FeCuNbSiB thin strip-based weak magnetic field measurement system

Abstract

The invention relates to the field of weak magnetic field detection, in particular to a weak magnetic field measuring system based on a FeCuNbSiB thin strip, which comprises an inner bias circuit based on the FeCuNbSiB thin strip, a Colpitts oscillating circuit, a peak detection circuit, an electronic compass system and a three-dimensional micro magnetic field measuring instrument, the FeCuNbSiB thin strip is prepared through raw material preparation, forming through a single-roller melt spinning method and annealing treatment; the electronic compass system comprises a magneto-sensitive element module, a signal generation module, a peak detection module, a signal acquisition module, an STM32 single chip microcomputer module and an OLED display module, and the magneto-sensitive element module is provided with two orthogonal and vertical GMI sensors; the three-dimensional micro magnetic field measuring instrument is composed of a frame, a lead screw and a motor. The three-dimensional GMI probe comprises three orthogonal GMI sensors. Measurement and analysis of the system cover measurement steps under various magnetic field conditions, high-precision weak magnetic field measurement can be achieved, and the system has wide application prospects in the fields of geological exploration and biomedicine.

Description

Technical Field

[0001] The present invention relates to the field of weak magnetic field detection, and in particular to a weak magnetic field measurement system based on FeCuNbSiB thin strips. Background Art

[0002] Weak magnetic fields generally refer to those with magnetic induction strengths below 10 gauss. Despite their low intensity, limited impact range, and minimal interference with the surrounding environment and equipment, they are of great significance in many fields. For example, they provide information on mineral deposits and geological structures in geological exploration; they are used in the biomedical field for disease diagnosis and treatment; they form the basis of magnetic resonance imaging (MRI); and they serve as a crucial tool in military submarine detection. With technological advancements, the demand for highly sensitive detection of weak magnetic fields is growing. Research is focused on improving sensor sensitivity and reducing susceptibility to environmental interference, exploring more materials and technologies to expand their application areas.

[0003] Magnetic sensors occupy a key position in sensing technology and can convert mechanical energy or electromagnetic energy into electrical energy. Their development mainly includes types such as Hall effect sensors, anisotropic magnetoresistive sensors and superconducting quantum interference devices. Hall sensors use the Hall effect to detect magnetic fields and have high precision and stability, but are easily affected by high temperatures and magnetic field interference, and have hysteresis, making them unable to accurately measure complex magnetic fields. Anisotropic magnetoresistive sensors determine the strength and direction of the magnetic field by measuring the change in resistance of Permalloy thin films. Although their performance is better than traditional Hall sensors, they have problems such as signal size being related to target speed, sensitivity being angle-dependent, and having hysteresis, which affect measurement accuracy and stability. Superconducting quantum interference sensors have extremely high sensitivity and resolution and can measure extremely weak magnetic fields. They are of great significance in scientific research on high-precision magnetic field measurements, but they require low-temperature superconducting conditions and have high manufacturing prices and refrigeration costs, making them difficult to implement.

[0004] The giant magneto-impedance (GMI) effect has garnered widespread attention since its discovery in 1992. It describes the phenomenon in which the impedance of a magnetic material changes significantly when exposed to an applied magnetic field. This phenomenon allows for the enhanced sensitivity of GMI magnetic sensors. Currently, sensors based on this effect developed by Aichi Corporation in Japan are highly sensitive. However, China, a relatively late starter in this field, has achieved some research results, but its performance in weak magnetic fields remains to be improved. Furthermore, related high-precision angle measuring instruments are often expensive or rely on imports. Therefore, developing a high-precision, low-cost device suitable for measuring weak magnetic fields is of great significance. Summary of the Invention

[0005] The purpose of the present invention is to solve the problems in the background technology and provide a weak magnetic field measurement system based on FeCuNbSiB thin ribbon.

[0006] The above technical objectives of the present invention are achieved through the following technical solutions:

[0007] An internal bias circuit design, a Colpitts oscillation circuit design, and a peak detection circuit design based on FeCuNbSiB thin strips; an electronic compass system and a three-dimensional micromagnetic field measuring instrument based on the GMI sensor module; the GMI sensor module is composed of the internal bias circuit module, the Colpitts oscillation circuit module, the peak detection circuit module, the subtraction amplifier circuit module, and the follower circuit module.

[0008] Preferably, the internal bias circuit design based on the FeCuNbSiB thin ribbon is specifically as follows: including a resistor RL1, a resistor RL2, a resistor RL3, an NPN transistor T1 and an inductor L, a +5V power supply and GND; one end of the resistor RL1 is connected to the +5V power supply, and the other end of the resistor RL1 is connected to the base of the NPN transistor T1; one end of the resistor RL2 is connected to the base of the NPN transistor T1, and the other end is grounded; one end of the resistor RL3 is connected to the emitter of the NPN transistor T1, and the other end is grounded; the collector of the NPN transistor T1 is connected to the inductor L, and the other end of the inductor L is connected to the +5V power supply;

[0009] When measuring weak magnetic fields, FeCuNbSiB thin strips will have linear deviation and zero-point offset, affecting the measurement accuracy. The traditional solution is to add a bias coil outside the instrument. Although it can solve the problems of zero-point offset and measurement sensitivity, it will introduce an external magnetic field, resulting in magnetic field non-uniformity, which in turn affects the performance and accuracy of the sensor and produces measurement errors or instability. The present invention is designed based on the theory of electromagnetic induction. By adjusting the RL1 resistor to change the base voltage UB of the NPN transistor T1, since IE=IB+IC, the current IC on the inductor L is changed to achieve precise control of the magnetic field. By calculating the high-sensitivity linear interval in the GMI characteristic curve of the thin strip, adjusting the bias current size, and biasing the zero point to the center of the linear interval, the linear deviation and zero-point offset are effectively reduced, the sensitivity and accuracy of measuring the magnetic field are improved, and the sensor performance is made more stable and reliable.

[0010] Preferably, the Colpitts oscillator circuit based on the FeCuNbSiB thin ribbon is specifically designed as follows: comprising a resistor R1, a resistor R2, a resistor R3, a resistor R4, and a transistor Q1; one end of the resistor R1 is connected to a power supply, and the other end of the resistor R1 is connected to the base of the transistor Q1; one end of the resistor R2 is connected to the base of the transistor Q1, and the other end is grounded; one end of the resistor R3 is connected to the emitter of the transistor Q1, and the other end is grounded; one end of the resistor R4 is connected to the power supply, and the other end is connected to the collector of the transistor Q1;

[0011] Research on the giant magneto-impedance characteristics of the FeCuNbSiB ribbon revealed that it is more sensitive at a drive frequency of 180 kHz. The Colpitts oscillator circuit of the present invention has frequency adjustability. Resistors R1, R2, R3, R4, and transistor Q1, among other components in the circuit, together form a stable oscillator circuit structure. This allows the frequency of the output cross-edge signal to be adjusted to 180 kHz, thereby matching the FeCuNbSiB ribbon and ensuring that the sensor provides a stable, sensitive, and distortion-free signal output during operation.

[0012] Preferably, the peak detection circuit based on the FeCuNbSiB thin ribbon is specifically designed as follows: comprising a diode D1, a resistor RL4, and a capacitor CL3; the anode of the diode D1 receives a signal input, the cathode is connected to the capacitor CL3, and is grounded through the capacitor CL3; one end of the resistor RL4 is connected to the cathode of the diode D1, and the other end is grounded;

[0013] The capacitor CL3 and resistor RL4 in the circuit form a low-pass filter. The non-ideal characteristics will leave some residual high-frequency voltage, which can generally suppress high-frequency interference signals, making the output DC signal more stable and improving the sensitivity and accuracy of subsequent measurements.

[0014] Preferably, the GMI sensor module comprises: the internal bias circuit module, the Colpitts oscillation circuit module, the peak detection circuit module, the subtraction amplifier circuit module and the follower circuit module;

[0015] The internal bias circuit module can accurately control the external magnetic field acting on the thin strip by adjusting the circuit bias, thereby solving the linear deviation and zero point offset problems of the thin strip when measuring weak magnetic fields, biasing the zero point to the center of the linear range, and improving sensitivity and accuracy; the Colpitts oscillation circuit module provides a stable excitation source for the thin strip by adjusting the frequency, so that the thin strip works at the optimal driving frequency, thereby enhancing the response ability of the thin strip to changes in weak magnetic fields, ensuring that the sensor can keenly capture the change information of weak magnetic fields, and improving the accuracy and reliability of measurements; the peak detection circuit module converts the magnetoelectric conversion The AC signal is converted into DC electricity and the signal peak characteristics are extracted. At the same time, its low-pass filtering characteristics can reduce the influence of high-frequency interference and noise, output a stable and pure DC signal, and provide accurate signal input for subsequent circuits, thereby ensuring the quality of the measurement signal and helping to improve measurement accuracy; the subtraction amplifier circuit module effectively suppresses signal interference by differentially amplifying the signal, further enhancing the sensor's ability to detect weak magnetic field signals; the follower circuit module has high input impedance and low output impedance characteristics, which effectively reduces distortion in signal transmission overcharge and ensures the stability and reliability of the entire sensor module.

[0016] Preferably, a method for preparing and processing the FeCuNbSiB thin ribbon comprises the following steps:

[0017] Step S1: preparing raw materials, the composition of which is Fe, Cu, Nb, Si and B, and the ratio of each atom thereof is Fe: 73-74, Cu: 0.5-1.5, Nb: 2.5-3.5, Si: 13-14, B: 8.5-9.5;

[0018] Step S2: The raw material of step S1 is melt-spinned by a single roller to form a thin strip with a length of 19.95 mm to 20.05 mm, a width of 0.44 mm to 0.54 mm, and a thickness of 25 μm to 27 μm;

[0019] Step S3: annealing the ribbon at a temperature of 470° C. to 630° C., and analyzing the magnetic permeability of the FeCuNbSiB ribbon at different annealing temperatures using X-ray imaging. The annealing temperature range for the optimal magnetic permeability is 520° C. to 560° C.

[0020] The atomic ratios of the FeCuNbSiB ribbon raw materials are strictly controlled within the ranges of Fe:73-74, Cu:0.5-1.5, Nb:2.5-3.5, Si:13-14, and B:8.5-9.5, resulting in excellent ribbon properties. During the single-roll melt spinning process, the metal solution is rapidly cooled and solidified by a copper roller into a ribbon. This rapid cooling process helps form a uniform amorphous microstructure. Annealing the ribbon at 530°C-560°C is a key step. XRD analysis of FeCuNbSiB ribbons annealed at different temperatures reveals that within this temperature range, the ribbons exhibit a moderate degree of crystallization, with a distinct crystallization peak. This temperature range also results in the lowest coercivity and highest magnetic permeability.

[0021] Preferably, the electronic compass system based on the GMI sensor module includes a magnetic sensor module, a signal generation circuit module, a peak detection module, a signal acquisition module, an STM32 single-chip microcomputer module and an OLED display module; in the magnetic sensor module, there are two GMI sensors that are orthogonal to each other;

[0022] The magnetic sensitive element module contains two orthogonal GMI sensors. When the angle between the direction of the geomagnetic field and the sensor changes, the sensor impedance will also change, causing the voltage to change. In the signal generating circuit module and the peak detection module, the peak detection module converts the AC oscillation signal of the signal generating circuit module into a DC signal, removes the interference in the AC signal, and improves the stability of the signal. The signal acquisition module and the STM32 single-chip microcomputer module accurately calculate the angle between the geomagnetic field and the sensor axis according to the voltage changes of the two orthogonal sensors, thereby realizing accurate geomagnetic azimuth measurement. The OLED display module realizes the visualization of the geomagnetic azimuth angle.

[0023] Preferably, a three-dimensional micromagnetic field measuring instrument based on the GMI sensor module includes: a frame, an x-axis screw, a first y-axis screw, a second y-axis screw, a z-axis screw, a first stepper motor, a second stepper motor, a third stepper motor, a fourth stepper motor, a three-dimensional GMI probe, a display system and a control box; the third stepper motor and the fourth stepper motor are symmetrically fixed on both sides of the top of the back side of the frame; the first y-axis screw and the third stepper motor are connected to the two ends inside the frame; the second y-axis screw and the fourth stepper motor are connected to the two ends inside the frame; one end of the x-axis screw is connected to the slider of the first y-axis screw; the other end of the x-axis screw is connected to the second stepper motor; the second stepper motor is connected to the slider of the second y-axis screw; the first stepper motor is connected to the slider of the x-axis screw; the z-axis screw is connected to the first stepper motor; the three-dimensional GMI probe is connected to the slider of the z-axis screw; the control box is fixed on the right side of the frame; the control box has the display system;

[0024] The x-axis screw, the first y-axis screw, the second y-axis screw, and the z-axis screw are cleverly arranged with the corresponding stepper motors to form a three-dimensional motion control system. The first stepper motor drives the z-axis screw through the slider of the x-axis screw, thereby controlling the position of the three-dimensional GMI probe in the x-direction; the second stepper motor is connected to the sliders of the x-axis screw and the second y-axis screw to realize the movement of the probe in the y-direction; the third stepper motor and the fourth stepper motor drive the first y-axis screw and the second y-axis screw respectively, and coordinately adjust the position of the probe in the y-direction. This layout makes the movement of the probe in three-dimensional space more precise and stable, and the coordinated work of the axis screws and motors can achieve high-precision spatial positioning.

[0025] Preferably, the weak magnetic field measurement and analysis method comprises the following steps:

[0026] Step V1: Measure the voltage response of the GMI sensor as the magnetic field of the Helmholtz coil changes;

[0027] Step V1.1: Place a compass on the Helmholtz axis so that the Helmholtz axis is perpendicular to the geomagnetic north and south poles.

[0028] Step V1.2: Connect the circuit of the experimental setup: Use wires to connect the power supply, Helmholtz coil, GMI sensor, and data acquisition equipment;

[0029] Step V1.3: Place the GMI sensor vertically in the middle of the Helmholtz axis and obtain the magnetic field magnitude when the Helmholtz coil is not energized.

[0030] Step V1.4: Wait for the GMI sensor voltage to stabilize, then change the voltage of the Helmholtz instrument to change the magnitude of the weak magnetic field and record the change in the sensor voltage value.

[0031] Step V1.5: Repeat the above steps five times without changing the position of the GMI sensor.

[0032] Step V2: Measure the GMI sensor changes with the geomagnetic field;

[0033] Step V2.1: Use the direction of the geomagnetic North Pole as the test reference point, and evenly divide the circular plane into 9° steps to calibrate the geomagnetic direction.

[0034] Step V2.2: Use a compass to calibrate so that the north direction coincides with 0° on the circular surface;

[0035] Step V2.3: Rotate the GMI geomagnetic sensor 360° clockwise starting from 0° and measure the change in output voltage.

[0036] Step V2.4: Use Arduino to collect the output voltage of the GMI sensor and plot the GMI sensor response voltage and the distribution of the Earth's magnetic field.

[0037] Step V2.5: Rotate 360° counterclockwise to reset to the initial position and measure the change in output voltage.

[0038] Step V2.6: Use Arduino to collect the output voltage of the GMI sensor and plot the GMI sensor response voltage and the distribution of the Earth's magnetic field.

[0039] Step V3: Repeatability and hysteresis measurement of GMI;

[0040] Step V3.1: Change the current direction and adjust the current of the Helmholtz coil so that the applied magnetic field changes from positive to negative between 0 and 350 mA, and record the output voltage signal of the GMI sensor;

[0041] Step V3.2: Change the current direction and adjust the current of the Helmholtz coil so that the applied magnetic field changes from negative to positive between 0 and 350 mA, and record the output voltage signal of the GMI sensor;

[0042] Step V3.3: Repeat the operations of steps V3.1-V3.2;

[0043] Step V4: electronic compass angle algorithm processing;

[0044] Step V4.1: Rotate 360° to obtain the voltage and angle relationship diagram of the GMI sensor;

[0045] Step V4.2: Perform linear fitting on the waveform output by the GMI sensor, determine the sensitivity and functional relationship of different angle ranges according to different regions, and use the angle algorithm to determine the angle value; the functional relationship of the region is Y=kX+b, and the angle value k is the slope, b is the intercept, and V is the probe output voltage;

[0046] Step V5: three-dimensional weak magnetic field distribution map;

[0047] Step V5.1: Use Arduino to collect the real-time x, y, and z coordinates of the Hall probe in the 3D micromagnetic field measurement instrument and the voltages of the three GMI components;

[0048] Step V5.2: After collecting the GMI voltage, perform analog-to-digital conversion and substitute it into the characteristic equation to obtain the magnetic induction intensity;

[0049] Step V5.3: Perform vector synthesis on the three magnetic induction intensity components to obtain the magnitude and direction of the total magnetic induction intensity. The vector synthesis is as follows: use three mutually orthogonal GMI sensors to measure the magnetic induction intensity of three directions at a certain position in the magnetic field as B. x ,B y ,B z , and according to the formula Get the magnitude of magnetic induction intensity;

[0050] Step V5.4: The Raspberry Pi first reads the data point values transmitted by the Arduino and saves the value points using the pre-stored matrix;

[0051] Step V5.5: Use the Origin function to fit the cubic function to draw the weak magnetic field. Use the Spectral function to create a mapping between data values and colors based on the radiation emittance values represented by the A array. Use the colorbar function to use this mapping to assign corresponding colors to the Python color palette to draw a three-dimensional weak magnetic field distribution map.

[0052] The accuracy of the three-dimensional micromagnetic field measuring instrument is evaluated by combining the Class A uncertainty with the uncertainty of the Arduino instrument itself. The Class A uncertainty formula is V i is the voltage value measured for the i-th time, is the average value of three measured voltage values, u B is the uncertainty of the Arduino instrument itself, and u is the final uncertainty.

[0053] By measuring the voltage response of the GMI sensor as the magnetic field of the Helmholtz coil changes, it is possible to further study the sensor's characteristics under different magnetic field strengths. The Helmholtz coil generates a uniform, known magnetic field. Placing a compass needle on the axis aligned with the geomagnetic north pole can reduce interference from the geomagnetic field on the measurement and provide a benchmark for accurate measurement. Placing the sensor vertically in the middle of the axis ensures that it is in a uniform magnetic field area. By repeatedly varying the coil voltage and recording the sensor voltage changes, key performance indicators such as sensitivity and linearity of the sensor under different magnetic field strengths can be obtained, providing an important basis for evaluating sensor performance and subsequent measurement calibration.

[0054] Measuring the GMI sensor's response to geomagnetic field changes, calibrating the orientation and rotating the sensor in 9° increments using the geomagnetic North Pole as a reference, allows for detailed analysis of the sensor's response characteristics in different directions within the natural geomagnetic field. Using a compass for calibration ensures the accuracy of the measurement starting direction. By rotating the sensor clockwise and counterclockwise and collecting voltage data and plotting graphs, the relationship between the sensor output and the geomagnetic field distribution can be visually demonstrated. This helps researchers understand the sensor's behavior in actual geomagnetic environments and further understand its ability to detect weak geomagnetic field changes, laying the foundation for accurate geomagnetic field measurement in practical applications.

[0055] GMI's repeatability and hysteresis measurements are performed by adjusting the Helmholtz coil current to vary the applied magnetic field between 0 and 350 mA in both positive and negative directions. This operation is repeated multiple times, and the sensor output voltage signal is recorded. This allows for an accurate assessment of the sensor's stability and reliability over time and under varying magnetic field conditions.

[0056] The electronic compass angle algorithm processes the GMI sensor voltage and angle relationship by rotating the sensor 360° and performing a linear fit. This process accurately establishes a mathematical model between the sensor's output voltage and angle. By analyzing the output of different regions and calculating sensitivity, and combining the known amplitude of the ordinate to derive the angle from the abscissa, high-precision measurement of the magnetic field direction is achieved.

[0057] To create a three-dimensional weak magnetic field distribution map, an Arduino was used to collect Hall probe coordinates and GMI element voltages. Analog-to-digital conversion and characteristic equation calculations were used to determine the magnetic induction intensity, which was then vector-synthesized to determine the magnitude and direction of the total magnetic induction intensity. A Raspberry Pi further processed the data, using the Origin function for fitting and the Spectral function for creating a color map, ultimately producing a three-dimensional weak magnetic field distribution map. This data processing pipeline transforms complex three-dimensional magnetic field data into intuitive visualizations, allowing researchers to clearly observe the distribution of the magnetic field in space.

[0058] In summary, the beneficial effects of the present invention are:

[0059] 1. High-sensitivity sensor design: The GMI sensor, based on FeCuNbSiB thin ribbon, improves the accuracy of the single-axis magnetic probe to 300mV / Gs and above. Compared with the sensitivity of traditional linear Hall elements of 13mV / Gs, this experiment has higher accuracy and sensitivity.

[0060] 2. Precise measurement methods and algorithms: By measuring sensor responses in the magnetic field of a Helmholtz coil, measuring in the geomagnetic field, and obtaining magnetic field characteristics using an electronic compass angle algorithm, and combining data acquisition and processing with technologies such as Arduino and Raspberry Pi, an accurate magnetic field distribution map is drawn, effectively improving the accuracy and reliability of the measurement results.

[0061] 3. Multifunctional module integration: Based on the GMI sensor, a dedicated electronic compass system and three-dimensional micromagnetic field measuring instrument are designed, which have practical value;

[0062] 4. Stable circuit and sensor performance: The internal bias circuit solves the linear deviation and zero offset problems when the FeCuNbSiB thin ribbon measures weak magnetic fields, improving measurement accuracy and stability. The Colpitts oscillation circuit generates a stable oscillation signal, providing stable excitation for the sensor. The peak detection circuit effectively converts the signal and reduces interference. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 The XRD patterns of the Fe-based alloy strips of the present invention as prepared and at different annealing temperatures are shown;

[0064] Figure 2 It is the longitudinal drive GMI curve of the temperature annealing series samples of the present invention;

[0065] Figure 3 It is the design diagram of the internal bias circuit of the present invention;

[0066] Figure 4 It is the design diagram of the Colpitts oscillator circuit of the present invention;

[0067] Figure 5 This is a design diagram of the peak detection circuit of the present invention;

[0068] Figure 6 This is a functional design module diagram of the electronic compass of the present invention;

[0069] Figure 7 This is a front view of the three-dimensional micromagnetic field measuring instrument of the present invention;

[0070] Figure 8 This is a top view of the three-dimensional micromagnetic field measurement of the present invention;

[0071] Figure 9 This is a linear fitting diagram of the output voltage of the GMI sensor of the present invention and the weak magnetic field;

[0072] Figure 10 is a graph showing the output characteristic of the GMI circuit of the present invention;

[0073] Figure 11 is a graph showing the relationship between the output voltage of the GMI sensor of the present invention and the angle of the Earth's magnetic field;

[0074] Figure 12 It is a repetitive data analysis diagram of the present invention;

[0075] Figure 13 It is the hysteresis data analysis diagram of the present invention;

[0076] Figure 14 It is the compass data diagram of the present invention;

[0077] Figure 15 This is the output diagram of the dual-probe GMI sensor in area A of the present invention;

[0078] Figure 16 This is the output diagram of the dual-probe GMI sensor in area B of the present invention;

[0079] Figure 17 This is the output diagram of the dual-probe GMI sensor in area C of the present invention;

[0080] Figure 18 is a diagram of magnetic induction intensity on the axis of the Möhltz coil of the present invention;

[0081] Figure 19 This is an actual diagram of the three-dimensional weak magnetic field distribution of the present invention;

[0082] Figure 20 This is a linear fitting diagram of the relationship between the linear displacement on the x-axis and the number of pulses of the present invention;

[0083] Figure 21 This is a diagram of the GMI sensor module of the present invention;

[0084] Markings in the figure: 1-Internal bias circuit design, 11-Resistor RL1, 12-Resistor RL2, 13-Resistor RL3, 14-NPN transistor T1, 15-Inductor L, 16-+5V power supply, 2-Colpitts oscillation circuit design, 21-Resistor R1, 22-Resistor R2, 23-Resistor R3, 24-Resistor R4, 25-Transistor Q1, 3-Peak detection circuit design, 31-Diode D1, 32-Resistor RL4, 33-Capacitor CL3, 4-GMI sensor module, 41-Electronic compass system, 411-Magnetic sensor module, 412-Signal generation circuit module, 413-Peak detection module, 414-Signal acquisition module, 415- STM32 single-chip computer module, 416-OLED display module, 42-three-dimensional micromagnetic field measuring instrument, 4201-frame, 4202-x-axis screw, 4203-first y-axis screw, 4204-second y-axis screw, 4205-z-axis screw, 4206-first stepper motor, 4207-second stepper motor, 4208-third stepper motor, 4209-fourth stepper motor, 4210-three-dimensional GMI probe, 4211-display system, 4212-control box, 431-internal bias circuit module, 432-Colpitts oscillator circuit module, 433-peak detection circuit module, 434-subtraction amplifier circuit module, 435-follower circuit module. DETAILED DESCRIPTION

[0085] The following specific embodiments are merely explanations of the present invention and are not limitations of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to the embodiments as needed. However, as long as they are within the scope of the claims of the present invention, they are protected by patent law.

[0086] The present invention will be described in detail below with reference to the accompanying drawings using embodiments.

[0087] Example 1: Preparation and characterization of a GMI sensor, comprising the following steps:

[0088] Step S1: Prepare raw materials, the composition of which is Fe, Cu, Nb, Si and B, and the atomic ratio of each of which is Fe: 73.5, Cu: 1, Nb: 3, Si: 13.5, B: 9;

[0089] Step S2: The raw materials of step 1 are melt-spinned by a single roller, and the amorphous master alloy is melted by high-frequency induction heating under argon protection. The solution is ejected through a nozzle by a pressure device and directly sprayed onto a roller. The metal solution is rapidly cooled and solidified by a copper roller into a thin strip with a length of 19.95 mm to 20.05 mm, a width of 0.44 mm to 0.54 mm, and a thickness of 25 μm to 27 μm.

[0090] Step S3: annealing the thin strip at 540°C.

[0091] Step S4: measuring the diffraction intensity of the ribbon using X-rays;

[0092] Step S5: using an HP4294A impedance meter to measure the giant magneto-impedance value of the amorphous ribbon in a longitudinal driving mode, wherein the driving frequency of the HP4294A impedance meter is 275 kHz;

[0093] Comparative Example 1:

[0094] The difference from the above embodiment 1 is that, in step S3, the thin strip is annealed at 320°C.

[0095] Comparative Example 2:

[0096] The difference from the above embodiment 1 is that, in step S3 , the thin strip is annealed at 400° C.

[0097] Comparative Example 3:

[0098] The difference from the above embodiment 1 is that, in step S3, the thin strip is annealed at 470°C.

[0099] Comparative Example 4:

[0100] The difference from the above embodiment 1 is that, in step S3 , the thin strip is annealed at 500° C.

[0101] Comparative Example 5:

[0102] The difference from the above embodiment 1 is that, in step S3, the thin strip is annealed at 530°C.

[0103] Comparative Example 6:

[0104] The difference from the above embodiment 1 is that, in step S3, the thin strip is annealed at 580°C.

[0105] Comparative Example 7:

[0106] The difference from the above embodiment 1 is that, in step S3, the thin strip is annealed at 600°C.

[0107] Application Example 1;

[0108] The diffraction intensity of the FeCuNbSiB ribbon prepared at different temperatures was tested by X-ray to prepare an XRD pattern, as shown below: Figure 1As shown in the figure, the annealing temperature is amorphous before 470℃, and the crystallization peak appears at 500℃, and the crystalline state appears; at 540℃, the crystallization peak is enhanced, the coercive force reaches the lowest value, and the magnetic permeability reaches the highest value; at 580℃, the crystallization is strengthened and a hard magnetic phase appears, and the magnetic permeability drops sharply; therefore, the crystal ribbon with a temperature of 540℃ is selected, which has a significant crystallization peak, the lowest coercive force, and the highest magnetic permeability.

[0109] Comparative Example 8:

[0110] The difference from the above embodiment 1 is that, in step S5, the giant magneto-impedance value of the amorphous ribbon is measured by using an HP4294A impedance meter in a longitudinal driving mode, and the driving frequency of the HP4294A impedance meter is 150 kHz.

[0111] Comparative Example 9:

[0112] The difference from the above embodiment 1 is that, in step S5, the giant magneto-impedance value of the amorphous ribbon is measured by using an HP4294A impedance meter in a longitudinal driving mode, and the driving frequency of the HP4294A impedance meter is 350 kHz.

[0113] Comparative Example 10:

[0114] The difference from the above embodiment 1 is that, in step S5, the giant magneto-impedance value of the amorphous ribbon is measured by using an HP4294A impedance meter in a longitudinal driving mode, and the driving frequency of the HP4294A impedance meter is 500 kHz.

[0115] Application Example 11:

[0116] The annealing temperature of the amorphous ribbon is set to 540℃. The maximum impedance ratio of the FeCuNbSiB ribbon is compared at the driving frequencies of 150KHz, 275KHz, 350KHz and 500KHz. Figure 2 As shown, when the driving frequency is 275kHz, the composition thin strip exhibits a maximum impedance ratio of up to 3305%, and has the highest sensitivity.

[0117] Example 2: A GMI sensor circuit design, comprising:

[0118] The internal bias circuit design 1 is as follows Figure 3 As shown: including resistor RL1 11, resistor RL2 12, resistor RL3 13, NPN transistor T1 14, inductor L15 and +5V power supply 16;

[0119] One end of the resistor RL1 11 is connected to the +5V power supply 16, and the other end of the resistor RL1 11 is connected to the base of the NPN transistor T1 14; one end of the resistor RL2 12 is connected to the base of the NPN transistor T1 14, and the other end is grounded; one end of the resistor RL3 13 is connected to the emitter of the NPN transistor T1 14, and the other end is grounded; the collector of the NPN transistor T1 14 is connected to the inductor L15, and the other end of the inductor L15 is connected to the +5V power supply 16.

[0120] By adjusting the resistance of RL1, the base voltage UB of the NPN transistor changes. Since IE = IB + IC, IC on the inductor L changes, which in turn changes the magnetic field acting in the axial direction of the ribbon due to electromagnetic induction. By calculating the highly sensitive linear range of the amorphous ribbon's GMI characteristic curve, the bias current is adjusted to shift the output zero point to the center of the linear range.

[0121] The Colpitts oscillator circuit design 2 is as follows Figure 4 As shown, it includes a resistor R1 21, a resistor R2 22, a resistor R3 23, a resistor R4 24, and a transistor Q1 25;

[0122] One end of the resistor R1 21 is connected to the power supply, and the other end of the resistor R1 21 is connected to the base of the transistor Q1 25; one end of the resistor R2 22 is connected to the base of the transistor Q1 25, and the other end is grounded; one end of the resistor R3 23 is connected to the emitter of the transistor Q1 25, and the other end is grounded; one end of the resistor R4 24 is connected to the power supply, and the other end is connected to the collector of the transistor Q1 25.

[0123] The peak detection circuit design 3 is as follows Figure 5 As shown, it includes a diode D1 31, a resistor RL4 32, and a capacitor CL3 33;

[0124] The anode of the diode D1 31 receives a signal input, and the cathode is connected to the capacitor CL3 33 and is grounded through the capacitor CL3 33 ; one end of the resistor RL4 32 is connected to the cathode of the diode D1 31 , and the other end is grounded.

[0125] Example 3: An electronic compass system, as follows Figure 6 As shown, the electronic compass system 41 includes a magnetic sensor module 411, a signal generating circuit module 412, a peak detection module 413, a signal acquisition module 414, an STM32 single chip microcomputer module 415 and an OLED display module 416; in the magnetic sensor module 411, the GMI sensor 4 has two and is orthogonal to each other.

[0126] Example 4: A three-dimensional micromagnetic field measuring instrument 42, as follows Figure 7 8, including: a frame 4201, an x-axis screw rod 4202, a first y-axis screw rod 4203, a second y-axis screw rod 4204, a z-axis screw rod 4205, a first stepper motor 4206, a second stepper motor 4207, a third stepper motor 4208, a fourth stepper motor 4209, a three-dimensional GMI probe 4210, a display system 4211 and a control box 4212;

[0127] The third stepper motor 4208 and the fourth stepper motor 4209 are symmetrically fixed on both sides of the top of the back of the frame 4201; the first y-axis screw rod 4203 and the third stepper motor 4208 are connected to the two ends of the interior of the frame 4201; the second y-axis screw rod 4204 and the fourth stepper motor 4209 are connected to the two ends of the interior of the frame 4201; one end of the x-axis screw rod 4202 is connected to the slider of the first y-axis screw rod 4203; the other end of the x-axis screw rod 4202 is connected to the slider of the first y-axis screw rod 4203; The second stepper motor 4207 is connected; the second stepper motor 4207 is connected to the slider of the second y-axis screw rod 4204; the first stepper motor 4206 is connected to the slider of the x-axis screw rod 4202; the z-axis screw rod 4205 is connected to the first stepper motor 4206; the three-dimensional GMI probe 4210 is connected to the slider of the z-axis screw rod 4205; the control box 4212 is fixed to the right side of the frame 4201; the display system 4211 is mounted on the control box 4212;

[0128] The three-dimensional GMI probe 4210 includes three mutually orthogonal GMI sensors.

[0129] Example 5: A method for measuring and analyzing a weak magnetic field comprises the following steps:

[0130] Step V1: Measure the voltage response of the GMI sensor as the magnetic field of the Helmholtz coil changes;

[0131] Step V1.1: Place a compass on the Helmholtz axis so that the Helmholtz axis is perpendicular to the geomagnetic north and south poles.

[0132] Step V1.2: Connect the circuit of the experimental setup: Use wires to connect the power supply, Helmholtz coil, GMI sensor, and data acquisition equipment;

[0133] Step V1.3: Place the GMI sensor vertically in the middle of the Helmholtz axis and obtain the magnetic field magnitude when the Helmholtz coil is not energized.

[0134] Step V1.4: Wait for the GMI sensor voltage to stabilize, then change the voltage of the Helmholtz instrument to change the magnitude of the weak magnetic field and record the changes in the sensor voltage value as follows: Figure 9 As shown, the Helmholtz axis current is set to 0mA, 5mA, 10mA, and 60mA, respectively. Using the Helmholtz formula, the weak magnetic field changes to 0Gs, 0.145Gs, 0.290Gs, and 1.74Gs. The output voltage of the GMI sensor under different weak magnetic fields is recorded. Using Origin, the following scatter plot is plotted. A linear fit is performed, yielding the relationship between output voltage Y and weak magnetic field X: Y = 339.06X + 1678.81. Therefore, within the range of 0-1.5Gs, the sensitivity of the GMI sensor is 339.06mV / Gs, and its standard deviation R is 2. 2 =0.99782 is close to 1, which shows that the fitting curve is consistent with the measured curve;

[0135] Step V1.5: Repeat the above steps five times without changing the position of the GMI sensor.

[0136] Step V2: Measure the GMI sensor changes with the geomagnetic field;

[0137] Step V2.1: Use the direction of the geomagnetic North Pole as the test reference point, and evenly divide the circular plane into 9° steps to calibrate the geomagnetic direction.

[0138] Step V2.2: Use a compass to calibrate so that the north direction coincides with 0° on the circular surface;

[0139] Step V2.3: Rotate the GMI geomagnetic sensor 360° clockwise starting from 0° and measure the change in output voltage as follows: Figure 10 As shown, the total bias is about 0.43503Gs, which makes it biased to the linear range;

[0140] Step V2.4: Use Arduino to collect the output voltage of the GMI sensor and plot the GMI sensor response voltage and the distribution of the Earth's magnetic field.

[0141] Step V2.5: Rotate 360° counterclockwise to reset to the initial position and measure the change in output voltage.

[0142] Step V2.6: Use Arduino to collect the output voltage value of the GMI sensor and draw an image of the GMI sensor response voltage and the distribution of the geomagnetic field, as shown below Figure 11As shown, the magnetic field sensed by the sensitive coil changes with the geomagnetic azimuth and is converted into a voltage output with cosine characteristics by the GMI geomagnetic azimuth sensor. The curve is divided into four regions within 0-360°: a, b, c, d, and e. Regions b and d are insensitive due to magnetic saturation, while regions a, c, and e exhibit high linearity and high sensitivity. By performing linear fitting on the a and b intervals, the sensitivity of interval a is 1.03mV / °, the sensitivity of interval c is 1.3mV / °, and the sensitivity of interval e is 1.4mV / °. The circuit output voltage is 3.3V, and the output signal voltage difference is 0.2V.

[0143] Step V3: Repeatability and hysteresis measurement of GMI;

[0144] Step V3.1: Change the current direction and adjust the current of the Helmholtz coil so that the applied magnetic field changes from positive to negative between 0 and 350 mA, and record the output voltage signal of the GMI sensor;

[0145] Step V3.2: Change the current direction and adjust the current of the Helmholtz coil so that the applied magnetic field changes from negative to positive between 0 and 350 mA, and record the output voltage signal of the GMI sensor;

[0146] Step V3.3: Repeat the operations of steps V3.1-V3.2 as follows Figure 12 As shown in the figure, in the repeatability experiment, curves a and b are the output curves of the external magnetic field changing from -1627.85A / m to 1627.85A / m under the same conditions. It can be seen from the two sets of curves that the output basically overlaps. The maximum deviation of the repeatability experiment is small through calculation, and the output has good stability. Figure 13 As shown in the figure, in the hysteresis experiment, curve a is the output curve when the external magnetic field changes from -1627.85A / m to 1627.85A / m, and curve b is the output curve when the external magnetic field changes from 1627.85A / m to -1627.85A / m. Calculation shows that the hysteresis on the left side of the curve is 0.427%, the hysteresis on the right side is 0.493%, and the total hysteresis is 0.4925%. The sensor has almost no hysteresis.

[0147] Step V4: electronic compass angle algorithm processing;

[0148] Step V4.1: Rotate 360° to obtain the voltage and angle relationship diagram of the GMI sensor, as shown below Figure 14As shown in the figure, the data changes of the two broken lines are shown. The horizontal axis in the figure represents the angle Angles, ranging from 0° to 350°, and the vertical axis represents the output voltage Vout, ranging from 1550mV to 1900mV. The black dotted line represents "amorphous thin ribbon 1". At 0°, the output voltage is 1800mV, at 150°, the output voltage is 1590mV, and at 350°, the output voltage is 1890mV; the red solid line represents "amorphous thin ribbon 2". At 0°, the output voltage is 1590mV, at 200°, the output voltage is 1850mV, and at 350°, the output voltage is 1700mV.

[0149] Step V4.2: Perform linear fitting on the waveform output by the GMI sensor, as follows Figure 15 , 16, 17, A and C areas are given by probe 1, and B is the area given by probe 2. Area A represents an output voltage greater than 1600mV, area B represents an output voltage between 1800mV and 2100mV, and area C represents an output voltage between 1600mV and 1800mV. According to the table below, when the output of probe 1 is used in the range of 0°-100°, the sensitivity is 1.8158mV / °, and the functional relationship is Y=-1.8158X+1802; when the output of probe 2 is used in the range of 100°-250°, the sensitivity is 0.57mV / °, and the functional relationship is Y=0.5709X+1917; when the output of probe 1 is used in the range of 250°-360°, the sensitivity is 1.2441mV / °, and the functional relationship is Y=1.2441X+1917;

[0150]

[0151] Step V5: Three-dimensional weak magnetic field distribution map:

[0152] Step V5.1: Use Arduino to collect the real-time x, y, and z coordinates of the Hall probe in the 3D micromagnetic field measurement instrument and the voltages of the three GMI components;

[0153] Step V5.2: After collecting the GMI voltage, perform analog-to-digital conversion and substitute it into the characteristic equation to obtain the magnetic induction intensity;

[0154] Step V5.3: Perform vector synthesis on the three magnetic induction intensity components to obtain the magnitude and direction of the total magnetic induction intensity. The vector synthesis is as follows: use three mutually orthogonal GMI sensors to measure the magnetic induction intensity of three directions at a certain position in the magnetic field as B. x ,B y ,B z , and according to the formula Get the magnitude of magnetic induction intensity;

[0155] Step V5.4: The Raspberry Pi first reads the data point values transmitted by the Arduino and saves the value points using the pre-stored matrix;

[0156] Step V5.5: Use the Origin function to fit the cubic function to draw the weak magnetic field. Use the Spectral function to create a mapping between data values and colors based on the radiation emittance value represented by the A array, and use the colorbar to use this mapping to assign corresponding colors to the Python color palette to draw a three-dimensional weak magnetic field distribution map, as shown below. Figure 18 As shown in Figure 19, the measured weak magnetic field range is between 1.25Gs and 1.3Gs, and the maximum error is 0.43%. It can be seen that a stable weak magnetic field distribution is generated within the Helmholtz axis with a small error. In addition, a large range of uniform magnetic field is generated in the inner center of the two coils. The magnetic induction intensity of this uniform magnetic field area is about 1.25Gs, and the direction is parallel to the Z axis.

[0157] The python code is as follows:

[0158] Python drawing:

[0159]

[0160]

[0161]

[0162]

[0163]

[0164]

[0165]

[0166]

[0167]

[0168] Example 6: The difference from Example 5 is that after obtaining the data of steps V1-V3, performing uncertainty analysis includes the following steps:

[0169] Step B4: Analyze the uncertainty of the X-axis GMI magnetic probe, as shown in the following table: For the Class A uncertainty of the X-axis magnetic sensor system, the maximum uncertainty is: U A (x) = 0.0194338, the uncertainty of the Arduino instrument itself is After uncertainty synthesis, we can get

[0170]

[0171] Step B5: Analyze the uncertainty of the Y-axis GMI magnetic probe, as shown in the following table: For the Class A uncertainty of the Y-axis magnetic sensor system, the maximum uncertainty is: U A (x) = 0.001451069, the uncertainty of the Arduino instrument itself is After uncertainty synthesis, we can get

[0172]

[0173]

[0174] Step B6: Analyze the uncertainty of the Z-axis GMI magnetic probe, as shown in the following table: For the Class A uncertainty of the Z-axis magnetic sensor system, the maximum uncertainty is: U A (x) = 0.005720979, the uncertainty of the Arduino instrument itself is After uncertainty synthesis, we can get

[0175]

[0176] Step B7: Positioning error test: Use the cumulative amplification method to measure the cumulative linear displacement generated by a certain number of pulses. Set the x-axis stepper motor driver to 3200 pulses, and use a millimeter ruler to measure the linear displacement of the probe in the x-axis direction. Repeat the experiment 10 times and calculate the average value. Change the number of pulses and repeat the above experiment. As shown in the table below, the linear displacement of the thermal radiation probe in the x-axis direction corresponding to different pulse numbers is plotted using Origin software. Figure 20 The pulse number-linear displacement curve shown in the figure shows that the slope of the curve represents the linear displacement corresponding to a single pulse. From the introduction of the three-dimensional motion structure, it can be seen that the theoretical linear displacement corresponding to one pulse of the stepper motor is 5.00×10 -3 mm, the slope of the straight line fitted according to the experimental data is 4.99821*10 -4 , calculate the relative error

[0177] The same test was performed on the y-axis and z-axis directions, and the relative errors of coordinate positioning were found to be 0.64% and 0.36% respectively.

[0178]

Claims

1. A weak magnetic field measurement system based on FeCuNbSiB thin ribbon, characterized in that: The invention comprises an internal bias circuit design (1), a Colpitts oscillation circuit design (2) and a peak detection circuit design (3) based on a FeCuNbSiB thin strip; an electronic compass system (41) and a three-dimensional micromagnetic field measuring instrument (42) based on the GMI sensor module (4); the GMI sensor module (4) is composed of the internal bias circuit module (431), the Colpitts oscillation circuit module (432), the peak detection circuit module (433), a subtraction amplifier circuit module (434) and a follower circuit module (435).

2. A weak magnetic field measurement system based on FeCuNbSiB thin ribbon according to claim 1, characterized in that: A preparation and processing method of the FeCuNbSiB thin strip includes the following steps: Step S1: preparing raw materials, the composition of which is Fe, Cu, Nb, Si and B, and the ratio of each atom thereof is Fe: 73-74, Cu: 0.5-1.5, Nb: 2.5-3.5, Si: 13-14, B: 8.5-9.5; Step S2: The raw material of step S1 is melt-spinned by a single roller to form a thin strip with a length of 19.95 mm to 20.05 mm, a width of 0.44 mm to 0.54 mm, and a thickness of 25 μm to 27 μm; Step S3: annealing the thin strip at a temperature of 470°C-630°C.

3. A weak magnetic field measurement system based on FeCuNbSiB thin ribbon according to claim 3, characterized in that: The magnetic permeability of the FeCuNbSiB ribbon at different annealing temperatures was analyzed using X-ray diffraction patterns, and the annealing temperature range for the optimal magnetic permeability was 520° C.-560° C.

4. A weak magnetic field measurement system based on FeCuNbSiB thin ribbon according to claim 2, characterized in that: The internal bias circuit design (1) includes a resistor RL1 (11), a resistor RL2 (12), a resistor RL3 (13), an NPN transistor T1 (14), an inductor L (15) and a +5V power supply (16); One end of the resistor RL1 (11) is connected to the +5V power supply (16), and the other end of the resistor RL1 (11) is connected to the base of the NPN transistor T1 (14); one end of the resistor RL2 (12) is connected to the base of the NPN transistor T1 (14), and the other end is grounded; one end of the resistor RL3 (13) is connected to the emitter of the NPN transistor T1 (14), and the other end is grounded; the collector of the NPN transistor T1 (14) is connected to the inductor L (15), and the other end of the inductor L (15) is connected to the +5V power supply (16); The Colpitts oscillator circuit design (2) includes a resistor R1 (21), a resistor R2 (22), a resistor R3 (23), a resistor R4 (24), and a transistor Q1 (25); One end of the resistor R1 (21) is connected to the power supply, and the other end of the resistor R1 (21) is connected to the base of the transistor Q1 (25); one end of the resistor R2 (22) is connected to the base of the transistor Q1 (25), and the other end is grounded; one end of the resistor R3 (23) is connected to the emitter of the transistor Q1 (25), and the other end is grounded; one end of the resistor R4 (24) is connected to the power supply, and the other end is connected to the collector of the transistor Q1 (25); The peak detection circuit design (3) includes a diode D1 (31), a resistor RL4 (32), and a capacitor CL3 (33); The anode of the diode D1 (31) receives a signal input, and the cathode is connected to the capacitor CL3 (33) and is grounded through the capacitor CL3 (33); one end of the resistor RL4 (32) is connected to the cathode of the diode D1 (31), and the other end is grounded.

5. A weak magnetic field measurement system based on FeCuNbSiB thin ribbon according to claim 4, characterized in that: The electronic compass system (41) comprises a magnetic sensor module (411), a signal generating circuit module (412), a peak detection module (413), a signal acquisition module (414), an STM32 single chip microcomputer module (415) and an OLED display module (416); in the magnetic sensor module (411), the GMI sensors (4) are two and are orthogonal to each other; The three-dimensional micromagnetic field measuring instrument (42) comprises: a frame (4201), an x-axis screw (4202), a first y-axis screw (4203), a second y-axis screw (4204), a z-axis screw (4205), a first stepper motor (4206), a second stepper motor (4207), a third stepper motor (4208), a fourth stepper motor (4209), a three-dimensional GMI probe (4210), a display system (4211) and a control box (4212). The three-dimensional GMI probe (4210) is composed of three mutually orthogonal GMI sensors; The third stepper motor (4208) and the fourth stepper motor (4209) are symmetrically fixed on both sides of the top of the back of the frame (4201); the first y-axis screw rod (4203) and the third stepper motor (4208) are connected to the two ends inside the frame (4201); the second y-axis screw rod (4204) and the fourth stepper motor (4209) are connected to the two ends inside the frame (4201); one end of the x-axis screw rod (4202) is connected to the slider of the first y-axis screw rod (4203); the other end of the x-axis screw rod (4202) is connected to the slider of the first y-axis screw rod (4203); The first stepper motor (4206) is connected to the slider of the x-axis screw rod (4202); the z-axis screw rod (4205) is connected to the first stepper motor (4206); the three-dimensional GMI probe (4210) is connected to the slider of the z-axis screw rod (4205); the control box (4212) is fixed on the right side of the frame (4201); and the display system (4211) is provided on the control box (4212).

6. A weak magnetic field measurement system based on FeCuNbSiB thin ribbon according to claim 5, characterized in that: The weak magnetic field measurement and analysis includes the following steps: Step V1: Measure the voltage response of the GMI sensor as the magnetic field of the Helmholtz coil changes; Step V1.1: Place a compass on the Helmholtz axis so that the Helmholtz axis is perpendicular to the geomagnetic north and south poles. Step V1.2: Connect the circuit of the experimental setup: Use wires to connect the power supply, Helmholtz coil, GMI sensor, and data acquisition equipment; Step V1.3: Place the GMI sensor vertically in the middle of the Helmholtz axis and obtain the magnetic field magnitude when the Helmholtz coil is not energized. Step V1.4: Wait for the GMI sensor voltage to stabilize, then change the voltage of the Helmholtz instrument to change the magnitude of the weak magnetic field and record the change in the sensor voltage value. Step V1.5: Repeat the above steps five times without changing the position of the GMI sensor. Step V2: Measure the GMI sensor changes with the geomagnetic field; Step V2.1: Use the direction of the geomagnetic North Pole as the test reference point, and evenly divide the circular plane into 9° steps to calibrate the geomagnetic direction. Step V2.2: Use a compass to calibrate so that the north direction coincides with 0° on the circular surface; Step V2.3: Rotate the GMI geomagnetic sensor 360° clockwise starting from 0° and measure the change in output voltage. Step V2.4: Use Arduino to collect the output voltage of the GMI sensor and plot the GMI sensor response voltage and the distribution of the Earth's magnetic field. Step V2.5: Rotate 360° counterclockwise to reset to the initial position and measure the change in output voltage. Step V2.6: Use Arduino to collect the output voltage of the GMI sensor and plot the GMI sensor response voltage and the distribution of the Earth's magnetic field. Step V3: Repeatability and hysteresis measurement of GMI; Step V3.1: Change the current direction and adjust the current of the Helmholtz coil so that the applied magnetic field changes from positive to negative between 0 and 350 mA, and record the output voltage signal of the GMI sensor; Step V3.2: Change the current direction and adjust the current of the Helmholtz coil so that the applied magnetic field changes from negative to positive between 0 and 350 mA, and record the output voltage signal of the GMI sensor; Step V3.3: Repeat the operations of steps V3.1-V3.2; Step V4: electronic compass angle algorithm processing; Step V4.1: Rotate 360° to obtain the voltage and angle relationship diagram of the GMI sensor; Step V4.2: Perform linear fitting on the waveform output by the GMI sensor; Step V5: Three-dimensional weak magnetic field distribution map: Step V5.1: Use Arduino to collect the real-time x, y, and z coordinates of the Hall probe in the 3D micromagnetic field measurement instrument and the voltages of the three GMI components; Step V5.2: After collecting the GMI voltage, perform analog-to-digital conversion and substitute it into the characteristic equation to obtain the magnetic induction intensity; Step V5.3: Perform vector synthesis on the three magnetic induction intensity components to obtain the magnitude and direction of the total magnetic induction intensity; Step V5.4: The Raspberry Pi first reads the data point values transmitted by the Arduino and saves the value points using the pre-stored matrix; Step V5.5: Use the Origin function to fit the cubic function to draw the weak magnetic field. Use the Spectral function to create a mapping between data values and colors based on the radiation emittance values represented by the A array, and use the colorbar function to use this mapping to assign corresponding colors to the Python color palette to draw a three-dimensional weak magnetic field distribution map.

7. A weak magnetic field measurement system based on FeCuNbSiB thin ribbon according to claim 6, characterized in that: In step V5.3, vector synthesis is specifically to use three mutually orthogonal GMI sensors to measure the magnetic induction intensity components B in three directions at a certain position in the magnetic field. x ,B y ,B z , and according to the formula Get the magnitude of the magnetic induction intensity.

8. A weak magnetic field measurement system based on FeCuNbSiB thin ribbon according to claim 7, characterized in that: The voltage and angle relationship diagram of the GMI sensor is obtained by rotating 360°, and the waveform is linearly fitted. The sensitivity and functional relationship of different angle ranges are determined according to different regions, and used for angle algorithm processing to determine the angle value; the functional relationship of the region is Y=kX+b, and the angle value k is the slope, b is the intercept, and V is the probe output voltage.

9. A weak magnetic field measurement system based on FeCuNbSiB thin ribbon according to claim 8, characterized in that: The accuracy of the three-dimensional micromagnetic field measuring instrument is evaluated by combining the Class A uncertainty with the uncertainty of the Arduino instrument itself. The Class A uncertainty formula is V i is the voltage value measured for the i-th time, is the average value of the three measured voltage values, u B is the uncertainty of the Arduino instrument itself, and u is the final uncertainty.

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