Zero flux current sensor based on double microwave driving

Abstract

The application relates to the technical field of smart power grids, in particular to a zero-flux current sensor based on double-microwave driving. The control scheme of the zero-flux current sensor is selected according to the application scene and debugging requirement of the zero-flux current sensor: when the zero-flux current sensor is in a first application debugging state, the working process of the zero-flux current sensor is controlled by a digital signal to obtain a to-be-measured current; when the zero-flux current sensor is in a second application debugging state, the working process of the zero-flux current sensor is controlled by an analog signal to obtain the to-be-measured current. The application solves the combination problem of double-microwave low-temperature drift driving and zero-flux control technology, avoids the risk of large calculation amount, long calculation time and poor stability when directly combined, and improves the use performance of a nitrogen-vacancy color center sensor.

Description

Technical Field

[0001] This application relates to the field of smart grid technology, and in particular to a zero flux current sensor based on dual microwave drive. Background Technology

[0002] Nitrogen-vacancy centers (NV centers), as quantum spin systems in diamond, can achieve high-precision magnetic measurements through photodetector magnetic resonance, and are currently being tested for microcurrent detection ranging from 10 mA to 100 A. The magnetic fields of these currents are weak and susceptible to environmental magnetic noise interference. Typically, they need to be paired with a magnetic ring to enhance the effective magnetic field and shield against interference. However, the magnetic ring exhibits nonlinear response and hysteresis, leading to significant current measurement errors. Furthermore, the magnetic resonance characteristics of NV centers are temperature-sensitive; laser irradiation and changes in ambient temperature can cause temperature drift, resulting in low-frequency noise and reading drift in the magnetic field measurement, affecting measurement stability.

[0003] In existing technologies, the zero-flux scheme can generate a reverse magnetic field through a feedback coil to cancel the magnetic field to be measured, avoiding the hysteresis and nonlinearity errors of the magnetic ring. Dual microwave drive and automatic frequency tracking technology utilize the difference between the two resonant frequencies of the NV color center to calculate the magnetic field, eliminating the influence of temperature on zero-field splitting and achieving low-drift magnetic measurement. However, directly combining these two schemes requires demodulating two fluorescent signals separately, locking the dual resonant frequencies, and controlling the secondary feedback current based on the frequency difference. This results in problems such as high computational load, high delay, and limited response speed; rapid changes in current can easily lead to tracking failure. Furthermore, the dual closed-loop cascaded control may induce self-excited oscillations, reducing system stability and noise performance, making it difficult to simultaneously meet the requirements of high precision, low drift, and stable and reliable current measurement.

[0004] In summary, the technical problems existing in the relevant technologies need to be improved. Summary of the Invention

[0005] The main objective of this application is to propose a zero-flux current sensor based on dual microwave drive, which can solve the problem of combining dual microwave low-temperature drift drive and zero-flux control technology, avoid the risks of large computational load, long computation time and poor stability when directly combined, and improve the performance of nitrogen-vacancy color center sensor.

[0006] To achieve the above objectives, one aspect of this application proposes a zero-flux current sensor based on dual microwave driving. The control scheme of the zero-flux current sensor is selected according to the application scenario and debugging requirements of the zero-flux current sensor. When the zero flux current sensor is in the first application debugging state, the operation process of the zero flux current sensor is controlled by digital signals to obtain the current to be measured. When the zero flux current sensor is in the second application debugging state, the operation of the zero flux current sensor is controlled by analog signals to obtain the current to be measured.

[0007] In some embodiments, when controlling the operation of the zero flux current sensor via the digital signal, the zero flux current sensor includes: A fluorescence signal acquisition module, which is used to acquire the fluorescence signal output by the nitrogen-vacancy color center sensor; A dual-channel phase-locked amplification and demodulation module, comprising a first phase-locked amplification adjustment unit and a second phase-locked amplification adjustment unit, wherein the first phase-locked amplification adjustment unit and the second phase-locked amplification adjustment unit are respectively used to demodulate the fluorescence signal and output a first demodulated signal and a second demodulated signal; A digital subtraction operation module is used to receive the first demodulated signal and the second demodulated signal, and perform a weighted subtraction operation on the first demodulated signal and the second demodulated signal based on a preset ratio coefficient to obtain an error control signal; A digital integral control module is provided, which receives the error control signal and performs integral calculation on the error control signal to obtain the closed-loop control quantity. A digital-to-analog converter module is used to receive the closed-loop control quantity and convert the closed-loop control quantity into an analog secondary current; A secondary feedback coil is wound on a magnetic ring. The secondary feedback coil is used to receive the simulated secondary current and generate a reverse magnetic field in the magnetic ring according to the simulated secondary current to cancel the magnetic field generated by the current under test. A current sampling module is used to collect the actual value of the secondary current and calculate the current to be measured based on the actual value of the secondary current.

[0008] In some embodiments, the first phase-locked amplification adjustment unit and the second phase-locked amplification adjustment unit in the dual-channel phase-locked amplification and demodulation module respectively include an analog-to-digital conversion unit, a digital multiplier unit, and a finite impulse response filter unit; The analog-to-digital conversion unit is used to convert the fluorescence signal into a digital fluorescence signal; The digital multiplier unit is used to receive a reference square wave signal with a specified frequency and phase output from the general input / output channel, and to perform multiplication calculation on the digital fluorescent signal and the reference square wave signal to obtain a mixed signal. The finite impulse response filtering unit is used to perform low-pass filtering on the mixing signal and then extract the demodulated signal to obtain the first demodulated signal and the second demodulated signal.

[0009] In some embodiments, the current sampling module includes a current sensing resistor, an analog-to-digital converter, and a resistor-capacitor filter unit; The current-sensing resistor is connected in series in the output circuit of the secondary current, and the current-sensing resistor is used to convert the actual value of the secondary current into an analog voltage signal. The analog-to-digital conversion unit is used to acquire the voltage signal across the current sensing resistor and convert the analog voltage signal into a digital current sampling signal. The resistor-capacitor filter unit filters the digital current sampling signal and outputs a secondary current sampling value. The measured current is obtained by calculating based on the sampled value of the secondary current and the number of turns of the secondary feedback coil.

[0010] In some embodiments, when the preset proportional coefficient is set to match the gyromagnetic ratio and demodulation gain of the two resonant frequencies of the nitrogen-vacancy color center sensor, the error control signal is only related to the magnetic field transformation generated by the current under test.

[0011] In some embodiments, the error control signal satisfies the following formula:

[0012] in, This represents the actual value of the secondary current output from the digital-to-analog converter to the secondary feedback coil during the nth control cycle. This represents the actual value of the secondary current after the update in the (n+1)th control cycle. and These represent the preset proportional coefficients for closed-loop control. This represents the first demodulated signal output by the first phase-locked amplifier and modulation unit in the dual-channel phase-locked amplifier and demodulation module during the nth control cycle. This indicates the second demodulated signal output by the second phase-locked amplifier and demodulation unit in the dual-channel phase-locked amplifier and demodulation module during the nth control cycle.

[0013] In some embodiments, the zero flux current sensor further includes a parameter configuration module and a measurement cycle control module; The parameter configuration module is used to configure the initial microwave frequency, modulation frequency, feedback control coefficient, feedback control period, and initial value of feedback coil drive voltage before the measurement begins. The measurement cycle control module is used to control the dual-channel lock-in amplification and demodulation module to read and demodulate the fluorescence signal of the nitrogen-vacancy color center sensor in each control cycle, generate the first demodulated signal and the second demodulated signal, and calculate the error control signal by the digital subtraction operation module based on the average value of the first demodulated signal and the second demodulated signal. The error control signal is superimposed on the feedback coil drive voltage of the previous cycle and then output to the digital-to-analog converter module.

[0014] In some embodiments, when the operation of the zero flux current sensor is controlled by the analog signal, the zero flux current sensor includes: A microwave driving module includes a first microwave source, a second microwave source, and a combiner. The first microwave source and the second microwave source respectively output a first microwave signal and a second microwave signal. After being combined by the combiner, a combined signal is obtained. The combined signal is input to a nitrogen-vacancy color center sensor, and the nitrogen-vacancy color center sensor generates a fluorescence signal based on the combined signal. A magnetic ring is sleeved on the conductor of the current to be measured to concentrate the magnetic field generated by the conductor of the current to be measured. The nitrogen-vacancy color center sensor is disposed in the magnetic circuit of the magnetic ring. A dual-channel analog phase-locked demodulation module includes a first phase-locked amplification and adjustment unit and a second phase-locked amplification and adjustment unit. The first phase-locked amplification and adjustment unit and the second phase-locked amplification and adjustment unit respectively receive the fluorescence signal and a first reference signal and a second reference signal with corresponding configured phases. After mixing and low-pass filtering the fluorescence signal, the module outputs a first demodulated signal and a second demodulated signal. The differential amplifier module receives the first demodulated signal and the second demodulated signal, performs differential subtraction on the two demodulated signals, and outputs an error control signal. The differential subtraction operation is used to offset the common-mode change of the demodulated signal caused by the zero-field splitting temperature drift of the nitrogen-vacancy color center sensor. An analog integral control module is provided, which receives the error control signal and performs analog integral calculation on the error control signal to obtain the closed-loop control quantity. A voltage-controlled current source, which receives the closed-loop control quantity and converts it into an analog secondary current; A secondary feedback coil is wound on the magnetic ring. The secondary feedback coil is used to receive the simulated secondary current and generate a reverse magnetic field in the magnetic ring to cancel the magnetic field generated by the conductor of the current under test. A current sampling module is used to collect the actual value of the secondary current and calculate the current to be measured based on the actual value of the secondary current.

[0015] In some embodiments, when the microwave frequency increases, the first demodulated signal and the second demodulated signal rise or fall synchronously. The phases of the first reference signal and the second reference signal are such that the amplitudes of the resonant peaks of the first demodulated signal and the second demodulated signal are proportional to the sine value of the corresponding demodulation phase.

[0016] In some embodiments, the current sampling module includes a current sensing resistor, a differential amplifier unit, and a high-precision analog-to-digital converter unit; The current-sensing resistor is connected in series in the output circuit of the secondary current, and the current-sensing resistor converts the actual value of the secondary current into an analog voltage signal; The differential amplifier unit differentially amplifies the voltage signal across the current sensing resistor; The high-precision analog-to-digital conversion unit acquires the amplified voltage signal, converts the voltage signal into a secondary current sampling value, and calculates the current to be measured based on the secondary current sampling value. The formula for calculating the current to be measured is:

[0017] in, This indicates the value of the current to be measured. This indicates the number of turns of the secondary feedback coil. This represents the sampled value of the secondary current.

[0018] The embodiments of this application include at least the following beneficial effects: This application provides a zero-flux current sensor based on dual microwave drive. This solution differentiates between digital signal control and analog signal control schemes based on different application scenarios and debugging requirements of the zero-flux current sensor: When the zero-flux current sensor is in the first application debugging state, it is controlled by digital signals to obtain the current to be measured. The difference in fluorescence response amplitude under the two microwave frequencies can be flexibly compensated by software configuration of differentiated feedback coefficients without hardware modification. At the same time, it avoids the risks of large computational load, high delay, and self-excited oscillation caused by two-stage feedback cascade, improving system debugging efficiency and control stability. When the zero-flux current sensor is in the second application debugging state, it is controlled by digital signals to obtain the current to be measured. The amplitude difference can be conveniently compensated by adjusting the demodulation phase of the lock-in amplifier without manually switching the integrator resistor. It relies on a fully analog circuit to achieve delay-free closed-loop control, which has both high anti-interference capability and long-term operational stability. This application effectively solves the combination problem of dual microwave low-temperature drift drive and zero-flux control technology, fundamentally avoiding the technical defects of large computational load, long computation time, and poor system stability when directly combined. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a zero-flux magnetic sensor for measuring nitrogen-vacancy color centers; Figure 2 This is a schematic diagram of a circuit structure based on microwave resonant frequency and output frequency; Figure 3 This is a schematic diagram of the circuit structure of a zero-flux current sensor controlled by digital signals. Figure 4 This is a schematic diagram of the circuit structure of a zero-flux current sensor controlled by analog signals. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit it. In the following description, when referring to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with those of this application; they are merely examples of apparatuses and methods consistent with some aspects of the embodiments of this application as detailed in the appended claims.

[0021] It is understood that the terms “first,” “second,” etc., used in this application may be used herein to describe various concepts, but unless otherwise stated, these concepts are not limited by these terms. These terms are only used to distinguish one concept from another. For example, without departing from the scope of the embodiments of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the words “if,” “when,” or “in response to a determination” as used herein may be interpreted as “when…” or “when…” or “in response to a determination.”

[0022] As used in this application, the terms "at least one", "multiple", "each", "any", etc., "at least one" includes one, two or more, "multiple" includes two or more, "each" refers to each of the corresponding multiples, and "any" refers to any one of the multiples.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing embodiments of this application only and is not intended to limit this application.

[0024] In related technologies, such as Figure 1 and Figure 2 As shown, in the field of high-precision current measurement based on nitrogen-vacancy color centers (NV color centers), the hysteresis effect and nonlinear response of the magnetic ring 120, and the temperature drift of NV color center magnetic measurement are the two core technical bottlenecks restricting measurement accuracy. To address the nonlinearity and hysteresis issues in the current-magnetic field response caused by the magnetic ring, a zero-flux magnetic measurement scheme can effectively suppress related measurement errors. The structure is as follows: Figure 1As shown, this scheme uses a magnetic ring 120 to enclose the conductor 110 of the current to be measured, and arranges the NV color center sensor 130 inside the magnetic ring. A laser drive excites the NV color center to generate a fluorescence signal. After photoelectric detection 150 and modulation / demodulation 160, the signal is controlled by a secondary current drive 170 to provide a secondary current to the secondary feedback coil 140 wound on the magnetic ring. This secondary current generates a reverse magnetic field within the magnetic ring to counteract the magnetic field changes of the current to be measured, maintaining the net magnetic field at the NV color center sensor at zero. This avoids triggering nonlinearity and hysteresis effects of the magnetic ring. Only the secondary current voltage divider data needs to be collected through the current sensing resistor 181 and the analog-to-digital converter 182 (ADC), combined with the secondary feedback... The number of coil turns can be converted into the current to be measured, realizing high-precision current measurement. For the temperature drift problem of magnetic measurement of NV color centers, the special temperature drift characteristics of its dual resonant frequencies can be used to realize anti-temperature drift detection: the two resonant frequencies of NV color centers coincide at 2.87GHz (zero field split) under zero magnetic field and room temperature conditions. After applying an external magnetic field, the two resonant frequencies will separate symmetrically, with a frequency shift rate of about 2.8MHz / Gs (gyromagnetic ratio). Temperature changes will only change the zero field split at a rate of about -74kHz / ℃, and the gyromagnetic ratio is almost unaffected by temperature. Therefore, by simultaneously measuring the two resonant frequencies and calculating the frequency difference to invert the magnetic field strength, the influence of temperature drift can be eliminated, realizing low-temperature magnetic drift measurement.

[0025] In practical applications, dual microwave drives are often used in conjunction with automatic frequency tracking technology, and the hardware circuit structure is as follows: Figure 2As shown, this scheme employs a dual-channel microwave system, configuring different modulation reference frequencies for the two microwave channels to achieve frequency modulation of the output microwaves. The fluorescence signal output from the NV color center is sampled by an ADC, and the first reference signal 211 and the second reference signal 212 are mixed with the corresponding reference signals by the first digital multiplier 221 and the second digital multiplier 222, respectively, within the FPGA chip. Then, the signals are processed by the first digital filter 223, the second digital filter 224, the first data sampler 225, and the second data sampler 226 to obtain two demodulated signals. The first PID calculator 227 and the second PID calculator 228 respectively provide feedback control of the two microwave output frequencies, locking them to the two resonant frequencies of the NV color center. Finally, the magnetic field strength data of the low temperature drift is obtained by dividing the difference between the two resonant frequencies by 5.6MHz / Gs. This achieves low temperature drift measurement while improving the range and response speed of magnetic field measurement. After completing the closed-loop control of the two microwave frequencies, the first phase-locked loop 231 and the second phase-locked loop 232 continuously lock the reference, providing a stable reference for the first direct digital frequency synthesizer 233 and the second direct digital frequency synthesizer 234. The first direct digital frequency synthesizer 233 and the second direct digital frequency synthesizer 234 output microwave signals that are precisely matched with the dual resonant frequencies of the NV color centers according to the frequency commands fed back by the first phase-locked loop 231 and the second phase-locked loop 232. After being up-converted to the target frequency band by the first mixer 235 and the second mixer 236, the microwave signal is synthesized by the combiner 237 and input to the NV color center sensor 238 to continuously excite it to generate a fluorescence signal. The fluorescence signal output by the NV color center sensor is sampled and converted into a digital signal by the analog-to-digital converter 239, and then sent back to the FPGA chip. It is then split into two paths and fed into the first digital multiplier 221 and the second digital multiplier 222, respectively, and mixed with the first reference signal 211 and the second reference signal 212. After being filtered by the first digital filter 223 and the second digital filter 224, and sampled by the first data sampler 225 and the second data sampler 226, the demodulated signal is fed back to the first PID calculator 227 and the second PID calculator 228 for calculation, forming a complete closed loop.

[0026] However, directly combining zero-flux control with dual microwave drive to simultaneously address the issues of nonlinearity / hysteresis in magnetic rings and temperature drift of the NV color center presents significant technical drawbacks: the direct combination scheme requires first configuring the demodulation frequencies of the two microwave channels, demodulating the fluorescence signal to obtain two demodulated data streams, and then using the two demodulated data streams to control the output frequencies of the two microwave channels, locking them to the two resonant frequencies of the NV color center. Subsequently, the frequency difference between the two microwave frequencies is calculated, and a secondary feedback current is configured based on the change in frequency difference to offset the magnetic field changes caused by the measured current, thereby achieving zero-flux control. Finally, the magnitude of the secondary feedback current is read, and the measured current is calculated in conjunction with the number of turns of the secondary feedback coil. The entire feedback control process is a two-stage feedback closed-loop cascade, which not only significantly increases the computational load and computational delay, but also raises the sensor power consumption and reduces the system frequency response speed. It is also prone to tracking failure when the current changes rapidly and may induce self-excited oscillation, severely degrading the system's stability and noise performance.

[0027] In view of this, this application provides a zero flux current sensor based on dual microwave drive. In order to combine the dual microwave drive scheme into the zero flux control structure, this scheme proposes two architectures: analog signal control and digital signal control. Both can solve the combination problem of dual microwave low temperature drift drive and zero flux control technology, avoiding the risks of large computational load, long computation time and poor stability when directly combined, and improving the functionality of nitrogen-vacancy color center sensor.

[0028] The control scheme for the zero-flux current sensor is selected differently based on the actual application scenario and debugging requirements: When the zero-flux current sensor is in the first application debugging state, a digital signal control scheme is used to acquire the measured current. The operational requirements in this first application debugging state include the need for flexible compensation of the fluorescence response amplitude difference of the nitrogen-vacancy color center sensor at two microwave frequencies, frequent adjustment of control parameters, requirement for automated calibration and data upload, or specific requirements for system power consumption, response speed, and anti-self-oscillation performance. When the zero-flux current sensor is in the second application debugging state, an analog control scheme is used to acquire the measured current. The operational requirements in this second application debugging state include pursuing the ultimate closed-loop response speed, possessing high anti-interference capability, requiring a simplified operation and maintenance mode, or only needing to complete phase calibration once to achieve long-term stable operation. By matching the corresponding control scheme according to different application debugging states, the advantages of digital signal control in terms of flexible parameter configuration and automated calibration can be combined with the characteristics of analog signal control in terms of response speed, anti-interference, and long-term stable operation, adapting to the efficient and reliable application of the zero-flux current sensor in different scenarios.

[0029] like Figure 3As shown, the zero-flux current sensor controlled by digital signals, with the NV color center sensor as its core, relies on a fully digital closed-loop control architecture to achieve low-temperature drift and high-precision zero-flux current measurement without microwave frequency locking and calculation. The core of the NV color center sensor consists of seven functional units: a fluorescence signal acquisition module, a dual-channel phase-locked amplifier and demodulation module, a digital subtraction operation module, a digital integration control module, a digital-to-analog conversion module, a secondary feedback coil, and a current sampling module. These units are cascaded through digital signal links to form a complete closed-loop control circuit.

[0030] During operation, the NV color center sensor generates a fluorescence signal upon microwave excitation. This signal is acquired by the fluorescence signal acquisition module and then input to the dual-channel lock-in amplification and demodulation module. This module contains two completely independent lock-in amplification and modulation units: a first lock-in amplification and modulation unit and a second lock-in amplification and modulation unit. These two units demodulate the same fluorescence signal in parallel, outputting the first demodulated signal. With the second demodulated signal Two demodulated signals are synchronously input to the digital subtractor 317 in the digital subtraction module. The digital subtractor 317 performs a weighted subtraction operation on the two signals based on preset proportional coefficients KP1 and KP2, generating an error control signal. Its core calculation formula is as follows:

[0031] in, This represents the actual value of the secondary current output from the digital-to-analog converter module to the secondary feedback coil during the nth control cycle. This represents the actual value of the secondary current updated within the (n+1)th control cycle. The error control signal is input to the digital integral control module, where the digital integrator 318 performs integration to generate a closed-loop control quantity. The digital-to-analog converter (DAC1) 319 then converts the digital control signal into an analog secondary current, which is output to the secondary feedback coil 320 wound on a magnetic ring. The secondary coil generates a compensating magnetic field within the magnetic ring that is opposite to the magnetic field of the current being measured, canceling out changes in the magnetic field of the current being measured and maintaining a zero net magnetic field at the NV color center sensor. This fundamentally avoids measurement errors caused by the nonlinear response and hysteresis effect of the magnetic ring. Finally, the actual value of the secondary current is acquired by the current sampling module, and the magnitude of the current being measured is calculated by combining this with the number of turns in the secondary coil. Throughout the closed-loop control process, the sensor does not calculate the microwave resonant frequency of the NV color center, nor does it control the output frequency of the microwave system. It directly controls the secondary current through the weighted difference of the two demodulated signals, completely solving the problems of calculation delay and self-oscillation caused by cascaded two-stage feedback in existing technologies.

[0032] Figure 3In this module, the dual-channel lock-in amplification and demodulation module is the core unit for realizing cryogenic magnetic drift measurement. Its two lock-in amplification and demodulation units are completely symmetrical. Each unit consists of a three-stage structure: an analog-to-digital converter (ADC1), a digital multiplier, and a finite impulse response (FIR) filter. First, the ADC1 converts the analog fluorescence signal (VL) output from the fluorescence signal acquisition module into a digital multiplier. fluo The analog-to-digital domain conversion is achieved by converting the signal into a digital fluorescent signal. Subsequently, the digital multiplier unit (digital multiplier 1 / digital multiplier 2) receives the reference square wave signal output from the corresponding first general-purpose input / output channel 311 and the second general-purpose input / output channel 312. The reference square wave is pre-configured with a specified frequency (freq1 / freq2) and phase (phase1 / phase2). The first digital multiplier 313 and the second digital multiplier 314 perform multiplication and mixing operations on the digital fluorescent signal and the reference square wave signal to complete the quadrature demodulation of the signal. Finally, the mixed signal is input to the first FIR filter 315 and the second FIR filter 316 in the finite impulse response filter unit. After low-pass filtering, the low-frequency demodulated signal related to the magnetic field and temperature is extracted, and the first demodulated signal and the second demodulated signal are output respectively. The two demodulated signals can be simultaneously uploaded to the host computer for system status monitoring and parameter calibration.

[0033] Among them, the matching of preset proportional coefficients KP1 and KP2 is the key to achieving anti-temperature drift: the coefficients are precisely matched according to the gyromagnetic ratio of the two resonant frequencies of the NV color center and the demodulation gain of the two lock-in amplifier units, so that the result of the weighted subtraction operation is only linearly related to the magnetic field change generated by the current under test, completely offsetting the common-mode temperature drift caused by the zero-field splitting of the NV color center with temperature change. Low-temperature magnetic drift measurement can be achieved without locking the microwave frequency and calculating the frequency difference, while retaining the high-precision advantage of zero flux control.

[0034] The current sampling module is located at the end of the closed-loop control and is responsible for the accurate acquisition of the secondary current and the conversion of the measured current. Its structure is as follows: Figure 3 As shown in the lower right corner of the signal chain, it consists of three parts: a current sensing resistor 321, an analog-to-digital converter (ADC3) 322, and a resistor-capacitor (RC) filter unit. The current sensing resistor is connected in series in the output circuit of the secondary current Iout, converting the actual value of the secondary current into a corresponding analog voltage signal based on Ohm's law. The ADC3 acquires the voltage signal across the current sensing resistor and converts the analog voltage signal into a digital current sampling signal. Subsequently, the digital signal is input to the RC filter 323 in the RC filter unit, where it undergoes low-pass filtering to suppress high-frequency noise and interference, outputting a stable secondary current sampling value. The sampling data can also be uploaded to a host computer for real-time calculation and recording of the measured current.

[0035] In the zero-flux closed-loop state, the total magnetic flux within the magnetic ring is zero. According to the ampere-turn balance principle, the measured primary current and the secondary feedback current satisfy the conversion relationship Ip = Ns × Iout, where Ns represents the number of turns in the secondary feedback coil. Therefore, by simply obtaining the actual value of the secondary current Iout through the current sampling module, the magnitude of the measured primary current can be quickly and accurately calculated, thus completing the current measurement function. The entire system relies on a fully digital signal control architecture, enabling flexible configuration of control parameters and precise control of the closed-loop response. It also avoids the cumbersome process of manually adjusting the integrator weights in analog signal control schemes, combining high stability, high sensitivity, and ease of debugging. It is suitable for high-precision micro-current measurement scenarios with a wide range of 10mA-100A.

[0036] In some embodiments, the closed-loop control process of the zero-flux current sensor controlled by digital signals is based on fully digital cyclic control. Relying on a complete link of parameter pre-configuration, periodic demodulation calculation, closed-loop feedback iteration, and real-time current calculation, it achieves high-precision and low-temperature drift current measurement without microwave frequency locking and calculation. Based on the fluorescence signal acquisition module, dual-channel phase-locked amplification and demodulation module, digital subtraction operation module, digital integration control module, digital-to-analog conversion module, secondary feedback coil, and current sampling module, a parameter configuration module and a measurement cycle control module are added, forming a complete closed-loop logic from parameter initialization to cyclic measurement. Throughout the process, the microwave resonant frequency of the NV color center is not calculated, nor is the output frequency of the microwave system controlled. The secondary current is directly controlled through feedback from the calculation of two demodulated signals, fundamentally avoiding the problems of calculation delay and self-oscillation caused by the two-stage feedback cascade in existing technologies.

[0037] After the measurement is started, the parameter configuration module first completes the initial parameter configuration of the entire system, which includes: initial microwave frequencies f1 and f2, modulation frequencies fm1 and fm2, feedback control coefficients Kp1 and Kp2, feedback control period TFB, and initial value of feedback coil drive voltage Vs[0]. Among them, the feedback control coefficients Kp1 and Kp2 are differentiated configurations, used to compensate for the difference in fluorescence signal response amplitude of NV color centers at microwave frequencies f1 and f2. This is one of the core advantages of digital signal control scheme compared with analog signal control scheme: analog scheme requires manual switching of integrator resistor to adjust weight, which is cumbersome to debug, while digital scheme only needs to configure coefficients through software to complete amplitude compensation without hardware modification, which greatly improves debugging efficiency and flexibility.

[0038] After parameter configuration, the system enters the cyclic measurement state, and the measurement cycle control module executes periodic closed-loop control: First, it determines whether the measurement has ended. If not, in the Nth cycle, the dual-channel lock-in amplifier demodulation module is controlled to read the fluorescence data of the NV color center, and the fluorescence signal is demodulated using modulation frequencies fm1 and fm2 respectively to obtain two demodulated voltages V1[N] and V2[N]. Subsequently, based on the average values ​​Ave(V1[N]) and Ave(V2[N]) of the two demodulated voltages, the feedback current increment KVs[N] is calculated by the digital subtraction operation module. The calculation formula is KVs[N] = Kp1 × Av e(V1[N])+Kp2×Ave(V2[N]), this increment is the error control signal. Its weighted operation can cancel the temperature drift of the NV color center and retain only the effective error component related to the magnetic field to be measured. Then, this increment is superimposed on the feedback coil driving voltage Vs[N-1] of the previous cycle to generate the driving voltage Vs[N] of the current cycle. The calculation formula is Vs[N]=Vs[N-1]+KVs[N], which completes the digital integral closed-loop control. The updated driving voltage is output to the digital-to-analog conversion module to drive the secondary feedback coil to generate a reverse compensation magnetic field to cancel the magnetic field of the current to be measured and realize zero magnetic flux closed loop.

[0039] After the closed-loop feedback of each control cycle is completed, the current sampling module synchronously performs real-time calculation of the current to be measured: it reads the current sensing voltage VFB[N] from the current sensing resistor connected in series in the secondary feedback coil circuit, and combines it with the number of turns Ns of the secondary feedback coil and the resistance value Rs of the current sensing resistor, and calculates the current to be measured Ip[N] for the Nth control cycle using the formula Ip[N]=Ns×VFB[N]÷Rs. This calculation is based on the ampere-turn balance principle under zero magnetic flux, that is, the magnetomotive force of the primary current to be measured and the magnetomotive force of the secondary feedback current completely cancel each other out. Therefore, the current to be measured can be accurately calculated using only the sampled value of the secondary current, fundamentally eliminating the measurement error caused by the nonlinearity and hysteresis effect of the magnetic ring. At the same time, the current sampling module supports real-time uploading of sampling data, realizing continuous monitoring and recording of the current to be measured, and adapting to the high-precision measurement requirements of microcurrents with a wide range (10mA~100A).

[0040] The digital signal control scheme, through parameterized configuration and a fully digital cyclic control architecture, firstly achieves the core advantages of the zero-flux scheme in suppressing magnetic ring errors and dual demodulation signals in suppressing temperature drift, while completely eliminating microwave frequency locking and calculation steps, simplifying the control chain, eliminating the risk of self-excited oscillation in two-stage feedback, and improving system response speed and stability. Secondly, it allows for software configuration of differentiated feedback coefficients, replacing the cumbersome manual adjustment of hardware resistors in analog schemes, significantly reducing system debugging difficulty and improving the flexibility and repeatability of parameter configuration. It combines high sensitivity, low temperature drift, high stability, and ease of debugging.

[0041] In some embodiments, such as Figure 4 As shown, the analog signal-controlled zero-flux current sensor, with an NV color center sensor as its core, relies on a fully analog closed-loop architecture to achieve low-temperature drift and high-precision zero-flux current measurement without digital computation or microwave frequency locking / calculation. The core consists of nine functional units: a microwave drive module, an NV color center sensor, a magnetic ring, a dual-channel analog phase-locked demodulation module, a differential amplifier module, an analog integral control module, a voltage-controlled current source, a secondary feedback coil, and a current sampling module. The entire process is controlled through analog hardware in a closed-loop manner, eliminating the need for user intervention in digital computation and parameter iteration. High-precision current measurement can be achieved simply by configuring the phases of the first reference signal 411 and the second reference signal 412. This fundamentally avoids the computational delay and self-oscillation problems inherent in digital signal control schemes, while also solving the pain point of cumbersome weight adjustment in traditional analog integrators.

[0042] During operation, the microwave drive module outputs a first microwave signal 413 and a second microwave signal 414, which are combined by a combiner 415 and input to the NV color center sensor 416 to excite the NV color centers to generate fluorescence signals. A magnetic ring 417 is fitted onto the conductor 418 under test to concentrate the magnetic field generated by the current under test. The probe of the NV color center sensor is placed inside the magnetic circuit of the magnetic ring to sense the magnetic field and output fluorescence signals. The dual-channel analog phase-locked demodulation module includes two independent phase-locked amplifier and adjustment units. The two units receive the fluorescence signal and correspondingly configured phase reference signals 411 and 412, respectively. The fluorescence signals are mixed and low-pass filtered by a first filter 419 and a second filter 420 to output the first demodulated signal and the second demodulated signal. Two demodulated signals are input to the split amplifier 421 in the differential amplifier module. After differential subtraction, an error control signal is generated. This operation completely cancels the common-mode variation of the demodulated signal caused by the zero-field splitting temperature drift of the NV color center, achieving low-temperature magnetic drift measurement. The error control signal is input to the analog integrator 422 in the analog integration control module. After analog integration, a closed-loop control quantity is generated. The voltage-controlled current source 423 (V / I conversion unit) then converts the control quantity into an analog secondary current, which is output to the secondary feedback coil 424 (N=1500 turns) wound on the magnetic ring. The secondary coil generates a compensating magnetic field within the magnetic ring that is opposite to the magnetic field of the conductor under test, canceling the magnetic field changes of the conductor and maintaining a zero net magnetic field at the NV sensor. This fundamentally avoids measurement errors caused by the nonlinear response and hysteresis effect of the magnetic ring. Finally, the actual value of the secondary current is acquired by the current sampling module, and the magnitude of the current under test is calculated by combining it with the number of turns of the secondary coil, completing the current measurement function.

[0043] The dual-channel analog phase-locked demodulation module is the core unit for achieving low temperature drift and amplitude compensation. The reference signal phases of its two phase-locked amplifier units need to be specially configured through microwave frequency sweeping to meet two core requirements: First, the resonant peaks of the fluorescent demodulated signals (microwave 1 and microwave 2) after demodulation of reference signal 1 and reference signal 2 have the same trend, that is, as the microwave frequency increases, the two demodulated signals rise or fall synchronously, and there should be no opposite trends, to ensure that the differential subtraction operation can effectively cancel the common-mode temperature drift; Second, the amplitudes of the two demodulated signals are proportional to the sine value of their respective demodulation phases. The phases need to be adjusted to make the amplitudes of the two resonant peaks as equal as possible, while maximizing the amplitude of the resonant peaks, to ensure measurement sensitivity and temperature drift cancellation effect.

[0044] Compared to the cumbersome operation of traditional analog schemes that require manually switching integrator resistors to adjust the accumulation weights, this scheme can proportionally reduce the demodulated signal amplitude by adjusting the demodulation phase of the lock-in amplifier. This compensates for the difference in fluorescence response amplitude of the NV color center at the two microwave frequencies without modifying the hardware circuit, significantly simplifying the system debugging process. After meeting the phase requirements, the two demodulated signals are subtracted in the differential amplifier, completely canceling out the common-mode change caused by temperature drift. Only the differential-mode error signal related to the magnetic field under test is retained, enabling low-temperature magnetic drift measurement. At the same time, there is no need to lock / calculate the microwave resonant frequency of the NV color center, simplifying the control link.

[0045] The current sampling module is located at the end of the closed-loop control and is responsible for the accurate acquisition of the secondary current and the conversion of the measured current. Its structure is as follows: Figure 4 As shown in the lower right corner of the signal chain, it consists of three parts: a current-sensing resistor 425, a differential amplifier unit 426, and a high-precision analog-to-digital converter unit 427 (24-bit ADC). The current-sensing resistor is connected in series in the secondary current output circuit, converting the actual value of the secondary current into a corresponding analog voltage signal based on Ohm's law. The differential amplifier unit differentially amplifies the voltage signal across the current-sensing resistor, effectively suppressing common-mode interference and improving the signal-to-noise ratio. The high-precision 24-bit ADC acquires the amplified voltage signal and converts the analog voltage signal into a digital secondary current sampling value, which is used to calculate the magnitude of the current to be measured.

[0046] In the zero-flux closed-loop state, the total magnetic flux within the magnetic ring is zero. According to the ampere-turn balance principle, the measured primary current Ip and the secondary feedback current Is satisfy the conversion relationship Ip = N × Is, where N is the number of turns in the secondary feedback coil (N = 1500 turns in this scheme). Therefore, by simply obtaining the secondary current sampling value Is through the current sampling module, the magnitude of the measured current Ip can be quickly and accurately calculated, completing the current measurement function. Simultaneously, the outputs of the two phase-locked loop demodulation units also output CW spectrum fluorescence signals through 16-bit ADCs for phase calibration and system status monitoring, achieving system debuggability and maintainability.

[0047] The core innovation of the analog signal control scheme lies in overcoming the dual pain points of cumbersome integrator weight debugging in traditional analog schemes and computational delay and self-oscillation in digital schemes. Through a fully analog closed-loop circuit architecture, combined with reference signal phase configuration, amplitude compensation and temperature drift cancellation are achieved. While retaining the core advantages of zero-flux schemes in suppressing magnetic ring errors and dual demodulation signals in suppressing temperature drift, it achieves an extremely simplified control link without digital computation or microwave frequency lock-in. The entire process is implemented through analog hardware, offering fast response speed and strong anti-interference capabilities. No user intervention is required for digital signal control and parameter iteration; debugging can be completed simply by configuring the reference signal phase. It combines high stability, high sensitivity, and ease of debugging, making it suitable for high-precision micro-current measurement scenarios with a wide range of 10mA to 100A.

[0048] In some embodiments, the digital signal control architecture, with a fully digital closed loop as its core, achieves high-precision, low-delay current measurement of the NV color center sensor. The fluorescence signal emitted by the NV color center is acquired by a lock-in amplifier module and demodulated at two different reference frequencies to obtain two independent demodulation voltages V1[N] and V2[N]. To address the potential difference in fluorescence response amplitude between the NV color center at the two microwave frequencies, different scaling factors K are configured for the two signals. p1 and K p2 The system eliminates amplitude deviation through gain compensation calculation; then, it directly calculates the increment of the secondary feedback coil drive voltage using the compensated signal, updates the secondary feedback current in real time, and maintains the magnetic field inside the magnetic ring in a zero-flux state, fundamentally avoiding the nonlinearity and hysteresis errors of the magnetic ring; finally, the system directly reads the voltage VFB[N] on the current sensing resistor, combines the number of turns of the secondary coil and the resistance value of the current sensing resistor, and calculates the magnitude of the primary current to be measured, thus completing the current measurement. This architecture abandons the complex automatic frequency tracking calculation process, significantly shortens the data processing path, improves the dynamic response capability of the NV color center sensor, accurately tracks rapidly changing currents, and reduces computational power consumption; at the same time, it optimizes the traditional dual-cascade feedback into a single-loop direct-drive feedback, eliminating the risk of self-excited oscillation easily caused by cascade control from the root, effectively reducing system noise, improving overall robustness, and providing a flexible digital implementation scheme for sensor hardware development.

[0049] The analog signal control architecture relies on a fully hardware circuit to achieve closed-loop control, providing a high-response and easily debugged engineering solution for the NV color core current sensor. The fluorescence signal output by the NV color core is demodulated by hardware with reference signal 1 and reference signal 2 respectively. The core lies in the precise configuration of the demodulation phase: through microwave frequency sweep calibration, the resonance peak trends of the two demodulated signals are ensured to be consistent (synchronously rising or falling when the microwave frequency changes), and the phase is adjusted to make the amplitude of the two resonance peaks as equal as possible and maximized, while compensating for the amplitude difference of the two fluorescence responses. After calibration, the two demodulated signals are input to a differential amplifier for subtraction. Since the signal change caused by temperature drift is a common-mode signal in the same direction in both channels, the temperature drift is naturally eliminated after subtraction, realizing low-temperature magnetic drift measurement. The pure error signal after subtraction is directly input to the analog integrator, which controls the voltage-controlled current source to drive the secondary feedback coil to generate feedback current, maintain the zero magnetic flux state of the magnetic ring, and cancel the nonlinearity and hysteresis error of the magnetic ring. Users only need to read the voltage division of the secondary side current sensing resistor through the analog-to-digital converter (ADC) to calculate the magnitude of the current to be measured. The pure hardware architecture of analog signal control eliminates the need for digital computation and microwave frequency locking. The entire process is completed autonomously by analog circuits, which combines high response speed and strong anti-interference capability, while simplifying the debugging process.

[0050] The control architecture combining digital and analog signal control solves the nonlinear / hysteresis errors of the magnetic ring and the temperature drift error of the diamond, achieving extremely high-precision current measurement. Both architectures eliminate the complex automatic frequency tracking calculation process, significantly shortening the data processing path and enabling the sensor to have better dynamic response capabilities, accurately tracking rapidly changing currents while significantly reducing computational power consumption. By optimizing the traditional dual-cascade feedback into a single-loop direct-drive feedback, the risk of self-excited oscillation easily caused by cascade control is fundamentally eliminated, effectively reducing system noise and significantly improving system robustness. Both digital and analog signal control are also provided as flexible engineering implementation options.

[0051] The embodiments described in this application are for the purpose of more clearly illustrating the technical solutions of the embodiments of this application, and do not constitute a limitation on the technical solutions provided by the embodiments of this application. As those skilled in the art will know, with the evolution of technology and the emergence of new application scenarios, the technical solutions provided by the embodiments of this application are also applicable to similar technical problems.

[0052] Those skilled in the art will understand that the technical solutions shown in the figures do not constitute a limitation on the embodiments of this application, and may include more or fewer steps than shown, or combine certain steps, or different steps.

[0053] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0054] Those skilled in the art will understand that all or some of the steps in the methods disclosed above, as well as the functional modules / units in the systems and devices, can be implemented as software, firmware, hardware, or suitable combinations thereof.

[0055] It should be understood that in this application, "at least one (item)" means one or more, and "more than" means two or more. "And / or" is used to describe the relationship between related objects, indicating that three relationships can exist. For example, "A and / or B" can represent three cases: only A exists, only B exists, and both A and B exist simultaneously, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one (item) of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one (item) of a, b, or c can represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, and c can be single or multiple.

[0056] In the several embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of the units described above is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0057] The units described above as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0058] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0059] The preferred embodiments of the present application have been described above with reference to the accompanying drawings, but this does not limit the scope of the claims of the present application. Any modifications, equivalent substitutions, and improvements made by those skilled in the art without departing from the scope and substance of the embodiments of the present application shall be within the scope of the claims of the present application.

Claims

1. A zero-flux current sensor based on dual microwave drive, characterized in that, The control scheme for the zero flux current sensor is selected based on the application scenario and debugging requirements of the zero flux current sensor: When the zero flux current sensor is in the first application debugging state, the operation process of the zero flux current sensor is controlled by digital signals to obtain the current to be measured. When the zero flux current sensor is in the second application debugging state, the operation of the zero flux current sensor is controlled by analog signals to obtain the current to be measured.

2. The zero-flux current sensor based on dual microwave drive according to claim 1, characterized in that, When controlling the operation of the zero flux current sensor via the digital signal, the zero flux current sensor includes: A fluorescence signal acquisition module, which is used to acquire the fluorescence signal output by the nitrogen-vacancy color center sensor; A dual-channel phase-locked amplification and demodulation module, comprising a first phase-locked amplification adjustment unit and a second phase-locked amplification adjustment unit, wherein the first phase-locked amplification adjustment unit and the second phase-locked amplification adjustment unit are respectively used to demodulate the fluorescence signal and output a first demodulated signal and a second demodulated signal; A digital subtraction operation module is used to receive the first demodulated signal and the second demodulated signal, and perform a weighted subtraction operation on the first demodulated signal and the second demodulated signal based on a preset ratio coefficient to obtain an error control signal; A digital integral control module is provided, which receives the error control signal and performs integral calculation on the error control signal to obtain the closed-loop control quantity. A digital-to-analog converter module is used to receive the closed-loop control quantity and convert the closed-loop control quantity into an analog secondary current; A secondary feedback coil is wound on a magnetic ring. The secondary feedback coil is used to receive the simulated secondary current and generate a reverse magnetic field in the magnetic ring according to the simulated secondary current to cancel the magnetic field generated by the current under test. A current sampling module is used to collect the actual value of the secondary current and calculate the current to be measured based on the actual value of the secondary current.

3. The zero-flux current sensor based on dual microwave drive according to claim 2, characterized in that, The first and second lock-in amplification adjustment units in the dual-channel lock-in amplification and demodulation module respectively include an analog-to-digital conversion unit, a digital multiplier unit, and a finite impulse response filter unit. The analog-to-digital conversion unit is used to convert the fluorescence signal into a digital fluorescence signal; The digital multiplier unit is used to receive a reference square wave signal with a specified frequency and phase output from the general input / output channel, and to perform multiplication calculation on the digital fluorescent signal and the reference square wave signal to obtain a mixed signal. The finite impulse response filtering unit is used to perform low-pass filtering on the mixing signal and then extract the demodulated signal to obtain the first demodulated signal and the second demodulated signal.

4. The zero-flux current sensor based on dual microwave drive according to claim 2, characterized in that, The current sampling module includes a current sensing resistor, an analog-to-digital conversion unit, and a resistor-capacitor filtering unit. The current-sensing resistor is connected in series in the output circuit of the secondary current, and the current-sensing resistor is used to convert the actual value of the secondary current into an analog voltage signal. The analog-to-digital conversion unit is used to acquire the voltage signal across the current sensing resistor and convert the analog voltage signal into a digital current sampling signal. The resistor-capacitor filter unit filters the digital current sampling signal and outputs a secondary current sampling value. The measured current is obtained by calculating based on the sampled value of the secondary current and the number of turns of the secondary feedback coil.

5. The zero-flux current sensor based on dual microwave drive according to claim 2, characterized in that, When the preset proportional coefficient is set to match the gyromagnetic ratio and demodulation gain of the two resonant frequencies of the nitrogen-vacancy color center sensor, the error control signal is only related to the magnetic field transformation generated by the current under test.

6. The zero-flux current sensor based on dual microwave drive according to claim 2, characterized in that, The error control signal satisfies the following formula: in, This represents the actual value of the secondary current output from the digital-to-analog converter to the secondary feedback coil during the nth control cycle. This represents the updated actual value of the secondary current during the (n+1)th control cycle. and These represent the preset proportional coefficients for closed-loop control. This represents the first demodulated signal output by the first phase-locked amplifier and modulation unit in the dual-channel phase-locked amplifier and demodulation module during the nth control cycle. This represents the second demodulated signal output by the second phase-locked amplifier and demodulation unit in the dual-channel phase-locked amplifier and demodulation module during the nth control cycle.

7. The zero-flux current sensor based on dual microwave drive according to claim 2, characterized in that, The zero flux current sensor also includes a parameter configuration module and a measurement cycle control module; The parameter configuration module is used to configure the initial microwave frequency, modulation frequency, feedback control coefficient, feedback control period, and initial value of feedback coil drive voltage before the measurement begins. The measurement cycle control module is used to control the dual-channel lock-in amplification and demodulation module to read and demodulate the fluorescence signal of the nitrogen-vacancy color center sensor in each control cycle, generate the first demodulated signal and the second demodulated signal, and calculate the error control signal by the digital subtraction operation module based on the average value of the first demodulated signal and the second demodulated signal. The error control signal is superimposed on the feedback coil drive voltage of the previous cycle and then output to the digital-to-analog converter module.

8. The zero-flux current sensor based on dual microwave drive according to claim 1, characterized in that, When controlling the operation of the zero flux current sensor via the analog signal, the zero flux current sensor includes: A microwave driving module includes a first microwave source, a second microwave source, and a combiner. The first microwave source and the second microwave source respectively output a first microwave signal and a second microwave signal. After being combined by the combiner, a combined signal is obtained. The combined signal is input to a nitrogen-vacancy color center sensor, and the nitrogen-vacancy color center sensor generates a fluorescence signal based on the combined signal. A magnetic ring is sleeved on the conductor of the current to be measured to concentrate the magnetic field generated by the conductor of the current to be measured. The nitrogen-vacancy color center sensor is disposed in the magnetic circuit of the magnetic ring. A dual-channel analog phase-locked demodulation module includes a first phase-locked amplification and adjustment unit and a second phase-locked amplification and adjustment unit. The first phase-locked amplification and adjustment unit and the second phase-locked amplification and adjustment unit respectively receive the fluorescence signal and a first reference signal and a second reference signal with corresponding configured phases. After mixing and low-pass filtering the fluorescence signal, the module outputs a first demodulated signal and a second demodulated signal. The differential amplifier module receives the first demodulated signal and the second demodulated signal, performs differential subtraction on the two demodulated signals, and outputs an error control signal. The differential subtraction operation is used to offset the common-mode change of the demodulated signal caused by the zero-field splitting temperature drift of the nitrogen-vacancy color center sensor. An analog integral control module is provided, which receives the error control signal and performs analog integral calculation on the error control signal to obtain the closed-loop control quantity. A voltage-controlled current source, which receives the closed-loop control quantity and converts it into an analog secondary current; A secondary feedback coil is wound on the magnetic ring. The secondary feedback coil is used to receive the simulated secondary current and generate a reverse magnetic field in the magnetic ring to cancel the magnetic field generated by the conductor of the current under test. A current sampling module is used to collect the actual value of the secondary current and calculate the current to be measured based on the actual value of the secondary current.

9. The zero-flux current sensor based on dual microwave drive according to claim 8, characterized in that, As the microwave frequency increases, the first demodulated signal and the second demodulated signal rise or fall synchronously. The phases of the first reference signal and the second reference signal are such that the amplitudes of the resonant peaks of the first demodulated signal and the second demodulated signal are proportional to the sine value of the corresponding demodulation phase.

10. The zero-flux current sensor based on dual microwave drive according to claim 8, characterized in that, The current sampling module includes a current sensing resistor, a differential amplifier unit, and a high-precision analog-to-digital converter unit; The current-sensing resistor is connected in series in the output circuit of the secondary current, and the current-sensing resistor converts the actual value of the secondary current into an analog voltage signal; The differential amplifier unit differentially amplifies the voltage signal across the current sensing resistor; The high-precision analog-to-digital conversion unit acquires the amplified voltage signal, converts the voltage signal into a secondary current sampling value, and calculates the current to be measured based on the secondary current sampling value. The formula for calculating the current to be measured is: in, This indicates the value of the current to be measured. This indicates the number of turns of the secondary feedback coil. This represents the sampled value of the secondary current.

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