Non-intrusive sensor with external excitation source and voltage measuring method

Abstract

The invention discloses a non-intrusive sensor with an external excitation source and a voltage measurement method, and the non-intrusive sensor comprises an induction signal collection unit, an induction signal conditioning unit, and a main control unit. The main control unit is respectively connected with the induction signal conditioning unit and the cable power supply, the induction signal conditioning unit is connected with the induction signal acquisition unit, and the induction signal acquisition unit is in non-contact inductive coupling connection with a cable to be detected; the main control unit is used for injecting the specific excitation signal into an alternating current loop of a cable power supply to form a composite signal, analyzing the composite signal based on a preset excitation source amplitude parameter, and calculating the power supply voltage of the to-be-detected cable; the induction signal acquisition unit generates a corresponding induction signal by capturing electric field energy generated by a composite signal in the to-be-detected cable; the induction signal conditioning unit carries out standardization processing on the induction signal. According to the invention, the technical problems of low external excitation voltage measurement precision, low system integration and single excitation source generation mode in the prior art are solved.

Description

Technical Field

[0001] This invention relates to the field of non-invasive voltage monitoring technology, and in particular to a non-invasive sensor with an external excitation source and a voltage measurement method. Background Technology

[0002] Non-invasive voltage detection technology is based on the principle of spatial electric field coupling. It captures the distribution characteristics of the alternating electric field around the conductor through a high-sensitivity sensing unit, and uses a signal conditioning circuit to convert the high-voltage signal into a small-amplitude voltage signal that can be processed. Finally, it realizes non-contact indirect detection of the voltage of the object being measured. The core advantage of this technology lies in its non-contact measurement characteristics, which avoids direct electrical connection with live lines and does not damage the original insulation performance of the power distribution network, thereby significantly improving the safety and long-term operational reliability of the measuring equipment.

[0003] In terms of improving accuracy, real-time online calibration and adaptive calibration of sensors are among the most effective technical approaches currently available. As smart grids rapidly evolve towards digitalization and intelligence, sensor calibration technology is also showing a trend towards intelligence, automation, and convenience. It is worth noting that the measurement accuracy of non-invasive voltage sensors is easily affected by environmental factors such as temperature, humidity, and electromagnetic interference. Relying solely on factory calibration cannot guarantee measurement consistency throughout the entire lifecycle of the equipment, potentially leading to significant long-term measurement errors.

[0004] Patent document CN202320855972.3 discloses a pressure sensor signal sampling circuit for measuring battery cell pressure, including at least one pressure sensor, an analog-to-digital converter (ADC), and a processor. Each pressure sensor is embedded within the battery cell, and an anti-aliasing filter module is connected in series with each pressure sensor. The output of each anti-aliasing filter module is connected to the ADC. Under pressure, each pressure sensor outputs a differential analog signal, which is filtered by the anti-aliasing filter module and then sent to the ADC. The ADC converts the filtered differential analog signal into a differential digital signal and transmits it to the processor via communication. A power supply module is electrically connected to the input terminals of the pressure sensor and the ADC, providing a reference voltage to the ADC. An active non-invasive voltage measurement calibration method based on external excitation has been proven applicable to non-invasive measurement of voltages in different types of conductors and has achieved good measurement results. Its core steps involve injecting a known heterogeneous frequency reference excitation into the measurement system. In the data processing stage, the composite signal is processed by FFT to achieve frequency separation, and the voltage to be measured is calculated based on the transmission relationship. In this method, the reliability and stability of the excitation source directly affect the measurement progress. Most existing external excitation technologies are based on traditional, mature power supply equipment or standardized power modules. While their design has engineering versatility, they often face problems such as high cost and limited flexibility in practical applications. Furthermore, the overall system is large and lacks portability, which is not conducive to achieving real-time measurement and on-site deployment, and fails to meet the high integration and adaptability requirements of modern power monitoring systems. Therefore, there is an urgent need to propose a non-invasive sensor and voltage measurement method with an external excitation source to solve the technical problems of low accuracy in existing external excitation voltage measurements, low system integration, and a single excitation source generation method. Summary of the Invention

[0005] The main objective of this invention is to propose a non-invasive sensor and voltage measurement method with an external excitation source, aiming to solve the technical problems of low accuracy, low system integration, and limited excitation source generation methods in existing external excitation voltage measurements.

[0006] To achieve the above objectives, the present invention provides a non-invasive sensor with an external excitation source, wherein the non-invasive sensor with an external excitation source includes:

[0007] The system comprises an inductive signal acquisition unit, an inductive signal conditioning unit, and a main control unit.

[0008] The main control unit is connected to the induction signal conditioning unit and the cable power supply respectively. The induction signal conditioning unit is connected to the induction signal acquisition unit. The induction signal acquisition unit is connected to the cable under test via non-contact induction coupling. The cable under test is connected to the cable power supply.

[0009] The main control unit is used to inject a specific excitation signal into the AC circuit of the cable power supply to form a composite signal, and to analyze the composite signal transmitted by the induction signal conditioning unit based on the preset excitation source amplitude parameters to calculate the power supply voltage of the cable under test.

[0010] The induction signal acquisition unit captures the electric field energy generated by the composite signal in the cable under test, generates a corresponding induction signal, and inputs it to the induction signal conditioning unit.

[0011] The induction signal conditioning unit performs standardization processing on the induction signal.

[0012] In one preferred embodiment, the sensing signal conditioning unit includes a first-stage operational amplifier circuit, a second-stage operational amplifier circuit, and a third-stage operational amplifier circuit connected in sequence.

[0013] In one preferred embodiment, the first-stage operational amplifier circuit includes operational amplifier U6; pin 1 of operational amplifier U6 is connected to the second-stage operational amplifier circuit and pin 4 of operational amplifier U6, pin 3 of operational amplifier U6 is connected to resistor R8, capacitor C31, capacitor C61 and pin 1 of connector J4, the other ends of resistor R8, capacitor C31 and capacitor C61 and pin 2 of connector J4 are grounded, and pins 2 and 5 of operational amplifier U6 are connected to the power supply.

[0014] In one preferred embodiment, the second-stage operational amplifier circuit includes an operational amplifier U11; pin 1 of the operational amplifier U11 is connected to capacitors C3 and C12, pin 4 of the operational amplifier U11, and the third-stage operational amplifier circuit; the other ends of capacitors C3 and C12 are connected to resistors R27 and R28, respectively; the other end of resistor R27 is connected to capacitor C57 and resistor R4, respectively; the other end of resistor R4 is connected to the first-stage operational amplifier circuit; the other end of resistor R28 is connected to capacitors C22 and C23, and pin 3 of the operational amplifier U11; the other ends of capacitors C57, C22, and C23 are grounded; and pins 2 and 5 of the operational amplifier U11 are connected to the power supply.

[0015] In one preferred embodiment, the three-stage operational amplifier circuit includes an operational amplifier U5. Pin 1 of the operational amplifier U5 is connected to resistor R23, capacitor C60, and resistor R9. The other end of resistor R9 is connected to resistor R25. The other end of resistor R25 is connected to resistor R22 and pin 4 of the operational amplifier U5. Pin 3 of the operational amplifier U5 is connected to resistor R21. The other end of resistor R21 is connected to capacitor C58 and the second-stage operational amplifier circuit. The other ends of capacitor C58, capacitor C60, and resistor R22 are grounded. Pins 2 and 5 of the operational amplifier U5 are connected to the power supply.

[0016] In one preferred embodiment, the main control unit includes an MCU, a communication module, a data processing and computing module, and a reference signal generation circuit; the data processing and computing module is connected to the induction signal conditioning unit and the communication module respectively, the MCU module is connected to the reference signal generation circuit, and the reference signal generation circuit is connected to the cable power supply.

[0017] The communication module is used for data communication with external devices;

[0018] The data processing and calculation module is used to sample and filter the signal-conditioned composite signal, and after FFT decomposition, calculate the power circuit of the cable under test through the transfer function and transmit it to the communication module.

[0019] The MCU is used to output a PWM modulation wave that satisfies a sinusoidal variation law;

[0020] The reference signal generation circuit is used to receive the PWM modulation wave output by the MCU, and after performing signal modulation processing on the PWM modulation wave, output a reference signal with a preset amplitude, and superimpose the reference signal with the voltage of the cable under test to form a composite signal.

[0021] In one preferred embodiment, the reference signal generation circuit includes a motor driver chip U12; pin 1 of the motor driver chip U12 is connected to capacitors C37 and C38 and the power supply terminal respectively; pins 2 and 3 of the motor driver chip U12 are connected to a filter network; pins 5, 6, and 7 of the motor driver chip U12 are connected to the MCU; pin 8 of the motor driver chip U12 is connected to resistor R5, capacitor C39, capacitor C40 and the power supply terminal respectively; the other end of resistor R5 is connected to pin 7 of the motor driver chip U12; pin 4 of the motor driver chip U12, and the other ends of capacitors C37, C38, C39 and C40 are grounded.

[0022] In one preferred embodiment, the motor drive chip U12 is a drive chip with the model number MD9927.

[0023] In one preferred embodiment, the filter network includes an inductor L1, a capacitor C43, and a transformer T2;

[0024] Pin 1 of transformer T2 is connected to capacitor C43 and inductor L1 respectively. The other end of inductor L1 is connected to pin 3 of motor drive chip U12. The other end of capacitor C43 is connected to pin 2 of motor drive chip U12 and pin 2 of transformer T2 respectively. Pin 3 of transformer T2 is grounded. Pin 4 of transformer T2 is connected to the cable power supply.

[0025] A voltage measurement method for a non-invasive sensor including an external excitation source, comprising the following steps:

[0026] The main control unit generates a reference signal with a preset amplitude and injects it into the circuit under test. The reference signal is superimposed on the original mains power of the circuit under test to form a composite signal.

[0027] The induction signal acquisition unit captures the electric field energy generated by the composite signal in the cable under test based on the principle of electric field induction and the capacitive coupling voltage division mechanism, and generates the corresponding induction signal. The induction signal is standardized by the induction signal conditioning unit and converted into a composite signal that can be processed by the main control unit.

[0028] The main control unit calculates the power supply voltage of the cable under test based on the excitation source amplitude parameters with preset amplitude through FFT decomposition and transfer function. The excitation source with preset amplitude is the reference signal with preset amplitude.

[0029] In the above technical solution of the present invention, the non-invasive sensor with an external excitation source includes: an induction signal acquisition unit, an induction signal conditioning unit, and a main control unit; the main control unit is connected to the induction signal conditioning unit and the cable power supply respectively; the induction signal conditioning unit is connected to the induction signal acquisition unit; the induction signal acquisition unit is non-contactly inductively coupled to the cable under test; and the cable under test is connected to the cable power supply. The main control unit is used to inject a specific excitation signal into the AC circuit of the cable power supply to form a composite signal, and to analyze the composite signal transmitted by the induction signal conditioning unit based on preset excitation source amplitude parameters to calculate the power supply voltage of the cable under test; the induction signal acquisition unit generates a corresponding induction signal by capturing the electric field energy generated by the composite signal in the cable under test and inputs it to the induction signal conditioning unit; and the induction signal conditioning unit performs standardization processing on the induction signal. The present invention solves the technical problems of low measurement accuracy, low system integration, and single excitation source generation method in existing external excitation voltage methods. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of 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 the structures shown in these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of a non-invasive sensor with an external excitation source according to an embodiment of the present invention;

[0032] Figure 2 This is a schematic diagram of the sensing signal conditioning unit according to an embodiment of the present invention;

[0033] Figure 3 This is a schematic diagram of the reference signal generation circuit in an embodiment of the present invention.

[0034] The realization of the objective, functional characteristics and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0037] See Figure 1 According to one aspect of the present invention, the present invention provides a non-invasive sensor with an external excitation source, wherein the non-invasive sensor with the external excitation source comprises:

[0038] The system comprises an inductive signal acquisition unit, an inductive signal conditioning unit, and a main control unit.

[0039] The main control unit is connected to the induction signal conditioning unit and the cable power supply respectively. The induction signal conditioning unit is connected to the induction signal acquisition unit. The induction signal acquisition unit is connected to the cable under test via non-contact induction coupling. The cable under test is connected to the cable power supply.

[0040] The main control unit is used to inject a specific excitation signal into the AC circuit of the cable power supply to form a composite signal, and to analyze the composite signal transmitted by the induction signal conditioning unit based on the preset excitation source amplitude parameters to calculate the power supply voltage of the cable under test.

[0041] The induction signal acquisition unit captures the electric field energy generated by the composite signal in the cable under test, generates a corresponding induction signal, and inputs it to the induction signal conditioning unit.

[0042] The induction signal conditioning unit performs standardization processing on the induction signal.

[0043] Specifically, in this embodiment, the inductive signal conditioning unit includes a first-stage operational amplifier circuit, a second-stage operational amplifier circuit, and a third-stage operational amplifier circuit connected in sequence. The inductive signal acquisition unit, based on the principle of electric field induction and capacitive coupling voltage division mechanism, captures the electric field energy generated by the composite signal in the cable under test, generates a corresponding inductive signal, and inputs it to the inductive signal conditioning unit. The inductive signal conditioning unit standardizes the signal, converting it into a signal form that meets the processing requirements of the main control unit. (See [link to relevant documentation]). Figure 2 Since the input side of the signal conditioning circuit is an inductive signal acquisition unit, it is more sensitive to signals input from traditional electrical connections. Furthermore, the signals in the cables are not single-frequency signals; that is, the sensed signals are composite waveforms. Simultaneously, the main control unit also has requirements for signal input. Therefore, signal conditioning for this situation requires a dedicated inductive signal conditioning circuit. This circuit must ensure that it does not interfere with the inductive sampling of the preceding system while maintaining signal integrity and stability as much as possible. The first-stage operational amplifier circuit uses a voltage follower structure, which can stably transmit the signal from the preceding circuit to the subsequent stage while reducing the impact of the subsequent stage on the preceding stage. The second-stage operational amplifier circuit further optimizes the signal characteristics, preparing for subsequent output. The third-stage operational amplifier circuit uses an amplifier structure, forming a feedback network with resistors R25, R9, R21, and R22. Amplification is set to ultimately amplify the signal processed by the preceding stage, ensuring that the output signal meets the measurement and usage requirements of the main control unit.

[0044] Specifically, in this embodiment, the first-stage operational amplifier circuit includes operational amplifier U6; pin 1 of operational amplifier U6 is connected to the second-stage operational amplifier circuit and pin 4 of operational amplifier U6, pin 3 of operational amplifier U6 is connected to resistor R8, capacitor C31, capacitor C61 and pin 1 of connector J4, the other ends of resistor R8, capacitor C31 and capacitor C61 and pin 2 of connector J4 are grounded, and pins 2 and 5 of operational amplifier U6 are connected to the power supply.

[0045] Specifically, in this embodiment, the second-stage operational amplifier circuit includes an operational amplifier U11; pin 1 of the operational amplifier U11 is connected to capacitors C3 and C12, pin 4 of the operational amplifier U11, and the third-stage operational amplifier circuit, respectively; the other ends of capacitors C3 and C12 are connected to resistors R27 and R28, respectively; the other end of resistor R27 is connected to capacitor C57 and resistor R4, respectively; the other end of resistor R4 is connected to the first-stage operational amplifier circuit; the other end of resistor R28 is connected to capacitors C22 and C23, and pin 3 of the operational amplifier U11, respectively; the other ends of capacitors C57, C22, and C23 are grounded; and pins 2 and 5 of the operational amplifier U11 are connected to the power supply.

[0046] Specifically, in this embodiment, the three-stage operational amplifier circuit includes an operational amplifier U5. Pin 1 of the operational amplifier U5 is connected to resistor R23, capacitor C60, and resistor R9. The other end of resistor R9 is connected to resistor R25. The other end of resistor R25 is connected to resistor R22 and pin 4 of the operational amplifier U5. Pin 3 of the operational amplifier U5 is connected to resistor R21. The other end of resistor R21 is connected to capacitor C58 and the second-stage operational amplifier circuit. The other ends of capacitor C58, capacitor C60, and resistor R22 are grounded. Pins 2 and 5 of the operational amplifier U5 are connected to the power supply.

[0047] Specifically, in this embodiment, the main control unit includes an MCU, a communication module, a data processing and computing module, and a reference signal generation circuit; the data processing and computing module is connected to the sensing signal conditioning unit and the communication module respectively, the MCU module is connected to the reference signal generation circuit, and the reference signal generation circuit is connected to the cable power supply;

[0048] The communication module is used for data communication with external devices;

[0049] The data processing and calculation module is used to sample and filter the signal-conditioned composite signal, and after FFT decomposition, calculate the power circuit of the cable under test through the transfer function and transmit it to the communication module.

[0050] The MCU is used to output a PWM modulation wave that satisfies a sinusoidal variation law;

[0051] The reference signal generation circuit is used to receive the PWM modulation wave output by the MCU, and after performing signal modulation processing on the PWM modulation wave, output a reference signal with a preset amplitude, and superimpose the reference signal with the voltage of the cable under test to form a composite signal.

[0052] In subsequent measurements, the measurement accuracy of the voltage under test can be calibrated based on the existing external excitation source active non-invasive voltage measurement calibration method, thereby improving the measurement accuracy of the induced voltage. The reference signal generation circuit generates a reference signal with a known amplitude. In this invention, the reference signal is a 40Hz sine wave, which is injected into the circuit under test through capacitive coupling. The original mains power (50Hz) in the circuit is superimposed with the reference signal to form a composite signal. The main control unit receives the conditioned composite signal, which includes the mains power and reference signal components. If only capacitive coupling sampling is used, the original mains voltage cannot be directly calculated due to the uncertainty of the induction method. However, after adding a reference signal with a known amplitude, due to the signal superposition principle, the amplitude ratio K of the two frequency components in the composite signal is approximately the same as the amplitude ratio in the actual circuit. The main control unit extracts the amplitude ratio K of the two frequency components in the composite signal through digital demodulation and FFT analysis. Since the amplitude Vref of the reference signal is known, the effective value of the mains voltage can be obtained using the relationship K×Vref, which is the power supply voltage of the cable under test.

[0053] Specifically, in this embodiment, see Figure 3 The reference signal generation circuit includes a motor driver chip U12; pin 1 of the motor driver chip U12 is connected to capacitors C37 and C38 and the power supply terminal respectively; pins 2 and 3 of the motor driver chip U12 are connected to a filter network; pins 5, 6, and 7 of the motor driver chip U12 are connected to the MCU; pin 8 of the motor driver chip U12 is connected to resistor R5, capacitor C39, capacitor C40 and the power supply terminal respectively; the other end of resistor R5 is connected to pin 7 of the motor driver chip U12; pin 4 of the motor driver chip U12, and the other end of capacitors C37, C38, C39 and C40 are grounded; in this invention, the motor driver chip U12 is a driver chip of model MD9927.

[0054] Specifically, in this embodiment, the filter network includes an inductor L1, a capacitor C43, and a transformer T2; pin 1 of the transformer T2 is connected to both the capacitor C43 and the inductor L1, the other end of the inductor L1 is connected to pin 3 of the motor drive chip U12, the other end of the capacitor C43 is connected to pin 2 of the motor drive chip U12 and pin 2 of the transformer T2, pin 3 of the transformer T2 is grounded, and pin 4 of the transformer T2 is connected to the cable power supply.

[0055] Specifically, in this embodiment, the reference signal generation circuit inputs the SVPWM signal output by the MCU (SVPWM is a space vector pulse width modulation signal) to the input stages INA and INB of the motor drive chip U12. The signals at the input stages drive the H-bridge in the motor drive chip U12, and then directly connect to the subsequent filter network via the output stages OUT1 and OUT2. The filter network is a second-order low-pass filter composed of a power inductor and a ceramic capacitor, with a cut-off frequency of 1.2 KHz, which can effectively filter out the carrier of the SVPWM signal and retain the sine signal, thereby converting the PWM signal into a sine wave. This waveform is amplified by the transformer T2, and the amplified PWM signal is used as an excitation source with a known amplitude and injected into the circuit.

[0056] Specifically, in this embodiment, the MCU integrates a dedicated PWM mode timer and output ports. The MCU first detects whether to stop the PWM signal output. If the stop condition is met, such as a system fault or a sleep instruction, it immediately disables the PWM signal output and terminates the process to ensure system safety; if there is no need to stop, it further determines whether the parameters of the PWM signal exceed the preset range, such as the frequency or duty cycle being over-limit. If it is over-limit, the process terminates to avoid hardware damage. Otherwise, it enters the initialization stage, successively configuring the PWM output ports, initializing the PWM output-related clocks, and configuring the PWM output timer-related settings, laying a hardware foundation for the SVPWM output. Finally, it loads the preset SVPWM frequency and duty cycle parameters, enables the output, and generates a PWM signal that conforms to the target model. The MCU supports dynamic configuration of SVPWM parameters to adapt to different inverter scenarios.

[0057] Specifically, in this embodiment, the pulse width modulation mode in the PWM mode timing can generate a signal whose frequency is determined by the TC_DN register and whose duty cycle is determined by the TC_CCDx register; it supports two PWM modes: PWM mode 1 and PWM mode 2: PWM mode 1: If TC_CNT < TC_CCDx, the output is at an effective level, otherwise it is at an invalid level; PWM mode 2: If TC_CNT >= TC_CCDx, the output is at an effective level, otherwise it is at an invalid level; in the loading link of the SVPWM frequency and duty cycle configuration of the present invention, the parameters of the TC_DN and TC_CCDx registers that need to be configured within one cycle of the preset signal are preset, so as to implement the target generated signal.

[0058] According to another aspect of the present invention, the present invention provides a voltage measurement method for a non-invasive sensor with an external excitation source, including the following steps:

[0059] The main control unit generates a reference signal with a preset amplitude and injects it into the待测线路 (to-be-measured circuit), which is superimposed with the original mains power of the to-be-measured circuit to form a composite signal;

[0060] The induction signal acquisition unit captures the electric field energy generated by the composite signal in the cable under test based on the principle of electric field induction and the capacitive coupling voltage division mechanism, and generates the corresponding induction signal. The induction signal is standardized by the induction signal conditioning unit and converted into a composite signal that can be processed by the main control unit.

[0061] The main control unit calculates the power supply voltage of the cable under test based on the excitation source amplitude parameters with preset amplitude through FFT decomposition and transfer function. The excitation source with preset amplitude is the reference signal with preset amplitude.

[0062] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A non-invasive sensor with an external excitation source, characterized in that, include: The system comprises an inductive signal acquisition unit, an inductive signal conditioning unit, and a main control unit. The main control unit is connected to the induction signal conditioning unit and the cable power supply respectively. The induction signal conditioning unit is connected to the induction signal acquisition unit. The induction signal acquisition unit is connected to the cable under test via non-contact induction coupling. The cable under test is connected to the cable power supply. The main control unit is used to inject a specific excitation signal into the AC circuit of the cable power supply to form a composite signal, and to analyze the composite signal transmitted by the induction signal conditioning unit based on the preset excitation source amplitude parameters to calculate the power supply voltage of the cable under test. The induction signal acquisition unit captures the electric field energy generated by the composite signal in the cable under test, generates a corresponding induction signal, and inputs it to the induction signal conditioning unit. The induction signal conditioning unit performs standardization processing on the induction signal.

2. The non-invasive sensor with an external excitation source according to claim 1, characterized in that, The inductive signal conditioning unit includes a first-stage operational amplifier circuit, a second-stage operational amplifier circuit, and a third-stage operational amplifier circuit connected in sequence.

3. A non-invasive sensor with an external excitation source according to claim 2, characterized in that, The first-stage operational amplifier circuit includes operational amplifier U6; pin 1 of operational amplifier U6 is connected to the second-stage operational amplifier circuit and pin 4 of operational amplifier U6, pin 3 of operational amplifier U6 is connected to resistor R8, capacitor C31, capacitor C61 and pin 1 of connector J4, the other ends of resistor R8, capacitor C31 and capacitor C61 and pin 2 of connector J4 are grounded, and pins 2 and 5 of operational amplifier U6 are connected to the power supply.

4. A non-invasive sensor with an external excitation source according to claim 2, characterized in that, The second-stage operational amplifier circuit includes operational amplifier U11; pin 1 of operational amplifier U11 is connected to capacitors C3 and C12, pin 4 of operational amplifier U11, and the third-stage operational amplifier circuit. The other ends of capacitors C3 and C12 are connected to resistors R27 and R28, respectively. The other end of resistor R27 is connected to capacitor C57 and R4, respectively. The other end of resistor R4 is connected to the first-stage operational amplifier circuit. The other end of resistor R28 is connected to capacitors C22 and C23, and pin 3 of operational amplifier U11, respectively. The other ends of capacitors C57, C22, and C23 are grounded. Pins 2 and 5 of operational amplifier U11 are connected to the power supply.

5. A non-invasive sensor with an external excitation source according to claim 2, characterized in that, The three-stage operational amplifier circuit includes operational amplifier U5. Pin 1 of operational amplifier U5 is connected to resistor R23, capacitor C60, and resistor R9. The other end of resistor R9 is connected to resistor R25. The other end of resistor R25 is connected to resistor R22 and pin 4 of operational amplifier U5. Pin 3 of operational amplifier U5 is connected to resistor R21. The other end of resistor R21 is connected to capacitor C58 and the second-stage operational amplifier circuit. The other ends of capacitor C58, capacitor C60, and resistor R22 are grounded. Pins 2 and 5 of operational amplifier U5 are connected to the power supply.

6. A non-invasive sensor with an external excitation source according to any one of claims 1-5, characterized in that, The main control unit includes an MCU, a communication module, a data processing and computing module, and a reference signal generation circuit; the data processing and computing module is connected to the induction signal conditioning unit and the communication module respectively, the MCU module is connected to the reference signal generation circuit, and the reference signal generation circuit is connected to the cable power supply. The communication module is used for data communication with external devices; The data processing and calculation module is used to sample and filter the signal-conditioned composite signal, and after FFT decomposition, calculate the power circuit of the cable under test through the transfer function and transmit it to the communication module. The MCU is used to output a PWM modulation wave that satisfies a sinusoidal variation law; The reference signal generation circuit is used to receive the PWM modulation wave output by the MCU, and after performing signal modulation processing on the PWM modulation wave, output a reference signal with a preset amplitude, and superimpose the reference signal with the voltage of the cable under test to form a composite signal.

7. A non-invasive sensor with an external excitation source according to claim 6, characterized in that, The reference signal generation circuit includes a motor driver chip U12; pin 1 of the motor driver chip U12 is connected to capacitors C37 and C38 and the power supply terminal respectively; pins 2 and 3 of the motor driver chip U12 are connected to a filter network; pins 5, 6, and 7 of the motor driver chip U12 are connected to the MCU; pin 8 of the motor driver chip U12 is connected to resistor R5, capacitor C39, capacitor C40 and the power supply terminal respectively; the other end of resistor R5 is connected to pin 7 of the motor driver chip U12; pin 4 of the motor driver chip U12, and the other end of capacitors C37, C38, C39 and C40 are grounded.

8. A non-invasive sensor with an external excitation source according to claim 7, characterized in that, The motor drive chip U12 is a drive chip with the model number MD9927.

9. A non-invasive sensor with an external excitation source according to claim 7, characterized in that, The filter network includes an inductor L1, a capacitor C43, and a transformer T2; Pin 1 of transformer T2 is connected to capacitor C43 and inductor L1 respectively. The other end of inductor L1 is connected to pin 3 of motor drive chip U12. The other end of capacitor C43 is connected to pin 2 of motor drive chip U12 and pin 2 of transformer T2 respectively. Pin 3 of transformer T2 is grounded. Pin 4 of transformer T2 is connected to the cable power supply.

10. A voltage measurement method for a non-invasive sensor comprising an external excitation source as described in any one of claims 1-9, characterized in that, Includes the following steps: The main control unit generates a reference signal with a preset amplitude and injects it into the circuit under test. The reference signal is superimposed on the original mains power of the circuit under test to form a composite signal. The induction signal acquisition unit captures the electric field energy generated by the composite signal in the cable under test based on the principle of electric field induction and the capacitive coupling voltage division mechanism, and generates the corresponding induction signal. The induction signal is standardized by the induction signal conditioning unit and converted into a composite signal that can be processed by the main control unit. The main control unit calculates the power supply voltage of the cable under test based on the excitation source amplitude parameters with preset amplitude through FFT decomposition and transfer function. The excitation source with preset amplitude is the reference signal with preset amplitude.

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