A high-precision three-component electromagnetic field sensor and its data transmission control system

Abstract

A high-precision three-component electromagnetic field sensor and a data transmission control system therefor. The high-precision three-component electromagnetic field sensor comprises a box body (1),

Description

TECHNICAL FIELD 5

[0001] The invention relates to the field of ground-air electromagnetic detection technology, in particular to a high-precision three-component electromagnetic field sensor and its data transmission control system. BACKGROUND OF THE TECHNOLOGY

[0002] The rapid economic development has continuously increased the demand for 10 mineral resources and energy; meanwhile, large-scale and rapid mining of mineral resources and energy has caused the destruction of the geological environment, resulting in a series of geological disasters, especially the large number of coal mined areas, which have had a greater impact on the sustainable development of the subsequent economy; said geological disasters are concealed, time-varying and 15 sudden, and most of them are located in complex geological conditions, such as alpine regions, gobi deserts, hilly areas, mountainous areas, dense vegetation, waters, etc., which has brought great difficulties to the exploration work of traditional geophysical technology; traditional geophysical exploration methods are difficult to meet the requirements for resource exploration and geological environment monitoring, and it 20 is difficult to achieve large-scale rapid and efficient fine detection in these areas; therefore, there is an urgent need to achieve high efficiency and high quality in areas with complex geological conditions; said detection device and construction method can improve the accurate detection of the geological environment damage program.

[0003] Ground-to-air electromagnetic method (also known as semi-aircraft 25 electromagnetic method) is based on the principle of electromagnetic induction; it transmits pulses or electromagnetic information of different frequencies to the ground through transmitting electrodes arranged on the ground, and is carried by drones, gyroplanes or airships; geological prospecting method in which high-precision electromagnetic sensors receive electromagnetic induction signals; said method 30 combines the advantages of ground electromagnetic method and aviation electromagnetic method, which has higher construction efficiency of aviation electromagnetic method, and also has the characteristics of large detection depth, high safety factor and high signal-to-noise ratio of ground high-power electromagnetic method; ground-to-air electromagnetic method combines the characteristics of ground electromagnetic method and aviation electromagnetic method, which has high field construction efficiency and detection accuracy, and is suitable for rapid and high-precision detection in areas with complex terrain conditions.

[0004] At present, theoretical research and application of ground-to-air electromagnetic methods at home and abroad focus on the detection method in the time domain; collected data is the response signal of the vertical magnetic field component (Hz), and the magnetic field component in the x and y directions (Hx and Hy); if said magnetic field component signals in the three directions are jointly collected and processed, data interpretation accuracy of the ground-air electromagnetic method can be improved. SUMMARY OF THE INVENTION

[0005] Aiming at the above-mentioned shortcomings in the prior art, this invention provides a high-precision three-component electromagnetic field sensor and its data transmission control system; said system uses the collected three-component electromagnetic field response values to perform joint inversion and interpretation, so as to improve the accuracy of electromagnetic exploration and interpretation and reduce the safety hazards of hidden geological disasters.

[0006] In order to achieve said purpose, technical solution adopted by this invention is as follows:

[0007] A high-precision three-component electromagnetic field sensor comprises cabinet, said cabinet is provided with X-direction coil structure, Y-direction coil structure, and Z-direction coil structure with the same structure; normal directions of said X-direction coil structure, Y-direction coil structure and Z-direction coil structure are orthogonally combined; leveler is arranged inside the cabinet; circuit control board and battery are provided inside this cabinet; said circuit control board is provided with a preamplifier respectively connected with the X-direction coil structure, the Y-direction coil structure and the Z-direction coil structure; noise filter is connected to preamplifier; signal collector is connected to said noise filter, and said signal collector is electrically connected with said battery; interface is connected to said signal collector to extend out of the cabinet.

[0008] Preferred, said interface includes Ethernet communication interface, SD card interface and indicator light interface.

[0009] Preferred, said Z-direction coil structure includes hollow spool and magnetic core arranged in said hollow spool, and induction coil is wound on the outside of said hollow spool.

[0010] Preferred, said battery is rechargeable lithium battery.

[0011] Preferred, said hollow spool is made of non-conductive material.

[0012] Preferred, said induction coil is enameled wire wound in layers on the outside of said hollow spool.

[0013] A high-precision three-component electromagnetic field sensor is characterized in that,

[0014] Three-component data acquisition system: said system includes sensor signal receiving and matching circuit and high-precision data sampling circuit, used for electromagnetic induction signal output, turning magnetic signal into electrical signal, after signal conditioning circuit, filter circuit and A / D conversion, it is sent to digital signal processing system for processing ;

[0015] Signal processing control system: said system includes the main control chip FPGA, preamplifier and digital filter, which is used to use the size of the sampled digital signal to amplify and filter it so that its amplitude meets the input range of the ADC, so as to make full use of the resolution of the ADC converter rate;

[0016] Data transmission and storage system: said system includes SD card, USB interface and RJ45 interface; these data are quickly transmitted and stored in the memory; said FPGA control parallel output is used in conjunction with the SD card; data collected by the FPGA is stored on the SD in real time; then export the data through the USB or RJ45 communication interface for subsequent interpretation of the software call.

[0017] Preferred, said control system also includes a time synchronization control unit, which includes a GPS and a stable clock for precise time control of the three-component data sampling points and synchronization with the transmitter.

[0018] Preferred, said high-precision data sampling circuit uses three-component independent A-S AD chips to realize multi-path differential data acquisition, which is used to convert the analog signal output by the signal receiving and matching equivalent circuit into a digital signal.

[0019] The beneficial effects of this invention are as follow:

[0020] This invention uses three-component electromagnetic field response values for joint inversion interpretation; it can improve the accuracy of electromagnetic exploration and interpretation, and reduce the safety hazards of hidden geological disasters; it applys combined control method of ARM and FPGA; FPGA can perform real-time acquisition, ARM can perform post-processing, storage and transmission; this can effectively improve the overall performance of said system; GPS timing device can make each sampling point have an accurate time stamp, and the deviation from the absolute time is less than 30nS, which ensures the accuracy of data transmission. DESCRIPTION OF THE DRAWING

[0021] FIG. 1 is schematic diagram of the planar structure of this invention;

[0022] FIG. 2 is schematic diagram of the data acquisition system of this invention;

[0023] FIG. 3 is schematic diagram of the construction method of this invention;

[0024] FIG. 4 is an equivalent circuit diagram of the induction coil of this invention;

[0025] FIG. 5 is a graph of the self noise FFT result of the time series of this invention;

[0026] FIG. 6 is a response curve of the sensor of this invention;

[0027] FIG. 7 is a schematic diagram of the coil structure;

[0028] As shown in the drawings, 1. cabinet, 2. X-direction coil structure, 3. Y-direction coil structure, 4. Z-direction coil structure, 5. leveler, 6. battery, 7. preamplifier, 8. noise filter, 9. signal collector, 10. interface, 11. hollow spool, 12. magnetic core, 13. induction coil. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] The specific embodiments of this invention will be further described below in conjunction with the drawings; same parts are indicated by the same reference numerals.

[0030] It should be noted that the words "front", "rear", "left", "right", "upper" and "lower" used in the following description refer to the directions in the drawings, and the words "inner" and "outer" respectively refers to the direction toward or away from the geometric center of a particular' component.

[0031] In order to make the content of this invention easier to be understood, technical solutions in the embodiments of this invention will be described clearly and completely in conjunction with the accompanying drawings in the embodiments of this invention.

[0032] A high-precision three-component electromagnetic field sensor comprises cabinet (1), said cabinet (1) is provided with X-direction coil structure (2), Y-direction coil structure (3), and Z-direction coil structure (4) with the same structure; normal directions of said X-direction coil structure (2), Y-direction coil structure (3) and Z-direction coil structure (4) are orthogonally combined; leveler (5) is arranged inside the cabinet (1); circuit control board and battery (6) are provided inside this cabinet (1); said circuit control board is provided with a preamplifier (7) respectively connected with the X-direction coil structure (2), the Y-direction coil structure (3) and the Z-direction coil structure (4); noise filter (8) is connected to preamplifier (7); signal collector (9) is connected to said noise filter (8), and said signal collector (9) is electrically connected with said battery (6); interface (10) is connected to said signal collector (9) to extend out of the cabinet (1).

[0033] Said interface (10) includes Ethernet communication interface, SD card interface and indicator light interface.

[0034] Said Z-direction coil structure (4) includes hollow spool (11) and magnetic core (12) arranged in said hollow spool (11), and induction coil (13) is wound on the outside of said hollow spool (11).

[0035] Said battery is rechargeable lithium battery.

[0036] Said hollow spool (11) is made of non-conductive material.

[0037] Said induction coil (13) is enameled wire wound in layers on the outside of said hollow spool (11).

[0038] A high-precision three-component electromagnetic field sensor is characterized in that,

[0039] Three-component data acquisition system: said system includes sensor signal receiving and matching circuit and high-precision data sampling circuit, used for electromagnetic induction signal output, turning magnetic signal into electrical signal, after signal conditioning circuit, filter circuit and A / D conversion, it is sent to digital signal processing system for processing ;

[0040] Signal processing control system: said system includes the main control chip FPGA, preamplifier and digital filter, which is used to use the size of the sampled digital signal to amplify and filter it so that its amplitude meets the input range of the ADC, so as to make full use of the resolution of the ADC converter rate;

[0041] Data transmission and storage system: said system includes SD card, USB interface and RJ45 interface; these data are quickly transmitted and stored in the memory; said FPGA control parallel output is used in conjunction with the SD card; data collected by the FPGA is stored on the SD in real time; then export the data through the USB or RJ45 communication interface for subsequent interpretation of the software call.

[0042] Said control system also includes a time synchronization control unit, which includes a GPS and a stable clock for precise time control of the three-component data sampling points and synchronization with the transmitter.

[0043] Said high-precision data sampling circuit uses three-component independent A-S AD chips to realize multi-path differential data acquisition, which is used to convert the analog signal output by the signal receiving and matching equivalent circuit into a digital signal.

[0044] As shown in FIF. 3, operation steps of the high-precision three-component electromagnetic sensor are as follows:

[0045] 1) Before the formal detection work, it is helpful for the time synchronization device to keep the synchronization of the transmitting and receiving time with the transmitter;

[0046] 2) In the ground-to-air electromagnetic exploration, rotor drone is used to hang high-precision three-component electromagnetic field sensors, and the flight measurement is carried out within the designed survey area; flying height is 50-100m, and the flying speed is not higher than 8m / s; during the flight detection process, realtime data, real-time space coordinates and flight trajectory of the three component magnetic fields can be obtained.

[0047] 3) In the conventional electromagnetic survey on the ground, artificial methods are used to place the high-precision three-component electromagnetic sensor at the location of the measuring point and make it in a horizontal state;

[0048] 4) Use the ground-to-air transient electromagnetic inverse synthetic aperture imaging algorithm and the three-dimensional "pre-stack migration" algorithm to process and interpret the collected three-component magnetic field response information to obtain reliable geological data.

[0049] As shown in FIG. 4, v (t) is the induced voltage of the induction coil, u(t) is the induced voltage actually connected to the amplifying circuit; L is the inductance of the receiving coil, r is the internal resistance, Cr is the distributed capacitance, Ra, Ca represents the input impedance and input capacitance of the preamplifier, and RT represents the matching resistance; filtering function is realized by the existing low-pass filtering and band-pass filtering circuit control technology.

[0050] As shown in FIG. 5, said high-precision three-component electromagnetic sensor needs to be tested for noise; test method is as follow: put said sensor in the magnetic shield barrel, connect the sensor signal to the analog input terminal of the data collector through the analog data line, and test the background peak-to-peak noise of the sensor, the sampling rate is 96K.

[0051] Result indicates that the peak noise is 0.3uVpp (l-10KHz), the self noise frequency band of the sensor is flat in the range of IHz-lOKHz, and the peak noise is less than 0.3uV.

[0052] As shown in FIG. 6, sensor sensitivity test is as follow: put the sensor into a calibration solenoid, and use said solenoid to excite signals of different frequencies to measure the response of the sensor at different frequencies; abscissa refers to the frequency, and ordinate refers to the response value.

[0053] Test Result: NO. Test Content Technical Index Requirements Test Result 1 Sensor Noise < 3nV / Hz 0. 3uVpp, >3nV / Hz 2 Sensor Sensitivity > 0. 15mv / nT • Hz > 0.15mv / nT • Hz

[0054] As shown in FIG. 8, time synchronization control unit includes as follow: GPS, stable clock; GPS timing function is mainly used for precise time control of three-component data sampling points and synchronization with the transmitter; said system uses GPS time service; deviation between the accurate time stamp of each sampling point and the absolute time is less than 30nS, and the system synchronization error of the three components is less than 30ns; stable clock has been added, and the time will be kept automatically when the GPS is lost in the middle; specific working process is that GPS time information generates a high-precision clock pulse (PPS) signal every 1 second, introduces the rising edge of the PPS signal to calibrate the synchronization time, and sends it to the FPGA control input interface; FPGA samples this interface to obtain PPS precise pulse signal; in this way, the purpose of sampling the digital signal of the AD input interface through the FPGA logic management method is achieved.

[0055] This invention applys combined control method of ARM and FPGA; FPGA can perform real-time acquisition, ARM can perform post-processing, storage and transmission; this can effectively improve the overall performance of said system; GPS timing device can make each sampling point have an accurate time stamp, and the deviation from the absolute time is less than 30nS; said system adds stable clock design, which automatically keeps the time after the GPS is lost in the middle; said equipment can be equipped with 4 external LED indicators to indicate the overall instrument status, which is convenient for status diagnosis; external RJ45 interface can be connected and operated through Ethernet, so the real-time status can be viewed; it can also be connected to external GPS antenna to facilitate the overall integration with the drone carrying platform; hot-swappable SD card can be replaced at any time.

[0056] Above mentioned are only the preferred embodiments of this invention, and are not intended to limit said invention; any modification, equivalent replacement and improvement made within the spirit and principle of this invention shall fall within the scope of protection of this invention.

Claims

1. A high-precision three-component electromagnetic field sensor comprises cabinet (1), said cabinet (1) is provided with X-direction coil structure (2), Y-direction coil structure (3), and Z-direction coil structure (4) with the same structure; normal directions of said X-direction coil structure (2), Y-direction coil structure (3) and Z-direction coil structure (4) are orthogonally combined; leveler (5) is arranged inside the cabinet (1); circuit control board and battery (6) are provided inside this cabinet (1); said circuit control board is provided with a preamplifier (7) respectively connected with the X-direction coil structure (2), the Y-direction coil structure (3) and the Z-direction coil structure (4); noise filter (8) is connected to preamplifier (7); signal collector (9) is connected to said noise filter (8), and said signal collector (9) is electrically connected with said battery (6); interface (10) is connected to said signal collector (9) to extend out of the cabinet (1).

2. A high-precision three-component electromagnetic field sensor as claimed in claim 1, wherein said interface (10) includes Ethernet communication interface, SD card interface and indicator light interface.

3. A high-precision three-component electromagnetic field sensor as claimed in claim 1, wherein said Z-direction coil structure (4) includes hollow spool (11) and magnetic core (12) arranged in said hollow spool (11), and induction coil (13) is wound on the outside of said hollow spool (11).

4. A high-precision three-component electromagnetic field sensor as claimed in claim 1, wherein said battery is rechargeable lithium battery.

5. A high-precision three-component electromagnetic field sensor as claimed in claim 3. wherein said hollow spool (11) is made of non-conductive material.

6. A high-precision three-component electromagnetic field sensor as claimed in claim 3, wherein said induction coil (13) is enameled wire wound in layers on the outside of said hollow spool (11).

7. A high-precision three-component electromagnetic field sensor is characterized in that,Three-component data acquisition system: said system includes sensor signal receiving and matching circuit and high-precision data sampling circuit, used for electromagnetic induction signal output, turning magnetic signal into electrical signal, after signal conditioning circuit, filter circuit and A / D conversion, it is sent to digital signal processing system for processing ;Signal processing control system: said system includes the main control chip FPGA, preamplifier and digital filter, which is used to use the size of the sampled digital signal to amplify and filter it so that its amplitude meets the input range of the ADC, so as to make full use of the resolution of the ADC converter rate;Data transmission and storage system: said system includes SD card, USB interface and RJ45 interface; these data are quickly transmitted and stored in the memory; said FPGA control parallel output is used in conjunction with the SD card; data collected by the FPGA is stored on the SD in real time; then export the data through the USB or RJ45 communication interface for subsequent interpretation of the software call.

8. A high-precision three-component electromagnetic field sensor as claimed in claim 7, wherein said control system also includes a time synchronization control unit, which includes a GPS and a stable clock for precise time control of the three-component data sampling points and synchronization with the transmitter.

9. A high-precision three-component electromagnetic field sensor as claimed in claim 7, wherein said high-precision data sampling circuit uses three-component independent A-S AD chips to realize multi-path differential data acquisition, which is used to convert the analog signal output by the signal receiving and matching equivalent circuit into a digital signal.