Pin 3 of the operational amplifier chip U1 is grounded through a resistor R4. Pin 7 of the operational amplifier chip U1 is connected to +5V. Pin 4 of the operational amplifier chip U1 is connected to -5V. Pin 6 of the operational amplifier chip U1 is connected to the AC voltage signal output terminal U_out through a resistor R3.

[0018] Preferably, in step S31, the AC voltage signal is shaped and filtered by the AC signal processing circuit, wherein the AC signal processing circuit includes operational amplifier chip NU2-A and operational amplifier chip NU2-B;

[0019] Pin 3 of the operational amplifier chip NU2-A is grounded through the filter capacitor LC3. Pin 3 of the operational amplifier chip NU2-A is connected to the AC voltage signal output terminal U_out through resistors R9 and R8. Pin 1 of the operational amplifier chip NU2-A is connected to the circuit between resistors R9 and R8 through the filter capacitor LC2. Pin 2 of the operational amplifier chip NU2-A is grounded through resistor R11. Resistor R10 is connected between pin 2 and pin 1 of the operational amplifier chip NU2-A.

[0020] Pin 5 of op-amp chip NU2-B is grounded through filter capacitor LC6. Pin 5 of op-amp chip NU2-B is connected to pin 1 of op-amp chip NU2-A through resistors R14, R13, and R12. Filter capacitor LC4 is connected to ground in the circuit between resistors R13 and R12. Pin 7 of op-amp chip NU2-B is connected to the circuit between resistors R14 and R13 through filter capacitor LC5. Pin 6 of op-amp chip NU2-B is grounded through resistor R16. Resistor R15 is connected between pins 6 and 7 of op-amp chip NU2-B. Pin 7 of op-amp chip NU2-B is connected to the power frequency line voltage signal output terminal U_PLASTIC through resistor R21.

[0021] Preferably, in step S32, the voltage and frequency signals converted by the first D / A converter are smoothed by the AC filter circuit to obtain the internal output AC drive signal. The AC filter circuit includes an operational amplifier chip U3-A. Pin 3 of the operational amplifier chip U3-A is connected to the voltage and frequency signals converted by the first D / A converter. A resistor R23 is connected between pin 2 and pin 1 of the operational amplifier chip U3-A. A capacitor C5 and a resistor R24 ​​are connected in parallel with the resistor R23.

[0022] Preferably, in step S33, the power amplifier includes a power amplifier circuit, which includes transistors 9014, 8050, and 8550. The base of transistor 9014 is connected to the AC drive signal output by the AC filter circuit through capacitor C7. The base of transistor 9014 is grounded through resistor R25, and the emitter of transistor 9014 is grounded through resistor R26.

[0023] The base of transistor 8550 is connected to the collector of transistor 9014. The collector of transistor 8550 is grounded. The emitter of transistor 8550 and the emitter of transistor 8050 are connected to capacitor C6 through resistors R27 and R28 respectively. Resistor R29 is connected between the base and collector of transistor 8050.

[0024] Preferably, in step S36, the attenuator includes an attenuation circuit, which includes an operational amplifier chip U12-A. Pin 3 of the operational amplifier chip U12-A is grounded through a resistor R108. Pin 3 of the operational amplifier chip U12-A is connected to the secondary output signal of the transformer through a resistor R107. Pin 2 and pin 1 of the operational amplifier chip U12-A are connected.

[0025] The third A / D converter includes an A / D conversion circuit, which includes an A / D conversion chip U20. Pin 3 of the A / D conversion chip U20 is connected to the output signal of the attenuator through a filter capacitor C54. Pins 14 and 15 of the A / D conversion chip U20 are connected and output the converted digital signal.

[0026] Preferably, in step S33, the secondary output signal of the transformer and the sensing line voltage of the first non-contact capacitive sensor are amplified by a differential current amplifier, which includes a differential current amplifier circuit.

[0027] The differential current amplifier circuit includes a differential chip U2. Pin 2 of the differential chip U2 is connected to the live wire voltage reconstruction electrode V2 through resistors R6 and R19. Pin 3 of the differential chip U2 is connected to the secondary output signal of the transformer through resistors R18 and R22. Resistor R20 is connected between resistors R22 and R19. Pin 3 of the differential chip U2 is grounded through resistor R17. Resistor R5 is connected between pins 2 and 6 of the differential chip U2. Pin 6 of the differential chip U2 is connected to the differential current amplifier output terminal U_OUT through resistor R7.

[0028] A non-contact AC voltage measuring device for power frequency, characterized in that it includes a live wire voltage reconstruction electrode, a live wire voltage sensing electrode, a neutral wire voltage reconstruction electrode, a neutral wire voltage sensing electrode, and a main circuit. The main circuit includes an I / V conversion circuit, an AC signal processing circuit, a first A / D converter, a main control MCU, a first D / A converter, an AC filter circuit, a power amplifier, a transformer, a differential current amplifier, a second D / A converter, an attenuator, and a third A / D converter. The live wire voltage sensing electrode A1 is connected to the I / V conversion circuit. The I / V conversion circuit is connected to the main control MCU through the AC signal processing circuit and the first A / D converter. The main control MCU is connected to the transformer through the first D / A converter, the AC filter circuit, and the power amplifier. The transformer is connected to the main control MCU through the differential current amplifier and the second D / A converter. The output of the differential current amplifier is connected to the second D / A converter after I / V conversion. The transformer is connected to the main control MCU through the attenuator and the third A / D converter.

[0029] This application has the following technical effects:

[0030] This application presents a non-contact measurement method, device, and algorithm for power frequency AC (live wire - neutral wire) line voltage. This method not only avoids damaging the insulation layer of the protected power line but also allows operators to safely and easily obtain the measured line voltage, greatly improving work safety and efficiency.

[0031] The present invention will be further described below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of the principle of the present invention;

[0034] Figure 2 This is a schematic diagram of the measurement circuit structure of the present invention;

[0035] Figure 3 This is a schematic diagram of the I / V conversion circuit of the present invention;

[0036] Figure 4 This is a schematic diagram of the AC signal processing circuit of the present invention;

[0037] Figure 5 This is a schematic diagram of the AC filter circuit of the present invention;

[0038] Figure 6 This is a circuit diagram of the power amplifier and transformer of the present invention;

[0039] Figure 7 This is a schematic diagram of the differential current amplifier circuit of the present invention;

[0040] Figure 8 This is a schematic diagram of the attenuation circuit and A / D conversion circuit of the present invention;

[0041] Figure 9 This is a flowchart of the algorithm of the present invention;

[0042] Figure 10 This is a waveform diagram of the signal converted by the first D / A converter in this invention;

[0043] Figure 11 This is a waveform diagram of the signal converted by the first D / A converter in this invention after smoothing.

[0044] Figure 12 This is a schematic diagram of the structure of the non-contact capacitive sensor in this invention, which is clipped onto the power frequency line. Detailed Implementation

[0045] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0046] In the description of this application, it should be understood that 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 technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0047] In the embodiments of this application, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0048] A non-contact method for measuring power frequency AC voltage, such as Figure 1 As shown, it includes the following steps:

[0049] S1. Clip the first non-contact capacitive sensor and the second non-contact capacitive sensor onto the sheath of the AC voltage line, with the first non-contact capacitive sensor as the voltage sensing terminal and the second non-contact capacitive sensor as the reference ground, to form a complete circuit.

[0050] In step S1, the first non-contact capacitive sensor includes a live wire voltage reconstruction electrode V2 and a live wire voltage sensing electrode A1. A parasitic capacitance C1 is formed between the live wire voltage sensing electrode A1 and the live wire voltage V1, and a parasitic capacitance C2 is formed between the live wire voltage reconstruction electrode V2 and the live wire voltage V1. The second non-contact capacitive sensor includes a neutral wire voltage reconstruction electrode V4 and a neutral wire voltage sensing electrode A2. A parasitic capacitance C3 is formed between the neutral wire voltage sensing electrode A2 and the neutral wire voltage V3, and a parasitic capacitance C4 is formed between the neutral wire voltage reconstruction electrode V4 and the neutral wire voltage V3. The current loop forms V1—C1—A1—A2—C3—V3—V1. Figure 12 As shown, the first non-contact capacitive sensor is clamped onto the power frequency line with live wire voltage using a clip.

[0051] S2. A tiny leakage current exists in the insulation layer between the metal conductor and the first non-contact capacitive sensor, and the micro-current is collected by a current signal sampler.

[0052] S3. The micro-current signal I / V collected by the current signal sampler is converted to obtain the converted AC voltage signal. The AC voltage signal is then processed and differentially compared with the sensing line voltage of the first non-contact capacitive sensor.

[0053] Furthermore, step S3 includes the following sub-steps:

[0054] S31. The acquired micro-current signal is converted from I / V to obtain the converted AC voltage signal. The AC voltage signal is shaped and filtered to restore the voltage signal of the power frequency line. This signal is an AC signal with the same frequency and phase but different amplitude after attenuation of the power supply in the power frequency line. Subsequently, the power frequency line voltage signal is sent to the first A / D converter for analog-to-digital conversion. The converted digital signal is sent to the MCU for calculation and processing to determine the currently acquired voltage and frequency values.

[0055] In step S31, the micro-current signal is converted from an AC voltage signal by an I / V conversion circuit, wherein, for example... Figure 3 As shown, the I / V conversion circuit includes an operational amplifier chip U1. Pin 2 of the operational amplifier chip U1 is connected to the live wire voltage sensing electrode A1 through a resistor R1. A resistor R2 is connected between pins 2 and 6 of the operational amplifier chip U1. Pin 3 of the operational amplifier chip U1 is grounded through a resistor R4. Pin 7 of the operational amplifier chip U1 is connected to +5V. Pin 4 of the operational amplifier chip U1 is connected to -5V. Pin 6 of the operational amplifier chip U1 is connected to the AC voltage signal output terminal U_out through a resistor R3.

[0056] Therefore, V1 is the live wire voltage, C1 is the capacitance between the live wire voltage V1 and the live wire voltage sensing electrode A1, and a small leakage current flows from V1 through C1 and then through the operational amplifier to the ground terminal. The current-to-voltage conversion is composed of U1, R1, R2, and R4.

[0057] Further, in step S31, the AC voltage signal is shaped and filtered by the AC signal processing circuit, wherein, for example... Figure 4As shown, the AC signal processing circuit includes operational amplifier chips NU2-A and NU2-B. Pin 3 of operational amplifier chip NU2-A is grounded through filter capacitor LC3. Pin 3 of operational amplifier chip NU2-A is connected to the AC voltage signal output terminal U_out through resistors R9 and R8. Pin 1 of operational amplifier chip NU2-A is connected to the circuit between resistors R9 and R8 through filter capacitor LC2. Pin 2 of operational amplifier chip NU2-A is grounded through resistor R11. Resistor R10 connects pin 2 and pin 1 of operational amplifier chip NU2-A. Pin 5 of operational amplifier chip NU2-B is grounded through filter capacitor LC6. Pin 5 of op-amp chip NU2-B is connected to pin 1 of op-amp chip NU2-A through resistors R14, R13 and R12. A filter capacitor LC4 is connected to ground in the circuit between resistors R13 and R12. Pin 7 of op-amp chip NU2-B is connected to the circuit between resistors R14 and R13 through a filter capacitor LC5. Pin 6 of op-amp chip NU2-B is grounded through resistor R16. A resistor R15 is connected between pins 6 and 7 of op-amp chip NU2-B. Pin 7 of op-amp chip NU2-B is connected to the power frequency line voltage signal output terminal U_PLASTIC through resistor R21.

[0058] Therefore, by using two-stage bandpass filtering, the AC voltage signal after I / V conversion is smoothed out, and interference signals that are not at the power frequency are removed, restoring the attenuated live wire voltage signal.

[0059] During the MCU's calculation and processing, V1 = N * U_PLASTIC, where V1 is the live wire voltage value, N is the attenuation factor, and U_PLASTIC is the voltage value that ADC1 can recognize after attenuation, shaping, and filtering. In this embodiment, the attenuation factor N is a fixed value of 385.

[0060] S32. After the MCU calculates the current voltage and frequency values, it performs digital-to-analog conversion through the first D / A converter to restore the voltage and frequency signals acquired by the first A / D converter, such as... Figure 10 The waveform diagram shown illustrates how the voltage and frequency signals converted by the first D / A converter are smoothed through an AC filter to obtain the internal output AC drive signal, as shown below. Figure 11 The waveform diagram shown.

[0061] In step S32, the voltage and frequency signals converted by the first D / A converter are smoothed by an AC filter circuit to obtain the internally output AC drive signal, wherein, as shown... Figure 5As shown, the AC filter circuit includes an operational amplifier chip U3-A. Pin 3 of the operational amplifier chip U3-A is connected to the voltage and frequency signals converted by the first D / A converter. A resistor R23 is connected between pin 2 and pin 1 of the operational amplifier chip U3-A. A capacitor C5 and a resistor R24 ​​are connected in parallel with the resistor R23.

[0062] The S32.AC drive signal, after passing through a power amplifier, has sufficient power to enable the transformer to step up the voltage. At this time, the primary / secondary ratio parameter of the transformer is designed to be consistent with the attenuation factor of the first non-contact capacitive sensor. The secondary output signal of the transformer and the sensing line voltage of the first non-contact capacitive sensor are amplified by a differential current amplifier.

[0063] In step S32, as Figure 6 As shown, the power amplifier includes a power amplification circuit, which includes transistors 9014, 8050, and 8550. The base of transistor 9014 is connected to the AC drive signal output by the AC filter circuit through capacitor C7. The base of transistor 9014 is grounded through resistor R25, and the emitter of transistor 9014 is grounded through resistor R26. The base of transistor 8550 is connected to the collector of transistor 9014, and the collector of transistor 8550 is grounded. The emitters of transistor 8550 and transistor 8050 are connected to capacitor C6 through resistors R27 and R28, respectively. Resistor R29 is connected between the base and collector of transistor 8050. The input signal is the output signal of DAC1 and has no driving capability. This is a power amplification. 8050 and 8550 are power amplification transistors. 1N4148 is used to keep the power amplification transistors in a static operating state so that the output will not produce crossover distortion.

[0064] In step S32, the secondary output signal of the transformer and the sensing line voltage of the first non-contact capacitive sensor are amplified by a differential current amplifier, which includes a differential current amplification circuit; for example... Figure 7 As shown, the differential current amplifier circuit includes a differential chip U2. Pin 2 of the differential chip U2 is connected to the live wire voltage reconstruction electrode V2 through resistors R6 and R19. Pin 3 of the differential chip U2 is connected to the secondary output signal of the transformer through resistors R18 and R22. Resistor R20 is connected between resistors R22 and R19. Pin 3 of the differential chip U2 is grounded through resistor R17. Resistor R5 is connected between pins 2 and 6 of the differential chip U2. Pin 6 of the differential chip U2 is connected to the differential current amplifier output terminal U_OUT through resistor R7.

[0065] S34. After being amplified by the differential current amplifier, the current is converted into an I / V signal to obtain a recognizable voltage signal. Subsequently, the recognizable voltage signal is sent to the second A / D converter for analog-to-digital conversion, and then the converted digital signal is sent to the MCU for calculation and processing.

[0066] S35. Determine whether the value calculated by the MCU is equal to zero. If it is equal to zero, it means that the internal reconstruction voltage is equal to the external induced voltage. If it is not equal to zero, the first D / A converter needs to be integrated until it is equal to zero. The integration is completed, and the output of the first D / A converter after integration is maintained.

[0067] S36. After processing in step S35, the current value of the differential amplifier is made equal to zero. At this time, the secondary output signal of the transformer is attenuated by the attenuator until it is attenuated to a voltage signal that can supply power to the signal processing circuit.

[0068] In step S36, as Figure 8 As shown, the attenuator includes an attenuation circuit, which includes an operational amplifier chip U12-A. Pin 3 of the operational amplifier chip U12-A is grounded through a resistor R108. Pin 3 of the operational amplifier chip U12-A is connected to the secondary output signal of the transformer through a resistor R107. Pins 2 and 1 of the operational amplifier chip U12-A are connected together. The third A / D converter includes an A / D conversion circuit, which includes an A / D conversion chip U20. Pin 3 of the A / D conversion chip U20 is connected to the output signal of the attenuator through a filter capacitor C54. Pins 14 and 15 of the A / D conversion chip U20 are connected together and output the converted digital signal.

[0069] S37. The attenuated voltage signal is sent to the AC signal processor for filtering and RMS conversion to obtain a standard DC voltage signal. This signal is proportional to the internal analog power frequency voltage output. The proportional DC voltage signal is sent to the third A / D converter for analog-to-digital conversion. The converted digital signal is sent to the MCU for processing, calculation and display.

[0070] A non-contact power frequency AC voltage measuring device, such as Figure 2-8As shown, it includes a live wire voltage reconstruction electrode, a live wire voltage sensing electrode, a neutral wire voltage reconstruction electrode, a neutral wire voltage sensing electrode, and a main circuit. The main circuit includes an I / V conversion circuit, an AC signal processing circuit, a first A / D converter, a main control MCU, a first D / A converter, an AC filter circuit, a power amplifier, a transformer, a differential current amplifier, a second D / A converter, an attenuator, and a third A / D converter. The live wire voltage sensing electrode A1 is connected to the I / V conversion circuit. The I / V conversion circuit is connected to the main control MCU through the AC signal processing circuit and the first A / D converter. The main control MCU is connected to the transformer through the first D / A converter, the AC filter circuit, and the power amplifier. The transformer is connected to the main control MCU through the differential current amplifier and the second D / A converter. The output of the differential current amplifier is connected to the second D / A converter after I / V conversion. The transformer is connected to the main control MCU through the attenuator and the third A / D converter.

[0071] A program algorithm for a non-contact power frequency AC voltage measuring device, such as Figure 9 As shown, it includes the following steps:

[0072] 1) Power-on initialization;

[0073] 2) The first A / D converter acquires data from the first non-contact capacitive sensor;

[0074] 3) First D / A converter output drive;

[0075] 4) The second A / D converter samples the differential current signal;

[0076] 5) Determine the differential current;

[0077] 6) If the value is zero, maintain the output of the first D / A converter;

[0078] 7) If the value is less than zero, the first D / A converter performs an integration operation and outputs the result; if the value is greater than zero, the first...

[0079] After the D / A converter performs the subtraction integral operation, it outputs the result and repeats step S5.

[0080] 8) The third A / D converter samples the internally reconstructed voltage signal;

[0081] 9) Calculate the internal voltage;

[0082] 10) LCD display.

[0083] The above description is merely a preferred embodiment of this application and does not constitute any limitation on this application. Any person skilled in the art can make many possible variations and modifications to the technical solution of this application, or modify it into equivalent embodiments, without departing from the scope of the technical solution of this application. Therefore, all equivalent changes made based on the shape, structure, and principle of this application without departing from the content of the technical solution of this application should be covered within the protection scope of this application.

Claims

1. A method of non-contact measurement of power frequency alternating voltage, characterized in that, Includes the following steps: S1. Clip the first non-contact capacitive sensor and the second non-contact capacitive sensor onto the outer sheath of the AC voltage line, with the first non-contact capacitive sensor as the voltage sensing terminal and the second non-contact capacitive sensor as the reference ground, to form a complete circuit. S2. There is leakage current in the insulation layer between the metal conductor and the first non-contact capacitive sensor, and the micro current is collected by the current signal sampler; S3. Convert the micro-current signal I / V collected by the current signal sampler to obtain the converted AC voltage signal, then process the AC voltage signal, and then perform differential comparison with the sensing line voltage of the first non-contact capacitive sensor. Step S3 includes the following sub-steps: S31. The collected micro-current signal is converted from I / V to obtain the converted AC voltage signal. The AC voltage signal is shaped and filtered to restore the voltage signal of the power frequency line. This signal is the AC signal of the same frequency and phase but different amplitude after the power supply in the power frequency line is attenuated. Subsequently, the power frequency line voltage signal is sent to the first A / D converter for analog-to-digital conversion, and the converted digital signal is sent to the MCU for calculation and processing to determine the currently acquired voltage and frequency values. After S32.MCU calculates the current voltage and frequency values, it performs digital-to-analog conversion through the first D / A converter to restore the voltage and frequency signals collected by the first A / D converter. The voltage and frequency signals converted by the first D / A converter are then smoothed through the AC filtering stage to obtain the internal output AC drive signal. The S33.AC drive signal is amplified by the power amplifier to boost the transformer voltage. At this time, the primary / secondary ratio parameter of the transformer is designed to be consistent with the attenuation factor of the first non-contact capacitive sensor. The secondary output signal of the transformer and the sensing line voltage of the first non-contact capacitive sensor are amplified by the differential current amplifier. S34. After being amplified by the differential current amplifier, the current is converted into an I / V signal to obtain a recognizable voltage signal. Subsequently, the recognizable voltage signal is sent to the second A / D converter for analog-to-digital conversion, and then the converted digital signal is sent to the MCU for calculation and processing. S35. Determine whether the value calculated by the MCU is equal to zero. If it is equal to zero, it means that the internal reconstruction voltage is equal to the external induced voltage. If the result is not equal to zero, the first D / A converter needs to be integrated until it equals zero, then the integration is complete, and the output of the first D / A converter after integration is maintained. S36. After processing in step S35, the current value of the differential amplifier is made equal to zero. At this time, the secondary output signal of the transformer is attenuated by the attenuator until it is attenuated to a voltage signal that can supply power to the signal processing circuit. S37. The attenuated voltage signal is sent to the AC signal processor for filtering and RMS conversion to obtain a standard DC voltage signal. This signal is proportional to the internal analog power frequency voltage output. The proportional DC voltage signal is sent to the third A / D converter for analog-to-digital conversion. The converted digital signal is sent to the MCU for processing, calculation and display.

2. A non-contact power frequency AC voltage measurement method according to claim 1, characterized in that, In step S1, the first non-contact capacitive sensor includes a live wire voltage reconstruction electrode V2 and a live wire voltage sensing electrode A1, with a parasitic capacitance C1 formed between the live wire voltage sensing electrode A1 and the live wire voltage V1, and a parasitic capacitance C2 formed between the live wire voltage reconstruction electrode V2 and the live wire voltage V1. The second non-contact capacitive sensor includes a neutral wire voltage reconstruction electrode V4 and a neutral wire voltage sensing electrode A2, with a parasitic capacitance C3 formed between the neutral wire voltage sensing electrode A2 and the neutral wire voltage V3, and a parasitic capacitance C4 formed between the neutral wire voltage reconstruction electrode V4 and the neutral wire voltage V3.

3. The non-contact AC voltage measurement method according to claim 2, characterized in that, In step S31, the micro-current signal is converted into an AC voltage signal by an I / V conversion circuit. The I / V conversion circuit includes an operational amplifier chip U1. Pin 2 of the operational amplifier chip U1 is connected to the live wire voltage sensing electrode A1 through a resistor R1. A resistor R2 is connected between pins 2 and 6 of the operational amplifier chip U1. Pin 3 of the operational amplifier chip U1 is grounded through a resistor R4. Pin 7 of the operational amplifier chip U1 is connected to +5V. Pin 4 of the operational amplifier chip U1 is connected to -5V. Pin 6 of the operational amplifier chip U1 is connected to the AC voltage signal output terminal U_out through a resistor R3.

4. The non-contact AC voltage measurement method according to claim 2, characterized in that, In step S31, the AC voltage signal is shaped and filtered by the AC signal processing circuit, which includes operational amplifier chip NU2-A and operational amplifier chip NU2-B. Pin 3 of the operational amplifier chip NU2-A is grounded through the filter capacitor LC3. Pin 3 of the operational amplifier chip NU2-A is connected to the AC voltage signal output terminal U_out through resistors R9 and R8. Pin 1 of the operational amplifier chip NU2-A is connected to the circuit between resistors R9 and R8 through the filter capacitor LC2. Pin 2 of the operational amplifier chip NU2-A is grounded through resistor R11. Resistor R10 is connected between pin 2 and pin 1 of the operational amplifier chip NU2-A. Pin 5 of op-amp chip NU2-B is grounded through filter capacitor LC6. Pin 5 of op-amp chip NU2-B is connected to pin 1 of op-amp chip NU2-A through resistors R14, R13, and R12. Filter capacitor LC4 is connected to ground in the circuit between resistors R13 and R12. Pin 7 of op-amp chip NU2-B is connected to the circuit between resistors R14 and R13 through filter capacitor LC5. Pin 6 of op-amp chip NU2-B is grounded through resistor R16. Resistor R15 is connected between pins 6 and 7 of op-amp chip NU2-B. Pin 7 of op-amp chip NU2-B is connected to the power frequency line voltage signal output terminal U_PLASTIC through resistor R21.

5. The non-contact AC voltage measurement method according to claim 2, characterized in that, In step S32, the voltage and frequency signals converted by the first D / A converter are smoothed by the AC filter circuit to obtain the internal output AC drive signal. The AC filter circuit includes an operational amplifier chip U3-A. Pin 3 of the operational amplifier chip U3-A is connected to the voltage and frequency signals converted by the first D / A converter. A resistor R23 is connected between pin 2 and pin 1 of the operational amplifier chip U3-A. A capacitor C5 and a resistor R24 ​​are connected in parallel with the resistor R23.

6. The non-contact AC voltage measurement method according to claim 5, characterized in that, In step S33, the power amplifier includes a power amplifier circuit, which includes transistors 9014, 8050, and 8550. The base of transistor 9014 is connected to the AC drive signal output by the AC filter circuit through capacitor C7. The base of transistor 9014 is grounded through resistor R25, and the emitter of transistor 9014 is grounded through resistor R26. The base of transistor 8550 is connected to the collector of transistor 9014. The collector of transistor 8550 is grounded. The emitter of transistor 8550 and the emitter of transistor 8050 are connected to capacitor C6 through resistors R27 and R28 respectively. Resistor R29 is connected between the base and collector of transistor 8050.

7. The non-contact AC voltage measurement method according to claim 5, characterized in that, In step S36, the attenuator includes an attenuation circuit, which includes an operational amplifier chip U12-A. Pin 3 of the operational amplifier chip U12-A is grounded through a resistor R108. Pin 3 of the operational amplifier chip U12-A is connected to the secondary output signal of the transformer through a resistor R107. Pin 2 and pin 1 of the operational amplifier chip U12-A are connected. The third A / D converter includes an A / D conversion circuit, which includes an A / D conversion chip U20. Pin 3 of the A / D conversion chip U20 is connected to the output signal of the attenuator through a filter capacitor C54. Pins 14 and 15 of the A / D conversion chip U20 are connected and output the converted digital signal.

8. A non-contact AC voltage measurement method according to claim 2, characterized in that, In step S33, the secondary output signal of the transformer and the sensing line voltage of the first non-contact capacitive sensor are amplified by a differential current amplifier, which includes a differential current amplifier circuit. The differential current amplifier circuit includes a differential chip U2. Pin 2 of the differential chip U2 is connected to the live wire voltage reconstruction electrode V2 through resistors R6 and R19. Pin 3 of the differential chip U2 is connected to the secondary output signal of the transformer through resistors R18 and R22. Resistor R20 is connected between resistors R22 and R19. Pin 3 of the differential chip U2 is grounded through resistor R17. Resistor R5 is connected between pins 2 and 6 of the differential chip U2. Pin 6 of the differential chip U2 is connected to the differential current amplifier output terminal U_OUT through resistor R7.

9. A non-contact power frequency AC voltage measuring device implementing the method of any one of claims 1 to 8, characterized in that, The device includes a live wire voltage reconstruction electrode, a live wire voltage sensing electrode, a neutral wire voltage reconstruction electrode, a neutral wire voltage sensing electrode, and a main circuit. The main circuit includes an I / V conversion circuit, an AC signal processing circuit, a first A / D converter, a main control MCU, a first D / A converter, an AC filter circuit, a power amplifier, a transformer, a differential current amplifier, a second D / A converter, an attenuator, and a third A / D converter. The live wire voltage sensing electrode A1 is connected to the I / V conversion circuit. The I / V conversion circuit is connected to the main control MCU through the AC signal processing circuit and the first A / D converter. The main control MCU is connected to the transformer through the first D / A converter, the AC filter circuit, and the power amplifier. The transformer is connected to the main control MCU through the differential current amplifier and the second D / A converter. The output of the differential current amplifier is connected to the second D / A converter after I / V conversion. The transformer is connected to the main control MCU through the attenuator and the third A / D converter.

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