A method for in-situ calibration of coil constant of a micro three-dimensional magnetic compensation coil

Abstract

The present application relates to a kind of in-situ calibration method of coil constant of micro three-dimensional magnetic compensation coil.The coil constant of micro coil is equivalently characterized based on the idea of volume average magnetic field, and the coil constant of micro coil is calibrated reversely using large coil whose coil constant has been calibrated, which effectively improves the precision of coil constant calibration of micro coil, thereby solving the problem that coil constant cannot be calibrated using traditional fluxgate magnetometer due to the micro volume (≤1cm 3 ) of micro coil and its easy bending deformation. The method is reasonable, and the experimental operation is simple. The coil constant of micro coil can be calibrated after its assembly, which effectively improves the accuracy of magnetic field measurement of single atomic magnetometer and the consistency of magnetic field measurement among multiple probes of array atomic magnetometer, and plays a great role in promoting the development of atomic magnetometer.

Description

Technical Field

[0001] This invention relates to the field of coil constant calibration technology for three-dimensional magnetic field coils, specifically to a method for in-situ calibration of the coil constant of a miniature three-dimensional magnetic compensation coil. Based on the idea of ​​volume-averaged magnetic field, the method equivalently characterizes the coil constant of the miniature coil. It uses a large coil whose coil constant has already been calibrated to calibrate the miniature coil in reverse, effectively improving the accuracy of the coil constant calibration for miniature coils, thereby solving the problem caused by the small size of the coil (≤1cm). 3 It is smaller than a fluxgate magnetometer and is prone to bending and deformation, making it impossible to use a traditional fluxgate magnetometer for coil constant calibration. Background Technology

[0002] With the intersection and integration of cutting-edge sciences such as quantum optics, atomic physics, and precision measurement, atomic magnetometers based on the interaction of magnetism, light, and atoms have made great strides in the theory and methods of magnetic field measurement. This has provided revolutionary measurement techniques for non-invasive functional neuroimaging. In particular, the spin-exchange relaxation-free (SERF) atomic magnetometer, invented at the beginning of this century, has achieved a significant breakthrough in sensitivity within just a few years, reaching sub-fT / Hz levels. 1 / 2 The magnitude of this is the highest level currently achieved by humankind in detecting weak magnetic fields, and it holds immense promise in biomedical and fundamental physics fields such as biomagnetic imaging, geological exploration, and dark matter discovery. There are numerous research directions related to SERF atomic magnetometers, one of which is the pursuit of miniaturization.

[0003] In the process of measuring magnetic fields using a SERF atomic magnetometer, a three-dimensional magnetic field coil is needed to compensate for the three-dimensional remanence in order to achieve an extremely weak magnetic environment. This allows alkali metal atoms to operate in the SERF state and perform magnetic field measurements. The accuracy of the coil constant calibration determines the accuracy of the magnetic field measurement. Generally, large composite coils wound on irregularly shaped frames use fluxgate magnetometers to calibrate their coil constants. However, miniature SERF atomic magnetometers typically use flexible FPC three-dimensional coils (FPC, Flexible Printed Circuit, with a coil volume ≤ 1 cm³). 3The coil volume of a micro-coil is much smaller than that of a typical fluxgate magnetometer. Therefore, the coil constant of a micro-coil cannot be calibrated using the same methods as for large coils. Furthermore, during assembly, the micro-coil is prone to bending and deformation, introducing significant magnetic field errors. Thus, coil constant calibration cannot be performed before assembly. To improve the accuracy of the magnetometer, the coil constant needs to be calibrated for each assembled flexible coil. Based on this, this invention proposes a method for equivalently characterizing the coil constant of a micro-coil using the concept of volume-averaged magnetic field. This method uses a large coil whose coil constant has already been calibrated to calibrate the coil constant of the micro-coil in reverse, effectively solving the above problems. Summary of the Invention

[0004] The technical problem this invention aims to solve is to overcome the shortcomings of existing technologies and propose a method for in-situ calibration of the coil constant of a miniature three-dimensional magnetic compensation coil. This method uses the concept of volume-averaged magnetic field to equivalently characterize the coil constant of the miniature coil. It employs a large coil whose coil constant has already been calibrated to calibrate the miniature coil in reverse, effectively improving the accuracy of the coil constant calibration for miniature coils. This solves the problem caused by the small size of the coil (≤1cm). 3 The traditional atomic magnetometer (smaller than a fluxgate magnetometer) is prone to bending and deformation, making coil constant calibration impossible. This new method is reasonable, simple to operate, and allows for coil constant calibration after the micro-coil is assembled. It effectively improves the accuracy of magnetic field measurements by a single atomic magnetometer and the consistency of magnetic field measurements among multiple probes in an array-type atomic magnetometer, significantly promoting the development of atomic magnetometers.

[0005] The technical solution of the present invention is as follows:

[0006] A method for in-situ calibration of the coil constant of a miniature three-dimensional magnetic compensation coil, characterized by comprising the following steps:

[0007] Step 1: Prepare a large three-dimensional magnetic compensation coil with a known coil constant. The coil constant is the ratio of the magnetic induction intensity B of the magnetic field generated by the coil to the current I flowing through the coil. Let the coil constant of the large three-dimensional magnetic compensation coil be k. L k L =B / I;

[0008] Step 2: Use a large three-dimensional magnetic compensation coil to compensate the three-dimensional remanence of the SERF atomic magnetometer to zero, so that the SERF atomic magnetometer is in normal working condition.

[0009] Step 3: Apply a sweep signal to the sensitive axis of the SERF atomic magnetometer using a large three-dimensional magnetic compensation coil to obtain the response coefficient K of the SERF atomic magnetometer. LThe response coefficient is the SERF atomic magnetometer response amplitude corresponding to a unit sweep current, K. L = Response amplitude / sweep current;

[0010] Step 4: Apply a sweep signal again to the same sensitive axis of the SERF atomic magnetometer using the micro-sized three-dimensional magnetic compensation coil to be tested, and obtain the response coefficient K of the SERF atomic magnetometer. S ;

[0011] Step 5, using k L K L and K S The coil constant k of the micro-sized three-dimensional magnetic compensation coil under test was calculated. S k S =k L (K S / K L ).

[0012] In step 1, the unit of B is nT, and the unit of I is mA, k L The unit is nT / mA; in step 3, K L The unit is V / mA; in step 4, K S The unit is V / mA; in step 5, k S The unit is nT / mA.

[0013] There are several ways to wind the large three-dimensional magnetic compensation coil. It can be a combination coil of a transverse saddle-shaped coil and a longitudinal Lee-Whiting coil wound on an irregularly shaped coil skeleton; or it can be a three-dimensional Helmholtz coil.

[0014] The coil volume of the miniature three-dimensional magnetic compensation coil is ≤1cm². 3 .

[0015] Step 3 includes performing linear fitting on the linear region of the response signal curve, where the slope of the fitted line corresponds to K. L .

[0016] Step 4 includes performing linear fitting on the linear region of the response signal curve, where the slope of the fitted line corresponds to K. S .

[0017] The micro-sized three-dimensional magnetic compensation coil is a flexible coil hexahedron (FPC) folded from a flexible printed circuit board (FPC).

[0018] k in step 1 L The calibration is performed using a fluxgate magnetometer, and the SERF atomic magnetometer in step 2 is pre-installed with a miniature three-dimensional magnetic compensation coil to be measured.

[0019] Step 2 includes the meter head of the SERF atomic magnetometer, which is equipped with a cable and has a miniature three-dimensional magnetic compensation coil to be measured inside. The meter head is located in the uniform magnetic field region of the large three-dimensional magnetic compensation coil with a coil frame, and the large three-dimensional magnetic compensation coil is located inside a magnetic shielding barrel.

[0020] The technical effects of this invention are as follows: This invention provides a method for in-situ calibration of the coil constant of a miniature three-dimensional magnetic compensation coil. This method can accurately calibrate the coil constant of the miniature coil, thus effectively solving the problem that the coil constant cannot be calibrated using a traditional fluxgate magnetometer due to the small size and easy bending deformation of the coil. Only a large coil with a known coil constant (which can be calibrated using a fluxgate magnetometer) needs to be prepared. Then, the large coil is used to compensate the three-dimensional remanence of the SERF atomic magnetometer to zero, putting the SERF atomic magnetometer into normal working condition. Next, sweep signals are applied to the same sensitive axis using both the large coil and the miniature coil, and the corresponding response coefficients are obtained respectively. Finally, the coil constant of the miniature coil can be deduced from the coil constant of the large coil.

[0021] The advantages of this invention are:

[0022] (1) The volume-averaged magnetic field method was used to equivalently characterize the coil constant of the miniature coil, and a large coil with a known coil constant was used to reverse-calibrate the coil constant of the miniature coil, which effectively improved the accuracy of the calibration of the coil constant of the miniature coil, thus solving the problem caused by the small size of the coil (≤1cm). 3 (It is smaller than a fluxgate magnetometer) and is prone to bending and deformation, making it impossible to use a traditional fluxgate magnetometer for coil constant calibration.

[0023] (2) After the coil is assembled, or even after the SERF atomic magnetometer is working properly, the coil constant can be calibrated using the method of this invention. This is equivalent to using this method to perform factory calibration of the coil constant of the small coil, which effectively improves the accuracy of the magnetic field measurement of a single SERF atomic magnetometer and the consistency of the magnetic field measurement between multiple probes of the array SERF atomic magnetometer.

[0024] (3) The experimental operation of the present invention is simple and can accurately calibrate the coil constant of the micro-integrated three-dimensional magnetic compensation coil, which effectively promotes the development of SERF atomic magnetometer towards miniaturization. Attached Figure Description

[0025] Figure 1 This is a schematic flowchart illustrating the method for in-situ calibration of the coil constant of a miniature three-dimensional magnetic compensation coil according to the present invention. Figure 1The process includes step 1, preparing a large three-dimensional magnetic compensation coil whose coil constant is known. The coil constant is the ratio of the magnetic induction intensity B (unit: nT) of the magnetic field generated by the coil to the current I (unit: mA) flowing through the coil; it is a scalar quantity, and the unit of the coil constant is nT / mA. Let the coil constant of the large three-dimensional magnetic compensation coil be k. L (Unit: nT / mA); Step 2: Use a large coil to compensate the three-dimensional remanence of the SERF atomic magnetometer to zero, so that the SERF atomic magnetometer is in normal working condition; Step 3: Use the large coil to apply a sweep signal to the sensitive axis of the SERF atomic magnetometer to obtain the magnetometer's response coefficient K. L (Unit is V / mA), the response coefficient refers to the response amplitude of the atomic magnetometer corresponding to a unit sweep current; Step 4, apply the sweep signal again to the same sensitive axis of the SERF atomic magnetometer using the micro-coil to be measured, and obtain the response coefficient K of the magnetometer at this time. S Its unit is V / mA; Step 5, using k L K L and K S The coil constant k of the micro-coil under test is calculated. S (Unit: nT / mA), k S =k L (K S / K L ).

[0026] Figure 2 The schematic diagram of the structure of the integrated SERF atomic magnetometer probe, the large three-dimensional magnetic compensation coil, and the micro-sized coil involved in implementing the method of in-situ calibration of the coil constant of a micro-sized three-dimensional magnetic compensation coil of the present invention is shown. Figure 2 The middle section shows the axial cross-sectional structure of the SERF atomic magnetometer prototype. The outermost layer is a magnetic shielding barrel. Closely adjacent to the magnetic shielding barrel is a large combined coil, namely the large three-dimensional magnetic compensation coil (whose coil constant has been calibrated). The large combined coil is wound on the coil skeleton. The central area inside the barrel is the uniform magnetic field region generated by the large coil. The meter head (also called the probe) of the small SERF atomic magnetometer is placed in the uniform magnetic field region. The meter head contains a small coil, namely the micro three-dimensional magnetic compensation coil.

[0027] Figure 3 This is a graph showing the relationship between the output response of a SERF atomic magnetometer and the coil sweep current, obtained by applying sweep signals using both a large coil and a small coil, respectively, in accordance with the method for in-situ calibration of the coil constant of a miniature three-dimensional magnetic compensation coil according to the present invention. The large coil refers to a large-scale three-dimensional magnetic compensation coil, and the small coil refers to a miniature three-dimensional magnetic compensation coil. Figure 3The left side of the middle figure shows the relationship between the magnetometer output response and the sweep current. The sweep current has a large range, and both curves exhibit the characteristics of dispersive curves. The dashed line represents the response curve after sweeping with the large coil, and the solid line represents the response curve after sweeping with the small coil. The linear regions of both curves are near the sweep current of 0mA. Figure 3 The right-hand side of the graph is the curve obtained by linearly fitting the linear region of the output response curve in the left-hand side graph. The straight line marked with a solid circle (a relatively gentle straight line) represents the fitted straight line of the large coil, and the straight line marked with a plus sign "+" (a relatively steep straight line) represents the fitted straight line of the small coil.

[0028] The following are the annotations in the attached diagram: 1-Magnetic shielding barrel; 2-Large coil or large three-dimensional magnetic compensation coil or large combined coil; 3-Signature of the SERF atomic magnetometer; 4-Miniature coil or miniature three-dimensional magnetic compensation coil or small coil; 5-Coil frame; 6-Uniform magnetic field area generated by the large coil; 7-Cables (various cables entering the signature of the integrated SERF atomic magnetometer, such as optical fibers). Detailed Implementation

[0029] The following is in conjunction with the attached diagram ( Figures 1-3 The invention will be described in the following sections and examples.

[0030] Figure 1 This is a schematic flowchart illustrating the method for in-situ calibration of the coil constant of a miniature three-dimensional magnetic compensation coil according to the present invention. Figure 2 The schematic diagram of the structure of the integrated SERF atomic magnetometer probe, the large three-dimensional magnetic compensation coil, and the micro-sized coil involved in implementing the method of in-situ calibration of the coil constant of a micro-sized three-dimensional magnetic compensation coil of the present invention is shown. Figure 3 This is a graph showing the relationship between the output response of a SERF atomic magnetometer and the coil sweep current, obtained by applying sweep signals using both a large and small coil, respectively, in accordance with the method for in-situ calibration of the coil constant of a miniature three-dimensional magnetic compensation coil according to the present invention. (Reference) Figures 1 to 3 As shown, a method for in-situ calibration of the coil constant of a miniature three-dimensional magnetic compensation coil is characterized by the following steps: Step 1, prepare a large three-dimensional magnetic compensation coil whose coil constant is known. The coil constant is the ratio of the magnetic induction intensity B of the magnetic field generated by the coil to the current I flowing through the coil. Let the coil constant of the large three-dimensional magnetic compensation coil be k. L k L =B / I; Step 2, use a large three-dimensional magnetic compensation coil to compensate the three-dimensional remanence of the SERF atomic magnetometer to zero, so that the SERF atomic magnetometer is in normal working condition; Step 3, use a large three-dimensional magnetic compensation coil to apply a sweep signal to the sensitive axis of the SERF atomic magnetometer to obtain the response coefficient K of the SERF atomic magnetometer. LThe response coefficient is the SERF atomic magnetometer response amplitude corresponding to a unit sweep current, K. L = Response amplitude / sweep current; Step 4: Apply a sweep signal again to the same sensitive axis of the SERF atomic magnetometer using the micro-sized three-dimensional magnetic compensation coil under test to obtain the response coefficient K of the SERF atomic magnetometer. S Step 5, using k L K L and K S The coil constant k of the micro-sized three-dimensional magnetic compensation coil under test was calculated. S k S =k L (K S / K L ).

[0031] In step 1, the unit of B is nT, and the unit of I is mA, k L The unit is nT / mA; in step 3, K L The unit is V / mA; in step 4, K S The unit is V / mA; in step 5, k S The unit is nT / mA. The large three-dimensional magnetic compensation coil can be wound in various ways, including by winding a combination of a transverse saddle-shaped coil and a longitudinal Lee-Whiting coil on an irregularly shaped coil frame; or it can be a three-dimensional Helmholtz coil. The volume of the miniature three-dimensional magnetic compensation coil is ≤1cm². 3 .

[0032] Step 3 includes performing linear fitting on the linear region of the response signal curve, where the slope of the fitted line corresponds to K. L Step 4 includes performing linear fitting on the linear region of the response signal curve, where the slope of the fitted line corresponds to K. S The miniature three-dimensional magnetic compensation coil is a flexible coil hexahedron folded from a flexible printed circuit board (FPC). In step 1, k... L The calibration is performed using a fluxgate magnetometer. In step 2, the SERF atomic magnetometer has a pre-installed miniature three-dimensional magnetic compensation coil to be measured. Step 2 includes the meter head 3 of the SERF atomic magnetometer, which has a cable 7. The miniature three-dimensional magnetic compensation coil 4 to be measured is assembled inside the meter head. The meter head is located within the uniform magnetic field region 6 of the large three-dimensional magnetic compensation coil 2, which has a coil frame 5. The large three-dimensional magnetic compensation coil 2 is located inside a magnetic shielding barrel 1.

[0033] This invention relates to a method for in-situ calibration of the coil constant of a miniature three-dimensional magnetic compensation coil. Based on the concept of volume-averaged magnetic field to equivalently characterize the coil constant of the miniature coil, a large coil whose coil constant has already been calibrated is used to reverse-calibrate the miniature coil, effectively improving the accuracy of the coil constant calibration of the miniature coil, thereby solving the problem caused by the small size of the coil (≤1cm). 3 The traditional atomic magnetometer (smaller than a fluxgate magnetometer) is prone to bending and deformation, making coil constant calibration impossible. This new method is reasonable, simple to operate, and allows for coil constant calibration after the micro-coil is assembled. It effectively improves the accuracy of magnetic field measurements by a single atomic magnetometer and the consistency of magnetic field measurements among multiple probes in an array-type atomic magnetometer, significantly promoting the development of atomic magnetometers.

[0034] This invention proposes a method for in-situ calibration of the coil constant of a miniature three-dimensional magnetic compensation coil. The concept of volume-averaged magnetic field used in this method is explained as follows:

[0035] Under the same operating conditions, the magnetometer responds to the same magnetic field size in the same way. That is, within the sensitive area of ​​the magnetometer, whether a large coil with high uniformity or a small coil with poor uniformity is used to apply a magnetic field to the atomic ensemble, as long as the average magnetic field in the sensitive area is the same, the magnetometer will respond to both in the same way.

[0036] This invention proposes a method for in-situ calibration of the coil constant of a miniature three-dimensional magnetic compensation coil. The miniature three-dimensional coil involved is generally a flexible coil hexahedron folded from a flexible FPC circuit board. Due to the small size and flexibility of the flexible coil, it is difficult to ensure the orthogonality of its assembly during installation. Therefore, the coil constant needs to be calibrated after the magnetometer is assembled. Otherwise, if the coil constant is calibrated before assembly, the flexible small coil will introduce a very large magnetic field measurement error due to bending and deformation during the assembly process.

[0037] This invention proposes a method for in-situ calibration of the coil constant of a miniature three-dimensional magnetic compensation coil. The definitions of the two terms involved, "coil constant" and "response coefficient," are as follows:

[0038] The coil constant is the ratio of the magnetic flux density B (in nT) of the magnetic field generated by the coil to the current I (in mA) flowing through the coil. It is a scalar quantity, and the unit of the coil constant is nT / mA. The response coefficient of a SERF atomic magnetometer refers to the response amplitude of the atomic magnetometer corresponding to a unit sweep current. The unit of the response coefficient is V / mA. Specifically, it is obtained by applying a sweep current to the coil along the sensitive axis of the magnetometer to obtain the magnetometer's response curve. A linear fit is then performed on the linear region of the response curve, and the slope of the fitted straight line is the response coefficient of the atomic magnetometer.

[0039] The specific implementation process of this invention is as follows: Figure 1 As shown, a method for in-situ calibration of the coil constant of a miniature three-dimensional magnetic compensation coil includes the following steps:

[0040] Step 1: Prepare a large composite coil (hereinafter referred to as the "large coil") wound in a specific manner, and calibrate its coil constant as k using a fluxgate magnetometer. L (Unit: nT / mA);

[0041] Step 2: Use a large coil to compensate the three-dimensional magnetic field of the SERF atomic magnetometer to zero, so that the SERF atomic magnetometer is in normal working condition.

[0042] Step 3: Apply a sweep signal to the sensitive axis of the SERF atomic magnetometer using a large coil to obtain the magnetometer's response coefficient K. L Its unit is V / mA;

[0043] Step 4: Apply a sweep signal to the same sensitive axis of the SERF atomic magnetometer again using the micro-coil to be tested, and obtain the response coefficient K of the magnetometer at this time. S Its unit is V / mA;

[0044] Step 5, the coil constant k of the miniature coil S (Unit: nT / mA) The calculation formula is as follows:

[0045]

[0046] Furthermore, in step 1, the large coil can be a combination of a transverse saddle-shaped coil and a longitudinal Lee-Whiting coil wound on an irregularly shaped coil frame. However, the winding of the coil is not limited to the above method; it can also be a three-dimensional Helmholtz coil. The magnetic field-current data of the large coil are measured using an existing fluxgate magnetometer and a precision current source, and then linear fitting is performed to calibrate its corresponding coil constant k. L(Unit: nT / mA). Here is the definition of coil constant: Coil constant is the ratio of the magnetic induction intensity B (unit: nT) of the magnetic field generated by the coil to the current I (unit: mA) flowing through the coil. It is a scalar quantity, and the unit of coil constant is nT / mA.

[0047] Furthermore, in step 2, the three-dimensional residual magnetic field of the SERF atomic magnetometer is first compensated to zero using a large coil, so that the SERF atomic magnetometer is in normal working condition.

[0048] Furthermore, K in step 3 L It utilizes a large coil to apply a sweep signal along the sensitive axis of the SERF atomic magnetometer. The magnetometer generates a response signal curve, and linear fitting is performed on the linear region of the curve. The slope of the fitted line corresponds to the magnetometer's response coefficient K. L The unit is V / mA. Here is the definition of the response coefficient of the SERF atomic magnetometer: The response coefficient refers to the response amplitude of the atomic magnetometer corresponding to a unit sweep current. The unit of the response coefficient is V / mA. Specifically, it is obtained by applying a sweep current to the coil along the sensitive axis of the magnetometer to obtain the response curve of the magnetometer. The linear region of the response curve is linearly fitted, and the slope of the fitted line is the response coefficient of the atomic magnetometer.

[0049] Furthermore, K in step 4 S The magnetometer response coefficient K is obtained by sweeping the field with a large coil. L Next, a sweep signal is applied to the same sensitive axis of the SERF atomic magnetometer using the small coil under test. The magnetometer will generate a response signal curve. Linear fitting is performed on the linear region of the curve, and the slope of the fitted line corresponds to the response coefficient K of the magnetometer at this time. S The unit is V / mA.

[0050] Contents not described in detail in this specification are prior art known to those skilled in the art. It is hereby indicated that the above description is intended to help those skilled in the art understand this invention, but does not limit the scope of protection of this invention. Any equivalent substitutions, modifications, improvements, and / or simplifications of the above descriptions that do not depart from the essential content of this invention fall within the scope of protection of this invention.

Claims

1. A method for in-situ calibration of the coil constant of a miniature three-dimensional magnetic compensation coil, characterized in that, Includes the following steps: Step 1: Prepare a large three-dimensional magnetic compensation coil with a known coil constant. The coil constant is the ratio of the magnetic induction intensity B of the magnetic field generated by the coil to the current I flowing through the coil. Let the coil constant of the large three-dimensional magnetic compensation coil be k. L k L =B / I; Step 2: Use a large three-dimensional magnetic compensation coil to compensate the three-dimensional remanence of the SERF atomic magnetometer to zero, so that the SERF atomic magnetometer is in normal working condition. Step 3: Apply a sweep signal to the sensitive axis of the SERF atomic magnetometer using a large three-dimensional magnetic compensation coil to obtain the response coefficient K of the SERF atomic magnetometer. L The response coefficient is the SERF atomic magnetometer response amplitude corresponding to a unit sweep current, K. L =Response amplitude / sweep current; Step 4: Apply a sweep signal again to the same sensitive axis of the SERF atomic magnetometer using the micro-sized three-dimensional magnetic compensation coil to be tested, and obtain the response coefficient K of the SERF atomic magnetometer. S ; Step 5, using k L K L and K S The coil constant k of the micro-sized three-dimensional magnetic compensation coil under test was calculated. S k S =k L (K) S / K L ); Step 2 includes the meter head of the SERF atomic magnetometer, the meter head is equipped with a cable, the meter head is equipped with a micro three-dimensional magnetic compensation coil to be measured, the meter head is located in the magnetic field uniform region of the large three-dimensional magnetic compensation coil with coil skeleton, and the large three-dimensional magnetic compensation coil is located in a magnetic shielding barrel. Step 3 includes performing linear fitting on the linear region of the response signal curve, where the slope of the fitted line corresponds to K. L ; Step 4 includes performing linear fitting on the linear region of the response signal curve, where the slope of the fitted line corresponds to K. S .

2. The method for in-situ calibration of the coil constant of a miniature three-dimensional magnetic compensation coil according to claim 1, characterized in that, In step 1, the unit of B is nT, and the unit of I is mA, k L The unit is nT / mA; in step 3, K L The unit is V / mA; in step 4, K S The unit is V / mA; in step 5, k S The unit is nT / mA.

3. The method for in-situ calibration of the coil constant of a miniature three-dimensional magnetic compensation coil according to claim 1, characterized in that, There are several ways to wind the large three-dimensional magnetic compensation coil, including by winding a combination coil of transverse saddle-shaped coil and longitudinal Lee-Whiting coil on an irregularly shaped coil skeleton, or by using a three-dimensional Helmholtz coil.

4. The method for in-situ calibration of the coil constant of a miniature three-dimensional magnetic compensation coil according to claim 1, characterized in that, The coil volume of the miniature three-dimensional magnetic compensation coil is ≤1cm². 3 .

5. The method for in-situ calibration of the coil constant of a miniature three-dimensional magnetic compensation coil according to claim 1, characterized in that, The micro-sized three-dimensional magnetic compensation coil is a flexible coil hexahedron folded from a flexible printed circuit board (FPC).

6. The method for in-situ calibration of the coil constant of a miniature three-dimensional magnetic compensation coil according to claim 1, characterized in that, k in step 1 L The calibration is performed using a fluxgate magnetometer, and the SERF atomic magnetometer in step 2 is pre-installed with a miniature three-dimensional magnetic compensation coil to be measured.

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