A differential non-diagonal giant magnetoimpedance current sensor, test system and current measurement method

Abstract

The application relates to a differential non-diagonal giant magnetoimpedance current sensor, a test system and a current measurement method, which comprises two non-diagonal giant magnetoimpedance current sensors with the same structure and based on the same working principle, the independent annular soft magnetic strips on the sensors and the solenoid coil are used to avoid the influence of the soft magnetic material itself on the measurement process; a compensation wire through which a current with the same size and opposite direction to the current in the wire to be measured is arranged to filter the disturbance of the geomagnetic field on the current measurement; meanwhile, a signal processing unit is arranged to carry out denoising and differential amplification processing on the induced voltage signals from the two non-diagonal giant magnetoimpedance current sensors, eliminate the disturbance of the geomagnetic field, suppress the common-mode noise of the magnetic sensor, and significantly improve the current detection precision and anti-interference ability of the sensor. The application focuses on the common problem of geomagnetic field interference in current measurement, effectively eliminates the interference signals while keeping the characteristics of simple sensor structure and high sensitivity.

Description

Technical Field

[0001] This invention relates to the field of electrical measurement technology, and in particular to a differential off-diagonal giant magnetoresistance current sensor, a testing system, and a current measurement method. Background Technology

[0002] In power electronics systems and industrial automation, accurate current measurement is crucial. Non-contact current detection methods infer current magnitude by measuring the magnetic field generated around a current-carrying conductor. They are widely used due to their advantages of not interfering with the measured circuit and not affecting the normal operation of the system. Common non-contact current sensors include Hall effect sensors, Rogowski coils, and fluxgate sensors. However, Hall effect elements suffer from large temperature drift and limited sensitivity; Rogowski coils are only suitable for AC measurements and require sophisticated winding processes; and fluxgate sensors are bulky and consume a lot of power.

[0003] In recent years, magnetic sensors based on the giant magneto-impedance (GMI) effect have become a research hotspot due to their advantages such as high sensitivity, fast response, and small size. The GMI effect refers to the phenomenon that the AC impedance of a soft magnetic material changes significantly with the applied magnetic field when a high-frequency alternating current is passed through it. Current sensors made using this effect can infer the magnitude of the current by measuring the magnetic field around a current-carrying conductor.

[0004] Existing GMI current sensors employing differential or shielded structures are mostly based on diagonal measurement modes, which suffer from hysteresis problems; or they use physical shielding to resist interference, increasing structural complexity. Addressing the common challenge of geomagnetic field interference in current measurement, how to effectively eliminate interference signals in non-diagonal measurement modes while maintaining the sensor's simple structure and high sensitivity is a problem urgently needing to be solved by those skilled in the art. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a differential off-diagonal giant magnetoresistance current sensor, a testing system, and a current measurement method, which solves the limitations of traditional methods such as hysteresis problems and high structural complexity.

[0006] To achieve the above technical objectives, the present invention provides the following technical solution: a differential off-diagonal giant magnetoresistance current sensor, comprising: The first off-diagonal giant magnetoresistive current sensor and the second off-diagonal giant magnetoresistive current sensor have the same working principle and structure. The conductor carrying the current to be measured passes through the geometric center of the first off-diagonal giant magnetoresistance current sensor along the axial direction to allow the current to be measured to pass through. A compensating wire is connected in series with the current-to-be-measured wire and carries a compensating current of the same magnitude but opposite direction to the current-to-be-measured; the compensating wire passes through the geometric center of the second off-diagonal giant magnetoresistance current sensor along the axial direction. The signal source, whose excitation output terminal is electrically connected to the excitation signal inflow terminals of the first off-diagonal giant magnetoresistive current sensor and the second off-diagonal giant magnetoresistive current sensor respectively, is used to provide the same AC excitation current to the first off-diagonal giant magnetoresistive current sensor and the second off-diagonal giant magnetoresistive current sensor. The signal processing unit has its signal input terminal electrically connected to the signal output terminals of the first off-diagonal giant magnetoresistive current sensor and the second off-diagonal giant magnetoresistive current sensor, respectively, and its reference input terminal connected to the reference signal output terminal of the signal source. It is used to combine the reference signal from the signal source to perform noise reduction and differential amplification processing on the two induced voltage signals from the first off-diagonal giant magnetoresistive current sensor and the second off-diagonal giant magnetoresistive current sensor, thereby eliminating the interference of the geomagnetic field and suppressing the common-mode noise of the magnetic sensor.

[0007] Optionally, both the first off-diagonal giant magnetoresistive current sensor and the second off-diagonal giant magnetoresistive current sensor include: A ring-shaped soft magnetic strip, with an open ring structure, serves as a magnetic sensitive element; The solenoid coil is uniformly wound on the annular soft magnetic strip; The excitation signal inflow end and the excitation signal outflow end are respectively located at both ends of the annular soft magnetic strip. The excitation signal inflow end is used to connect to the AC excitation current provided by the signal source. The signal output terminal is located at both ends of the solenoid coil and is used to output the induced voltage signal to the signal processing unit.

[0008] Optionally, the annular soft magnetic ribbon is a cobalt-based amorphous ribbon, which has been annealed at 653K for 8 hours and its surface has been thinned by hydrofluoric acid etching to 1.5±0.1μm.

[0009] Optionally, both the current-to-be-tested conductor and the compensation conductor are arranged perpendicular to the annular plane of the annular soft magnetic strip.

[0010] The present invention also provides a test system for the aforementioned differential off-diagonal giant magnetoresistance current sensor, comprising: A sine wave signal generation module and a V / I conversion module are used to form a signal source; The first phase-locked amplifier module, the second phase-locked amplifier module, the differential amplifier module, and the data acquisition module are used to form a signal processing unit. The sinusoidal signal generating module is used to generate a high-frequency sinusoidal voltage signal with an adjustable frequency in the range of 100kHz to 1MHz, and its reference signal output terminal serves as the reference signal output terminal of the signal source. The V / I conversion module has its input terminal connected to the sinusoidal signal generation module to receive a high-frequency sinusoidal voltage signal. Its output terminal serves as the excitation output terminal of the signal source and is connected to the excitation signal input terminals of the first off-diagonal giant magnetoresistive current sensor and the second off-diagonal giant magnetoresistive current sensor, respectively. It is used to convert the high-frequency sinusoidal voltage signal generated by the sinusoidal signal generation module into an AC excitation current with an adjustable amplitude in the range of 1mA to 10mA, and provide it to the first off-diagonal giant magnetoresistive current sensor and the second off-diagonal giant magnetoresistive current sensor. The input terminals of the first lock-in amplifier module and the second lock-in amplifier module serve as the signal input terminals of the signal processing unit, and are respectively connected to the signal output terminals of the first off-diagonal giant magnetoresistive current sensor and the second off-diagonal giant magnetoresistive current sensor. Both the first and second phase-locked-loop amplifier modules have their reference input terminals connected to the reference signal output terminal of the sinusoidal signal generation module. They use the high-frequency sinusoidal voltage signal from the sinusoidal signal generation module as a reference signal to extract the first induced voltage amplitude related to the magnetic field of the current under test from the two noisy induced voltage signals from the first and second off-diagonal giant magnetoresistive current sensors. Second induced voltage amplitude ; The differential amplifier module has its first input terminal connected to the output terminal of the first lock-in amplifier module, and its second input terminal connected to the output terminal of the second lock-in amplifier module, for processing the extracted first induced voltage amplitude. Second induced voltage amplitude Perform differential amplification and output the difference signal. ; The data acquisition module has its input end connected to the output end of the differential amplifier module, and its output end connected to the host computer. It is used to perform digital-to-analog conversion, converting the difference signal output by the differential amplifier module into a digital signal and storing and displaying it.

[0011] Optionally, the V / I conversion module includes a first operational amplifier, a second operational amplifier, a third operational amplifier, a transistor, and a feedback resistor network, forming a voltage-current negative feedback circuit to achieve linear conversion from voltage to current.

[0012] Optionally, both the first and second phase-locked loop amplifier modules include a multiplier and a low-pass filter connected in sequence. The multiplier is used to multiply the induced voltage signal with a reference signal, and the cutoff frequency of the low-pass filter is set to one ten-thousandth of the frequency of the AC excitation current to filter out high-frequency components and noise and extract the DC component.

[0013] Optionally, the sampling frequency of the data acquisition module is set to be more than 500 times the frequency of the high-frequency sinusoidal voltage signal generated by the sinusoidal signal generation module.

[0014] The present invention also provides a current measurement method for the test system, comprising: S1. Pass the current to be measured into the conductor of the current to be measured, and at the same time pass the compensation current into the compensation conductor, which is the same in magnitude but opposite in direction to the current to be measured. S2. Start the signal source to generate AC excitation current, and simultaneously drive the first off-diagonal giant magnetoresistive current sensor and the second off-diagonal giant magnetoresistive current sensor. S3. The first off-diagonal giant magnetoresistive current sensor generates a first induced voltage signal containing the magnetic field component of the measured current and the geomagnetic field component at both ends of the solenoid coil; the second off-diagonal giant magnetoresistive current sensor generates a second induced voltage signal containing the reverse magnetic field component of the measured current and the geomagnetic field component at both ends of the solenoid coil. S4. The first and second phase-locked loop (PLL) amplifier modules, combined with the reference signal from the sine wave signal generation module, filter noise from the first and second induced voltage signals to generate the amplitude of the first induced voltage. Second induced voltage amplitude ; S5, Differential amplifier module measures the amplitude of the first induced voltage. Second induced voltage amplitude Perform differential amplification to obtain the difference signal. The mathematical representation is as follows: ; in The difference signal is the amplification factor. It is proportional to the amplitude of the current being measured; S6, Data acquisition module acquires difference signal After analog-to-digital conversion, the data is sent to the host computer for display and analysis.

[0015] Optionally, in step S5, the amplification factor is adjusted. , the difference signal The amplitude is adjusted to the optimal input range of the data acquisition module.

[0016] By employing the above technical solution, the present invention provides a differential off-diagonal giant magnetoresistance current sensor, a testing system, and a current measurement method, which has at least the following beneficial effects: (1) The present invention adopts an off-diagonal measurement mode. The AC excitation current is applied to both ends of the annular soft magnetic thin strip, and the induced voltage signal is taken out from both ends of the solenoid coil that is independent of the annular soft magnetic thin strip. This structure of excitation and detection separation makes the final output voltage signal come from electromagnetic induction rather than the nonlinear change of the impedance of the soft magnetic material itself, thereby avoiding the influence of the inherent hysteresis loop of the soft magnetic material on the measurement results. (2) The dual-sensor-dual-wire differential structure proposed in this invention is an innovative electrical anti-interference scheme. By using two off-diagonal giant magnetoresistive current sensors with similar structures and electromagnetic characteristics to form a differential measurement structure, the first off-diagonal giant magnetoresistive current sensor is exposed to "the signal to be measured + geomagnetic noise", and the second off-diagonal giant magnetoresistive current sensor is exposed to "the reverse signal to be measured + geomagnetic noise". After the two signals are differentially amplified, the geomagnetic field component is eliminated and the magnetic field component of the current to be measured is enhanced, thereby effectively mitigating the interference of the geomagnetic field on the current measurement. At the same time, this invention can also effectively suppress the common-mode noise of magnetic sensing and further improve the detection accuracy. (3) The sensor probe of the present invention consists only of a ring-shaped soft magnetic thin strip and a solenoid coil. It has a simple structure and mature manufacturing process. It does not require complex semiconductor processes such as precision photolithography and coating, so it is easy to achieve mass production and low cost. At the same time, the non-contact measurement method ensures the safety of operation under high pressure environment, making it very suitable for a wide range of industrial applications such as industrial field power monitoring, smart grid, new energy management, electric vehicle battery management, and aerospace power systems. Attached Figure Description

[0017] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a schematic diagram of a differential off-diagonal giant magnetoresistive current sensor according to the present invention; Figure 2 This is a schematic diagram of the off-diagonal giant magnetoresistance current sensor structure of the present invention; Figure 3 This is a schematic diagram of the annular soft magnetic thin strip structure of the present invention; Figure 4 This is a schematic diagram of the solenoid coil structure of the present invention; Figure 5 This is a block diagram of the overall architecture of the test system in an embodiment of the present invention.

[0018] The labels in the attached figures are as follows: 1-First off-diagonal giant magnetoresistive current sensor, 2-Second off-diagonal giant magnetoresistive current sensor, 3-Current under test wire, 4-Compensation wire, 5-Signal source, 6-Signal processing unit, 7-Annular soft magnetic strip, 8-Solenoid coil. Detailed Implementation

[0019] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. This will allow for a full understanding of how the present application uses technical means to solve technical problems and achieve technical effects, and to facilitate its implementation.

[0020] Please refer to Figures 1-5 This illustration shows a specific implementation of the present embodiment. This embodiment uses two off-diagonal giant magnetoresistive current sensors with identical structures and based on the same working principle. Independent annular soft magnetic strips and solenoid coils on the sensors are used to avoid the influence of the soft magnetic material itself on the measurement process. A compensating conductor carrying a current of the same magnitude but opposite direction to that in the conductor carrying the current to be measured is used to filter out interference from the Earth's magnetic field on the current measurement. Simultaneously, a signal processing unit is used to denoise and differentially amplify the induced voltage signals from the two off-diagonal giant magnetoresistive current sensors, eliminating interference from the Earth's magnetic field and suppressing common-mode noise of the magnetic sensors, significantly improving the current detection accuracy and anti-interference capability of the sensors.

[0021] Please refer to Figure 1 This embodiment proposes a differential off-diagonal giant magnetoresistive current sensor, comprising: The first off-diagonal giant magnetoresistive current sensor 1 and the second off-diagonal giant magnetoresistive current sensor 2 adopt the same structural design and have undergone strict screening and matching to ensure that their electromagnetic characteristics are similar, so as to ensure that they have similar output responses under the same excitation and magnetic field environment, thereby ensuring the effect of subsequent differential processing.

[0022] The current-to-be-measured conductor 3 passes through the geometric center of the first off-diagonal giant magnetoresistive current sensor 1 along the axial direction to allow the current to be measured to pass through, thereby generating a ring magnetic field around it according to the Biot-Savart law. The strength of this magnetic field is proportional to the current to be measured. The first off-diagonal giant magnetoresistive current sensor 1 senses the superimposed magnetic field of the magnetic field to be measured and the Earth's magnetic field.

[0023] The compensating wire 4 is connected in series with the current-to-be-measured wire 3, so the current flowing through it is exactly the same as the current to be measured. However, by adjusting the wiring direction, the current direction is reversed to form a compensating current. The compensating wire 4 passes through the geometric center of the second off-diagonal giant magnetoresistive current sensor 2 axially to ensure that the magnetic fields generated at the location of the second off-diagonal giant magnetoresistive current sensor 2 are equal in magnitude and opposite in direction.

[0024] Signal source 5, whose excitation output terminal is electrically connected to the excitation signal inflow terminals of the first off-diagonal giant magnetoresistive current sensor 1 and the second off-diagonal giant magnetoresistive current sensor 2 respectively, is used to provide AC excitation current with the same frequency and amplitude to the first off-diagonal giant magnetoresistive current sensor 1 and the second off-diagonal giant magnetoresistive current sensor 2.

[0025] The signal processing unit 6 has its signal input terminal electrically connected to the signal output terminals of the first off-diagonal giant magnetoresistive current sensor 1 and the second off-diagonal giant magnetoresistive current sensor 2, respectively, and its reference input terminal connected to the reference signal output terminal of the signal source 5, respectively. It is used to combine the reference signal from the signal source 5 to perform noise reduction and differential amplification processing on the two induced voltage signals from the first off-diagonal giant magnetoresistive current sensor 1 and the second off-diagonal giant magnetoresistive current sensor 2, thereby eliminating geomagnetic field interference and effectively suppressing the common-mode noise of the magnetic sensor.

[0026] The differential off-diagonal giant magnetoresistive current sensor of the present invention, based on the above structure, operates on the following principle: The first off-diagonal giant magnetoresistive current sensor 1 measures the superposition signal of the magnetic field generated by the current-to-be-measured conductor 3 and the Earth's magnetic field; simultaneously, since the magnetic fields generated by the current-to-be-measured conductor 3 and the compensating conductor 4 are equal in magnitude and opposite in direction, the second off-diagonal giant magnetoresistive current sensor 2 measures the superposition signal of the reverse magnetic field generated by the current-to-be-measured conductor 3 and the Earth's magnetic field. The signal processing unit 6 performs noise reduction and differential operations on the two signals, completely eliminating the influence of the Earth's magnetic field and effectively suppressing the common-mode noise of the magnetic sensor; the output signal is only related to the current to be measured.

[0027] Please refer to Figures 2-3 Both the first off-diagonal giant magnetoresistive current sensor 1 and the second off-diagonal giant magnetoresistive current sensor 2 adopt off-diagonal measurement mode, and their specific structures include: The annular soft magnetic strip 7, with an open annular structure, serves as a magnetic sensing element and is the core sensitive part of the entire sensor. Its permeability changes significantly with the external magnetic field, which in turn affects its high-frequency impedance characteristics.

[0028] Solenoid coil 8, please refer to Figure 4 An independent pickup coil is formed by uniformly and tightly winding insulated wires around the outer circumference of the annular soft magnetic strip 7.

[0029] An excitation signal inlet and an excitation signal outlet are respectively located at both ends of the annular soft magnetic strip 7, for receiving the AC excitation current provided by the signal source 5, so that the AC excitation current flows through the soft magnetic strip 7. The excitation signal outlet is connected to a power supply.

[0030] The signal output terminal is located at both ends of the solenoid coil 8 and is used to output the induced voltage signal to the signal processing unit 6.

[0031] This structure, which physically separates the excitation circuit (ring-shaped soft magnetic strip) from the detection circuit (solenoid coil), is called the off-diagonal measurement mode. Compared to the traditional diagonal mode (where excitation and detection share the same pair of electrodes), the output signal of the off-diagonal mode comes from the coil induced voltage, rather than the impedance change of the soft magnetic material itself. Therefore, it fundamentally eliminates the influence of the inherent hysteresis phenomenon of the soft magnetic material on the measurement results.

[0032] The annular soft magnetic thin strip 7 designed in this invention is a cobalt-based amorphous thin strip. This material has a near-zero magnetostriction coefficient, which is beneficial for reducing the influence of stress and temperature on magnetic properties. The specific component selected in this invention is Co. 66 Fe4B 15 Si 15 To achieve a significant GMI effect, the cobalt-based amorphous ribbon needs to undergo annealing at 653K for 8 hours to eliminate internal stress generated during the preparation process and improve magnetic anisotropy. Subsequently, hydrofluoric acid is used to etch the surface of the ribbon to reduce its thickness by 1.5±0.1μm, thereby removing the surface oxide layer and defect layer, further optimizing its high-frequency soft magnetic properties, and improving the sensitivity of the skin effect to changes in permeability.

[0033] Both the current-to-be-measured conductor 3 and the compensation conductor 4 are arranged perpendicular to the annular plane of the annular soft magnetic strip 7. This perpendicular arrangement allows the annular magnetic field generated by the conductor in the energized state to act along the circumferential direction of the annular soft magnetic strip 7 to the maximum extent, thereby most effectively driving the magnetization process, exciting changes in the circumferential permeability, and improving the sensitivity of the sensor. If the conductor is not perpendicular to the plane of the annular soft magnetic strip, the circumferential component of the magnetic field will decrease, leading to a decrease in sensitivity.

[0034] Please refer to Figure 5 This application also provides a test system for the aforementioned differential off-diagonal giant magnetoresistance current sensor, comprising: The sine wave generator module and the V / I converter module are used to form signal source 5.

[0035] The sinusoidal signal generation module is used to generate a high-frequency sinusoidal voltage signal with an adjustable frequency in the range of 100kHz to 1MHz. This frequency range is the frequency band where the GMI effect is most significant. Its reference signal output terminal serves as the reference signal output terminal of the signal source 5.

[0036] The V / I conversion module has its input connected to the sinusoidal signal generation module to receive a high-frequency sinusoidal voltage signal. Its output serves as the excitation output of the signal source 5, and is connected to the excitation signal input of the first off-diagonal giant magnetoresistive current sensor 1 and the second off-diagonal giant magnetoresistive current sensor 2, respectively. It is used to convert the high-frequency sinusoidal voltage signal generated by the sinusoidal signal generation module into an AC excitation current with an adjustable amplitude in the range of 1mA to 10mA. This current amplitude range can ensure that a sufficient magnetic field is generated to drive the soft magnetic strip, but will not cause the strip to heat up due to excessive current and affect its performance. Then, the AC excitation current is provided to the first off-diagonal giant magnetoresistive current sensor 1 and the second off-diagonal giant magnetoresistive current sensor 2.

[0037] The first phase-locked amplifier module, the second phase-locked amplifier module, the differential amplifier module, and the data acquisition module are used to form the signal processing unit 6.

[0038] The input terminals of the first phase-locked amplifier module and the second phase-locked amplifier module serve as the signal input terminals of the signal processing unit 6, and are respectively connected to the signal output terminals of the first off-diagonal giant magnetoresistive current sensor 1 and the second off-diagonal giant magnetoresistive current sensor 2.

[0039] Both the first and second phase-locked loop amplifier modules have their reference input terminals connected to the reference signal output terminal of the sinusoidal signal generation module. Using the high-frequency sinusoidal voltage signal from the sinusoidal signal generation module as a reference signal, they are used to extract the first induced voltage amplitude related to the magnetic field of the current under test from two noisy induced voltage signals from the first off-diagonal giant magnetoresistive current sensor 1 and the second off-diagonal giant magnetoresistive current sensor 2, respectively, based on the principle of coherent detection. Second induced voltage amplitude .

[0040] The differential amplifier module has its first input terminal connected to the output terminal of the first lock-in amplifier module, and its second input terminal connected to the output terminal of the second lock-in amplifier module, for use in adjusting the extracted first induced voltage amplitude as needed. Second induced voltage amplitude Perform differential amplification and output the difference signal. ;

[0041] The data acquisition module has its input end connected to the output end of the differential amplifier module, and its output end connected to the host computer. It is used to perform digital-to-analog conversion, converting the difference signal output by the differential amplifier module into a digital signal for data storage, display, and subsequent analysis.

[0042] The V / I conversion module includes a first operational amplifier, a second operational amplifier, a third operational amplifier, a transistor, and a feedback resistor network, forming a voltage-to-current negative feedback circuit to achieve linear conversion from voltage to current. The working principle of the V / I conversion module is as follows: Input voltage With feedback voltage An error voltage is generated after comparison by the first operational amplifier. This voltage controls the output current of the second operational amplifier and the transistor. ,and The voltage generated across the sampling resistor is buffered by the third operational amplifier to form the feedback voltage. Deep negative feedback ensures the output current. With input voltage It maintains a strictly linear relationship, unaffected by load changes and power supply fluctuations. By appropriately selecting the resistance value of the feedback resistor network, a precise linear conversion from 0-5V input voltage to 0-10mA output current can be achieved.

[0043] In this embodiment, the sampling resistor is a precision resistor (usually connected in series in the output circuit) used to detect the output current. Its function is to convert the output current... Converted to feedback voltage This ensures that the output current is controlled only by the input voltage, and is independent of load changes and power supply fluctuations.

[0044] Both the first and second phase-locked loop (PLL) amplifier modules include a multiplier and a low-pass filter connected in sequence. The multiplier is used to convert the induced voltage signal from the corresponding off-diagonal giant magnetoresistance current sensor into a multiplier. Reference signal with the same frequency and phase Multiplying them yields a mixed signal containing a sum-frequency term and a difference-frequency term, where Indicates induced voltage signal The amplitude; Indicates reference signal The amplitude; Indicates induced voltage signal The angular frequency (unit: rad / s) of the reference signal Their angular frequencies are equal; Indicates time; Indicates induced voltage signal The initial phase, Indicates reference signal The initial phase, Represents the sine operation. This indicates that it is superimposed on the induced voltage signal. Noise on the surface.

[0045] The cutoff frequency of the low-pass filter is set to one ten-thousandth of the frequency of the AC excitation current. For example, for an AC excitation current frequency of 100 kHz, the cutoff frequency of the low-pass filter is set to 10 Hz. This extremely low cutoff frequency can filter out high-frequency noise and sum-frequency components (approximately 200 kHz), retaining only the DC component proportional to the signal amplitude. By adjusting the phase of the reference signal, This allows for the precise extraction of signal amplitude, where This represents the cosine operation.

[0046] The data acquisition module has a sampling frequency set to at least 500 times the frequency of the high-frequency sinusoidal voltage signal generated by the sinusoidal signal generation module. For example, when the frequency of the high-frequency sinusoidal voltage signal is 1MHz, the sampling frequency is set to at least 500MHz. This setting far exceeds the minimum requirement of the Nyquist sampling theorem (which requires the sampling frequency to be no less than twice the highest frequency of the signal), ensuring that the acquired digital signal completely retains the waveform characteristics of the original analog signal, thus laying the foundation for subsequent digital signal processing and high-precision measurement.

[0047] This application embodiment also provides a current measurement method for the test system, including: S1. The current to be measured is passed into the conductor 3, and at the same time, a compensation current with the same magnitude but opposite direction to the current to be measured is passed into the compensation conductor 4 connected in series with the conductor 3.

[0048] S2. Start signal source 5 to generate AC excitation current with stable frequency and amplitude, and simultaneously drive the annular soft magnetic strip 7 of the first off-diagonal giant magnetoresistive current sensor 1 and the second off-diagonal giant magnetoresistive current sensor 2.

[0049] S3. Based on electromagnetic induction and the GMI effect, the solenoid coil 8 of the first off-diagonal giant magnetoresistive current sensor 1 generates a first induced voltage signal containing the magnetic field component of the current to be measured and the geomagnetic field component; at the same time, the solenoid coil 8 of the second off-diagonal giant magnetoresistive current sensor 2 generates a second induced voltage signal containing the reverse magnetic field component of the current to be measured and the geomagnetic field component.

[0050] S4. The first and second phase-locked loop (PLL) amplifier modules, combined with the reference signal from the sine wave signal generation module, filter noise from the first and second induced voltage signals to generate the amplitude of the first induced voltage. Second induced voltage amplitude .

[0051] S5, Differential amplifier module measures the amplitude of the first induced voltage. Second induced voltage amplitude Perform differential amplification to obtain the difference signal. The mathematical representation is as follows: ; in The difference signal is the amplification factor. The amplification factor is proportional to the amplitude of the current being measured. Determined by system parameters, during the actual implementation process, the operator or the host computer can automatically adjust the amplification factor through software commands based on the estimated magnitude of the current to be measured. When the current to be measured is small, increase The value should be reduced to fully utilize the input dynamic range of the data acquisition module; when the measured current is large, the value should be reduced. To prevent signal saturation, this adaptive gain adjustment maintains high measurement accuracy over a wide range.

[0052] S6, Data acquisition module acquires difference signal The data is converted into a digital quantity by a built-in analog-to-digital converter and sent to the host computer via a communication interface. The software running on the host computer processes the data, displays the waveform, calculates the current value, and stores the record, completing the entire measurement process.

[0053] To achieve automated control of the current testing process and intelligent management of measurement data, a software platform developed using the LabVIEW graphical programming language is installed on the host computer. This platform integrates the following functional modules: a hardware driver module for communicating with the data acquisition module and controlling sampling parameters; a data reading module for real-time reading of acquired data; a digital signal processing module for filtering and FFT analysis of the raw data; a user interface module for real-time display of current waveforms, amplitude, frequency, and other information; and a file input / output module for saving measurement data into a universal format file for subsequent analysis and report generation.

[0054] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of those different embodiments or examples.

[0055] The above embodiments provide a detailed description of the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A differential off-diagonal giant magnetoresistive current sensor, characterized in that, include: The first off-diagonal giant magnetoresistive current sensor (1) and the second off-diagonal giant magnetoresistive current sensor (2) have the same working principle and structure. The current to be measured wire (3) passes through the geometric center of the first off-diagonal giant magnetoresistance current sensor (1) along the axial direction to allow the current to be measured to pass through; The compensation wire (4) is connected in series with the current wire (3) to be measured, and carries a compensation current of the same magnitude as the current to be measured but opposite in direction to the current to be measured; the compensation wire (4) passes through the geometric center of the second off-diagonal giant magnetoresistance current sensor (2) along the axial direction; The signal source (5) is electrically connected to the excitation signal input terminals of the first off-diagonal giant magnetoresistive current sensor (1) and the second off-diagonal giant magnetoresistive current sensor (2), respectively, to provide the same AC excitation current to the first off-diagonal giant magnetoresistive current sensor (1) and the second off-diagonal giant magnetoresistive current sensor (2). The signal processing unit (6) has its signal input terminal electrically connected to the signal output terminals of the first off-diagonal giant magnetoresistive current sensor (1) and the second off-diagonal giant magnetoresistive current sensor (2), respectively, and its reference input terminal is connected to the reference signal output terminal of the signal source (5), respectively. It is used to combine the reference signal from the signal source (5) to perform noise reduction and differential amplification processing on the two induced voltage signals from the first off-diagonal giant magnetoresistive current sensor (1) and the second off-diagonal giant magnetoresistive current sensor (2), thereby eliminating the interference of the geomagnetic field and suppressing the common-mode noise of the magnetic sensor.

2. A differential off-diagonal giant magnetoresistive current sensor according to claim 1, characterized in that: Both the first off-diagonal giant magnetoresistive current sensor (1) and the second off-diagonal giant magnetoresistive current sensor (2) include: The annular soft magnetic strip (7) has an open annular structure and serves as a magnetic sensitive element; The solenoid coil (8) is uniformly wound on the annular soft magnetic strip (7); The excitation signal inflow end and the excitation signal outflow end are respectively set at both ends of the annular soft magnetic strip (7), and the excitation signal inflow end is used to connect to the AC excitation current provided by the signal source (5); The signal output terminal is located at both ends of the solenoid coil (8) and is used to output the induced voltage signal to the signal processing unit (6).

3. A differential off-diagonal giant magnetoresistive current sensor according to claim 2, characterized in that: The annular soft magnetic strip (7) is a cobalt-based amorphous strip, which has been annealed at 653K for 8 hours and its surface has been thinned by hydrofluoric acid etching to 1.5±0.1μm.

4. A differential off-diagonal giant magnetoresistive current sensor according to claim 2, characterized in that: Both the current-to-be-tested conductor (3) and the compensation conductor (4) are arranged perpendicular to the annular plane of the annular soft magnetic strip (7).

5. A test system for the differential off-diagonal giant magnetoresistive current sensor according to any one of claims 1-4, characterized in that, include: A sinusoidal signal generation module and a V / I conversion module are used to form a signal source (5); The first phase-locked amplifier module, the second phase-locked amplifier module, the differential amplifier module, and the data acquisition module are used to form a signal processing unit (6). The sinusoidal signal generating module is used to generate a high-frequency sinusoidal voltage signal with an adjustable frequency in the range of 100kHz to 1MHz, and its reference signal output terminal serves as the reference signal output terminal of the signal source (5). The V / I conversion module has its input end connected to the sinusoidal signal generation module to receive a high-frequency sinusoidal voltage signal. Its output end serves as the excitation output end of the signal source (5) and is connected to the excitation signal inflow ends of the first off-diagonal giant magnetoresistive current sensor (1) and the second off-diagonal giant magnetoresistive current sensor (2), respectively. It is used to convert the high-frequency sinusoidal voltage signal generated by the sinusoidal signal generation module into an AC excitation current with an amplitude adjustable in the range of 1mA to 10mA, and provide it to the first off-diagonal giant magnetoresistive current sensor (1) and the second off-diagonal giant magnetoresistive current sensor (2). The input terminals of the first phase-locked amplifier module and the second phase-locked amplifier module serve as the signal input terminals of the signal processing unit (6), and are respectively connected to the signal output terminals of the first off-diagonal giant magnetoresistive current sensor (1) and the second off-diagonal giant magnetoresistive current sensor (2); Both the first and second lock-in amplifier modules have their reference input terminals connected to the reference signal output terminal of the sinusoidal signal generation module. The high-frequency sinusoidal voltage signal from the sinusoidal signal generation module is used as the reference signal to extract the first induced voltage amplitude from the two noisy induced voltage signals from the first off-diagonal giant magnetoresistive current sensor (1) and the second off-diagonal giant magnetoresistive current sensor (2). Second induced voltage amplitude ; The differential amplifier module has its first input terminal connected to the output terminal of the first lock-in amplifier module, and its second input terminal connected to the output terminal of the second lock-in amplifier module, for processing the extracted first induced voltage amplitude. Second induced voltage amplitude Perform differential amplification and output the difference signal. ; The data acquisition module has its input end connected to the output end of the differential amplifier module, and its output end connected to the host computer. It is used to perform digital-to-analog conversion, converting the difference signal output by the differential amplifier module into a digital signal and storing and displaying it.

6. The testing system according to claim 5, characterized in that: The V / I conversion module includes a first operational amplifier, a second operational amplifier, a third operational amplifier, a transistor, and a feedback resistor network, forming a voltage-current negative feedback circuit to achieve linear conversion from voltage to current.

7. A testing system according to claim 5, characterized in that: Both the first phase-locked amplifier module and the second phase-locked amplifier module include a multiplier and a low-pass filter connected in sequence. The multiplier is used to multiply the induced voltage signal with a reference signal. The cutoff frequency of the low-pass filter is set to one ten-thousandth of the frequency of the AC excitation current to filter out high-frequency components and noise and extract the DC component.

8. A testing system according to claim 5, characterized in that: The sampling frequency of the data acquisition module is set to be more than 500 times the frequency of the high-frequency sinusoidal voltage signal generated by the sinusoidal signal generation module, so as to satisfy the Nyquist sampling theorem.

9. A current measurement method for the test system according to any one of claims 6-8, characterized in that, include: S1. Pass the current to be measured into the current-to-be-measured conductor (3), and at the same time pass the compensation conductor (4) with the same magnitude but opposite direction to the current to be measured. S2. Start signal source (5) to generate AC excitation current, and simultaneously drive the first off-diagonal giant magnetoresistive current sensor (1) and the second off-diagonal giant magnetoresistive current sensor (2). S3. The first off-diagonal giant magnetoresistive current sensor (1) generates a first induced voltage signal containing the magnetic field component of the current to be measured and the geomagnetic field component at both ends of the solenoid coil (8); the second off-diagonal giant magnetoresistive current sensor (2) generates a second induced voltage signal containing the reverse magnetic field component of the current to be measured and the geomagnetic field component at both ends of the solenoid coil (8). S4. The first and second phase-locked loop (PLL) amplifier modules, combined with the reference signal from the sine wave signal generation module, filter noise from the first and second induced voltage signals to generate the amplitude of the first induced voltage. Second induced voltage amplitude ; S5, Differential amplifier module measures the amplitude of the first induced voltage. Second induced voltage amplitude Perform differential amplification to obtain the difference signal. The mathematical representation is as follows: ； in The difference signal is the amplification factor. It is proportional to the amplitude of the current being measured; S6, Data acquisition module acquires difference signal After analog-to-digital conversion, the data is sent to the host computer for display and analysis.

10. A current measurement method according to claim 9, characterized in that: In step S5, adjust the amplification factor. , the difference signal The amplitude is adjusted to the optimal input range of the data acquisition module.

Images