CN108227022B - Ground-air magnetic resonance detection device and detection method based on SQUID - Google Patents
Ground-air magnetic resonance detection device and detection method based on SQUID Download PDFInfo
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Abstract
The invention relates to a ground-air magnetic resonance detection device based on SQUID, comprising: the transmitter is connected with the transmitting coil through a transmitting switching control circuit, direct current is introduced into the transmitting coil to generate a pre-polarization magnetic field, the magnetization intensity of hydrogen protons in the underground water body is increased, alternating current with Larmor frequency is introduced into the transmitting coil to excite the hydrogen protons to move in a precession manner, the excitation current is stopped, and the hydrogen protons generate a relaxation phenomenon under the action of the geomagnetic field; the SQUID receives the magnetic resonance signal, is connected with the SQUID reading circuit and converts the magnetic signal collected by the SQUID into an electric signal; the receiver is carried on the aircraft and is connected with the SQUID reading circuit; the upper computer sends out control signals through communication connection with the receiver and the transmitter, controls the transmitter to transmit switching and switching off of the direct current and the alternating current, and controls the receiver to collect signals. The invention has the advantages of large detection range, high efficiency, strong environmental adaptability, high sensitivity, signal-to-noise ratio and the like.
Description
Technical Field
The invention relates to a Magnetic Resonance (NMR) prospecting instrument and a method, in particular to ground-air Magnetic Resonance underground water detection equipment and a detection method based on Superconducting QUantum Interference Devices (SQUIDs).
Background
The magnetic resonance technology is applied to underground water detection for decades, has the advantages of direct detection, quantitative determination, high resolution and the like, and is widely applied to aspects of industrial and agricultural and civil shallow underground water detection, high-efficiency regional hydrogeological exploration and the like. In the ground magnetic resonance detection method widely used nowadays, one-dimensional or multi-dimensional underground water exploration and imaging in a detection area are completed by laying dozens to hundreds of meters of transmitting coils on the ground and matching with one or more corresponding receiving coils. However, in some regions with complex surface environments and wide water body distribution, such as mountainous regions and hills, the difficulty of laying a plurality of large-size receiving coils is high, and the detection range is limited, so that it is necessary to develop a magnetic resonance underground water detection method suitable for complex environments.
Patent CN106908847A discloses a ground-air nuclear magnetic resonance underground water detection system and detection method, which is connected with a ground main control system and an aerial vehicle through a communication module, wherein a ground transmitter transmits an excitation current with local larmor frequency to the ground by changing the transmission current of a ground electrode, a receiving coil carried on the aerial vehicle is used for collecting nuclear magnetic resonance signals generated by macroscopic magnetic moment precession, the ground main control system remotely controls the transmission and stop of the excitation current through the communication module, and controls a receiver connected with the receiving coil to collect nuclear magnetic resonance signals at the interval when the excitation current stops, and the collected nuclear magnetic resonance signals are transmitted to an upper computer through the communication module. Patent CN106873044A discloses an array SQUID nuclear magnetic resonance underground water detection device and imaging method, utilize the pre-polarization coil to produce the pre-polarization magnetic field that the magnetic strength is far greater than the natural earth's magnetic field to improve the whole magnetization intensity of water, adopt the SQUID that magnetic field sensitivity is high to replace receiving coil acquisition signal, can detect extremely weak earth's electric signal, gather more accurate magnetic field signal, and then improved the signal-to-noise ratio, realize the imaging method that can carry out underground nuclear magnetic resonance under strong noise environment and survey.
The ground-air nuclear magnetic resonance underground water detection system and the detection method of the invention provide the ground-air magnetic resonance detection method aiming at the detection of underground water in complex environments such as mountainous regions, hills and the like, better solve the problem of laying of a receiving coil, have wide detection range and high efficiency, but have limited survey depth due to the limitation of the size of the receiving coil by the carrying capacity of an aircraft, and introduce a large amount of electrical noise in the flying process of the aircraft, so that the signal-to-noise ratio and the reliability of the detection are difficult to ensure; the array SQUID nuclear magnetic resonance underground water detection device and the imaging method improve the amplitude of magnetic resonance signals by applying a prepolarization field, and utilize the SQUID with high sensitivity to detect, thereby avoiding the common electric noise interference, obviously improving the detection signal-to-noise ratio, but the detection form is limited by ground detection, the detection efficiency is lower, and the receiving system consists of a plurality of SQUID sensors, has complex wiring and higher manufacturing cost, and is not suitable for large-scale regional hydrogeological exploration.
Disclosure of Invention
In order to solve the problems of complex wiring, high cost and unsuitability for large-scale regional hydrogeological exploration in the prior art, the invention provides a SQUID-based ground-air magnetic resonance detection device,
the invention also provides a ground-air magnetic resonance detection method based on the SQUID.
The purpose of the invention is realized by the following technical scheme:
SQUID-based ground-air magnetic resonance detection device, comprising:
the transmitter is connected with the transmitting coil through a transmitting switching control circuit, and is used for introducing direct current into the transmitting coil to generate a pre-polarized magnetic field, increasing the magnetization intensity of hydrogen protons in the underground water body, cutting off the direct current, introducing alternating current with Larmor frequency into the transmitting coil to excite the hydrogen protons to move, stopping exciting the current, and enabling the hydrogen protons to generate a relaxation phenomenon under the action of a geomagnetic field;
the SQUID receives a magnetic resonance signal generated by hydrogen proton relaxation, is connected with a SQUID reading circuit, and converts the magnetic signal collected by the SQUID into an electric signal;
the receiver is carried on an aircraft and is connected with the SQUID reading circuit;
and the upper computer is in communication connection with the receiver and the transmitter, sends out control signals, controls the switching and the switching-off of the alternating current and direct current emission of the transmitter, and controls the acquisition of signals by the receiver.
Further, the transmitter includes:
the adjustable direct current transmitting circuit is connected with the transmitting switching control circuit and provides direct current for the transmitting coil;
the adjustable alternating current transmitting circuit is connected with the transmitting switching control circuit and provides alternating current for the transmitting coil;
and the transmission main control unit receives the control signal of the upper computer and controls the adjustable direct current transmission circuit and the adjustable alternating current transmission circuit.
Further, the receiver includes:
the amplifying circuit is connected with the SQUID reading circuit and is used for amplifying the electric signals output by the SQUID reading circuit;
the A/D acquisition unit is connected with the amplifying circuit and converts the amplified signals into digital signals;
and the receiving main control unit is used for receiving the signals of the A/D acquisition unit, transmitting the signals with an upper computer through a wireless communication module and controlling the SQUID to acquire magnetic resonance signals.
Further, the aircraft flies at a constant speed along a measuring line, and the measuring line is matched with the terrain condition to be measured and the size of the transmitting coil.
A detection method of a ground-air magnetic resonance detection device based on SQUID,
controlling the switching and the switching off of the alternating current and direct current emission of the transmitter;
the device is connected with a transmitting coil through a transmitting switching control circuit, a direct current is introduced into the transmitting coil to generate a pre-polarization magnetic field, the magnetization intensity of hydrogen protons in the underground water body is increased, the direct current is cut off, the alternating current with Larmor frequency is introduced into the transmitting coil to excite the hydrogen protons to move, the excitation current is stopped, and the hydrogen protons generate a relaxation phenomenon under the action of the geomagnetic field;
receiving a magnetic resonance signal generated by hydrogen proton relaxation in a superconducting quantum interference mode, and converting the received magnetic signal into an electric signal;
and receiving and acquiring the electric signals, processing the signals, and wirelessly transmitting the signals to an upper computer for storage.
Further, the controlling of the switching and switching off process of the transmitter alternating current and direct current emission:
controlling the adjustable direct current transmitting circuit to provide direct current of the transmitting coil, and turning off the current after keeping for a period of time;
and controlling the adjustable alternating current transmitting circuit to provide alternating current of the transmitting coil, and keeping the alternating current for a period of time to turn off the current.
Further, the method comprises the following steps:
a. laying a transmitting coil in a detection target area, and determining a measuring line, an aircraft speed and a flight height according to the actual measurement condition and the size of the transmitting coil;
b. connecting and debugging a transmitting and receiving loop to ensure normal communication between the upper computer and the transmitter and the receiver, and driving the aircraft into a test line;
c. the upper computer controls a transmitting main control unit in the transmitter, is connected with the adjustable direct current transmitting circuit, is introduced with constant direct current of the transmitting coil through the transmitting switching control circuit, and is kept for a period of time and then is switched off;
d. after the direct current is cut off, the upper computer controls a transmitting main control unit in the transmitter, is connected with the adjustable alternating current transmitting circuit, is introduced with Larmor frequency alternating current with certain amplitude of the transmitting coil through the transmitting switching control circuit, and is cut off after being kept for a period of time;
e. at the moment of turning off the alternating current, the aircraft keeps constant height and speed and flies along a measuring line, and the upper computer controls a receiving main control unit in the receiver to start to collect signals through the communication module;
f. the magnetic resonance signals collected by the SQUID are amplified by an amplifying circuit, and data are collected to a receiving main control unit through an A/D (analog/digital) collecting unit;
g. the receiving main control unit transmits data to the upper computer through the communication module.
Furthermore, in the step c, constant direct current is introduced into the transmitting coil, the alternating current is changed according to the size and the number of turns of the transmitting coil and a detection target, and the process of c-g is repeated to finish the measurement of different pulse moments.
The invention has the beneficial effects that:
1. according to the invention, by applying the pre-polarization field, the hydrogen proton macroscopic magnetic moment in the underground water can be effectively increased, the magnetic resonance signal is indirectly increased, and the detection signal-to-noise ratio is improved; hydrogen protons in groundwater are excited to release magnetic signals, a coil in the prior art patent 201710130504.9 receives an electric signal induced according to the magnetic signals, an SQUID in the invention directly receives the magnetic signals, an electric field is a derivative of a magnetic field according to a Faraday's law of electromagnetic induction, and the SQUID directly receives the magnetic field, so that the bottleneck of a magnetic resonance detection distance of 150m can be effectively broken through; SQUID acts as a superconducting receiver, whose sensitivity to magnetic fields is itself superior to that of coils.
2. The ground-air magnetic resonance detection device and the detection method based on the SQUID, disclosed by the invention, use the SQUID with high sensitivity as a magnetic resonance signal receiver, and improve the detection reliability. Compared with the prior art, the method has the advantages of large detection range, high efficiency, strong environmental adaptability, high sensitivity, signal-to-noise ratio and the like, and has great significance for further application and popularization of the magnetic resonance technology.
3. The SQUID-based ground-air magnetic resonance detection device and the detection method are suitable for large-range and high-signal-to-noise-ratio underground water exploration in complicated mountainous regions, hills and other regions, and the magnetic resonance detection efficiency is improved.
Drawings
FIG. 1 is a field work schematic diagram of a ground-air magnetic resonance detection device based on SQUID
FIG. 2 is a block diagram of a SQUID-based ground-air magnetic resonance detection device transmitter system
FIG. 3 is a SQUID-based ground-air magnetic resonance detection device receiver system block diagram
Wherein: 1. the system comprises an upper computer, a transmitter, a transmitting coil, a wireless communication module, a vehicle, a receiver, a SQUID, an 8, a measuring line, a 9, a transmitting main control unit, a 10, an adjustable direct current transmitting circuit, a 11, an adjustable alternating current transmitting circuit, a 12, a transmitting switching control circuit, a 13, a SQUID reading circuit, a 14, an amplifying circuit, a 15, an A/D acquisition unit and a 16, and a receiving main control unit.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The invention provides a ground-air magnetic resonance detection device based on SQUID7, which comprises: the device comprises a transmitter 2, a receiver 6, an upper computer 1, a wireless communication module 4, a transmitting coil 3, a SQUID7 and an aircraft 5, wherein the transmitter 1 is connected with the transmitting coil through a transmitting switching control circuit 12, direct current is introduced into the transmitting coil 3 to generate a pre-polarization magnetic field, the magnetization intensity of hydrogen protons in underground water is increased, direct current is cut off to flow to the transmitting coil, alternating current with Larmor frequency is introduced into the transmitting coil to excite the hydrogen protons to move, excitation current is stopped, and the hydrogen protons generate a relaxation phenomenon under the action of a geomagnetic field; the SQUID7 receives magnetic resonance signals generated by hydrogen proton relaxation, is connected with the SQUID readout circuit 13, and converts the magnetic signals collected by the SQUID7 into electric signals; the receiver 6 is mounted on the aircraft 5 and connected with the SQUID readout circuit 13; the upper computer 1 is in communication connection with the receiver 6 and the transmitter 2, sends out control signals, controls the switching and the switching off of the alternating current and direct current emission of the transmitter 2, and controls the acquisition of the signals by the receiver 6. And the wireless communication module 4 completes signal transmission between the upper computer 1 and receiving.
The transmitter 2 includes: the device comprises an adjustable direct current transmitting circuit 10, an adjustable alternating current transmitting circuit 11, a transmitting main control unit 9 and a transmitting switching control circuit 12, wherein the adjustable direct current transmitting circuit 10 is connected with the transmitting switching control circuit 12; the adjustable alternating current transmitting circuit 11 is connected with the transmitting switching control circuit 12; and the transmission main control unit 9 receives a control signal of the upper computer 1 and controls the adjustable direct current transmission circuit 10 and the adjustable alternating current transmission circuit 11. The transmitting main control unit 9 in the transmitter 2 controls the adjustable direct current transmitting circuit 10, the transmitting switching control circuit 12 is connected with the direct current of the transmitting coil 3 to generate a pre-polarized magnetic field, the magnetization intensity of hydrogen protons in underground water is increased, then the direct current is cut off, the upper computer 1 controls the transmitting main control unit 9 in the transmitter 2 to control the adjustable alternating current transmitting circuit 11, the transmitting switching control circuit 12 is connected with the alternating current of the Larmor frequency of the transmitting coil 3 to excite the hydrogen protons to move, the excitation current is stopped, and the hydrogen protons generate relaxation under the action of the geomagnetic field.
The receiver 6 includes: the device comprises an amplifying circuit 14, an A/D acquisition unit 15 and a receiving main control unit 16, wherein the amplifying circuit 14 is connected with a SQUID readout circuit 13 and is used for amplifying an electric signal output by the SQUID readout circuit 13; the A/D acquisition unit 14 is connected with the amplifying circuit 13 and converts the amplified signals into digital signals; the receiving main control unit 15 receives the signals of the a/D acquisition unit 14, performs signal transmission with the wireless communication module, and controls the SQUID7 to acquire magnetic resonance signals. The upper computer 1 is communicated with the receiver 6 through the wireless communication module 4, controls the SQUID7 to receive magnetic resonance signals generated by hydrogen proton relaxation, is amplified by the amplifying circuit 13, is collected by the A/D collecting unit 14 and is transmitted to the receiving main control unit 15, and is synchronously transmitted back to the upper computer 1 through the wireless communication module 4 for storage.
The SQUID 7-based ground-air magnetic resonance detection device is a high-sensitivity high-efficiency hydrogeological exploration method suitable for complex environmental conditions, the working process of the device is that a transmitting coil 3 is laid on the ground, a ground transmitter 2 is controlled by an upper computer 1, an adjustable direct current transmitting circuit 10 is controlled by a transmitting main control unit 9 in the transmitter 2, direct current is introduced into the transmitting coil 3 through a transmitting switching control circuit 12 to generate a pre-polarized magnetic field, the magnetization intensity of hydrogen protons in underground water is increased, then the direct current is cut off, the upper computer 1 controls the transmitting main control unit 9 in the transmitter 2 to control an adjustable alternating current transmitting circuit 11, alternating current with the Larmor frequency of the transmitting coil 3 is introduced through the transmitting switching control circuit 12 to excite the hydrogen protons to move and stop exciting the current, the hydrogen protons generate a relaxation phenomenon under the action of the geomagnetic field, the upper computer 1 is communicated with a receiver 6 through a wireless communication module 4, and the SQUID7 is controlled to receive magnetic resonance signals generated by hydrogen proton relaxation, the SQUID reading circuit 13 converts the received magnetic signals into analog electric signals, the analog electric signals are amplified by the amplifying circuit 14, and the analog electric signals are collected and transmitted to the receiving main control unit 16 by the A/D collecting unit 15 and are synchronously transmitted back to the upper computer 1 for storage through the wireless communication module 4.
The detection method of the ground-air magnetic resonance detection device based on the SQUID7 comprises the following steps:
a. laying a transmitting coil 3 in a detection target area, and determining a measuring line 8, the speed of an aircraft 5 and the flying height according to the actual measurement condition and the size of the transmitting coil 3;
b. connecting and debugging a transmitting and receiving loop to ensure normal communication between the upper computer 1 and the transmitter 2 and the receiver 6, and driving the aircraft 5 into the measuring line 8;
c. the upper computer 1 controls a transmitting main control unit 9 in the transmitter 2, is connected with an adjustable direct current transmitting circuit 10, is introduced with constant direct current of the transmitting coil 3 through a transmitting switching control circuit 12, and cuts off the current in an adiabatic mode after transmitting for 8 s;
d. after the direct current is cut off, the upper computer 1 controls a transmitting main control unit 9 in the transmitter 2, is connected with an adjustable alternating current transmitting circuit 11, is introduced with Larmor frequency alternating current with certain amplitude of a transmitting coil 3 through a transmitting switching control circuit 12, and cuts off the current after transmitting for 40 ms;
e. at the moment of turning off the alternating current, the aircraft 5 keeps constant altitude and speed and flies along the measuring line 8, and the upper computer 1 controls a receiving main control unit 15 in the receiver 6 to start to collect signals through the wireless communication module 4;
f. after the magnetic resonance signals collected by the SQUID7 are converted into analog electric signals by the SQUID reading circuit 13, the analog electric signals are amplified by the amplifying circuit 14, and data are collected to the receiving main control unit 16 through the A/D collecting unit 15;
g. the receiving main control unit 16 transmits data to the upper computer 1 through the wireless communication module 4;
h. repeating the step c-g for a plurality of times to ensure the reliability of the measurement result;
i. and (4) keeping the direct current unchanged, changing the magnitude of the alternating current according to the magnitude and the number of turns of the transmitting coil 3 and a detection target, and repeating the c-h process to finish the measurement of different pulse moments.
Examples
In this embodiment, the ground-air magnetic resonance detection apparatus and detection method based on SQUID7 include the following steps:
a. laying a circular transmitting coil 3 with the diameter of 200m in a detection target area, determining a measuring line 8 according to the actual situation, wherein the speed of an aircraft 5 is 20m/s, and the flying height is 10 m;
b. connecting and debugging a transmitting and receiving loop to ensure normal communication between the upper computer 1 and the transmitter 2 and the receiver 6, and driving the aircraft 5 into the measuring line 8;
c. the upper computer 1 controls a transmission main control unit 9 in the transmitter 2, is connected with an adjustable direct current transmission circuit 10, is introduced into a constant direct current of a transmission coil 3120A through a transmission switching control circuit 12, and cuts off the current in an adiabatic mode after transmitting for 8 s;
d. after the direct current is cut off, the upper computer 1 controls a transmitting main control unit 9 in the transmitter 2, is connected with an adjustable alternating current transmitting circuit 11, is introduced with Larmor frequency alternating current with the amplitude of 50A of a transmitting coil 3 through a transmitting switching control circuit 12, and cuts off the current after transmitting for 40 ms;
e. at the moment of turning off the alternating current, the aircraft 5 flies along the measuring line 8 at a speed of 10m and 20m/s away from the ground, and the upper computer 1 controls a receiving main control unit 15 in the receiver to start to collect signals through the wireless communication module 4;
f. after the magnetic resonance signals collected by the SQUID7 are converted into analog electric signals by the SQUID reading circuit 13, the analog electric signals are amplified by the amplifying circuit 14, and data are collected to the receiving main control unit 16 through the A/D collecting unit 15;
g. the receiving main control unit 16 transmits data to the upper computer 1 through the wireless communication module 4;
h. repeating the step c-g sixteen times to ensure the reliability of the measurement result;
i. and d, keeping the direct current unchanged, changing the magnitude of the alternating current, repeating the c-h process for ten times, and completing the measurement of different pulse moments.
While the invention has been described with reference to specific embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.
Claims (3)
1. Ground-air magnetic resonance detection device based on SQUID, its characterized in that includes:
the transmitter is connected with the transmitting coil through a transmitting switching control circuit, and is used for introducing direct current into the transmitting coil to generate a pre-polarized magnetic field, increasing the magnetization intensity of hydrogen protons in the underground water body, cutting off the direct current, introducing alternating current with Larmor frequency into the transmitting coil to excite the hydrogen protons to move, stopping exciting the current, and enabling the hydrogen protons to generate a relaxation phenomenon under the action of a geomagnetic field;
the SQUID receives a magnetic resonance signal generated by hydrogen proton relaxation, is connected with a SQUID reading circuit, and converts the magnetic signal collected by the SQUID into an electric signal;
the receiver is carried on an aircraft and is connected with the SQUID reading circuit;
the upper computer is in communication connection with the receiver and the transmitter, sends out control signals, controls the switching and the switching-off of the alternating current and direct current emission of the transmitter, and controls the acquisition of the signals by the receiver;
the aircraft flies at a constant speed along a measuring line, the measuring line is matched with the terrain condition to be measured and the size of a transmitting coil, and the transmitting coil is a circular transmitting coil with the diameter of 200 m;
the transmitter includes:
the adjustable direct current transmitting circuit is connected with the transmitting switching control circuit and provides direct current for the transmitting coil;
the adjustable alternating current transmitting circuit is connected with the transmitting switching control circuit and provides alternating current for the transmitting coil;
the transmission main control unit receives a control signal of the upper computer and controls the adjustable direct current transmission circuit and the adjustable alternating current transmission circuit;
the receiver includes:
the amplifying circuit is connected with the SQUID reading circuit and is used for amplifying the electric signals output by the SQUID reading circuit;
the A/D acquisition unit is connected with the amplifying circuit and converts the amplified signals into digital signals;
the receiving main control unit receives the signals of the A/D acquisition unit, transmits the signals with an upper computer through a wireless communication module and controls the SQUID to acquire magnetic resonance signals;
the working process comprises the following steps:
a. laying a transmitting coil in a detection target area, determining a measuring line, an aircraft speed and a flight height according to the actual measurement condition and the size of the transmitting coil, wherein the transmitting coil is a circular transmitting coil with the diameter of 200 m;
b. connecting and debugging a transmitting and receiving loop to ensure normal communication between the upper computer and the transmitter and the receiver, and driving the aircraft into a test line;
c. the upper computer controls a transmitting main control unit in the transmitter, is connected with the adjustable direct current transmitting circuit, is introduced with constant direct current of the transmitting coil through the transmitting switching control circuit, and cuts off the current in an adiabatic mode after keeping for a period of time;
d. after the direct current is cut off, the upper computer controls a transmitting main control unit in the transmitter, is connected with the adjustable alternating current transmitting circuit, is introduced with Larmor frequency alternating current with certain amplitude of the transmitting coil through the transmitting switching control circuit, and cuts off the current after keeping for a period of time;
e. at the moment of turning off the alternating current, the aircraft keeps constant height and speed and flies along a measuring line, and the upper computer controls a receiving main control unit in the receiver to start to collect signals through the communication module;
f. the magnetic resonance signals collected by the SQUID are amplified by an amplifying circuit, and data are collected to a receiving main control unit through an A/D (analog/digital) collecting unit;
g. the receiving main control unit transmits data to the upper computer through the communication module.
2. The detection method of the ground-air magnetic resonance detection device based on the SQUID is characterized in that,
controlling the switching and the switching off of the alternating current and direct current emission of the transmitter;
the device is connected with a transmitting coil through a transmitting switching control circuit, a direct current is introduced into the transmitting coil to generate a pre-polarization magnetic field, the magnetization intensity of hydrogen protons in the underground water body is increased, the direct current is cut off, the alternating current with Larmor frequency is introduced into the transmitting coil to excite the hydrogen protons to move, the excitation current is stopped, and the hydrogen protons generate a relaxation phenomenon under the action of the geomagnetic field;
receiving a magnetic resonance signal generated by hydrogen proton relaxation in a superconducting quantum interference mode, and converting the received magnetic signal into an electric signal;
receiving and acquiring an electric signal, processing the signal, and wirelessly transmitting the signal to an upper computer for storage;
and the process of controlling the switching and the switching off of the alternating current and direct current emission of the transmitter comprises the following steps:
controlling the adjustable direct current transmitting circuit to provide direct current of the transmitting coil, and turning off the current after keeping for a period of time;
controlling an adjustable alternating current transmitting circuit to provide alternating current of a transmitting coil, and keeping the alternating current for a period of time and then switching off the current;
the method comprises the following steps:
a. laying a transmitting coil in a detection target area, determining a measuring line, an aircraft speed and a flight height according to the actual measurement condition and the size of the transmitting coil, wherein the transmitting coil is a circular transmitting coil with the diameter of 200 m;
b. connecting and debugging a transmitting and receiving loop to ensure normal communication between the upper computer and the transmitter and the receiver, and driving the aircraft into a test line;
c. the upper computer controls a transmitting main control unit in the transmitter, is connected with the adjustable direct current transmitting circuit, is introduced with constant direct current of the transmitting coil through the transmitting switching control circuit, and cuts off the current in an adiabatic mode after keeping for a period of time;
d. after the direct current is cut off, the upper computer controls a transmitting main control unit in the transmitter, is connected with the adjustable alternating current transmitting circuit, is introduced with Larmor frequency alternating current with certain amplitude of the transmitting coil through the transmitting switching control circuit, and cuts off the current after keeping for a period of time;
e. at the moment of turning off the alternating current, the aircraft keeps constant height and speed and flies along a measuring line, and the upper computer controls a receiving main control unit in the receiver to start to collect signals through the communication module;
f. the magnetic resonance signals collected by the SQUID are amplified by an amplifying circuit, and data are collected to a receiving main control unit through an A/D (analog/digital) collecting unit;
g. the receiving main control unit transmits data to the upper computer through the communication module.
3. The detection method according to claim 2, wherein in the step c, constant direct current is introduced into the transmitting coil, the alternating current is changed according to the size and the number of turns of the transmitting coil and a detection target, and the c-g process is repeated to measure different pulse moments.
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| Publication number | Publication date |
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| CN108227022A (en) | 2018-06-29 |
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