Device and method for measuring weak static magnetic field by Lissajous figure method

Abstract

The invention discloses a device and a method for measuring a weak static magnetic field by a Lissajous figure method. Comprising a Faraday magneto-optical sensing system, a signal processing module, an oscilloscope and a signal generator. The Faraday magneto-optical sensing system and the signal processing module are arranged along an optical path, and the Faraday magneto-optical sensing system transmits an optical signal to the signal processing module; the oscilloscope is respectively connected with the signal processing module and the signal generator, signals sent by the signal processing module and the signal generator are coupled by the oscilloscope to form a Lissajous figure, the Faraday magneto-optical sensing system is arranged in a static magnetic field to be measured, and the Lissajous figure is used for reflecting the magnetic induction intensity of the static magnetic field to be measured. The square wave signal frequency is measured by adjusting the signal frequency of the signal generator, so that the magnetic induction intensity is accurately measured, and the measurement precision and the measurement stability of a weak static magnetic field are greatly improved.

Description

Technical Field

[0001] This invention relates to the field of measuring weak magnetic fields, and specifically to an apparatus and method for measuring weak static magnetic fields using the Lissajous figure method. Background Technology

[0002] There are many tools available for measuring weak magnetic fields in physics experiments, including superconducting quantum interference devices, atomic magnetometers, nuclear spin precession magnetometry, giant magnetoresistance sensors, and Hall effect sensors. Accurate magnetic field measurement techniques are crucial for modern detection technologies and are of great significance for both production and daily life, as well as basic research. Summary of the Invention

[0003] To address the problems existing in the background technology, the present invention provides a device and method for measuring weak static magnetic fields using the Lissajous figure method. It is an experimental instrument system for measuring weak static magnetic fields that integrates optics, electricity, and magnetism.

[0004] The technical solution adopted in this invention is: I. A device for measuring weak static magnetic fields using the Lissajous figure method The device includes a Faraday magneto-optical sensing system, a signal processing module, an oscilloscope, and a signal generator. The Faraday magneto-optical sensing system and the signal processing module are arranged along an optical path, and the Faraday magneto-optical sensing system transmits optical signals to the signal processing module. The oscilloscope is connected to both the signal processing module and the signal generator. The signals emitted by the signal processing module and the signal generator are coupled through the oscilloscope to form a Lissajous figure. The Faraday magneto-optical sensing system is placed in the static magnetic field to be measured, and the Lissajous figure is used to reflect the magnitude of the magnetic induction intensity of the static magnetic field to be measured.

[0005] The Faraday magneto-optical sensing system mainly consists of a laser, a polarizer group, and a Faraday rotator crystal. The laser and the polarizer group are arranged sequentially at intervals along the light propagation direction. The Faraday rotator crystal is placed within the polarizer group and located in the middle of the polarizer group. The Faraday rotator crystal is placed in the static magnetic field to be measured, and the polarization plane of the laser is rotated by the influence of the magnetic induction intensity of the static magnetic field to be measured.

[0006] The polarizer group includes a first polarizer and a second polarizer with adjustable polarization direction, and the Faraday rotator crystal is disposed between the first polarizer and the second polarizer and located in the direction of light propagation.

[0007] The signal processing module includes a photodiode, a transimpedance amplifier, and a voltage-to-frequency converter. The photodiode is used to receive the optical signal output by the Faraday magneto-optical sensing system. The photodiode is located in the direction of light propagation and the receiving end faces the output end of the second polarizer of the polarizer group. The output end is electrically connected to the transimpedance amplifier, the voltage-to-frequency converter, and an oscilloscope.

[0008] The center of the laser beam emitted by the laser, the center of the first polarizer, the center of the Faraday rotator crystal, the center of the second polarizer, and the center of the photodiode are arranged along the same optical propagation line.

[0009] II. Lissajous Figure Method for Measuring Weak Static Magnetic Fields: The Lissajous Figure Method for Measuring Weak Static Magnetic Fields S1: The laser emits a beam of light, which enters the first polarizer to form linearly polarized light. The linearly polarized light exits onto a Faraday rotator crystal placed on the static magnetic field to be measured. After passing through the Faraday rotator crystal, it undergoes optical rotation. After passing through the second polarizer, it enters the photodiode to form a photocurrent. The photocurrent output by the photodiode is positively correlated with the magnitude of the magnetic induction intensity. After passing through the signal processing module, the photocurrent forms a square wave signal affected by the magnetic induction intensity of the static magnetic field. The square wave signal is transmitted to the oscilloscope and displayed. The frequency of the square wave signal and the magnitude of the magnetic induction intensity have a linear relationship within the measurement range. Therefore, the frequency of the square wave signal can be used to characterize the magnitude of the magnetic induction intensity.

[0010] S2: The sine wave signal generated by the signal generator is connected to the oscilloscope for display, so that the sine wave signal and the square wave signal are coupled in the oscilloscope to obtain a Lissajous figure of "square wave-sine wave".

[0011] S3: By adjusting the frequency of the sinusoidal signal of the signal generator, the Lissajous figure flicker frequency is minimized. The frequency of the square wave signal affected by the magnetic induction intensity of the static magnetic field at the minimum flicker frequency of the Lissajous figure is taken. The frequency of the square wave signal affected by the magnetic induction intensity of the static magnetic field is analyzed and processed to calculate the magnitude of the magnetic induction intensity of the static magnetic field where the Faraday optical rotator crystal is located.

[0012] Before step S1 begins, the first polarizer is adjusted so that its polarization direction is parallel to the light propagation direction, and the second polarizer is adjusted so that its polarization direction is nearly perpendicular to the polarization direction of the first polarizer, so that the photodiode can receive the signal and is not saturated.

[0013] When no static magnetic field to be measured is applied, the frequency of the square wave signal when no static magnetic field to be measured is measured through steps S1, S2 and S3.

[0014] In step S3, the frequency of the square wave signal affected by the static magnetic field is analyzed and processed to calculate the measurement result of the magnetic induction intensity of the static magnetic field to be measured. That is, the magnetic induction intensity of the static magnetic field to be measured is obtained by the following formula: in, B This indicates the magnitude of the magnetic induction intensity of the static magnetic field to be measured. △f This represents the difference in frequency between the square wave signal when the static magnetic field to be measured is applied and when no static magnetic field to be measured is applied.k This represents the proportionality coefficient, the value of which is calibrated using a standard static magnetic field. The magnetic flux density of the standard static magnetic field is constant.

[0015] The beneficial effects of this invention are: (1) This invention constructs an experimental device for measuring weak static magnetic fields using the Lissajous figure method, and measures the frequency difference of square wave signals using a signal processing module and the Lissajous figure method, thereby improving the measurement accuracy and achieving good results. Because the use of photodiodes and signal processing modules accurately measures the weak static magnetic field, the ratio of the change in the square wave signal frequency to the change in the weak static magnetic field is increased, thus greatly improving the measurement accuracy of the weak static magnetic field.

[0016] (2) This invention uses the Faraday rotation effect, photoelectric effect, and signal processing module to represent the magnetic field intensity with a square wave signal frequency, and couples it with a sinusoidal wave generated by a signal generator to measure the weak static magnetic field using the Lissajous figure method. By converting the weak static magnetic field into a square wave signal frequency difference for measurement, the measurement accuracy of the weak static magnetic field is improved. Furthermore, by using the Lissajous figure method, the problems of unstable digital displays in conventional measuring instruments, which lead to difficulty in reading and large reading errors, are effectively avoided. The analysis and processing are then used to accurately obtain the measurement of the weak static magnetic field.

[0017] (3) This invention derives the relationship between magnetic induction intensity and frequency difference. B = k△f The linear relationship between magnetic induction intensity and frequency difference was analyzed, and the relationship between frequency difference and weak static magnetic field was derived using theoretical calculations, enabling the calculation and measurement of weak static magnetic field. This reduces the impact of laser intensity instability, optical path setup errors, and external environmental interference on the measurement, further minimizing measurement error. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the core of the experimental instrument system; Figure 2 Data group for the example - Relationship diagram; Figure 3 A table showing the frequency difference between the magnetic fields of the coil and the corresponding magnetic fields of the coil. Figure 4 The experimental data table for the current and magnetic field of the embodiment is shown in the figure. Figure 5 The actual magnetic field measurement error is shown in the table for the example.

[0019] In the diagram: 1. Laser, 2. First polarizer, 3. Faraday crystal, 4. Second polarizer, 5. Photodiode, 6. Transimpedance amplifier, 7. Voltage-to-frequency converter, 8. Oscilloscope, 9. Signal generator. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] like Figure 1 As shown, the specific device includes a Faraday magneto-optical sensing system, a signal processing module, an oscilloscope 8, and a signal generator 9. The Faraday magneto-optical sensing system and the signal processing module are arranged along the optical path, and the Faraday magneto-optical sensing system transmits optical signals to the signal processing module. The CH1 and CH2 channels of the oscilloscope 8 are connected to the signal processing module and the signal generator 9, respectively. The signals emitted by the signal processing module and the signal generator 9 are coupled through the oscilloscope 8 to form a Lissajous figure. The Faraday magneto-optical sensing system is placed in the static magnetic field to be measured, and the Lissajous figure is used to reflect the magnitude of the magnetic induction intensity of the static magnetic field to be measured.

[0022] The Faraday magneto-optical sensing system mainly consists of a laser 1, a polarizer group, and a Faraday rotator crystal 3. The laser 1 and the polarizer group are arranged sequentially at intervals along the direction of light propagation. The Faraday rotator crystal 3 is placed within the polarizer group and located in the middle of the polarizer group. The Faraday rotator crystal 3 is placed in the static magnetic field to be measured. The Faraday rotator crystal 3 rotates the polarization plane by the change in the magnetic induction intensity of the static magnetic field to be measured.

[0023] The polarizer assembly includes a first polarizer 2 and a second polarizer 4 with adjustable polarization directions. The first polarizer 2 is a polarizer, and the second polarizer 4 is an analyzer. A Faraday rotator crystal 3 is disposed between the first polarizer 2 and the second polarizer 4 and is located in the direction of light propagation. The laser 1, the first polarizer 2, the Faraday rotator crystal 3, and the second polarizer 4 are arranged sequentially and at intervals along the direction of light propagation. The polarization directions of the first polarizer 2 and the second polarizer 4 are adjustable, and can be adjusted to a polarization direction close to 90°.

[0024] The signal processing module includes a photodiode 5, a transimpedance amplifier 6, and a voltage-to-frequency converter 7. The photodiode 5 receives the optical signal transmitted by the Faraday magneto-optical sensing system. The photodiode 5 is located in the direction of light propagation, with one end facing the output of the second polarizer 4 in the polarizer group, and the other end electrically connected to the transimpedance amplifier 6, the voltage-to-frequency converter 7, and the CH1 port of the oscilloscope 8. The outputs of the voltage-to-frequency converter 7 and the signal generator 9 are connected to the CH1 and CH2 channels of the oscilloscope, respectively.

[0025] The voltage-frequency converter 7 has good linearity, and the signal generator 9 can generate sine waves with adjustable frequency.

[0026] The center of the beam emitted by laser 1, the center of the first polarizer 2, the center of the Faraday rotator crystal 3, the center of the second polarizer 4, and the center of the photodiode 5 are arranged along the same optical propagation line.

[0027] The specific apparatus employs the Lissajous figure method to measure weak static magnetic fields as follows: S1: Laser 1 emits a beam of light, which enters the first polarizer 2 to form linearly polarized light. The linearly polarized light exits onto the Faraday rotator crystal 3, which is placed in the static magnetic field to be measured. After being scattered by the Faraday rotator crystal 3, it passes through the second polarizer 4 and finally enters the photodiode 5 to form a photocurrent. The photocurrent is processed by the signal processing module to form a square wave signal affected by the static magnetic field. The square wave signal is transmitted to the oscilloscope 8 and displayed.

[0028] S2: Signal generator 9 generates an adjustable sine wave signal, which is then connected to oscilloscope 8 for display. This couples the sine wave signal with the square wave signal in oscilloscope 8 to obtain a Lissajous figure of "square wave-sine wave".

[0029] S3: By traversing and scanning, the frequency of the sinusoidal signal of the signal generator 9 is adjusted to make the Lissajous pattern flicker frequency the lowest. The frequency of the square wave signal affected by the static magnetic field at the lowest Lissajous pattern flicker frequency is taken. The frequency of the square wave signal affected by the static magnetic field is analyzed and processed to calculate the magnitude of the magnetic induction intensity of the static magnetic field where the Faraday optical rotator crystal 3 is located.

[0030] The magnetic flux density of the standard static magnetic field is obtained by measuring the frequency difference between cases with and without a standard static magnetic field. By adjusting the signal frequency of the signal generator 9 to measure the frequency of the square wave signal, the magnetic flux density is accurately measured, greatly improving the measurement accuracy and stability of weak static magnetic fields.

[0031] Before step S1 begins, i.e. before the experimental measurement, the first polarizer 2 is adjusted so that its polarization direction is parallel to the light propagation direction, and the second polarizer 4 is adjusted so that it is nearly perpendicular to the first polarizer 2. This ensures that the photodiode 5 can receive a small signal and is not saturated. When the light signal received by the photodiode 5 approaches 0, the signal-to-noise ratio is large. When the light signal received by the photodiode 5 reaches saturation, the photocurrent output by the photodiode 5 will remain unchanged. Therefore, when the photodiode 5 receives a small signal and is not saturated, the photocurrent output by the photodiode 5 has the smallest and most effective signal-to-noise ratio.

[0032] When no static magnetic field to be measured is applied, i.e., the static magnetic field to be measured is in the closed state, the frequency of the square wave signal when no static magnetic field to be measured is measured through steps S1, S2 and S3.

[0033] A standard static magnetic field is applied to the Faraday optically active crystal 3. The magnitude of the magnetic induction intensity of the standard static magnetic field is constant. Specifically, a Helmholtz coil can be used as the standard static magnetic field. The frequency corresponding to the magnetic induction intensity of the standard static magnetic field is measured through steps S1-S3.

[0034] In step S3, the frequency of the square wave signal affected by the static magnetic field is analyzed and processed to calculate the measurement result of the magnetic induction intensity of the static magnetic field to be measured. Specifically, the magnetic induction intensity of the static magnetic field to be measured is obtained using the following formula: in, B This indicates the magnitude of the magnetic induction intensity of the static magnetic field to be measured. △f This represents the difference in frequency between the square wave signal when the static magnetic field to be measured is applied and when no static magnetic field to be measured is applied. k This represents the proportionality coefficient, the value of which is calibrated using a standard static magnetic field. The magnetic flux density of the standard static magnetic field is constant.

[0035] This invention transforms a weak static magnetic field using the Lissajous figure method. Through the Faraday rotation effect, photoelectric effect, and signal processing module, the magnetic induction intensity is represented by a square wave signal frequency. This signal is then coupled with a sinusoidal wave generated by a signal generator 9, and the weak static magnetic field is measured using the Lissajous figure method. Because the use of a photodiode 5 and the signal processing module accurately measures the weak static magnetic field, the ratio of the change in square wave signal frequency to the change in the weak static magnetic field is increased, significantly improving the sensitivity of the weak static magnetic field measurement. Finally, theoretical calculations and analysis are used to derive the relationship between the frequency difference and the weak static magnetic field, realizing the calculation and measurement of the weak static magnetic field.

[0036] The working process of the embodiments of the present invention is as follows: Before the specific experimental measurement, adjust the laser 1, the first polarizer 2, the Faraday rotator crystal 3, the second polarizer 4, and the photodiode 5 so that the centers of each component are coaxial and the first polarizer 2 and the second polarizer 4 are perpendicular to the axis; connect the output of the photodiode 5 in series with the transimpedance amplifier 6 and the voltage-frequency converter 7; connect the output of the voltage-frequency converter 7 and the signal generator 9 to the CH1 and CH2 channels of the oscilloscope, respectively.

[0037] The specific implementation uses a Helmholtz coil (132 turns, R=0.3m) as the standard static magnetic field, and the laboratory geomagnetic field as the static magnetic field to be measured. The specific equipment used includes a semiconductor laser (GCI-07-632-20), a Faraday rotator crystal 3 (TGG crystal, Φ3mm×8mm), an adjustable polarizer (FLP25-VIS-M), several coaxial cables, an adjustable power supply (for powering the Helmholtz coil), a multi-linear power supply (for powering the transimpedance amplifier 6 and the voltage-to-frequency converter 7), the transimpedance amplifier 6 (AD825), and the voltage-to-frequency converter 7 (LM331).

[0038] Adjust the position of the measurement system so that the Faraday optical rotator crystal 3 is located at the center of the Helmholtz coil and the Faraday optical rotator crystal 3 is coaxial with the direction of the magnetic field; set the output of the signal generator 9 to a sine wave, and adjust the signal generator 9 and the oscilloscope 8 so that the Lissajous figure of "square wave-sine wave" is coupled out in the oscilloscope 8.

[0039] The frequency of the current square wave signal is measured using the Lissajous figure method. Specifically, the frequency of the sine wave in signal generator 9 is adjusted to minimize the Lissajous figure flicker frequency, and the frequency of the square wave signal at this point is then read. f 1. Apply 0.632A to the Helmholtz coil (corresponding to B=500.09μT), and measure the frequency of the square wave signal again using the Lissajous figure method. f 2. Find the difference, and you will get... (The symbol indicates the direction of the magnetic field).

[0040] According to the formula Calculate the proportionality coefficient k .

[0041] The experimental data are as follows: Figure 2 and Figure 3 .

[0042] Experiment on frequency difference After repeating the measurement 10 times, the analysis yielded the following results: .

[0043] Then you can get B and Relationship: In other words, by obtaining the frequency difference between two Lissatogram methods, the magnitude of the magnetic induction intensity of a weak static magnetic field can be measured. The measured frequency is when the Helmholtz coil is not energized. f 1 Measurement results without applying a magnetic field The objective of the data set experiment was to analyze the minimum magnetic field value that the instrument could measure. By gradually decreasing the current flowing through the Helmholtz coil, and given the theoretical magnetic induction intensity B of the coil, the Lissajous figure method was used to measure the corresponding frequency difference of the magnetic field. , make Scatter plot, with the marked straight lines To make a comparison. For example... Figure 4 As shown in the results, the theoretical values ​​and actual values ​​are in excellent agreement.

[0044] Depend on Figure 5 It can be seen that when the actual value of the magnetic field is less than At that time, due to the limitations of instrument reading resolution, accurate readings are difficult to obtain. When the magnetic induction intensity... Subsequently, the relative error decreases with increasing magnetic induction intensity, and the maximum absolute error of the measurement... The minimum value that the instrument can measure is .

[0045] Based on Malus's law, Faraday's law, and actual experimental optical and electrical paths, the following formula for calculating magnetic flux density B can be derived: in, The angle between the polarizer and the analyzer. The light intensity when the polarizer and analyzer are perfectly perpendicular, and the angle between them is... Light intensity without an external magnetic field These are the Verdet constant and the effective optical rotation length of the optically active crystal, respectively. For the measured frequency, , These are parameters set according to the actual optical path and circuit configuration. The Taylor expansion of the formula for calculating magnetic flux density B is performed, first rewriting the above formula as: Where the coefficient , .

[0046] Take the absolute value and record it. hour The value is ,exist Expanding the nearby Taylor terms to first order, we get: Where C is a constant, that is: in, B 0 represents the frequency measured when no magnetic field is applied. kf The value of +C is used to subtract the two equations, resulting in the final formula for calculating the magnetic field. B x : The formula has extremely small nonlinear error. Only the proportionality coefficient needs to be calibrated experimentally. This allows for a more accurate measurement of the magnetic field.

[0047] The above explanation illustrates the linear relationship between magnetic induction intensity and frequency difference. Theoretical calculations were used to derive the relationship between frequency difference and weak static magnetic field, enabling the calculation and measurement of the weak static magnetic field. This reduces the impact of laser intensity instability, optical path setup errors, and external environmental interference on the measurement, further minimizing measurement errors.

[0048] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A device for measuring weak static magnetic fields using the Lissajous figure method, characterized in that: The system includes a Faraday magneto-optical sensing system, a signal processing module, an oscilloscope (8), and a signal generator (9). The Faraday magneto-optical sensing system and the signal processing module are arranged along the optical path, and the Faraday magneto-optical sensing system transmits optical signals to the signal processing module. The oscilloscope (8) is connected to the signal processing module and the signal generator (9) respectively. The signals emitted by the signal processing module and the signal generator (9) are coupled through the oscilloscope (8) to form a Lissajous figure. The Faraday magneto-optical sensing system is placed in the static magnetic field to be measured, and the Lissajous figure is used to reflect the magnitude of the magnetic induction intensity of the static magnetic field to be measured.

2. The device for measuring weak static magnetic fields using the Lissajous figure method according to claim 1, characterized in that: The Faraday magneto-optical sensing system mainly consists of a laser (1), a polarizer group, and a Faraday rotator crystal (3). The laser (1) and the polarizer group are arranged sequentially at intervals along the light propagation direction. The Faraday rotator crystal (3) is placed in the polarizer group and located in the middle of the polarizer group. The Faraday rotator crystal (3) is placed in the static magnetic field to be measured. The polarization plane of the laser is rotated due to the influence of the magnetic induction intensity of the static magnetic field to be measured.

3. The apparatus for measuring weak static magnetic fields using the Lissajous figure method according to claim 2, characterized in that: The polarizer group includes a first polarizer (2) and a second polarizer (4) with adjustable polarization direction. The Faraday rotator crystal (3) is disposed between the first polarizer (2) and the second polarizer (4) and is located in the direction of light propagation.

4. The apparatus for measuring weak static magnetic fields using the Lissajous figure method according to claim 1, characterized in that: The signal processing module includes a photodiode (5), a transimpedance amplifier (6), and a voltage-to-frequency converter (7). The photodiode (5) is used to receive the optical signal output by the Faraday magneto-optical sensing system. The photodiode (5) is located in the direction of light propagation and the receiving end faces the output end of the second polarizer (4) of the polarizer group. The output end is electrically connected to the transimpedance amplifier (6), the voltage-to-frequency converter (7), and the oscilloscope (8).

5. A device for measuring weak static magnetic fields using the Lissajous figure method according to claim 3 or 4, characterized in that: The center of the laser beam emitted by the laser (1), the center of the first polarizer (2), the center of the Faraday rotator crystal (3), the center of the second polarizer (4), and the center of the photodiode (5) are arranged along the same optical propagation line.

6. A method for measuring weak static magnetic fields using the Lissajous figure method applied to the apparatus described in any one of claims 1-4, characterized in that: S1: The laser (1) emits a beam of light, which enters the first polarizer (2) to form linearly polarized light. The linearly polarized light is emitted to the Faraday optical rotator crystal (3) set on the static magnetic field to be measured. After passing through the Faraday optical rotator crystal (3), the light undergoes optical rotation. After passing through the second polarizer (4), the light enters the photodiode (5) to form a photocurrent. The photocurrent is processed by the signal processing module to form a square wave signal affected by the magnetic induction intensity of the static magnetic field. The square wave signal is transmitted to the oscilloscope (8) and displayed. S2: The sine wave signal generated by the signal generator (9) is connected to the oscilloscope (8) for display, so that the sine wave signal and the square wave signal are coupled in the oscilloscope (8) to obtain the Lissajous figure of "square wave-sine wave"; S3: By adjusting the frequency of the sinusoidal signal of the signal generator (9), the Lissajous pattern flicker frequency is minimized. The frequency of the square wave signal affected by the magnetic induction intensity of the static magnetic field at the minimum flicker frequency of the Lissajous pattern is taken. The frequency of the square wave signal affected by the magnetic induction intensity of the static magnetic field is analyzed and processed to calculate the magnitude of the magnetic induction intensity of the static magnetic field where the Faraday optical rotator crystal (3) is located.

7. The method for measuring weak static magnetic fields using the Lissajous figure method according to claim 6, characterized in that: Before step S1 begins, the first polarizer (2) is adjusted so that its polarization direction is parallel to the direction of light propagation, and the second polarizer (4) is adjusted so that its polarization direction is nearly perpendicular to the polarization direction of the first polarizer (2), so that the photodiode (5) can receive the signal and is not saturated.

8. The method for measuring weak static magnetic fields using the Lissajous figure method according to claim 6, characterized in that: When no static magnetic field to be measured is applied, the frequency of the square wave signal when no static magnetic field to be measured is measured through steps S1, S2 and S3.

9. The method for measuring weak static magnetic fields using the Lissajous figure method according to claim 8, characterized in that: In step S3, the frequency of the square wave signal affected by the static magnetic field is analyzed and processed to calculate the measurement result of the magnetic induction intensity of the static magnetic field to be measured. That is, the magnetic induction intensity of the static magnetic field to be measured is obtained by the following formula: in, B This indicates the magnitude of the magnetic induction intensity of the static magnetic field to be measured. △f This represents the difference in frequency between the square wave signal when the static magnetic field to be measured is applied and when no static magnetic field to be measured is applied. k This represents the proportionality coefficient.

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