Magnetic source transient electromagnetic detection device

Abstract

The invention discloses a magnetic source transient electromagnetic detection device, relates to the technical field of electromagnetic detection, and solves the problem of useful signal detection caused by direct coupling of an excitation magnetic field generated by a transmitting coil to a receiving coil in the prior art. The device comprises a control unit, a signal transmitting unit, a signal receiving unit and a data acquisition unit, a quick turn-off circuit of the signal transmitting unit is responsible for controlling on and off of a signal transmitting coil, and the signal transmitting coil generates a primary field for exciting a grounding grid to generate a secondary field; after the signal transmitting coil transmits a primary field, the signal receiving coil and the compensating coil are responsible for receiving a secondary field signal from a grounding grid, and the interference of the primary field is shielded through the combination of positions. On the basis, the signal integrity can be ensured by optimizing the waveform of the emission current and shortening the turn-off time, so that the exploration precision and the application effect of the transient electromagnetic method in a complex environment are improved.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic detection technology, and in particular to a transient electromagnetic detection device for a magnetic source. Background Technology

[0002] The Transient Electromagnetic Method (TEM) is a time-domain artificial source geophysical exploration technique based on the principle of electromagnetic induction. The measurement system of this method mainly consists of two core components: a transmitting coil and a receiving coil. Its complete workflow can be systematically divided into three key stages: the transmission stage, the electromagnetic induction stage, and the signal reception stage. In the transmission stage, the system supplies a precisely controlled step current I to the transmitting coil, and then causes the current to decay to zero within an extremely short time (typically on the order of microseconds). According to Maxwell's electromagnetic field theory, this rapid change in current induces a time-varying magnetic field in the space surrounding the transmitting coil, known as the primary magnetic field.

[0003] In transient electromagnetic methods, primary field coupling refers to the interference caused by the direct coupling of the excitation magnetic field (primary field) generated by the transmitting coil to the receiving coil, affecting the detection of the useful signal. In simulations, the coupled signal can be 10²-10³ times larger than the pure secondary field, making it difficult to distinguish the pure secondary field signal and creating a shallow detection blind zone. Furthermore, the mutual inductance between the transmitting and receiving coils is strongly related to the size of the transmitting coil; the larger the transmitting coil, the lower the impact of primary field coupling on the actual received signal. However, in grounding grid corrosion detection, due to the need for equipment portability, the size of the transmitting coil should not be too large. Therefore, it is necessary to design a suitable hardware structure to reduce the mutual inductance between the transmitting and receiving coils, thereby minimizing the interference of primary field coupling on the secondary field signal.

[0004] Therefore, a transient electromagnetic detection device for magnetic sources is needed. Summary of the Invention

[0005] To address the problem in existing technologies where the excitation magnetic field (primary field) generated by the transmitting coil is directly coupled to the receiving coil, causing issues with useful signal detection, this invention provides a magnetic source transient electromagnetic detection device. After the primary field is transmitted by the signal transmitting coil, the signal receiving coil and compensation coil are responsible for receiving the secondary field signal from the grounding grid. Furthermore, interference from the primary field is shielded through a specific combination of positions, and signal integrity is ensured by optimizing the transmission current waveform and shortening the turn-off time. This improves the exploration accuracy and application effectiveness of transient electromagnetic methods in complex environments. The specific technical solution is as follows: A transient electromagnetic detection device for a magnetic source includes a transmitter and a receiver. The transmitter includes a control unit and a signal transmitting unit, and the receiver includes a signal receiving unit, a data acquisition unit, and a control unit, wherein: The signal transmitting unit mainly consists of two parts: a fast shutdown circuit and a signal transmitting coil. The fast shutdown circuit is responsible for controlling the opening and closing of the signal transmitting coil, while the signal transmitting coil generates a primary field to excite the grounding grid to generate a secondary field. The signal receiving unit consists of three parts: a grounding grid, a compensation coil, and a signal receiving coil. After the signal transmitting coil transmits the primary field signal, the signal receiving coil and the compensation coil are responsible for receiving the secondary field signal from the grounding grid. They also shield the primary field interference through a combination of their positions, thereby transmitting the acquired secondary field signal to the data transmission unit.

[0006] Preferably, the transmitter circuit includes a current shutdown circuit, an RCD absorption circuit, and a control circuit. The current shutdown circuit is a unipolar transmitting circuit, which is responsible for generating an electromagnetic pulse at the moment the charging circuit is turned off. The RCD absorption circuit is used to optimize the shutdown waveform and protect the driver chip and MOSFET. The control circuit is used to receive the drive signal and amplify it to transmit it to the MOSFET terminal, thereby controlling the opening and closing of the charging circuit.

[0007] Preferably, the data acquisition unit includes a PLL module, a serial port receiving / transmitting module, an instruction receiving / parsing module, a bit width conversion module, an SDRAM controller module, and a status control module, wherein: The PLL module generates corresponding clocks by multiplying and dividing the system's clock and then sends them to the corresponding modules. The instruction configuration information is sent from the host computer to the FPGA via the serial port. The FPGA receives the instruction information from the serial port and sets the amount of data to be sampled, the sampling channel and the sampling frequency. The received instruction information will be parsed by the next module. The instruction receiving / parsing module disassembles and identifies the instructions received from the serial port; The bit-width conversion module converts 12-bit data into 16-bit data for storage; The SDRAM controller module consists of a controller module and two FIFOs for reading and writing. The write FIFO is responsible for buffering the acquired data, which is then read by the SDRAM controller and controlled to be stored in the off-chip SDRAM. The read FIFO is responsible for buffering the data to be read from the SDRAM and outputting it under the control of the SDRAM controller. The status control module coordinates and controls the data writing of the SDRAM controller module based on the data acquisition information provided by the instruction receiving / parsing module and the relevant signals of the SDRAM controller module. At the same time, it controls the reading of data from the SDRAM controller module, converts the data read from the SDRAM controller module, and controls the output to the instruction receiving / parsing module.

[0008] Preferably, the current-cut-off circuit comprises a diode, a coil, and a resistor, wherein the coil and the resistor are connected in series, and two diodes connected in series are connected in parallel.

[0009] Preferably, the RCD absorption circuit includes a resistor, a diode, and a capacitor, wherein the resistor and the diode are connected in parallel, and then the resistor and the capacitor are connected in series.

[0010] Preferably, the receiving coil should meet the following conditions: in: N T The number of turns of the transmitting coil. N 内 and N 外 These represent the number of turns of the inner and outer receiving coils, respectively.

[0011] Preferred, Where m = r / a (0 <m<b / a), , K , E These are the first and second type elliptic integrals, respectively. .

[0012] Preferred, .

[0013] A method for detecting transient electromagnetic fields from a magnetic source, using the apparatus described above, includes the following steps: The S1 control unit outputs a pulse signal; S2. The signal amplification chip, powered by the step-down power supply chip, receives the pulse signal sent by the control unit, amplifies the signal, and outputs it to the MOSFET. S3. After receiving a pulse signal, the MOSFET performs a turn-on / turn-off operation, thereby controlling the switching on and off of the transmitting circuit. The transmitting coil then transmits the pulse signal to the grounding grid. Compared with the prior art, the beneficial effects of the present invention are as follows: This invention includes a transmitter and a receiver. The transmitter includes a control unit and a signal transmitting unit, while the receiver includes a signal receiving unit, a data acquisition unit, and a control unit. The signal transmitting unit mainly comprises two parts: a fast-shutdown circuit and a signal transmitting coil. The fast-shutdown circuit controls the switching on and off of the signal transmitting coil, which generates a primary field to excite the grounding grid to generate a secondary field. The signal receiving unit comprises a grounding grid, a compensation coil, and a signal receiving coil. After the signal transmitting coil transmits the primary field, the signal receiving coil and the compensation coil receive the secondary field signal from the grounding grid and shield the primary field interference through a combination of their positions, thereby transmitting the acquired secondary field signal to the data transmission unit. Based on this, this invention can improve the exploration accuracy and application effect of transient electromagnetic methods in complex environments by optimizing the transmission current waveform and shortening the turn-off time to ensure signal integrity. Attached Figure Description

[0014] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0015] Figure 1 This is a schematic diagram of the transient electromagnetic method device of the present invention; Figure 2 This is the overall circuit diagram of the transmission circuit; Figure 3 Here is the charging circuit diagram; Figure 4 This is a flowchart of the receiver's workflow. Figure 5 This is a diagram of the cross-ring decoupling structure; Figure 6 This is a functional block diagram of the signal acquisition device; Figure 7 This is a schematic diagram of the state machine for the AD sampling function; Figure 8 This is a block diagram of the system modules. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0018] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0019] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0020] like Figure 1 As shown, the transient electromagnetic detection device is divided into four units: a signal transmitting unit, a signal receiving unit, a control unit, and a data transmission unit. The signal transmitting unit mainly consists of two parts: a fast shutdown circuit and a signal transmitting coil. The fast shutdown circuit is responsible for controlling the opening and closing of the signal transmitting coil, while the signal transmitting coil generates a primary field to excite the grounding grid to generate a secondary field.

[0021] The signal receiving unit consists of three parts: a grounding grid, a compensation coil, and a signal receiving coil. After the signal transmitting coil transmits the primary field signal, the signal receiving coil and the compensation coil are responsible for receiving the secondary field signal from the grounding grid. They also shield the primary field interference through a combination of special positions, thereby transmitting the acquired secondary field signal to the signal conditioning circuit.

[0022] The data transmission unit consists of a signal conditioning circuit and a data acquisition card (ADC). Since the data acquisition card has a limited acquisition range, the signal conditioning circuit needs to adjust the signal from the receiving coil before transmitting it to the data acquisition card. The data acquisition card then completes the AD conversion and sends the result to the industrial control computer (PC). The control unit consists of an industrial control computer (microcontroller, PC), which is responsible for controlling the switching of the signal transmission unit and receiving data from the data transmission unit.

[0023] Therefore, based on the transmission and reception functions, transient electromagnetic devices can be divided into two parts: a transmitter (including a control unit and a signal transmission unit) and a receiver (including a signal reception unit, a data acquisition unit, and a control unit). For ease of description, the design and functions of the transmitter and receiver will be introduced in detail below.

[0024] The specific working process of the transmitter of the portable magnetic source transient electromagnetic detection equipment is as follows: 1. The control unit gives a pulse signal; 2. The signal amplification chip powered by the step-down power supply chip receives the pulse signal sent by the control unit, amplifies the signal and outputs it to the MOSFET; 3. After receiving the pulse signal, the MOSFET performs a turn-on and turn-off operation, thereby controlling the opening and closing of the transmitting circuit, and the transmitting coil transmits the pulse signal to the grounding grid.

[0025] The overall circuit diagram of the transmitting circuit is as follows: Figure 2 As shown, it includes a current-shutdown circuit, an RCD snubber circuit, and a control circuit. The current-shutdown circuit is a unipolar transmitting circuit, responsible for generating an electromagnetic pulse at the moment the charging circuit is turned off. The RCD snubber circuit is used to optimize the turn-off waveform and protect the driver chip and MOSFET. The control circuit is used to receive the drive signal and amplify it to transmit it to the MOSFET terminal, thereby controlling the opening and closing of the charging circuit.

[0026] When the MOSFET is turned on, the overall turn-on circuit is as follows: Figure 3 As shown in the figure, U S The main circuit charging voltage. L 1 represents the equivalent inductance of the coil. R Let 1 be the total circuit resistance (including the circuit resistance and the equivalent coil resistance). Then, the change in inductor current when the MOSFET is turned on is as follows: (2-8) After a sufficiently long period of time, the current flowing through the inductor will tend to stabilize, which means that the inductor's charging is basically complete. At this point, the energy stored in the inductor is: (2-9) At the moment the MOSFET is turned off, due to the inductor's current-holding characteristic, it will break down the Zener diode, according to KVL: (2-10) in the formula L The equivalent inductance of the shut-off circuit, R and V These are the total resistance of the shutdown circuit and the breakdown voltage of the Zener diode, respectively.

[0027] Boundary conditions: (2-11) Solving the first differential equation yields the current in the coil as a function of time: (2-12) Furthermore when I When = 0, the requirements are: (2-13) Set coil parameters, L =125μH, R =2.5Ω, τ =0.192μs, when required t =10μs, I When = 0, we can obtain V =679V.

[0028] While MOSFETs offer the significant advantage of high switching speed, they face serious challenges in practical applications. Due to stray inductance in the circuit, their rapid switching process generates severe transient voltage overshoot and high-frequency oscillations. The faster the switching speed, the more pronounced these negative effects become, specifically manifesting as increased voltage stress on the device, reduced reliability, intensified electromagnetic interference, and deterioration of the switching waveform quality. These problems not only limit further increases in switching frequency but also increase the design difficulty of filter circuits, ultimately creating a conflict between the high-speed switching characteristics of MOSFETs and their advantages in high-frequency applications, thus hindering performance improvements in efficiency and power density of power electronic devices.

[0029] Due to the oscillations caused by the MOSFET turn-off process, the MOSFET's GS voltage becomes unstable, which further affects the turn-off status of the main circuit. Therefore, optimizing the MOSFET turn-off waveform plays an important role in the quality control of the transmitter waveform.

[0030] To improve the switching waveform, a snubber circuit is typically added across the MOSFET to improve the turn-on and turn-off waveforms, eliminate voltage spikes, and thus protect the device for safe operation. However, the snubber circuit also increases switching losses, so the structure and parameters of the snubber circuit need to be adjusted to optimize the MOSFET's switching performance.

[0031] RC and RCD snubber circuits effectively suppress oscillations due to their excellent damping characteristics, but their inherent drawbacks limit their application range: on the one hand, they prolong turn-off time and increase switching losses, requiring a trade-off design for snubber parameters; on the other hand, the discharge current of the snubber capacitor during turn-on increases the current stress on the device. Therefore, RC snubbers are more suitable for low-power switching power supplies, while RCD snubbers are suitable for high-capacity IGBT applications. In contrast, clamped RCDs have significant advantages under smaller capacity conditions: they only operate when the capacitor voltage exceeds the bus voltage, maintaining excellent oscillation suppression without affecting switching performance, and their parameter design is simple and insensitive to changes in operating conditions, thus finding wide application in low-to-medium power applications such as flyback converters. Since the transmitter needs to operate under high power conditions, RCD-type circuits are more suitable for project requirements.

[0032] The value of the buffer capacitor has a significant dual impact on switching characteristics: during turn-off, increasing the buffer capacitor improves energy absorption, effectively suppresses oscillation amplitude, and shortens the oscillation period, but it also reduces the rate of change of voltage and current, leading to prolonged turn-off time and degraded device turn-off performance. During turn-on, the discharge effect of the buffer capacitor intensifies with increasing capacitance, generating higher turn-on current spikes and worsening the current waveform quality. Therefore, it is necessary to rationally select the parameters of the buffer capacitor to achieve a balance between oscillation suppression and switching characteristics.

[0033] Conversely, the buffer resistor has a relatively small impact on the switching characteristics of the device. As shown in the figure below, changes in the buffer resistor value have almost no effect on the operating characteristics of the MOSFET. Therefore, a buffer capacitor of 1μF and a buffer resistor of 5Ω are selected across the MOSFET.

[0034] The design of the control circuit primarily considers the protection of the driver chip, such as... Figure 2 As shown, the protection of the driver chip is mainly reflected in the following two aspects: First, a MOSFET-like buffer absorption circuit was added to the OUT terminal of the chip. C2 is composed of capacitors of two specifications: 10μF and 0.1μF. The capacitors of different sizes are used to absorb energy and suppress high-frequency noise, respectively. Meanwhile, the main circuit and the control circuit are powered separately. According to experimental tests, a large voltage fluctuation occurs across the battery terminals at the moment the main circuit is turned on and off. If the main circuit and the driver chip are powered by the same battery, this voltage fluctuation will cause the chip to burn out. Therefore, the main circuit and the chip are ultimately powered separately.

[0035] like Figure 4 As shown, the receiver's workflow includes: 1. The substation grounding grid generates an induced secondary field under the excitation of the primary field of the transmitting coil; 2. After receiving the signal, the weak magnetic coupling structure transmits the analog signal to the ADC; 3. The ADC converts the analog signal into a digital signal and sends the digital signal to the DMA for storage; 4. The DMA sends the stored data to the computer via the serial port.

[0036] The core component of the receiver is the control of primary field coupling. As described in Chapter 2, primary field coupling causes the transmitted signal generated by the transmitting coil to be directly coupled to the receiving coil, and its amplitude is much larger than the received signal, resulting in early interference with the received signal and causing a shallow blind zone in grounding grid detection. Ideally, a weak magnetic coupling structure should be designed to reduce the mutual inductance between the transmitting and receiving coils to zero, so that the received signal collected by the receiving coil comes entirely from the secondary field of the grounding grid. However, in actual operation, since the signal generated by the transmitting coil is coupled to the receiving coil through the air path, it is difficult to reduce the mutual inductance between the transmitting and receiving coils to zero. This embodiment uses a weak magnetic coupling structure, utilizing the special structure of the receiving coil and its spatial relationship with the transmitting coil, to reduce the coupling between the transmitting and receiving coils, thereby reducing the interference of the primary field on the secondary field signal.

[0037] The weak magnetic coupling structure uses a special structure, a special placement position, or the use of a compensation coil to minimize the mutual inductance between the transmitting coil and the receiving coil, thereby avoiding interference between the primary field signal and the secondary field signal of the grounding grid and improving the problem of shallow detection blind zone of the grounding grid.

[0038] To eliminate the influence of the transmitting coil on the receiving coil, the receiving coil should meet the following conditions: (3-1) in: N T The number of turns of the transmitting coil. N 内 and N 外 These represent the number of turns in the inner and outer receiving coils, respectively. The above formula can be simplified to: (3-2) If according to Figure 5 Establishing a coordinate system, we have the following in the xoy plane: (3-3) Further, there are: (3-4) Simplifying, we get: (3-5) Where m = r / a (0 <m<b / a), , K , E These are the first and second type elliptic integrals, respectively. .

[0039] Similarly, we can conclude that: (3-6) Based on the results of equations 4-5 and 4-6, if the selected a =0.25m, b =0.125m, c =0.3m, d =0.4m, then we can obtain Φ 内 and Φ 外 They are 3.079×10 -7 and 2.221×10 -7 Wb, then N 外 : N 内 =1.386:1.

[0040] After the receiving coil acquires the received signal, a suitable signal acquisition circuit needs to be designed to convert the analog signal received by the receiving coil into a digital signal and send it to the host computer for further processing. FPGA has the advantages of high design flexibility and reprogrammability. Its parallel processing characteristics are suitable for applications with fixed processing tasks and high-speed data acquisition, transmission, and processing. Considering both cost and system complexity, the prototype selected the Intel Cyclone IV series EP4CE10F17C8 FPGA as the main controller to implement the data processing function. Simultaneously, Analog Devices' AD9238 chip was selected to implement the AD sampling function. It can achieve 12-bit resolution sampling of ±5V analog signals at a maximum sampling rate of 50MHz.

[0041] The signal acquisition device operates as follows: First, the host computer sends instructions to the FPGA via serial port to configure the sampling frequency, number of data samples, and sampling channels of the AD9238 module. After acquisition, the data is buffered in SDRAM and then transmitted back to the host computer via serial port. The functional block diagram of the signal acquisition device is shown below. Figure 6 As shown A simplified state machine for the AD sampling process, such as Figure 7 As shown.

[0042] The core of the program state machine is mainly divided into four parts: power-on, idle, ADC sampling, and serial port upload.

[0043] After the program is powered on, it enters state 2, the idle state. At this time, the number of samples and the sampling frequency can be set through serial port commands, and a start sampling command can be sent.

[0044] After receiving the start sampling command, the FPGA enters state 3 to begin ADC sampling. Simultaneously, the data is directly stored in the SDRAM. If the required number of samples has not been reached, the FPGA enters state 3 in a loop; if the required number of samples has been reached, the FPGA enters state 4 for serial port upload. Once the serial port upload is complete, the FPGA returns to the idle state; otherwise, it continues with the serial port upload.

[0045] To achieve the above functions, nine sub-modules are designed, such as... Figure 8 As shown.

[0046] The functions of each internal submodule are as follows: U0: Command receiving function of the serial port receiving module; U1 and U2: Parse and classify the received instructions; U3: State machine module, which coordinates the signal control of various modules and is the overall control module for program state; U4 and U5: These are the sampling rate control modules that convert the 12-bit data input from the AD9238 to 16-bit data. U6: SDRAM with FIFO package module, mainly responsible for the entire data storage function; U7: Serial port data output function.

[0047] (1) PLL module The PLL clock module is mainly responsible for multiplying and dividing the system's 50MHz clock to generate corresponding clocks and sending them to the corresponding modules. It is mainly responsible for generating the working clocks for the SDRAM_control_top module and other modules in the system.

[0048] (2) Serial port receiving / serial port transmitting module The instruction configuration information is sent from the host computer to the FPGA via the serial port. The FPGA receives the instruction information from the serial port and sets the amount of data to be sampled, the sampling channel, and the sampling frequency. The received instruction information will be parsed by the next module.

[0049] The data acquired by the AD9238 is buffered in SDRAM. The data in SDRAM is read out through the SDRAM read FIFO, and the serial port transmission module sends the acquired data to the host computer. However, since the output data width of the SDRAM read FIFO is 16 bits, it is necessary to perform bit width conversion in the ad9238_12bit_16bit module to finally convert it into 8-bit data.

[0050] (3) Command receiving / parsing module The function of these two modules is to decompose and identify the commands received from the serial port. After receiving command data from the serial port, the uart_byte_rx module converts the serial data from a serial signal into 8-bit parallel data, uart_rx_data. Within the module, the validity of the 8-byte command information is determined based on the packet header and trailer information. If the command is valid, uart_cmd reads the register address settings and the configuration data for data acquisition.

[0051] (4) Bit width conversion module (ad9238_12bit_16bit) The 12-bit data acquired by the AD9238 data acquisition module is not convenient for computer storage because computers use 8-bit or 16-bit data as a unified storage standard when analyzing and storing data. Therefore, it is necessary to use the data bit extension module (ad9238_12bit_16bit) to convert the 12-bit data into 16-bit data for storage.

[0052] (5) SDRAM controller module (sdram_control_top) The controller module and the two FIFOs (read and write FIFOs) together form the SDRAM control module. The write FIFO is responsible for buffering the acquired data, which is then read by the SDRAM controller and stored in the off-chip SDRAM. The read FIFO is responsible for buffering the data to be read from the SDRAM and outputting it under the control of the SDRAM controller. Adding two FIFOs to the SDRAM controller effectively solves the problem that, at certain times, some reads or writes might be ignored, and that data writing or reading cannot continuously buffer the data stream, but can only intermittently read or write SDRAM data, leading to missed data storage or retrieval.

[0053] (6) State control module (state_ctrl) The status control module is the core control module of this system. Based on the data acquisition information provided by the uart_byte_rx module and the relevant signals of the SDRAM controller module, it coordinates and controls the data writing of the SDRAM controller module, controls the data reading of the SDRAM controller module, converts the data read from the SDRAM controller module, and controls the output to the uart_byte_tx module.

[0054] Those skilled in the art will recognize that the units of the various examples described in connection with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of the invention.

[0055] In the embodiments provided by the present invention, it should be understood that the division of units is only a logical functional division. In actual implementation, there may be other division methods, such as multiple units can be combined into one unit, one unit can be split into multiple units, or some features can be ignored.

[0056] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0057] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, read-only memory (ROM), random access memory (RAM), portable hard drives, magnetic disks, or optical disks.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A magnetic source transient electromagnetic detection apparatus, characterized by, The transmitter comprises a control unit and a signal transmitting unit, and the receiver comprises a signal receiving unit, a data acquisition unit and a control unit, wherein: The signal transmitting unit mainly comprises two parts: a fast-off circuit and a signal transmitting coil, the fast-off circuit is responsible for controlling the opening and closing of the signal transmitting coil, and the signal transmitting coil generates a primary field for exciting the grounding grid to generate a secondary field; The signal receiving unit comprises a grounding grid, a compensation coil and a signal receiving coil, after the signal transmitting coil transmits a primary field, the signal receiving coil and the compensation coil are responsible for receiving the secondary field signal from the grounding grid, shielding the interference of the primary field through the combination of positions, and transmitting the collected secondary field signal to the data transmission unit.

2. The magnetic source transient electromagnetic detection apparatus of claim 1, wherein, The circuit of the transmitter comprises a current-off loop, an RCD absorption loop and a control circuit, wherein the current-off loop is a single-polarity transmitting loop, responsible for exciting an electromagnetic pulse at the moment of closing the charging loop, the RCD absorption loop is used to optimize the off waveform and protect the safety of the driving chip and MOSFET, and the control circuit is used to receive the driving signal and amplify and transmit it to the MOSFET end, thereby controlling the opening and closing of the charging loop.

3. The magnetic source transient electromagnetic detection apparatus of claim 1, wherein, The data acquisition unit comprises a PLL module, a serial port receiving / serial port sending module, an instruction receiving / analyzing module, a bit width conversion module, an SDRAM controller module and a state control module, wherein: The PLL module multiplies and divides the clock of the system to generate corresponding clock signals for the corresponding modules; The instruction configuration information is sent from the upper computer to the FPGA through the serial port, the FPGA receives the instruction information from the serial port, sets the data amount, sampling channel and sampling frequency, and the received instruction information will be analyzed by the next module; The instruction receiving / analyzing module disassembles and identifies the instructions received by the serial port; The bit width conversion module converts 12-bit data into 16-bit data for storage; The SDRAM controller module is composed of a controller module and two FIFOs for reading and writing, wherein the write FIFO is responsible for buffering the collected data, which is read by the SDRAM controller and stored in the off-chip storage device SDRAM, and the read FIFO is responsible for buffering the data to be read out from the SDRAM and outputting it under the control of the SDRAM controller; The state control module coordinates and controls the data writing of the SDRAM controller module according to the data acquisition amount information given by the instruction receiving / analyzing module and the related signals of the SDRAM controller module, controls the reading of the SDRAM controller module, converts and controls the output of the data read from the SDRAM controller module to the instruction receiving / analyzing module.

4. The magnetic source transient electromagnetic detection apparatus of claim 2, wherein, The current-off loop comprises diodes, coils and resistors, wherein the coils and resistors are connected in series and the two series-connected diodes are connected in parallel.

5. The magnetic source transient electromagnetic detection apparatus of claim 2, wherein, The RCD absorption loop comprises resistors, diodes and capacitors, wherein the resistors and diodes are connected in parallel, and then connected in series with the capacitors.

6. The magnetic source transient electromagnetic detection apparatus of claim 1, wherein, The receiving coil should satisfy the following conditions: wherein: N T Ntis the number of turns of the transmitting coil, N 内 and N 外 Ntis the number of turns of the transmitting coil, 7. The magnetic source transient electromagnetic detection device according to claim 6, characterized in that, where m = r / a (0 < m < b / a), , K , E are the first and second kind elliptic integrals, respectively, .

8. The magnetic source transient electromagnetic detection device according to claim 7, characterized in that, 。 9. A magnetic source transient electromagnetic detection method, applying the magnetic source transient electromagnetic detection device according to any one of claims 1-8, comprising the following steps: S1. The control unit sends a pulse signal; S2. The signal amplification chip powered by the voltage reduction power supply chip receives the pulse signal sent by the control unit, and outputs the amplified signal to the MOSFET; S3. The MOSFET receives the pulse signal and performs a turn-on-off operation, thereby controlling the turn-on and turn-off of the transmitting circuit, and the transmitting coil thus transmits the pulse signal to the grounding net.

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