CN110596770B - Method for advancing receiving effective time of nuclear magnetic resonance water meter - Google Patents
Method for advancing receiving effective time of nuclear magnetic resonance water meter Download PDFInfo
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- CN110596770B CN110596770B CN201910821673.6A CN201910821673A CN110596770B CN 110596770 B CN110596770 B CN 110596770B CN 201910821673 A CN201910821673 A CN 201910821673A CN 110596770 B CN110596770 B CN 110596770B
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 37
- 238000000034 method Methods 0.000 title claims abstract description 27
- 238000005481 NMR spectroscopy Methods 0.000 title claims abstract description 11
- 230000008569 process Effects 0.000 claims description 12
- 229920006395 saturated elastomer Polymers 0.000 abstract description 6
- 238000000605 extraction Methods 0.000 abstract description 2
- 238000005259 measurement Methods 0.000 abstract description 2
- 238000001514 detection method Methods 0.000 description 4
- 230000005672 electromagnetic field Effects 0.000 description 3
- 125000004435 hydrogen atom Chemical group [H]* 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 230000004907 flux Effects 0.000 description 2
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- PXGOKWXKJXAPGV-UHFFFAOYSA-N Fluorine Chemical compound FF PXGOKWXKJXAPGV-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 239000000460 chlorine Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 210000003608 fece Anatomy 0.000 description 1
- 230000005669 field effect Effects 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 239000003673 groundwater Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N24/00—Investigating or analyzing materials by the use of nuclear magnetic resonance, electron paramagnetic resonance or other spin effects
- G01N24/08—Investigating or analyzing materials by the use of nuclear magnetic resonance, electron paramagnetic resonance or other spin effects by using nuclear magnetic resonance
- G01N24/081—Making measurements of geologic samples, e.g. measurements of moisture, pH, porosity, permeability, tortuosity or viscosity
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
- G01V3/14—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with electron or nuclear magnetic resonance
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Abstract
The invention belongs to the field of nuclear magnetic resonance water measurement, and particularly relates to a method for advancing receiving effective time of a nuclear magnetic resonance water meter. The protection switch between the receiving coil and the preamplifier is removed, the counteracting magnetic field coil is added, when the MRS water detector is in a transmitting working state, the magnetic field generated by the transmitting coil at the receiving magnetic rod is counteracted, the preamplifier is guaranteed not to be burnt by induced voltage and not to be saturated by the amplifier, the switch jitter invalid time is eliminated, the receiving valid time is moved forward, and then the secondary field signal which is excited to disappear in the switch jitter invalid time can be received. And the excited secondary field signal is an attenuation signal, the receiving effective time is advanced, the amplitude of the secondary field signal initially received by the magnetic bar receiving coil is increased, and the extraction of the secondary field signal is facilitated.
Description
Technical Field
The invention belongs to the field of nuclear magnetic resonance water measurement, and particularly relates to a method for advancing receiving effective time of a nuclear magnetic resonance water meter.
Background
At present, the problem of water resource shortage is increasingly serious, and a nuclear magnetic resonance water detection (MRS) technology is the only international detection method capable of directly measuring the occurrence state of underground water at the present stage. The method has the advantages of high resolution, high efficiency, rich information content, unique interpretation result and the like, and the nuclear magnetic resonance water detection technology is widely applied to underground water detection.
The MRS water detector is a water detector developed by utilizing MRS technology, and the general water detector mainly comprises a transmitting coil, a transmitting device, a receiving magnetic rod, a receiving device, a protection switch and the like, wherein the transmitting coil and the transmitting device form a transmitting system, and the magnetic rod receiving coil, the receiving device and the protection switch form a receiving system.
The MRS water detector comprises a transmitting working state and a receiving working state.
When the transmitter is in a transmitting working state, a transmitting coil in a transmitting system induces a primary electromagnetic field by a current signal with a specific frequency and a specific amplitude, wherein the frequency is the local Larmor frequency.
And the primary electromagnetic field induced by the transmitting coil, and the hydrogen protons in the groundwater are subjected to energy level transition under the action of the primary electromagnetic field.
When the transmitting coil is converted from the transmitting working state to the receiving working state or from the receiving working state to the transmitting working state, a receiving induced voltage of several kilovolts is induced in a receiving magnetic rod in the receiving system, and the voltage can cause the preamplifier to be in a saturated state and even burn the preamplifier, so that the connection between the receiving magnetic rod and the preamplifier is disconnected through the protection switch 5 in the transmitting working state, and the receiving system stops working. Because the withstand voltage value of analog switches such as a field effect transistor switch and the like cannot meet the voltage requirement, mechanical switches such as a relay switch and the like can be used as protection switches.
When the receiving working state is in, the emitting device is turned off firstly, the hydrogen protons present an attenuation state and restore to the original energy level under the stable state, and in the process, the hydrogen protons emit an attenuation signal to generate a secondary field. Then the receiving magnetic bar is connected with the preamplifier through a mechanical switch such as a relay switch. And receiving the secondary field by the receiving magnetic rod, and obtaining underground water information after signal processing.
However, when the receiving bar magnet is connected to the preamplifier through the mechanical switch, there is a switch shake during the closing process of the mechanical switch, and the switch shake dead time t0About 10ms and at t0If the secondary field signal cannot be received, then for t0The secondary field signal such as chlorine, fluorine and the like which is excited and disappeared by the internal feces cannot be received. And as time goes by, the secondary field signal will gradually decay, and the maximum amplitude of the received secondary field signal will decrease.
Disclosure of Invention
The invention aims to solve the technical problem of providing a method for advancing the receiving effective time of a nuclear magnetic resonance water meter, which is characterized in that a protection switch in an MRS water meter is removed, a magnetic field counteracting coil is added, when the MRS water meter is in a transmitting working state, the magnetic field generated by a transmitting coil at a receiving magnetic rod is counteracted, the pre-amplifier is ensured not to be burnt by induced voltage and not to be saturated, so that the protection switch between the receiving coil and the pre-amplifier is removed, the switch jitter ineffective time is eliminated, and the receiving effective time is advanced.
The present invention is achieved in such a way that,
a method of advancing the effective time of reception of a nuclear magnetic resonance water meter, the method comprising:
the method comprises the steps of removing a protection switch in a receiving device circuit of the MRS water detector, arranging a magnetic rod receiving coil which is coaxial with a transmitting coil, arranging a counteracting magnetic field coil coaxially between the receiving coil and the transmitting coil, wherein the counteracting coil generates a counteracting magnetic field, the direction of the counteracting magnetic field is opposite to that of the magnetic field generated by the transmitting coil, the radius of the counteracting magnetic field coil is 3-5% of that of the transmitting coil, the radius of the magnetic rod receiving coil is 1-2.5% of that of the transmitting coil, and signals collected by the magnetic rod receiving coil are received through a receiving device.
Furthermore, the working process of the MRS water detector with the counteracting coil is divided into a receiving working state changing into a transmitting working state, a transmitting working state changing into a receiving working state and a receiving working state, and in the whole process, the receiving device is not turned off; when the receiving working state is changed into the transmitting working state: and judging the voltage of the receiving coil detected by the receiving device and the saturation voltage value Ux of a preamplifier in the circuit of the receiving device, and when the voltage value of the receiving coil detected by the receiving device is greater than the saturation voltage value Ux, starting the counteracting magnetic field coil to generate a counteracting magnetic field which is opposite to the direction of the magnetic field generated by the transmitting coil, and reducing induced electromotive force generated by the transmitting coil through the counteracting magnetic field.
Furthermore, the magnitude of the counteracting magnetic field generated by the counteracting coil is controlled by judging the magnitude of the voltage of the receiving coil detected by the receiving device and the saturation voltage value Ux of the preamplifier in the circuit of the receiving device.
Further, in the transmitting working state, the transmitting coil and the offsetting coil are simultaneously electrified.
Further, when the transmitting working state is changed into the receiving working state, the voltage of the receiving coil detected by the receiving device and the saturation voltage value Ux of the preamplifier in the circuit are judged, when the voltage value of the receiving coil detected by the receiving device is larger than the saturation voltage value Ux, the offset magnetic field coil is started to generate an offset magnetic field, the direction of the offset magnetic field is opposite to that of the magnetic field generated by the transmitting coil, and induced electromotive force generated by the transmitting coil is reduced through the offset magnetic field.
Further, during the receiving operation: the sending coil and the counteracting coil stop supplying current at the same time.
Compared with the prior art, the invention has the beneficial effects that:
the invention provides a method for removing a protection switch in an MRS water detector to enable the receiving effective time to move forward. The protection switch between the receiving coil and the preamplifier is removed, the counteracting magnetic field coil is added, when the MRS water detector is in a transmitting working state, the magnetic field generated by the transmitting coil at the receiving magnetic rod is counteracted, the preamplifier is guaranteed not to be burnt by induced voltage and not to be saturated by the amplifier, the switch jitter invalid time is eliminated, the receiving valid time is moved forward, and then the secondary field signal which is excited to disappear in the switch jitter invalid time can be received. And the excited secondary field signal is an attenuation signal, the receiving effective time is advanced, the amplitude of the secondary field signal initially received by the magnetic bar receiving coil is increased, and the extraction of the secondary field signal is facilitated.
Drawings
FIG. 1 is a schematic structural diagram of an MRS water detector;
fig. 2 is a schematic structural diagram of an MRS water detector with a counteracting coil.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following 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 MRS water detector has a basic structure shown in figure 1 and comprises a transmitting coil 1, a transmitting device 2, a magnetic rod receiving coil 3, a receiving device 4 and a protection switch 5. On the basis of the MRS water detector, a counteracting magnetic field coil and a counteracting device are added to remove a protection switch. The basic structure of the MRS water detector is shown in figure 2, and the MRS water detector comprises a transmitting coil 1, a transmitting device 2, a magnetic rod receiving coil 3, a receiving device 4, a counteracting coil 5 and a counteracting device 6.
Radius of the transmitting coil is R1Amplitude of the current flowing through is I1The current frequency being the local larmor frequency f1The number of turns is n1Dielectric constant of air is u1The radius of the receiving coil of the magnetic bar is R2The number of turns is n2Dielectric constant u of magnetic rod2. The whole working process of the MRS water detector with the offset coil is divided into a receiving working state, a transmitting working state, a receiving working state and a receiving working state.
The invention removes a protection switch in a receiving device circuit of an MRS water detector, and is provided with a magnetic bar receiving coil which is coaxial with the axis of a transmitting coil, wherein a counteracting magnetic field coil is coaxially arranged between the receiving coil and the transmitting coil, the counteracting coil generates a counteracting magnetic field, the direction of the counteracting magnetic field is opposite to that of the magnetic field generated by the transmitting coil, the radius of the counteracting magnetic field coil is 3-5% of that of the transmitting coil, and the radius of the magnetic bar receiving coil is 1-2.5% of that of the transmitting coil.
The working process of the MRS water detector with the counteracting coil is divided into a receiving working state changing into a transmitting working state, a transmitting working state changing into a receiving working state and a receiving working state, and in the whole process, a receiving device is not turned off; wherein,
(1) when changing from the receiving operating state to the transmitting operating state: the magnetic field changes from 0 to B in the center of the transmitting coil1In which B is1：
Due to R1Far greater than R2At R2The magnetic flux of the receiving coil of the magnetic bar is changed from 0 to uniform magnetic field in the range
Setting the time t taken for the procedure1. The average induced electromotive force in the bar magnet receiving coil by the transmitting coil is E1: at t1At the moment, the instantaneous electromotive force is Et1。
The receiver is designed to amplify the instantaneous electromotive force by a factor a. The voltage detected by the receiving means is Ut1，
Ut1＝AEt1
To protect the preamplifier in the receiver coil from high voltage burnout and to prevent the preamplifier from becoming too saturated. According to the parameters of the preamplifier, when U ist1Value greater than UxWhen the transmitter is used, the offset magnetic field coil is opened through the offset device to generate an offset magnetic field, the direction of the offset magnetic field is opposite to that of the magnetic field generated by the transmitter coil, and the induced electromotive force generated by the transmitter coil is reduced through the offset magnetic field. By means of offsetting the induced electromotive force, a protection switch between the magnetic bar receiving coil and the preamplifier can be removed, so that the switch jitter invalid time is eliminated, and the receiving valid time is moved forward. And the unsaturation of the preamplifier is ensured, and the desaturation time of the preamplifier is reduced.
(2) In the transmitting process: the transmitting coil and the counteracting coil work simultaneously, and the radius R of the counteracting coil3Is much smaller than the transmitting coil R1So that the magnetic field generated by the bucking coil has little effect on the magnetic field generated by the transmitter coil.
(3) When changing from the transmitting operating state to the receiving operating state: the central magnetic field of the transmitting coil is B1Is changed to 0, wherein B1：
Due to R1Far greater than R2At R2In the range of the magnetic rod receiving coil, the magnetic flux is similar to a uniform magnetic field
Becomes 0.
Setting the time t taken for the procedure2. The average induced electromotive force in the bar magnet receiving coil by the transmitting coil is E2: at t2At the moment, the instantaneous electromotive force is Et2。
The receiver is designed to amplify the instantaneous electromotive force by a factor a. The voltage detected by the receiving means is Ut2，
Ut2＝AEt2
To protect the preamplifier in the receiver coil from high voltage burnout and to prevent the preamplifier from becoming too saturated. According to the parameters of the preamplifier, when U ist2Value greater than UxWhen the transmitter is used, the offset magnetic field coil is opened through the offset device to generate an offset magnetic field, the direction of the offset magnetic field is opposite to that of the magnetic field generated by the transmitter coil, and the induced electromotive force generated by the transmitter coil is reduced through the offset magnetic field. By means of offsetting the induced electromotive force, a protection switch between the magnetic bar receiving coil and the preamplifier can be removed, so that the switch jitter invalid time is eliminated, and the receiving valid time is moved forward. And the unsaturation of the preamplifier is ensured, and the desaturation time of the preamplifier is reduced.
(2) In the receiving process: the transmitting coil and the counteracting coil stop working.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (2)
1. A method of advancing the effective time of reception of a nuclear magnetic resonance water meter, the method comprising:
removing a protection switch in a receiving device circuit of the MRS water detector, arranging a magnetic bar receiving coil which is coaxial with the axis of a transmitting coil, arranging a counteracting magnetic field coil coaxially between the receiving coil and the transmitting coil, wherein the counteracting coil generates a counteracting magnetic field, the direction of the counteracting magnetic field coil is opposite to that of the magnetic field generated by the transmitting coil, the radius of the counteracting magnetic field coil is 3-5% of that of the transmitting coil, the radius of the magnetic bar receiving coil is 1-2.5% of that of the transmitting coil, and signals collected by the magnetic bar receiving coil are received through a receiving device;
controlling the working process of the MRS water detector with the offset coil to be divided into a receiving working state changing into a transmitting working state, a transmitting working state changing into a receiving working state and a receiving working state, wherein in the whole process, a receiving device is not turned off; when the receiving working state is changed into the transmitting working state: judging the voltage of a receiving coil detected by a receiving device and the saturation voltage value Ux of a preamplifier in a circuit of the receiving device, and when the voltage value of the receiving coil detected by the receiving device is larger than the saturation voltage value Ux, starting a counteracting magnetic field coil to generate a counteracting magnetic field, wherein the direction of the counteracting magnetic field is opposite to that of the magnetic field generated by a transmitting coil, and the induced electromotive force generated by the transmitting coil is reduced through the counteracting magnetic field;
in the transmitting working state, the transmitting coil and the offsetting magnetic field coil are simultaneously electrified with current;
when the transmitting working state is changed into the receiving working state, the voltage of the receiving coil detected by the receiving device and the saturation voltage value Ux of a preamplifier in the circuit are judged, when the voltage value of the receiving coil detected by the receiving device is larger than the saturation voltage value Ux, the counteracting magnetic field coil is started to generate a counteracting magnetic field, the direction of the counteracting magnetic field is opposite to that of the magnetic field generated by the transmitting coil, and the induced electromotive force generated by the transmitting coil is reduced through the counteracting magnetic field;
in the receiving process: the transmitting coil and the counteracting magnetic field coil stop supplying current at the same time.
2. The method of claim 1, wherein the magnitude of the canceling magnetic field generated by the canceling coil is controlled by determining the magnitude of the voltage of the receiving coil sensed by the receiving device and the saturation voltage value Ux of a preamplifier in the circuitry of the receiving device.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JPS638543A (en) * | 1986-06-30 | 1988-01-14 | Mitsubishi Electric Corp | Receiving probe for magnetic resonance experiment |
| US7098663B1 (en) * | 2005-03-18 | 2006-08-29 | Timothy James Hollis | Systems, methods and apparatus of an actively shielded superconducting magnet drift compensation coil |
| CN102879753B (en) * | 2012-10-11 | 2015-04-08 | 中国科学院近代物理研究所 | Automatic implementation method for high-uniformity magnet shim coil design |
| CN105022005B (en) * | 2014-04-23 | 2018-02-13 | 中国科学院上海微系统与信息技术研究所 | A kind of method, apparatus and system of raising SQUID Magnetic Sensor measurement sensitivities |
| CN109884718B (en) * | 2019-01-29 | 2021-04-13 | 吉林大学 | Magnetic resonance water detection device and method capable of effectively reducing dead time |
| CN109917478B (en) * | 2019-04-01 | 2020-04-24 | 吉林大学 | Magnetic resonance water detection system and method for improving amplitude of acquired signal |
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