WO2019047396A1

WO2019047396A1 - Dynamic magnet detection system and detection method, and electromagnetic array control method

Info

Publication number: WO2019047396A1
Application number: PCT/CN2017/114485
Authority: WO
Inventors: 郭静波; 朴冠宇; 胡铁华
Original assignee: 清华大学
Priority date: 2017-09-11
Filing date: 2017-12-04
Publication date: 2019-03-14
Also published as: CN109490406A; CN109490406B

Abstract

A dynamic magnet detection system (10) and detection method, and an electromagnetic array control method, the dynamic magnet detection system (10) comprising: a magnetic field applying device (100) for applying a magnetic field to a ferromagnetic object (900) to be detected; a dynamic magnetic stimulation device (200) for generating a transient exciting magnetic field; and a magnetic field detection device (300) for detecting an induction magnetic signal around the object (900) to be detected. The present invention can detect the defect of a small dimension and has a high precision, and keeps a stable detection performance while moving at a high speed.

Description

Dynamic magnetic detection system, detection method and electromagnetic array method

Related application

The present application claims the benefit of priority to the benefit of the benefit of the benefit of the benefit of the benefit of the benefit of the benefit of the benefit of the benefit of the benefit of the benefit of the benefit of the benefit of the present disclosure.

Technical field

The present application relates to the field of electronic information technology, and in particular, to a dynamic magnetic detection system, a detection method, and an electromagnetic array method.

Background technique

The industrialization and practical application of detection technology and equipment in oil and gas pipeline defects are of great significance.

Magnetic flux leakage detection is a technology for detecting pipeline defects in the industry at home and abroad. The magnetic flux leakage detection technology is based on the constant magnetic field magnetization detection region wall provided by the permanent magnet, and the magnetic leakage sensing signal generated by the wall defect is measured by a magnetic field sensing component such as a Hall sensor, and the pipeline defect information is identified according to the magnetic leakage signal characteristic.

Magnetic flux leakage testing generally only detects defects with large scales such as corrosion, and the detection accuracy of defects with small scales such as cracks is very poor.

Summary of the invention

Based on this, it is necessary to provide a dynamic magnetic detection system, a detection method, and an electromagnetic array method with high precision for detecting defects having a small scale, and the system includes:

a magnetic field applying device for applying a magnetic field to the object to be tested having ferromagnetism;

a dynamic magnetic excitation device for generating a transient excitation magnetic field;

A magnetic field detecting device for detecting an induced magnetic signal around the object to be tested.

In one embodiment, the magnetic field application device comprises a permanent magnet or an electromagnet.

In one embodiment, the moving magnetic excitation device comprises a moving magnetic excitation coil.

In one embodiment, the dynamic magnetic detection system further includes a high frequency pulse current generating device electrically coupled to the moving magnetic excitation device.

In one embodiment, the high frequency pulse current generating device includes a metal oxide semiconductor field effect transistor for generating a pulse current, the pulse excitation current having a pulse width of 1-5 μs, a rising edge and a falling edge of 0.05, respectively. -0.2 μs.

In one embodiment, the magnetic field detecting device includes a receiving coil, the receiving coil is a differential receiving coil, and the differential receiving coil includes a first receiving coil and a second receiving coil, the first receiving coil and the second receiving The coil is reversely wound, and the first receiving coil and the second receiving coil are connected end to end.

In one embodiment, the dynamic magnetic detection system further includes a Hilbert transformer coupled to the magnetic field detecting device for performing a Hilbert variation of the magnetic signal.

In one embodiment, the dynamic magnetic detection system further includes:

a first low noise amplifier disposed between the Hilbert transformer and the magnetic field detecting device;

a second low noise amplifier connected to the output of the Hilbert transformer signal;

A low pass filter is disposed between the Hilbert transformer and the second low noise amplifier.

In one embodiment, the dynamic magnetic detection system further includes a magnetic flux leakage detecting device, wherein the magnetic flux leakage detecting device is a multi-channel Hall chip array, and each channel includes three vertical direction Halls of X, Y, and Z axes. Chip for detecting spatial magnetic flux leakage signals.

In one embodiment, the dynamic magnetic detection system further includes:

And a control device for controlling the magnetic field applying device, the moving magnetic excitation device, the magnetic field detecting device, the magnetic flux leakage detecting device, and the Hilbert transformer.

The application also provides a dynamic magnetic detection method, the method comprising:

Applying a magnetic field to the object to be tested, so that the object to be tested enters a magnetic saturation state;

Applying a transient excitation magnetic field to the object to be measured;

After superimposing the transient excitation magnetic field, a magnetic signal around the probe is detected.

In an embodiment, after the superimposing the transient excitation magnetic field, the step of detecting a magnetic signal around the probe further includes:

Performing a Hilbert transform on the magnetic signal by a Hilbert transformer and outputting a waveform signal;

Determining whether the object to be tested has a defect according to the waveform signal.

In one embodiment, the method further includes: acquiring a three-dimensional magnetic field signal by the magnetic flux leakage detecting device, and analyzing the three-dimensional magnetic signal to obtain a defect condition.

In one embodiment, the transient excitation magnetic field is generated by a dynamic magnetic excitation device, and is connected to the dynamic magnetic excitation device by a high frequency pulse current generating device, and a pulse width of 1-5 μs is input to the dynamic magnetic excitation device. The rising and falling edges are pulse excitation currents of 0.05-0.2 μs, respectively, to generate a transient excitation magnetic field.

The application also provides a method of electromagnetic array, comprising:

Providing any of the foregoing dynamic magnetic detection systems of any of the claims;

The dynamic magnetic detection system is controlled by a sequential control array by a control system using a sequential control method.

In the dynamic magnetic detecting system provided by the present application, the magnetic field applying device applies a magnetic field to the object to be tested with ferromagnetism to cause the object to be tested to enter a magnetic saturation state, and the moving magnetic excitation device generates a transient exciting magnetic field on the surface of the object to be tested, and the magnetic field detecting device An induced magnetic signal is detected at a location of the magnetic field detecting device. If the object to be tested has a small scale defect, the defect information is given by comparing the detected magnetic signal with the magnetic signal without defect. This application can detect defects with small scale and has high precision.

DRAWINGS

1 is a schematic structural view of a magnetic field detecting system of an embodiment;

2 is a structural diagram of processing a dynamic magnetic signal of a magnetic field detecting system of an embodiment;

3 is a schematic structural view of a magnetic field detecting system of another embodiment;

4 is a flow chart of a dynamic magnetic detecting method of a dynamic magnetic detecting system of an embodiment;

Figure 5 is a B-H curve evolution diagram of the object to be tested when a magnetic field applying device applies a magnetic field;

Figure 6 is a magnetic field distribution diagram of a defect on an outer surface of the object to be tested;

Figure 7 is a magnetic field distribution diagram of a defect on an inner surface of the object to be tested;

Figure 8 is the measured voltage data when the defect is on the inner surface of the material;

Figure 9 is the measured voltage data when the defect is on the outer surface of the material;

Figure 10 shows the evolution of the dynamic magnetic signal voltage at different moving speeds;

Figure 11 is a schematic diagram of a sequential control array of an electromagnetic array method of one embodiment.

Detailed ways

The technical solutions of the present application are further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the technical solutions of the present application, and are not intended to limit the technical solutions of the present application.

Referring to FIG. 1 , a magnetic field detecting system 10 according to an embodiment of the present invention includes: a magnetic field applying device 100 , a moving magnetic excitation device 200 , and a magnetic field detecting device 300 . The magnetic field applying device 100 is for applying a magnetic field to the object 900 having ferromagnetism. The moving magnetic excitation device 200 is used to generate a transient excitation magnetic field. The magnetic field detecting device 300 is configured to detect an induced magnetic signal at a position where the magnetic field detecting device 300 is located.

The magnetic field applying device 100 applies a magnetic field to the object 900 having ferromagnetism, so that the object to be tested 900 reaches a magnetic saturation state, and the object to be tested has a constant magnetic field around the object. The moving magnetic excitation device 200 is disposed on the surface of the object to be tested 900 to generate a transient excitation magnetic field whose direction is perpendicular to the constant magnetic field and whose magnetic field strength is much smaller than the constant magnetic field. The magnetic field detecting device 300 detects a dynamic magnetic response caused by the transient excitation magnetic field to obtain a magnetic signal at a position where the magnetic field detecting device 300 is located. The magnetic signal includes an earth magnetic field signal, a magnetic field applying device, and a magnetic signal induced by the moving magnetic excitation device. The magnetic field detecting device 300 may be an existing magnetic field measuring instrument, or may be a conductive coil or a plurality of conductive coils or the like.

In one embodiment, the moving magnetic excitation device 200 and the magnetic field detecting device 300 may be integrated together and movably disposed adjacent to the object to be tested 900 in which the magnetic field applying device 100 is disposed.

The dynamic magnetic detecting system 10 provided by the present application, the magnetic field applying device 100 applies a magnetic field to a test object having ferromagnetism to cause a test object to enter a magnetic saturation state, and the dynamic magnetic excitation device 200 generates an instantaneous moment on the surface of the object to be tested. The magnetic field detecting means 300 detects the magnetic signal of the position of the magnetic field detecting means 300. The small scale defects of the object to be tested can be expressed by the detected changes in the magnetic signal. This application can detect defects with small scale and has high precision.

In one embodiment, the magnetic field application device 100 is a permanent magnet or an electromagnet. The magnetic field applying device 100 may also be other devices that magnetize the object to be tested.

In one embodiment, the moving magnetic excitation device 200 is a moving magnetic excitation coil.

In one embodiment, the magnetic field detecting system 10 further includes a high frequency pulse current generating device 210, and the moving magnetic field The excitation device is electrically connected for applying a current to the dynamic magnetic excitation device to cause the dynamic magnetic excitation device to generate an induced transient magnetic field. The dynamic magnetic excitation device can also pass a varying current generated by other devices, such as alternating current. In one embodiment, the high frequency pulse current generating device 210 includes a metal oxide semiconductor field effect transistor (MOSFET) for generating a pulse current having a pulse width of 1-5 μs, rising edge and falling. The edges are 0.05-0.2 μs, respectively. Preferably, by controlling the switching of the MOSFET, a pulse excitation current having a pulse width of 1-5 μs and rising and falling edges of 0.05-0.2 μs is generated. In one embodiment, the switches of the MOSFET are controlled in real time by a program. When the magnetic field is detected at the falling edge of the pulse current, the magnetic signal that can be obtained is relatively high in signal-to-noise.

Referring to FIG. 2, in one embodiment, the magnetic field detecting device 300 is a receiving coil, the receiving coil is a differential receiving coil, and the differential receiving coil includes a first receiving coil 310 and a second receiving coil 320. The first receiving coil 310 and the second receiving coil 320 are reversely wound, and the first receiving coil 310 and the second receiving coil 320 are connected end to end. The coil designed in this way can effectively eliminate the interference magnetic signal and improve the signal-to-noise ratio of the dynamic magnetic signal.

In one embodiment, the magnetic field detecting system 10 further includes the Hilbert transformer 400 coupled to the magnetic field detecting device 300 for performing a Hilbert change of the magnetic signal.

Specifically, the magnetic field detecting device 300 receives the transient excitation magnetic field generated by the moving magnetic excitation device 200. The Hilbert transformer 400 receives the magnetic signal output by the magnetic field detecting device 300, and performs a Hilbert change on the magnetic signal to output. The use of the Hilbert variator 400 increases the signal-to-noise ratio of the magnetic signal output by the magnetic field detecting device 300, extends the observation time of the magnetic signal, and converts the analog information.

In one embodiment, the magnetic field detection system 10 further includes a first low noise amplifier 510, a second low noise amplifier 520, and a low pass filter 530. The first low noise amplifier 510 is disposed between the Hilbert transformer 400 and the magnetic field detecting device 300. The second low noise amplifier 520 is coupled to the signal output of the Hilbert transformer 400. The low pass filter 530 is disposed between the Hilbert transformer 400 and the second low noise amplifier 520. By employing the first low noise amplifier 510, the second low noise amplifier 520, and the low pass filter 530, the final output signal is more accurate.

Referring to FIG. 3, in one embodiment, the magnetic field detecting system 10 further includes a magnetic flux leakage detecting device 600. The magnetic flux leakage detecting device 600 is a multi-channel Hall chip array, and each channel includes an X, Y, and Z axis. Three vertical direction Hall chips for detecting spatial magnetic flux leakage signals. In use, the magnetic flux leakage detecting device 600 is disposed inside the object to be tested. Fusion leak After the magnetic detection, the magnetic field detecting system 10 can detect the large-scale defects of the pipeline waiting for the measuring object and can detect the small-scale defects, thereby improving the application range and precision.

In one embodiment, the magnetic field detecting system 10 further includes: a control device (not shown) for controlling the magnetic field applying device 100, the moving magnetic excitation device 200, the magnetic field detecting device 300, the leak Magnetic detection device 600. In one embodiment, the control device can also simultaneously control the magnetic field applying device 100, the moving magnetic excitation device 200, the magnetic field detecting device 300, the magnetic flux leakage detecting device 600, and the Hilbert Inverter 400 or other device within magnetic field detection system 10 described above. In one embodiment, the control device 800 controls the magnetic flux leakage detecting device 600, the magnetic field applying device 100, the moving magnetic excitation device 200, and the magnetic field detecting device 300. By allocating the collection work timing, reducing the instantaneous working current of the system, all the acquisition work is efficiently performed in a short enough time window, so that the whole dynamic magnetic detection system has high collection efficiency, low power consumption and good safety.

Referring to FIG. 4, the present application further provides a dynamic magnetic detecting method, the method comprising:

S100: applying a magnetic field to the object to be tested, so that the object to be tested enters a magnetic saturation state;

S200, applying a transient excitation magnetic field to the object to be tested;

S300: After superimposing the transient excitation magnetic field, detecting a magnetic signal around the probe.

In an embodiment, after the step S300, the method further includes:

S400, performing a Hilbert transform on the magnetic signal by using a Hilbert transformer and outputting a waveform signal;

S500. Determine, according to the waveform signal, whether the object to be tested has a defect.

In one embodiment, the dynamic magnetic detection method further includes:

S110: Acquire a three-dimensional magnetic field signal by a magnetic flux leakage detecting device, and analyze the three-dimensional magnetic signal to obtain a defect condition.

In one embodiment, the dynamic magnetic detection method further includes:

S110, generating a pulse excitation current with a pulse width of 1-5 μs and a rising edge and a falling edge of 0.05-0.2 μs by a high-frequency pulse current generating device;

S120, the pulse excitation current is passed into the conductive coil to generate a transient excitation magnetic field.

The specific application process of the magnetic field detecting system 10 described in the present application is:

Turning on the magnetic field applying device 100 by the control device to apply a magnetic field to the object to be tested to cause the object to be tested to enter a magnetic saturation And status. The control device then controls the magnetic flux leakage detecting device 600 to turn on the magnetic flux leakage signal in the three-dimensional space. The control device controls to sequentially turn on the magnetic field applying device 100, the moving magnetic excitation device 200, the magnetic field detecting device 300, the first low noise amplifier 510, the Hilbert transformer 400, the The low pass filter 530 and the second low noise amplifier 520 start dynamic magnetic detection to obtain a magnetic signal.

Finally, the magnetic signal outputted by the second low noise amplifier 520 is analyzed, and at the same time, the magnetic flux leakage signal is analyzed.

Referring to FIG. 5, the B-H curve evolution of the object to be tested when the magnetic field applying device applies a magnetic field. When the ferromagnetic object to be tested is magnetized by a strong magnetic field applied externally, the BH curve operating point of the object to be tested is at a static working point Q (B, H), and the working point is in a saturated region on the BH curve. . When the externally applied magnetic field H is further increased, the magnetic induction intensity B inside the object to be tested increases slowly and enters a saturated state. At this time, a dynamic magnetic excitation b is applied in a direction perpendicular to the field H, and the dynamic operating point of the object to be tested is moved to Q' (B+b, H+h).

Please refer to FIG. 6 , a magnetic field distribution diagram of the defect on the outer surface of the object to be tested. When the defect is on the outer surface of the object to be tested, a transient excitation magnetic field is generated near the inner surface of the object to be tested. Since the magnetic field leaks outside the edge of the material opening, and the direction of the dynamic excitation is turned from the original moving direction, the density of the transient excitation magnetic field at the edge of the defect opening is larger than the density of the transient excitation magnetic field at the position of the defect. As shown, the larger the circle, the greater the density of the transient excitation magnetic field.

Please refer to FIG. 7 , a magnetic field distribution diagram of the defect on the inner surface of the object to be tested. When a defect occurs on the inner surface of the object to be tested, the air region of the defect position becomes magnetic permeability, the conductivity decreases to zero, and the depression is distant from the transient excitation magnetic field, resulting in a depression The density of the transient excitation magnetic field is reduced, as illustrated in Figure 7, and the smaller the circle, the smaller the transient excitation magnetic field density.

When the defect is on the outer surface of the object to be tested, the density of the defect edge and the internal transient excitation magnetic field is large at the inner surface position, and the transient excitation magnetic field density on both sides of the defect is small; when the defect is on the inner surface, the defect is presented. The density of the defect edge and the internal transient excitation magnetic field is small, and the density of the transient excitation magnetic field on both sides of the defect is large.

Further, the trend of the transient excitation magnetic field density caused by the defects in the inner and outer surfaces along the moving direction is opposite. With this feature, the dynamic magnetic excitation and differential reception are used to realize the high-speed moving state, inside and outside. Reliable detection of surface defects and the ability to distinguish between internal and external surface distribution (ID/OD).

Referring to Figure 8, the measured voltage data is measured on the inner surface of the material. The measured data shows that when the defect is on the inner surface of the material, the output signal of the magnetic signal along the moving direction is first negative envelope and then positive envelope.

Referring to FIG. 9, the voltage data is measured when the defect is on the outer surface of the object to be tested. The measured data shows that when the defect is on the outer surface of the object to be tested, the magnetic signal is differentially output, and the waveform after the Hilbert transform is positive and negative first; further, the length interval of the positive and negative waveform peaks is The length dimensions of the defects are very close, which indicates that the front and rear differential receiving coils are very sensitive to the length of the defect length, and it is also proved that the transient excitation magnetic field density at this position changes greatly.

Please refer to Figure 10 for the evolution of the magnetic signal voltage at different moving speeds. The abscissa is the direction of movement in millimeters (mm) and the ordinate is the magnetic signal voltage in volts (V). As can be seen from FIG. 10, when the moving speed range actually measured by the magnetic field detecting system 10 is 1-8 m/s, the differential output waveforms of the same defect substantially overlap and are less affected by the moving speed. It can realize reliable and stable detection under high-speed moving conditions. And the magnetic field detecting system 10 maintains stable detection performance under high speed movement.

Referring to FIG. 11, the embodiment further provides an electromagnetic array method, including:

S100' provides a plurality of the aforementioned dynamic magnetic detection systems;

S200' controls the dynamic magnetic detection system through a sequential control array by a control system using a sequential control method.

Specifically, each module in FIG. 11 corresponds to one of the dynamic magnetic detection systems. The control module is a control module for the control system. The control module allocates a specific acquisition work sequence to control different dynamic magnetic detection systems by a sequential control method. In one embodiment, multiple modules can be grouped. Controlled separately by sequential control methods. The sequential control array in the electromagnetic array method refers to adopting a sequential trigger mode, and by sequentially allocating the working timing, sequentially starting the work of each module, reducing the instantaneous working current of the system, and high efficiency in a sufficiently short time window. Complete all module collection work, making the whole detection system high in efficiency, low power consumption and good security.

In the several embodiments provided in the present application, it should be understood that the related apparatus and method disclosed may be implemented in other manners. For example, the device embodiments described above are only illustrative. For example, the division of the modules or units is only a logical function division. In actual implementation, there may be another division manner, for example, multiple units or components may be used. Combinations can be integrated into another system, or some features can be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection through some interface, device or unit, and may be in an electrical, mechanical or other form.

The unit described as a separate component may or may not be physically separated as a unit display unit The pieces may or may not be physical units, ie may be located in one place or may be distributed over multiple network elements. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of the embodiment.

In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above integrated unit can be implemented in the form of hardware or in the form of a software functional unit.

A person skilled in the art can understand that all or part of the process of implementing the above embodiments can be completed by a computer program to instruct related hardware, and the program can be stored in a computer readable storage medium, such as the present application. In an embodiment, the program may be stored in a storage medium of a computer system and executed by at least one processor in the computer system to implement a process comprising an embodiment of the methods described above. The storage medium may be a magnetic disk, an optical disk, a read-only memory (ROM), or a random access memory (RAM).

The technical features of the above-described embodiments may be arbitrarily combined. For the sake of brevity of description, all possible combinations of the technical features in the above embodiments are not described. However, as long as there is no contradiction between the combinations of these technical features, All should be considered as the scope of this manual.

The above-mentioned embodiments are merely illustrative of several embodiments of the present application, and the description thereof is more specific and detailed, but is not to be construed as limiting the scope of the invention. It should be noted that a number of variations and modifications may be made by those skilled in the art without departing from the spirit and scope of the present application. Therefore, the scope of the invention should be determined by the appended claims.

Claims

A dynamic magnetic detection system, comprising:

a magnetic field applying device for applying a magnetic field to the object to be tested having ferromagnetism;

a dynamic magnetic excitation device for generating a transient excitation magnetic field;

A magnetic field detecting device for detecting an induced magnetic signal around the object to be tested.
A dynamic magnetic detecting system according to claim 1, wherein said magnetic field applying means comprises a permanent magnet or an electromagnet.
The dynamic magnetic detection system of claim 1 wherein said moving magnetic excitation means comprises a moving magnetic excitation coil.
A dynamic magnetic detecting system according to claim 1, wherein said dynamic magnetic detecting system further comprises a high frequency pulse current generating means electrically connected to said moving magnetic exciting means.
A dynamic magnetic detecting system according to claim 4, wherein said high frequency pulse current generating means comprises a metal oxide semiconductor field effect transistor for generating a pulse current, said pulse exciting current having a pulse width of 1- The 5 μs, rising edge and falling edge are 0.05-0.2 μs, respectively.
A dynamic magnetic detecting system according to claim 1, wherein said magnetic field detecting means comprises a receiving coil, said receiving coil is a differential receiving coil, and said differential receiving coil comprises a first receiving coil and a second receiving coil, The first receiving coil and the second receiving coil are reversely wound, and the first receiving coil and the second receiving coil are connected end to end.
A dynamic magnetic detecting system according to claim 1, wherein said dynamic magnetic detecting system further comprises a Hilbert transformer connected to said magnetic field detecting means for performing said magnetic signal to Hilbert Special changes.
The dynamic magnetic detection system of claim 7 wherein said dynamic magnetic detection system further comprises:

a first low noise amplifier disposed between the Hilbert transformer and the magnetic field detecting device;

a second low noise amplifier connected to the output of the Hilbert transformer signal;

A low pass filter is disposed between the Hilbert transformer and the second low noise amplifier.
A dynamic magnetic detecting system according to claim 7, wherein said dynamic magnetic detecting system further comprises a magnetic flux leakage detecting means, said magnetic flux leakage detecting means being a multi-channel Hall chip array, each channel comprising X, Y Three vertical direction Hall chips of Z-axis are used to detect spatial magnetic flux leakage signals.
The dynamic magnetic detection system of claim 9 wherein said dynamic magnetic detection system further comprises:

And a control device for controlling the magnetic field applying device, the moving magnetic excitation device, the magnetic field detecting device, the magnetic flux leakage detecting device, and the Hilbert transformer.
A dynamic magnetic detection method, characterized in that the method comprises:

Applying a magnetic field to the object to be tested, so that the object to be tested enters a magnetic saturation state;

Applying a transient excitation magnetic field to the object to be measured;

After superimposing the transient excitation magnetic field, a magnetic signal around the probe is detected.
The dynamic magnetic detecting method according to claim 11, wherein the step of detecting the magnetic signal around the probe after the superimposing the transient excitation magnetic field further comprises:

Performing a Hilbert transform on the magnetic signal by a Hilbert transformer and outputting a waveform signal;

Determining whether the object to be tested has a defect according to the waveform signal.
The dynamic magnetic detecting method according to claim 11, further comprising:

The three-dimensional magnetic field signal is acquired by the magnetic flux leakage detecting device, and the three-dimensional magnetic signal is analyzed to obtain a defect condition.
The dynamic magnetic detecting method according to claim 11, wherein said transient excitation magnetic field is generated by a moving magnetic excitation device, and is connected to said dynamic magnetic excitation device by a high frequency pulse current generating device to said moving magnetic field The excitation device inputs a pulse excitation current having a pulse width of 1-5 μs, a rising edge and a falling edge of 0.05-0.2 μs, respectively, to generate a transient excitation magnetic field.
An electromagnetic array method, comprising:

Providing a plurality of dynamic magnetic detection systems according to any of claims 1-10;

The dynamic magnetic detection system is controlled by a sequential control array by a control system using a sequential control method.