Uniform magnetic field control method in X-Y plane and detection equipment

Abstract

The invention provides a method for controlling a uniform magnetic field in an X-Y plane, and the method comprises the steps: forming a magnetic field parallel to the X-Y plane in an X-axis, a Y-axis or a direction in a preset region through a pole head and a corresponding first excitation coil and second excitation coil, achieving a larger uniform region, and enabling the control to be more convenient; by means of the interval between the pole heads, the probe used for transmitting electric signals to a measured object extends into and is in contact with the measured object, extending of the probe is facilitated, and interference of a magnetic field on the signals transmitted by the probe is reduced. The invention further provides detection equipment, a large magnetic field uniform area can be formed, so that a larger area can be detected, meanwhile, a probe can conveniently stretch into the area to be inserted, and operation is convenient.

Description

Technical Field

[0001] The present invention belongs to the technical field of magnetic material detection, relates to a device for generating a magnetic field environment, and specifically relates to an in-plane vector magnetic field control method and detection device. Background Art

[0002] Magnetic material detection is of great significance in physics, materials science, electronics and industrial production. In some cases, it is necessary to build a certain magnetic field environment at the location of the object to be tested, detect the magnetic characteristics of the object under the corresponding magnetic field environment, and analyze the magnetic properties of the object under test. Therefore, the device that generates the magnetic field environment is an important component required for magnetic detection.

[0003] Among the magnetic detection methods, the magnetic detection method using the magneto-optical Kerr effect detects the Kerr rotation angle of the light reflected by the object to be measured, thereby obtaining the magnetism of the object to be measured, and can perform non-destructive detection on the object to be measured. It is an important magnetic detection method. CN102252969A discloses a magneto-optical Kerr effect and magnetocrystalline anisotropy field measurement system and measurement method, wherein the measurement system includes two parts: a magnet control part and a laser detection part. The magnet control part mainly includes a magnet frame, a power supply, an ADDA card and a computer. The computer controls the magnitude and direction of the output current of the two power supplies respectively through the ADDA card, and controls the magnitude and direction of the magnetic field respectively, to obtain the required synthetic magnetic field. In this technical solution, the iron cores of four electromagnets extend toward the sample from four directions around the sample to form a synthetic magnetic field at the sample. However, since the magnetic field gradually diverges from the pole head to the direction away from the pole head, when multiple pole heads work together to form a synthetic magnetic field, the iron cores that are far away from each other make it difficult to control the size, direction and other characteristics of the magnetic field, and on the other hand, the uniformity of the magnetic field formed is low; however, if the distance between the iron cores is reduced, the storage space for samples and other related equipment will be drastically reduced, affecting the use of the equipment.

[0004] The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Summary of the invention

[0005] In view of the problem of low magnetic field uniformity in the prior art, the present invention is limited to provide a uniform magnetic field control method in an XY plane, wherein four poles in the XY plane are respectively arranged in four areas divided by an X-axis and a Y-axis, and the ends of the four poles are extended at the intersection of the X-axis and the Y-axis and are provided with intervals, the magnetic circuit where the four poles are located is connected to the yoke magnetic connection, and a first excitation coil and a second excitation coil are provided in the magnetic circuit where each pole head is located, and the X-axis component of the magnetic field between the pole heads is formed by making the first excitation coils in the magnetic circuit where the four pole heads are located work at the same time, and the Y-axis component of the magnetic field between the pole heads is formed by making the second excitation coils in the magnetic circuit where the four pole heads are located work at the same time; the excitation directions of the first excitation coils in the magnetic circuit where non-adjacent pole heads are located are opposite, and the excitation directions of the second excitation coils in the magnetic circuit where non-adjacent pole heads are located are opposite.

[0006] Preferably, the poles located on both sides of the X-axis are symmetrically arranged with respect to each other; the poles located on both sides of the Y-axis are symmetrically arranged with respect to each other; the magnetic field strength generated by each of the first excitation coils is the same; the magnetic field strength generated by each of the second excitation coils is the same.

[0007] Further preferably, the four first excitation coils have the same coil structure, and the currents flowing through the four first excitation coils have the same magnitude; the four second excitation coils have the same coil structure, and the currents flowing through the four second excitation coils have the same magnitude.

[0008] Still further preferably, the four first excitation coils are connected in series and connected to a first current source; the four second excitation coils are connected in series and connected to a second current source.

[0009] Further preferably, the first excitation coil and the second excitation coil have the same structure, and the control method also includes: when a rotating magnetic field is generated, the following relationship exists between the current I1 passed through the first excitation coil and the current I2 passed through the second excitation coil: I1=Acosθ, I2=Asinθ, where θ is the rotation angle of the vector magnetic field direction, and A is a preset parameter.

[0010] Preferably, the end of the pole head is provided with a first end face and a second end face which are perpendicular to each other, and the first end faces and the second end faces of the four pole heads form a cross-shaped gap at the intersection of the X-axis and the Y-axis.

[0011] Optionally, the combinations of excitation directions of the first excitation coil and the second excitation coil in the magnetic circuits where different pole heads are located are different.

[0012] Optionally, the excitation directions of the first excitation coil and the second excitation coil located in the same magnetic circuit where the pole head is located are opposite.

[0013] The present invention also provides a detection device, including four pole heads generally arranged in the XY plane, the pole heads are respectively arranged in four areas divided by the X-axis and the Y-axis, the ends of the four pole heads extend toward the intersection of the X-axis and the Y-axis and are provided with intervals, the object to be measured is generally arranged at the intersection of the X-axis and the Y-axis, the test probe extends from the intervals toward the object to be measured, the four pole heads are respectively connected to the yoke magnetic conductor through the magnetic cores connected thereto, each of the magnetic cores is provided with a first excitation coil and a second excitation coil, the excitation directions of non-adjacent first excitation coils are opposite, the excitation directions of non-adjacent second excitation coils are opposite, the first excitation coil and the second excitation coil are respectively connected to a first power supply and a second power supply.

[0014] Preferably, the pole heads located on both sides of the X-axis are symmetrically arranged with respect to each other; and the pole heads located on both sides of the Y-axis are symmetrically arranged with respect to each other.

[0015] The present invention has at least the following beneficial effects: the first excitation coil and the second excitation coil can be controlled independently of each other, so as to independently form a magnetic field along the X-axis, the Y-axis or a direction parallel to the XY plane in a preset area, and the control of the first excitation coil and the second excitation coil can also be related to each other, and the direction and strength of the magnetic field parallel to the XY plane can be controlled together, so as to have a larger uniform area, be able to detect a larger area, and be more convenient to control; through the gap between the poles, a probe used to transmit an electrical signal to the object to be measured is inserted and contacts with the object to be measured, which facilitates the insertion of the probe and reduces the interference of the magnetic field on the signal transmitted by the probe. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the overall structure involved in one embodiment of the present invention.

[0017] Figure 2 for Figure 1 A view from another angle of the schematic diagram shown.

[0018] Figure 3 for Figure 1 A view from yet another angle of the schematic diagram shown.

[0019] Figure 4 for Figure 3 An enlarged view of section A of the schematic diagram shown.

[0020] Figure 5 Schematic diagram of the magnetic field near the pole tip end according to one embodiment of the present invention.

[0021] Figure 6 Schematic diagram of the magnetic field near the pole head end under the prior art. Implementation

[0022] In order to make the purpose and features of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are further described below in conjunction with the accompanying drawings. It should be noted that the accompanying drawings are all in a very simplified form and use inaccurate ratios, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0023] Next, combine Figures 1 to 5 The present invention is described below. The present invention provides a method for controlling a uniform magnetic field in an XY plane. An implementation of the magnetic field control device is as follows: Figure 1 As shown, four pole heads are provided, such as the first pole head 110, the second pole head 210, the third pole head 310, and the fourth pole head 410 shown in the figure. The ends of the four pole heads are close to each other and are provided with a gap. The gaps between the ends of the pole heads form a magnetic field region V, and a magnetic field is formed substantially along the direction of the XY plane in a range at least including the region V. For the convenience of explanation, in the present invention, the XY plane is divided by two axial directions of the XY plane, see Figure 3 , Figure 4 , the X-axis and the Y-axis divide the XY plane into four areas, and the four pole heads are respectively located in the four areas and extend to the intersection of the X-axis and the Y-axis. In order to make the end of the pole head have an extended magnetic field, it is necessary to set up a corresponding magnetic field generating device, and make the magnetic field generated by the magnetic field generating device extend outward through the pole head. The magnetic circuits where the four pole heads are located are respectively connected to the yoke 500, and each of the magnetic circuits where the pole heads are located is provided with a first excitation coil and a second excitation coil. In one embodiment of the present invention, a magnetic core is set so that the magnetic circuit where the pole head is located is connected to the yoke 500, and the excitation coil is sleeved on the magnetic core, and the magnetic core is connected to the pole head through magnetic conductivity, so that the magnetic field generated by the excitation coil passes through the magnetic core, the pole head and extends outward from the pole head. More specifically, the number of excitation coils sleeved on a magnetic core is set to two, namely the first excitation coil and the second excitation coil.

[0024] When controlling the magnetic field in region V, four first excitation coils are used to generate a magnetic field along the X axis. More specifically, see Figures 1 to 3The first excitation coil 121 sleeved on the magnetic core 130 of the first pole 110 and the first excitation coil 421 sleeved on the magnetic core of the fourth pole 410 generate magnetic fields in the same direction; the first excitation coil 221 sleeved on the magnetic core 230 of the second pole 210 and the first excitation coil 321 sleeved on the magnetic core of the third pole 310 generate magnetic fields in the same direction; the first excitation coils 121 and 421 in the magnetic circuit where the first pole 110 and the fourth pole 410 are located have opposite excitation directions to the first excitation coils 221 and 321 in the magnetic circuit where the second pole 210 and the third pole 310 are located. In this case, the first pole head 110, the second pole head 210, the third pole head 310, and the fourth pole head 410 jointly form a magnetic field substantially along the X-axis direction in the region V. For example, the magnetic field extends from the first pole head 110 and the fourth pole head 410 substantially along the X-axis direction to the second pole head 210 and the third pole head 310, or in the opposite direction. The excitation direction of the first excitation coil in the aforementioned form can be summarized as follows: the excitation directions of the first excitation coils in the magnetic circuits where the non-adjacent pole heads are located are opposite. Similarly, the second excitation coil also has a similar configuration. The excitation directions of the second excitation coils sleeved on the magnetic cores of the first pole head 110 and the second pole head 210 are the same, and the excitation directions of the second excitation coils sleeved on the magnetic cores of the third pole head 310 and the fourth pole head 410 are the same. Furthermore, the excitation directions of the second excitation coils 122 and 222 in the magnetic circuits where the first pole head 110 and the second pole head 210 are located are opposite to the excitation directions of the second excitation coils 322 and 422 in the magnetic circuits where the third pole head 310 and the fourth pole head 410 are located. In this case, the first pole head 110, the second pole head 210, the third pole head 310, and the fourth pole head 410 jointly form a magnetic field substantially along the Y-axis direction in the region V. The excitation directions of the second excitation coils in the aforementioned form can be summarized as follows: the excitation directions of the second excitation coils in the magnetic circuits where the non-adjacent pole heads are located are opposite.

[0025] On the basis of the above scheme, a magnetic field generally along the X-axis direction is formed by controlling the combination of the first excitation coils 121, 221, 321, and 421, and a magnetic field generally along the Y-axis direction is formed by controlling the combination of the second excitation coils 122, 222, 322, and 422. The first excitation coil can be independently controlled from the second excitation coil, so as to independently form a magnetic field along the X-axis, the Y-axis, or a direction parallel to the XY plane in an area at least including area V. The control of the first excitation coil and the second excitation coil can also be interconnected to jointly control the direction and strength of the magnetic field parallel to the XY plane. Furthermore, when the electromagnet is used in a probe detection device, the measured surface of the object to be measured can be located at Figure 2The plane P shown in the figure is used to extend the probe used to transmit the electrical signal to the object under test into the area V through the gap between the poles and contact the object under test. Since the probe needs to be roughly parallel to the magnetic field in which it is located, please refer to Figure 5 The method provided by the present invention can generate a magnetic field along the X-axis and the Y-axis, and at the same time leave a gap in the direction of the X-axis and the Y-axis to facilitate the insertion of the probe.

[0026] See also Figure 5 , showing a specific implementation effect of forming a magnetic field in the X direction in region V using the method provided by the present invention, wherein the diameter of the 90% uniformity region is Φ6.68mm, the diameter of the 95% uniformity region is Φ4.6mm, and the diameter of the 98% uniformity region is Φ2.9mm; Figure 6 The figure shows the magnetic field formed in region V when only two non-adjacent poles are used to generate a magnetic field and other conditions remain unchanged, i.e., the magnetic field generated by the prior art, wherein the diameter of the 90% uniformity region is Φ5.54mm, the diameter of the 95% uniformity region is Φ3.86mm, and the diameter of the 98% uniformity region is Φ2.40mm. Figure 5 , Figure 6 From the implementation results shown, it can be seen that the method provided by the present invention can increase the diameter of the 90% uniformity area by about 20.58% and the area by about 45.39%; the diameter of the 95% uniformity area by about 19.17% and the area by about 42.02%; the diameter of the 98% uniformity area by about 20.83% and the area by about 46.01%. It can be seen that the method provided by the present invention can greatly increase the range of the uniform area, thereby enabling the detection of a larger area of ​​the object to be tested. In addition, please continue to refer to Figure 5 , Figure 6 , Figure 5 The magnetic field strength B in the center of the magnetic field is approximately between 122.46 and 123.75. Figure 6 The magnetic field strength B in the central area of ​​the magnetic field is approximately between 109.06 and 110.20, and the magnetic field strength is increased by approximately 12.29%. The method provided by the present invention can significantly improve the magnetic field strength in the uniform area, thereby meeting more extensive testing requirements.

[0027] When the poles on both sides of the X-axis are symmetrical to each other and the poles on both sides of the Y-axis are symmetrical to each other, the magnetic field strengths generated by the first excitation coils 121, 221, 321, and 421 can be made the same, thereby forming a magnetic field roughly along the X-axis direction in region V; similarly, the magnetic field strengths generated by the second excitation coils 122, 222, 322, and 422 can be made the same, thereby forming a magnetic field roughly along the Y-axis direction in region V. Furthermore, the four first excitation coils 121, 221, 321, and 421 have the same coil structure, and the currents flowing through the four first excitation coils 121, 221, 321, and 421 are the same, so that the magnetic field strengths generated by the four first excitation coils 121, 221, 321, and 421 are the same; the four second excitation coils 122, 222, 322, and 422 have the same coil structure, and the currents flowing through the four second excitation coils 122, 222, 322, and 422 are the same, so that the magnetic field strengths generated by the four second excitation coils 122, 222, 322, and 422 are the same. It should be noted that, although the first excitation coils 121, 221, 321, 421 have the same structure, and the second excitation coils 122, 222, 322, 422 have the same structure, the direction of the first excitation coil or the second excitation coil 122, 222, 322, 422 can be configured according to actual needs, for example, they can be installed forward or reverse on the magnetic core, or the direction of the current can be configured accordingly, so as to achieve the aforementioned magnetic field direction at least along the X-axis and the Y-axis. The specific configuration method can be selected by those skilled in the art based on the above discussion, and will not be repeated here.

[0028] When the first excitation coils 121, 221, 321, and 421 have the same coil structure and the same current size, the four first excitation coils 121, 221, 321, and 421 can be connected in series and connected to a first current source to provide energy to the first excitation coils 121, 221, 321, and 421; similarly, the four second excitation coils 122, 222, 322, and 422 can be connected in series and connected to a second current source to provide energy to the second excitation coils 122, 222, 322, and 422.

[0029] On the basis of the above technical solution, when the magnetic field strength generated by the first excitation coil 121, 221, 321, 421 is controlled by current, and the magnetic field strength generated by the second excitation coil 122, 222, 322, 422 is controlled by current, the control method provided by the present invention also includes: when a rotating magnetic field is generated, the current I1 passed through the first excitation coil and the current I2 passed through the second excitation coil have the following relationship: I1=Acosθ, I2=Asinθ, where θ is the rotation angle of the vector magnetic field direction, and A is a preset parameter. In this case, the magnetic field strength of the composite magnetic field in region V can be kept unchanged when the direction rotates.

[0030] See also Figure 3 , Figure 4 , shows a specific structure of the pole head involved in the present invention, wherein the end of the pole head is provided with a first end face and a second end face perpendicular to each other, so as to form a cross-shaped gap at the intersection of the X-axis and the Y-axis to form a more uniform magnetic field in region V.

[0031] In addition, when a magnetic field composed of an X-axis component and a Y-axis component is generated, the combinations of excitation directions of the first excitation coils 121, 221, 321, 421 and the second excitation coils 122, 222, 322, 422 covered by different magnetic cores are different. As an example of an optional solution, the first excitation coil 121 provided on the magnetic circuit where the first pole head 110 is located generates a positive magnetic field, and the second excitation coil 122 generates a positive magnetic field; the first excitation coil 221 provided on the magnetic circuit where the second pole head 210 is located generates a negative magnetic field, and the second excitation coil 122 generates a positive magnetic field; the first excitation coil 321 provided on the magnetic circuit where the third pole head 310 is located generates a negative magnetic field, and the second excitation coil 322 generates a negative magnetic field; the first excitation coil 421 provided on the magnetic circuit where the fourth pole head 410 is located generates a positive magnetic field, and the second excitation coil 422 generates a negative magnetic field. On this basis, the first excitation coils 121, 221, 321, and 421 on the magnetic circuits where the poles are located work together to form a magnetic field along the X axis; similarly, the second excitation coils 122, 222, 322, and 422 on the magnetic circuits where the poles are located work together to form a magnetic field along the Y axis. At this time, the intensity of the magnetic field along the X axis is controlled by the first excitation coils 121, 221, 321, and 421, and the intensity of the magnetic field along the Y axis is controlled by the second excitation coils 122, 222, 322, and 422. In other words, the control of the magnetic field components in the X axis and Y axis directions is independent of each other, so that it is easy to control the magnetic field and its direction in region V.

[0032] In addition, similarly, on the basis of the present invention, the excitation directions of the first excitation coils 121, 221, 321, 421 and the second excitation coils 122, 222, 322, 422 which are sleeved on the same magnetic core are opposite. Specifically, as an example of an optional scheme, the first excitation coil 121 arranged on the magnetic circuit where the first pole head 110 is located generates a positive magnetic field, and the second excitation coil 122 generates a negative magnetic field; the first excitation coil 221 arranged on the magnetic circuit where the second pole head 210 is located generates a negative magnetic field, and the second excitation coil 122 generates a positive magnetic field; the first excitation coil 321 arranged on the magnetic circuit where the third pole head 310 is located generates a negative magnetic field, and the second excitation coil 322 generates a positive magnetic field; the first excitation coil 421 arranged on the magnetic circuit where the fourth pole head 410 is located generates a positive magnetic field, and the second excitation coil 422 generates a negative magnetic field. On this basis, the first excitation coils 121, 221, 321, 421 jointly form a magnetic field in one direction along the X-axis, and the second excitation coils 122, 222, 322, 422 jointly form a magnetic field in another direction along the X-axis, and the two directions are opposite. At this time, the magnetic field strength of the first excitation coils 121, 221, 321, 421 and the second excitation coils 122, 222, 322, 422 can be controlled to adjust the magnetic field in the X-axis direction. Similarly, on the basis of the above technical solution, certain adjustments can be made to adjust the magnetic field in the Y-axis direction.

[0033] In addition, based on the above technical solution, the present invention also provides a detection device, including four pole heads 110, 210, 310, 410 generally arranged in the XY plane, the pole heads 110, 210, 310, 410 are respectively arranged in four areas divided by the X axis and the Y axis, the ends of the four pole heads extend to the intersection of the X axis and the Y axis and are provided with intervals, the object to be measured is generally arranged at the intersection of the X axis and the Y axis, more specifically, the measured surface of the object to be measured is located in the plane P and in the area V. It can be understood that, please refer to Figure 2, plane P is relatively close to the pole heads, and the magnetic field at plane P is substantially the same as the magnetic field between the pole heads. Therefore, near region V, the magnetic field between the pole heads can be used as the magnetic field at plane P for calculation and use. The test probe extends from the interval to the object under test, and the four pole heads 110, 210, 310, and 410 are magnetically connected to the yoke 500 through the magnetic cores connected thereto, respectively. Each of the magnetic cores is covered with a first excitation coil and a second excitation coil. The excitation directions of the non-adjacent first excitation coils 121, 221, 321, and 421 are opposite, and the excitation directions of the non-adjacent second excitation coils 122, 222, 322, and 422 are opposite. The first excitation coils 121, 221, 321, and 421 and the second excitation coils 122, 222, 322, and 422 are respectively connected to the first power supply and the second power supply. Through this device, the magnetic field of the measured surface of the object to be measured can be tested using the aforementioned magnetic field control method, and a larger magnetic field uniformity area can be formed, so that a larger area can be tested, while making it easier for the probe to be inserted for acupuncture and easier to operate.

[0034] The above shows and describes the basic principles, main features and advantages of the present invention, so the above is only an embodiment of the present invention. It should be understood by those skilled in the art that the present invention is not limited by the above embodiments, and the above embodiments and descriptions only describe the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention also includes various equivalent changes and improvements, which will fall within the scope of the present invention to be protected.

Claims

1. A method for controlling a uniform magnetic field in an XY plane, characterized in that: The four poles in the XY plane are respectively arranged in four areas divided by the X axis and the Y axis, the ends of the four poles are extended at the intersection of the X axis and the Y axis and are provided with intervals, the magnetic circuit where the four poles are located is connected to the yoke, and the magnetic circuit where each pole is located is provided with a first excitation coil and a second excitation coil, and the X-axis component of the magnetic field between the poles is formed by making the first excitation coils in the magnetic circuit where the four poles are located work at the same time, and the Y-axis component of the magnetic field between the poles is formed by making the second excitation coils in the magnetic circuit where the four poles are located work at the same time; The excitation directions of the first excitation coils in the magnetic circuits where non-adjacent poles are located are opposite, and the excitation directions of the second excitation coils in the magnetic circuits where non-adjacent poles are located are opposite.

2. A uniform magnetic field control method in an XY plane as claimed in claim 1, characterized in that: The poles located on both sides of the X-axis are symmetrically arranged; the poles located on both sides of the Y-axis are symmetrically arranged; the magnetic field strength generated by each of the first excitation coils is the same; the magnetic field strength generated by each of the second excitation coils is the same.

3. A uniform magnetic field control method in an XY plane as claimed in claim 2, characterized in that: The four first excitation coils have the same coil structure, and the currents flowing through the four first excitation coils have the same magnitude; the four second excitation coils have the same coil structure, and the currents flowing through the four second excitation coils have the same magnitude.

4. A uniform magnetic field control method in an XY plane as claimed in claim 3, characterized in that: The four first excitation coils are connected in series and connected to a first current source; the four second excitation coils are connected in series and connected to a second current source.

5. A uniform magnetic field control method in an XY plane as claimed in claim 4, characterized in that: The first excitation coil and the second excitation coil have the same structure, and the control method also includes: when a rotating magnetic field is generated, there is the following relationship between the current I1 passed through the first excitation coil and the current I2 passed through the second excitation coil: I1=Acosθ, I2=Asinθ, where θ is the rotation angle of the vector magnetic field direction, and A is a preset parameter.

6. The method for controlling a uniform magnetic field in an XY plane according to claim 1, wherein: The end of the pole head is provided with a first end face and a second end face perpendicular to each other, and the first end faces and the second end faces of the four pole heads form a cross-shaped gap at the intersection of the X-axis and the Y-axis.

7. The uniform magnetic field control method in the XY plane according to claim 1, characterized in that: The combinations of the excitation directions of the first excitation coil and the second excitation coil in the magnetic circuits where different poles are located are different.

8. The uniform magnetic field control method in the XY plane according to claim 1, characterized in that: The excitation directions of the first excitation coil and the second excitation coil located in the same magnetic circuit where the pole head is located are opposite.

9. A detection device, characterized in that: The invention comprises four poles which are generally arranged in the XY plane, and the poles are respectively arranged in four areas divided by the X axis and the Y axis, and the ends of the four poles extend toward the intersection of the X axis and the Y axis and are provided with intervals, and the object to be measured is generally arranged at the intersection of the X axis and the Y axis, and the test probe extends from the intervals toward the object to be measured, and the four poles are respectively connected to the yoke through the magnetic cores connected thereto, and each of the magnetic cores is provided with a first excitation coil and a second excitation coil, and the excitation directions of the non-adjacent first excitation coils are opposite, and the excitation directions of the non-adjacent second excitation coils are opposite, and the first excitation coil and the second excitation coil are respectively connected to a first power supply and a second power supply.

10. A detection device as claimed in claim 9, characterized in that: The pole heads located on both sides of the X-axis are symmetrically arranged with respect to each other; the pole heads located on both sides of the Y-axis are symmetrically arranged with respect to each other.

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