A detection method

Abstract

The present invention discloses a detection method, comprising the following steps: respectively determining the coil parameters of the transmitting coil and the receiving coil; eliminating the mutual inductance between the receiving coil and the transmitting coil according to the coil parameters; exciting the transmitting coil to generate an exciting current so as to form a primary electromagnetic field; magnetizing the object to be measured to form a secondary electromagnetic field corresponding to the primary electromagnetic field; determining the output signal of the induced electromotive force of the receiving coil with respect to the secondary electromagnetic field, and determining the in-phase signal and the quadrature signal of the output signal; determining the physical parameters of the object to be measured according to the in-phase signal, the quadrature signal and the electrical signal related to the exciting current; and determining the object to be measured according to the physical parameters. The large data redundancy of the present invention greatly improves the reliability and accuracy of detecting the object to be measured.

Description

[0001] This invention is a divisional application of the invention application with the application number 202211646276.8, the application date of December 21, 2022, and the invention title of "A Detection Method". Technical Field

[0002] The present invention relates to the electromagnetic field, and specifically to a detection method. Background Art

[0003] As a geophysical exploration method, the electromagnetic induction detection method is widely used in geological surveys, mineral exploration, underground metal detection, archaeology and other fields. The main principle of the electromagnetic induction detection instrument is as follows: an alternating primary magnetic field signal is emitted by an emitting coil, and a receiving coil or a magnetic sensor is used to receive the secondary electromagnetic field signal generated by the interaction between the primary electromagnetic field and the object to be detected to obtain information about the object to be detected. Since the primary electromagnetic field of the emitting coil is very strong, while the secondary electromagnetic field signal is weak and has the same frequency as the primary electromagnetic field signal, in order to accurately detect the secondary electromagnetic field signal, it is necessary to cancel or suppress the interference of the primary electromagnetic field signal.

[0004] In the prior art, the following three detection methods are generally included to identify the object to be detected:

[0005] (1) Two emitting coils are set, one of the emitting coils generates a stable frequency, and a loop antenna is set in the frequency setting circuit of the other emitting coil. The object to be detected is identified by reading the difference in the pulse frequencies from the two generator coils. However, in this method, the instrument has a large volume, there are also limitations on the size of the emitting coil and the distance between the emitting coil and the receiving coil, and the requirements for inversion and data processing are relatively high;

[0006] (2) Two receiving coils are set to generate an additional signal difference, and special algorithms are used to process the signals in the two receiving coils to identify the object to be detected. However, the calculation accuracy of this method depends on the positioning accuracy of the coils, and it is very difficult to control its positioning accuracy in actual operation. In addition, environmental changes during operation will seriously interfere with the signal difference generated by the two receiving coils;

[0007] (3) One emitting coil and one receiving coil are set. During the operation, the receiving coil is linearly moved along the extension direction of the object to be detected and the intensity of the secondary magnetic field signal is detected. However, this method will complicate the measurement process, generate a large amount of time and labor costs, and at the same time has low reliability.

[0008] The present invention aims to provide a detection method to solve the problem of large interference of the primary electromagnetic field and the system itself in existing electromagnetic detection. Summary of the Invention

[0009] The present invention aims to provide a detection method that can solve the problem of large interference of the primary electromagnetic field and the system itself in existing electromagnetic detection.

[0010] According to one aspect of the present invention, a detection method is provided, including the following steps: respectively determining the coil parameters of the transmitting coil and the receiving coil; eliminating the mutual inductance between the receiving coil and the transmitting coil according to the coil parameters; exciting the transmitting coil to generate an exciting current, thereby forming a primary electromagnetic field; magnetizing the object to be measured to form a secondary electromagnetic field corresponding to the primary electromagnetic field; determining the output signal of the induced electromotive force of the receiving coil for the secondary electromagnetic field; determining the in-phase signal and the quadrature signal of the output signal; determining the physical parameters of the object to be measured according to the in-phase signal, the quadrature signal and the electrical signal related to the exciting current; and determining the object to be measured according to the physical parameters.

[0011] Preferably, the coil parameters of the transmitting coil and the receiving coil satisfy the following characteristics: the first receiving coil and the transmitting coil are in the same horizontal plane, and the radius r1 of the first receiving coil is greater than the radius r of the transmitting coil T ; the second receiving coil is spaced apart from the transmitting coil by a distance d in the vertical direction, and the radius r of the transmitting coil T is greater than the radius r2 of the second receiving coil; the first receiving coil, the second receiving coil and the transmitting coil are coaxial; the number of turns of the first receiving coil is N1, and the number of turns of the second receiving coil is N2, where N1 is less than N2; the output end of the second receiving coil is connected in series with the input end of the first receiving coil, and the winding directions of the second receiving coil and the first receiving coil are the same.

[0012] Preferably, respectively determining the coil parameters of the transmitting coil and the receiving coil includes the following steps: respectively determining the radius r1 of the first receiving coil and the radius r2 of the second receiving coil according to the inductance L1 of the first receiving coil and the inductance L2 of the second receiving coil, where r1 / r2 = L1 / L2; determining r T such that r T is between r1 and r2; determining the number of turns N of the transmitting coil according to the required transmitting magnetic moment P T , where N T = P / πr1 2 I T , I T is the stable value of the exciting current; for the determined r1, r2, r T , matching n turns of the second receiving coil for each turn of the first receiving coil so that the total magnetic flux passing through the first receiving coil and the second receiving coil is 0; repeating the above steps m times to obtain the number of turns N1 = m of the first receiving coil and the number of turns N2 = m×n of the second receiving coil.

[0013] Preferably, determining the output signal of the induced electromotive force of the receiving coil with respect to the secondary electromagnetic field includes the following steps: determining the total output signal U of the receiving coil; determining the induced electromotive forces ε s (t) generated by the first receiving coil and the second receiving coil; determining the change value ΔU of the output signal caused by the induced electromotive force ε s (t); based on the output signal U of the receiving coil and the change value ΔU of the output signal caused by the induced electromotive force ε s (t), determining the output signal of the induced electromotive force of the receiving coil with respect to the secondary electromagnetic field as |U - ΔU|.

[0014] Preferably, determining the induced electromotive forces ε s (t) generated by the first receiving coil and the second receiving coil includes the following steps: , where i L (t) represents the current flowing through the first receiving coil and the second receiving coil, and M LR is the mutual inductance between the first receiving coil and the second receiving coil, where μ0 represents the vacuum permeability, r1 is the radius of the first receiving coil, r2 is the radius of the second receiving coil, and d is the vertical spacing distance between the second receiving coil and the transmitting coil, is the integration variable,

[0015] Preferably, determining the change value ΔU of the output signal caused by the induced electromotive force ε s (t) includes the following steps: where S is the equivalent area of the first receiving coil and the second receiving coil, S = m(nS2 + S1), where S1 is the single - turn area of the first receiving coil, S2 is the single - turn area of the second receiving coil, where L is the equivalent inductance of the first receiving coil and the second receiving coil, C is the equivalent distributed capacitance of the first receiving coil and the second receiving coil, R is the equivalent resistance of the first receiving coil and the second receiving coil, and R b is the medium resistance connected to the first receiving coil and the second receiving coil.

[0016] Preferably, determining the vertical distance d between the second receiving coil and the transmitting coil includes the following steps: obtaining the radius r1 of the initial first receiving coil, the radius r2 of the initial second receiving coil, and the vertical distance d between the initial second receiving coil and the transmitting coil; constructing a waveform coordinate system of the output signal of the induced electromotive force of the receiving coil for the secondary electromagnetic field; exciting the transmitting coil with different frequencies to generate an exciting current; calculating the signal deviation degree of the output signal of the induced electromotive force of the receiving coil for the secondary electromagnetic field; determining whether the signal deviation degree is less than the threshold Q1, otherwise proceeding to the next step; adjusting the relationship between r1, r2, and d through the formula Repeating the above steps until the signal deviation degree is less than the threshold Q1, and taking the obtained distance at this time as the vertical distance d between the second receiving coil and the transmitting coil.

[0017] Preferably, determining the in-phase signal includes: obtaining the output signal of the induced electromotive force of the receiving coil for the secondary electromagnetic field; calculating the phase Φ of the exciting current; obtaining the in-phase signal according to the formula U 同相 = K 第一 |U - △U|sinΦ, where K 第一 is the first static conversion parameter.

[0018] Preferably, determining the quadrature signal includes: obtaining the output signal of the induced electromotive force of the receiving coil for the secondary electromagnetic field; calculating the phase Φ of the exciting current; obtaining the quadrature signal according to the formula U 正交 = K 第二 |U - △U|cosΦ, where K 第二 is the second static conversion parameter.

[0019] Preferably, determining the electrical signal related to the exciting current of the transmitting coil includes: filtering and amplifying the exciting current at the exciting frequency to obtain the electrical signal I 电信号 .

[0020] Preferably, determining the physical parameters of the object to be measured according to the in-phase signal, the quadrature signal, and the electrical signal related to the exciting current includes the following steps: determining the first conversion coefficient K1 and the second conversion coefficient K2 between the in-phase signal and the physical electrical parameter R and the magnetic parameter E of the object to be measured; determining the third conversion coefficient K3 and the fourth conversion coefficient K4 between the quadrature signal and the physical electrical parameter R and the magnetic parameter E of the object to be measured; determining the fifth conversion coefficient K5 and the sixth conversion coefficient K6 between the electrical signal related to the exciting current of the transmitting coil and the magnetic parameter E and the position parameter D of the object to be measured; determining the physical parameters of the object to be measured according to the determined conversion coefficients.

[0021] Preferably, determining the physical parameter of the analyte according to the determined conversion coefficient includes,

[0022] U 同相 = K1*R + K2*E;

[0023] U 正交 = K3*R + K4*E;

[0024] I 电信号 = K5*E + K6*D

[0025] The present invention provides a detection method. By reasonably setting the coil parameters of the transmitting coil and the receiving coil, the mutual inductance between the receiving coil and the transmitting coil is theoretically eliminated. Thus, when determining the output signal of the induced electromotive force of the receiving coil for the secondary electromagnetic field, the interference of the primary electromagnetic field signal is cancelled or suppressed. At the same time, the physical parameter of the analyte is jointly determined according to the in-phase signal, the quadrature signal and the electrical signal related to the excitation current, and the reliability and accuracy of detecting the analyte are greatly improved by using data redundancy. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings described herein are used to provide a further understanding of the present invention, and form a part of this application. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0027] Figure 1 is a flowchart of a detection method according to an embodiment of the present invention;

[0028] Figure 2 is a schematic diagram of a transmitting coil and a receiving coil according to an embodiment of the present invention;

[0029] Figure 3 is a flowchart of a method for respectively determining the coil parameters of the transmitting coil and the receiving coil according to an embodiment of the present invention; and

[0030] Figure 4 is a flowchart of a method for determining the vertical distance d between the second receiving coil and the transmitting coil according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0032] An embodiment of the present invention provides a detection method, Figure 1 which is a flowchart of a detection method according to an embodiment of the present invention. As Figure 1As shown, the method includes the following steps: S102: Determine the coil parameters of the transmitting coil and the receiving coil respectively; S104: Eliminate the mutual inductance between the receiving coil and the transmitting coil according to the coil parameters; S106: Excite the transmitting coil to generate an excitation current, thereby forming a primary electromagnetic field; S108: Magnetize the object to be measured to form a secondary electromagnetic field corresponding to the primary electromagnetic field; S110: Determine the output signal of the induced electromotive force of the receiving coil for the secondary electromagnetic field; S112: Determine the in-phase signal and the quadrature signal of the output signal; S114: Determine the physical parameters of the object to be measured according to the in-phase signal, the quadrature signal and the electrical signal related to the excitation current; S116: Determine the object to be measured according to the physical parameters.

[0033] Among them, the coil parameters of the transmitting coil and the receiving coil respectively determined in step S102 include: position, radius, number of turns, winding direction. By reasonably setting the coil parameters of the transmitting coil and the receiving coil, the mutual inductance between the receiving coil and the transmitting coil can be eliminated, so as to cancel or suppress the interference of the primary electromagnetic field signal when determining the output signal of the induced electromotive force of the receiving coil for the secondary electromagnetic field.

[0034] In steps S106 - S116, the transmitting coil is excited to generate an excitation current, thereby forming a primary electromagnetic field. If there is a buried object to be measured, the primary electromagnetic field will magnetize the object to be measured and induce eddy currents in the object to be measured, and the eddy currents will generate a secondary electromagnetic field. The secondary electromagnetic field will induce an electromotive force in the receiving coil to generate an output signal. Subsequently, the output signal is converted into an in-phase signal and a quadrature signal. Among them, the in-phase signal is mainly proportional to the conductivity of the object to be measured, while the quadrature signal is mainly proportional to the magnetic permeability of the object to be measured.

[0035] The direction of the secondary electromagnetic field generated by the induced eddy currents in the object to be measured is opposite to the excitation magnetic field. The intensity of the magnetic component in the receiving coil is equal to the difference between the magnetic component intensities of the primary / secondary electromagnetic fields. Therefore, as long as the supply voltage of the transmitting coil is constant, the eddy currents in the object to be measured will increase its impedance, thereby reducing the current flowing through the transmitting coil. Therefore, the impedance of the transmitting coil will depend on the eddy current distribution of the object to be measured, that is, on the conductivity and depth of the object to be measured. In this case, the physical parameters of the object to be measured can be determined according to the in-phase signal, the quadrature signal and the electrical signal related to the excitation current. This data redundancy greatly improves the reliability and accuracy of detecting the object to be measured.

[0036] According to the embodiment of the present invention, the coil parameter characteristics of the transmitting coil and the receiving coil are further defined. Figure 2 It is a schematic diagram of the transmitting coil and the receiving coil according to the embodiment of the present invention. As Figure 2 shown, the first receiving coil and the transmitting coil are in the same horizontal plane, and the radius r1 of the first receiving coil is greater than the radius r of the transmitting coil T; The second receiving coil is vertically spaced from the transmitting coil by a distance d, and the radius of the transmitting coil is r T is greater than the radius r2 of the second receiving coil; the first receiving coil, the second receiving coil, and the transmitting coil are coaxial; the number of turns of the first receiving coil is N1, and the number of turns of the second receiving coil is N2, where N1 is less than N2; the output end of the second receiving coil is connected in series with the input end of the first receiving coil, and the winding directions of the second receiving coil and the first receiving coil are the same.

[0037] In this embodiment, through specific parameter settings, the coupling strength between the transmitting coil, the receiving coil, and the object to be measured is improved, and the influence of the center distance of the receiving coil on the shielding effect of the primary electromagnetic field is eliminated.

[0038] According to another embodiment of the present invention, a method for separately determining the coil parameters of the transmitting coil and the receiving coil is provided. Figure 3 is a flowchart of a method for separately determining the coil parameters of the transmitting coil and the receiving coil according to an embodiment of the present invention. As Figure 3 shown, the radius r1 of the first receiving coil and the radius r2 of the second receiving coil are respectively determined according to the inductance L1 of the first receiving coil and the inductance L2 of the second receiving coil, where r1 / r2 = L1 / L2; determine r T such that r T is between r1 and r2; the number of turns N of the transmitting coil is determined according to the required transmission magnetic moment P T , where N T = P / πr1 2 I T , I T is the stable value of the excitation current; for the determined r1, r2, r T , n turns of the second receiving coil are matched for each turn of the first receiving coil so that the total magnetic flux passing through the first receiving coil and the second receiving coil is 0; the above steps are repeated m times to obtain the number of turns N1 = m of the first receiving coil and the number of turns N2 = m×n of the second receiving coil.

[0039] In this embodiment, by the above method, the receiving coil is avoided from being arranged in the area where the magnetic force lines of the primary electromagnetic field are densely distributed.

[0040] According to still another embodiment of the present invention, a method for determining the output signal of the induced electromotive force of the receiving coil for the secondary electromagnetic field is provided, including determining the total output signal U of the receiving coil; determining the induced electromotive forces ε s (t) generated by the first receiving coil and the second receiving coil; determining the output signal change value △U caused by the induced electromotive force ε s (t); according to the output signal U of the receiving coil and the induced electromotive force ε s(t) The change value △U of the output signal caused is used to determine that the output signal of the induced electromotive force of the receiving coil for the secondary electromagnetic field is |U - △U|.

[0041] In this embodiment, the influence of the mutual inductance between the first receiving coil and the second receiving coil on the detection accuracy is reduced by the above method.

[0042] Furthermore, in order to determine the induced electromotive force ε s (t) generated by the first receiving coil and the second receiving coil, it is calculated through the formula where i L (t) represents the current flowing through the first receiving coil and the second receiving coil, M LR is the mutual inductance between the first receiving coil and the second receiving coil. Among them, since the radii of the two parallel coaxial circular coils are r1 and r2 respectively, and the distance between the coil centers is d, the mutual inductance M between the two coils LR can be expressed in the cylindrical coordinate system as μ0 represents the vacuum magnetic permeability, r1 is the radius of the first receiving coil, r2 is the radius of the second receiving coil, d is the distance between the second receiving coil and the transmitting coil in the vertical direction, is the integration variable,

[0043] Furthermore, in order to determine the change value △U of the output signal caused by the induced electromotive force ε s (t), it is calculated through the following formula,

[0044]

[0045] where S is the equivalent area of the first receiving coil and the second receiving coil, S = m(nS2 + S1), where S1 is the single-turn area of the first receiving coil, S2 is the single-turn area of the second receiving coil. Among them, L is the equivalent inductance of the first receiving coil and the second receiving coil, C is the equivalent distributed capacitance of the first receiving coil and the second receiving coil, R is the equivalent resistance of the first receiving coil and the second receiving coil, and R b is the medium resistance connected to the first receiving coil and the second receiving coil.

[0046] In this embodiment, during the process of determining the change value △U of the output signal caused by the induced electromotive force ε s (t), the influence of the medium resistance connected to the first receiving coil and the second receiving coil on the detection accuracy is considered.

[0047] Although the primary field response component in the detection signal can be completely eliminated by adjusting the parameters of the coil, it is difficult to achieve in practice. This is because there are tolerances in the manufacturing and installation of the coil, and it cannot be guaranteed that the actual size of the coil is exactly the same as the theoretical calculation result. Even if the tolerances can be ignored, the structural deformation caused by material aging or electromagnetic force will also reduce the suppression effect of the device on the primary field. Therefore, it is necessary to ensure that the shielding effect of the distance d between the second receiving coil and the transmitting coil in the vertical direction has sufficient stability during actual operation.

[0048] To achieve the above object, the present invention provides a method for determining the distance d between the second receiving coil and the transmitting coil in the vertical direction. Figure 4 It is a flowchart of a method for determining the distance d between the second receiving coil and the transmitting coil in the vertical direction according to an embodiment of the present invention. Specifically, the radius r1 of the initial first receiving coil, the radius r2 of the initial second receiving coil, and the distance d between the initial second receiving coil and the transmitting coil in the vertical direction are obtained; a waveform coordinate system of the output signal |U - ΔU| of the induced electromotive force of the receiving coil for the secondary electromagnetic field is constructed; the transmitting coil is excited with different frequencies to generate an excitation current; the signal deviation degree of the output signal |U - ΔU| of the induced electromotive force of the receiving coil for the secondary electromagnetic field is calculated; it is judged whether the signal deviation degree is less than the threshold Q1, otherwise the next step is continued; through the formula The relationship between r1, r2, and d is adjusted; the above steps are repeated until the signal deviation degree is less than the threshold Q1, and the obtained distance at this time is used as the distance d between the second receiving coil and the transmitting coil in the vertical direction.

[0049] According to another embodiment of the present invention, determining the in-phase signal includes: obtaining the output signal of the induced electromotive force of the receiving coil for the secondary electromagnetic field; calculating the phase Φ of the excitation current; according to the formula U 同相 = K 第一 |U - ΔU|sinΦ, the in-phase signal is obtained, where K 第 is a first static conversion parameter. Determining the quadrature signal includes: obtaining the output signal of the induced electromotive force of the receiving coil for the secondary electromagnetic field; calculating the phase Φ of the excitation current; according to the formula U 正交 = K 第二 |U - ΔU|cosΦ, the quadrature signal is obtained, where K 第二 is the second static conversion parameter. Determining the electrical signal related to the excitation current of the transmitting coil includes: filtering and amplifying the excitation current at the excitation frequency to obtain the electrical signal I 电信号 related to the excitation current of the transmitting coil.

[0050] Determining the physical parameters of the object to be measured based on the in-phase signal, the quadrature signal, and the electrical signal related to the excitation current includes the following steps: determining a first conversion coefficient K1 and a second conversion coefficient K2 between the in-phase signal and the physical electrical parameter R and the magnetic parameter E of the object to be measured; determining a third conversion coefficient K3 and a fourth conversion coefficient K4 between the quadrature signal and the physical electrical parameter R and the magnetic parameter E of the object to be measured; determining a fifth conversion coefficient K5 and a sixth conversion coefficient K6 between the electrical signal related to the excitation current of the transmitting coil and the magnetic parameter E and the position parameter D of the object to be measured; determining the physical parameters of the object to be measured according to the determined conversion coefficients.

[0051] Specifically, the physical parameters of the object to be measured are determined according to the following formula:

[0052] U 同相 = K1 * R + K2 * E;

[0053] U 正交 = K3 * R + K4 * E;

[0054] I 电信号 = K5 * E + K6 * D

[0055] It should be noted that K 第一 、K 第二 、K1, K2, K3, K4, K5, K6 can be determined by testing a reference object with known physical parameters. The electrical parameter R is specifically the conductivity, the magnetic parameter E is specifically the magnetic permeability, and the position parameter D is specifically the burial depth.

[0056] In summary, by reasonably setting the coil parameters of the transmitting coil and the receiving coil, the mutual inductance between the receiving coil and the transmitting coil is theoretically eliminated. Thus, when determining the output signal of the induced electromotive force of the receiving coil for the secondary electromagnetic field, the interference of the primary electromagnetic field signal is canceled or suppressed. At the same time, the physical parameters of the object to be measured are jointly determined according to the in-phase signal, the quadrature signal, and the electrical signal related to the excitation current, and the reliability and accuracy of detecting the object to be measured are greatly improved by using data redundancy.

[0057] The above is only the preferred embodiment of the present invention and is not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A detection method, characterized in that, It includes the following steps: S102: Determine the coil parameters of the transmitting coil and the receiving coil respectively; S104: Eliminate the mutual inductance between the receiving coil and the transmitting coil according to the coil parameters; S106: Excite the transmitting coil to generate an exciting current, thereby forming a primary electromagnetic field; S108: Magnetize the object to be measured to form a secondary electromagnetic field corresponding to the primary electromagnetic field; S110: Determine the output signal of the induced electromotive force of the receiving coil for the secondary electromagnetic field, including: Determine the total output signal U of the receiving coil; Determine the induced electromotive force ε s (t) generated by the first receiving coil and the second receiving coil. The output end of the second receiving coil is connected in series with the input end of the first receiving coil, and the winding directions of the second receiving coil and the first receiving coil are the same; Determine the change value ΔU of the output signal caused by the induced electromotive force ε s (t); Based on the output signal U of the receiving coil and the change value ΔU of the output signal caused by the induced electromotive force ε s (t), determine that the output signal of the induced electromotive force of the receiving coil for the secondary electromagnetic field is |U - ΔU|; S112: Determine the in-phase signal and the quadrature signal of the output signal. Determining the in-phase signal includes: Obtain the output signal of the induced electromotive force of the receiving coil for the secondary electromagnetic field; Calculate the phase Φ of the exciting current; According to the formula U 同相 = K 第一 |U - △U| sin Φ, the in-phase signal is obtained, where K 第 is a first static conversion parameter; Determining the quadrature signal includes: Obtain the output signal of the induced electromotive force of the receiving coil for the secondary electromagnetic field; Calculate the phase Φ of the exciting current; According to the formula U 正交 = K 第二 |U - ΔU| cos φ, the orthogonal signal is obtained, where K 第二 is the second static conversion parameter; Determining the electrical signal related to the excitation current of the transmitting coil includes: filtering and amplifying the excitation current at the excitation frequency to obtain an electrical signal I related to the excitation current of the transmitting coil 电信号 ; S114: Determine the physical parameters of the object to be measured according to the in-phase signal, the quadrature signal and the electrical signal related to the exciting current, including: Determine the first conversion coefficient K1 and the second conversion coefficient K2 between the in-phase signal and the physical electrical parameter R and the magnetic parameter E of the object to be measured; determine the third conversion coefficient K3 and the fourth conversion coefficient K4 between the quadrature signal and the physical electrical parameter R and the magnetic parameter E of the object to be measured; determine the fifth conversion coefficient K5 and the sixth conversion coefficient K6 between the electrical signal related to the exciting current of the transmitting coil and the magnetic parameter E and the position parameter D of the object to be measured; determine the physical parameters of the object to be measured according to the determined conversion coefficients; determine the physical parameters of the object to be measured according to the following formula: U 同相 = K1*R + K2*E; U 正交 = K3 * R + K4 * E; I 电信号 = K5*E + K6*D K 第一 、K 第二 、K1, K2, K3, K4, K5, K6 are determined by a reference object with known physical parameters through testing. The electrical parameter R is specifically the conductivity, the magnetic parameter E is specifically the magnetic permeability, and the position parameter D is specifically the burial depth; S116: Determine the object to be measured according to the physical parameters.

2. The method according to claim 1, wherein The first receiving coil and the transmitting coil are in the same horizontal plane, and the radius r1 of the first receiving coil is greater than the radius r of the transmitting coil T ; The second receiving coil is spaced apart from the transmitting coil by a distance d in the vertical direction, and the radius of the transmitting coil is r T which is greater than the radius r2 of the second receiving coil; The first receiving coil, the second receiving coil and the transmitting coil are coaxial; The number of turns of the first receiving coil is N1, and the number of turns of the second receiving coil is N2, where N1 is less than N2; determine the radius r1 of the first receiving coil and the radius r2 of the second receiving coil respectively according to the inductance L1 of the first receiving coil and the inductance L2 of the second receiving coil, where r1 / r2 = L1 / L2; Determine r T such that r T is between r1 and r2; Determine the number of turns N of the transmitting coil according to the required transmitting magnetic moment P T , where N T = P / πr1 2 I T , I T is the stable value of the excitation current; For determined r1, r2, r T , match n turns of the second receiving coil to each turn of the first receiving coil, so that the total magnetic flux passing through the first receiving coil and the second receiving coil is 0; Repeat the above steps m times to obtain the number of turns N1 = m of the first receiving coil and the number of turns N2 = m×n of the second receiving coil.

3. The method according to claim 2, wherein Determine the induced electromotive force ε s (t) generated by the first receiving coil and the second receiving coil, including the following steps: where i L (t) represents the current flowing through the first receiving coil and the second receiving coil, and M LR is the mutual inductance between the first receiving coil and the second receiving coil Among them, μ0 represents the magnetic permeability of vacuum, r1 is the radius of the first receiving coil, r2 is the radius of the second receiving coil, and d is the vertical interval distance between the second receiving coil and the transmitting coil, is the integration variable, 4. The method according to claim 3, characterized in that Determine the change value △U of the output signal caused by the induced electromotive force ε s (t) It includes the following steps: Wherein, S is the equivalent area of the first receiving coil and the second receiving coil, S = m(nS2 + S1), S1 is the single-turn area of the first receiving coil, and S2 is the single-turn area of the second receiving coil. Wherein, L is the equivalent inductance of the first receiving coil and the second receiving coil, C is the equivalent distributed capacitance of the first receiving coil and the second receiving coil, R is the equivalent resistance of the first receiving coil and the second receiving coil, and R b is the dielectric resistance connected to the first receiving coil and the second receiving coil.

5. The method according to any one of claims 1 to 3, characterized in that Determining the vertical spacing distance d between the second receiving coil and the transmitting coil includes the following steps: Obtain the initial radius r1 of the first receiving coil, the initial radius r2 of the second receiving coil, and the initial vertical spacing distance d between the second receiving coil and the transmitting coil; Construct a waveform coordinate system for the output signal of the induced electromotive force of the receiving coil for the secondary electromagnetic field; Excite the transmitting coil to generate an exciting current at different frequencies; Calculate the signal deviation degree of the output signal of the induced electromotive force of the receiving coil for the secondary electromagnetic field; Determine whether the signal deviation degree is less than the threshold value Q1, otherwise proceed to the next step; Adjust the relationship among r1, r2, and d through the formula where r1 is the radius of the first receiving coil, r2 is the radius of the second receiving coil, and d is the vertical separation distance between the second receiving coil and the transmitting coil is the integration variable Repeat the above steps until the signal deviation degree is less than the threshold value Q1, and use the obtained interval distance at this time as the interval distance d in the vertical direction between the second receiving coil and the transmitting coil.

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