CN214473874U - Same-frequency resonance polarization synchronous magnetic field measuring device - Google Patents
Same-frequency resonance polarization synchronous magnetic field measuring device Download PDFInfo
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- CN214473874U CN214473874U CN202023298318.2U CN202023298318U CN214473874U CN 214473874 U CN214473874 U CN 214473874U CN 202023298318 U CN202023298318 U CN 202023298318U CN 214473874 U CN214473874 U CN 214473874U
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Abstract
The utility model discloses a same frequency resonance polarization synchronous magnetic field measuring device, which comprises a probe, a polarization circuit, a high precision frequency generation circuit, a high resolution ADC acquisition circuit and an MCU processor; the probe comprises a polarization coil and a receiving coil, the polarization circuit is driven by a linear voltage stabilizing source at constant voltage, square wave signals with certain polarization frequency are generated by controlling a switch circuit to polarize protons in the probe, the MCU processor sends required frequency signals for polarizing the protons through the frequency generation circuit to drive the polarization circuit to send the waves to the polarization coil in the probe, ADC data acquisition and integral calculation are carried out while the frequency is sent, synchronous whole-period acquisition is achieved, effective amplitude is calculated, and finally magnetic field frequency is determined through the polarization frequency corresponding to the maximum amplitude. The measuring device has the advantages of high precision, low hardware cost, small volume, synchronous measurement support and high measuring efficiency.
Description
Technical Field
The utility model relates to an electromagnetic exploration equipment field especially relates to a same frequency resonance polarization synchronous magnetic field measuring device.
Background
The proton magnetometer conducts electric field polarization on internal protons through the magnetic field measurement probe, after polarization is stopped, all protons conduct Larmor precession according to the direction of an electric field, the frequency of the Larmor precession corresponds to a proportional relation according to different magnetic fields, the relation ratio of the magnetic field to the frequency is B (23.4874 f), the amplitude of a frequency signal generated by the magnetic field measurement probe is in direct proportion to the number of the proton precession, namely the number of the proton precession is larger, the signal amplitude is larger, all the proton precession directions tend to be balanced finally due to isotropic repulsion along with the increase of time, finally, an output signal of the magnetic field measurement probe corresponds to the frequency according to an environmental magnetic field, and the amplitude is output according to an exponential attenuation form, so that the proton magnetometer generally converts the earth magnetic field into the measurement frequency. The traditional proton magnetometer measurement mode is that a magnetic field measurement probe is polarized by a certain voltage, a Larmor precession signal is generated after polarization, the precession signal passes through a resonance circuit, an amplifying circuit and a frequency measurement circuit, the frequency is finally calculated, and the actual magnetic field value is calculated through a relation between the magnetic field and the frequency.
However, since the earth magnetic field signal is very weak, the signal generated by the magnetic field measurement probe is very small, generally at several uV, so that the noise required by the whole hardware circuit, especially the amplifying circuit, is very small, otherwise the noise will mask the effective signal and make it unable to measure, and the amplifying circuit needs to amplify 100000 times at minimum, the self-noise of the whole system needs to be controlled at 10nV level, and because the small difference of the same components will make different instruments have large difference, so it has very high difficulty in hardware design. The general accuracy requirement of the proton magnetometer is 0.01nT, the conversion frequency is about 0.000426Hz with the minimum resolution, so the measurement frequency accuracy is 10-4The order of magnitude can ensure the measurement accuracy, which requires ultra-high accuracyAnd measuring the frequency, and ensuring the temperature stability and accuracy of the frequency measurement crystal. Magnetic field measurement is to output analog tiny signals, after amplification and shaping, the frequency of the analog tiny signals is liable to generate phase jitter to cause an unstable phenomenon, and for subsequent frequency measurement, not only the high accuracy of the frequency needs to be ensured, but also the stability of the frequency needs to be ensured, and higher requirements are provided on hardware and software algorithms.
For example, patent application "CN 201010147845-an OVERHAUSER magnetometer" discloses a magnetometer, which generates an electron-nuclear double resonance phenomenon (OVERHAUSER effect) in a nitroxide radical solution by using a radio frequency excitation signal, enhances the magnetization intensity of hydrogen protons along the direction of a geomagnetic field, and solves the problem that a hydrogen proton precession signal in a proton magnetometer is too weak, so as to improve the magnetic measurement accuracy of a sensor, however, a polarization object of the magnetometer is electrons, an oscillation high-frequency signal needs to be above MHZ frequency, a class-c high-frequency power amplifier 8 needs to be additionally installed to amplify the oscillation high-frequency signal, a resonance amplification circuit 12 needs to be installed in the amplifier to amplify a received signal when the signal is received, and the probe has a complex and precise structure, and is composed of a high-frequency resonance cavity 9, a sealed glass bottle 10 with a radical solution therein, and a low-frequency receiving coil 11 wound outside the glass bottle, and a dc pulse generator 3 needs to be installed to generate a dc pulse for the probe, and the frequency measurement mode of the frequency meter 5 is an intermittent measurement mode (that is, the measurement frequency cannot be synchronously determined while the probe is polarized, and the two are separately performed), so in order to realize the Overhauser effect to complete the high-precision measurement of the magnetic field frequency, the magnetometer needs relatively high hardware cost and relatively complex measurement procedures, and the measurement efficiency is not high enough.
Therefore, it is urgently needed to design a magnetic field measuring device to accurately measure the frequency of the geological magnetic field, reduce the development and production cost of hardware, simplify the measuring mode and improve the measuring efficiency.
SUMMERY OF THE UTILITY MODEL
Technical problem to be solved
Based on this, to prior art not enough, the utility model provides a same frequency resonance polarization synchronous magnetic field measuring device, its high accuracy measurement that not only can realize magnetic field frequency has still reduced the hardware cost to simplify measurement procedure, degree of automation is high, has realized the synchronous on-line measurement of magnetic field frequency when lasting polarization proton through the twin coil in the probe simultaneously, has improved measuring speed and efficiency.
(II) technical scheme
For solving the technical problem, the utility model discloses a main technical scheme include:
a same-frequency resonance polarization synchronous magnetic field measuring device comprises a probe, a polarization circuit, a high-precision frequency generation circuit, a high-resolution ADC acquisition circuit and an MCU processor;
the probe is a proton magnetic field measuring probe, and comprises a polarizing coil and a receiving coil, wherein the polarizing coil is connected with a polarizing circuit, and the receiving coil is connected with an ADC (analog-to-digital converter) acquisition circuit;
the polarization circuit is driven by a linear voltage stabilizing source at constant voltage, and generates a square wave signal with required polarization frequency by controlling the switch circuit so as to polarize protons in the probe through the polarization coil;
the frequency generating circuit generates a signal with the frequency of 800 HZ-4000 HZ;
the ADC acquisition circuit is used for carrying out ADC data acquisition on the received signals of the receiving coil;
the MCU processor is respectively connected with the frequency generation circuit and the ADC acquisition circuit, sends a required frequency signal for polarizing the protons through the frequency generation circuit to drive the polarization circuit to send a wave to a polarization coil in the probe, and simultaneously carries out ADC data acquisition and integral calculation while sending the frequency signal so as to achieve synchronous whole-period acquisition, calculate effective amplitude, and finally determine the magnetic field frequency through the polarization frequency corresponding to the maximum amplitude.
Furthermore, the receiving coil and the polarization coil have the same parameters and are reversely wound in an 8 shape.
Further, the polarizing coil and the receiving coil are sealed in kerosene medium inside the probe.
Further, a DDS generator or a CPLD is used as a frequency generation circuit in the frequency generation circuit, the MCU processor is an STM32F4 series single chip microcomputer, and the voltage of the linear voltage stabilization source is 12V.
Further, the ADS1271 is specifically used in the ADC acquisition circuit to acquire signals.
Further, the MCU processor performs integration acquisition on 5 whole periods of the received signal and performs normalization processing, wherein each frequency scanning frequency step scans sequentially at 20Hz, 0.1Hz, and 0.0001Hz, and each frequency scanning period has 5 periods.
Further, no signal amplifier is arranged between the receiving coil and the ADC acquisition circuit.
Further, when the polarization frequency is measured, a dichotomy quick scanning mode is adopted, namely, corresponding frequency is selected in the global magnetic field range for polarization, the amplitude is recorded, coarse frequency scanning is firstly carried out, and fine frequency scanning is carried out in a determined coarse frequency interval, so that the polarization frequency corresponding to the maximum amplitude is obtained.
Further, the square wave signal of the polarization circuit is replaced by a sine wave signal.
(III) advantageous effects
Compared with the prior art, the utility model discloses a same frequency resonance polarization synchronous magnetic field measuring device has following beneficial effect:
1. the utility model uses the high-precision frequency generation circuit to generate the polarization frequency aiming at the proton, effectively improves the magnetic field measurement precision, the polarization coils of the high-precision frequency generation circuit carry out square wave polarization in the same voltage mode (certainly, the sine wave which is more complex can be controlled), the corresponding value of the external magnetic field frequency is judged by receiving the signal integral voltage generated by different frequencies, the coils are polarized in a certain frequency, the current frequency and the frequency generated by the external magnetic field form resonance, so that the proton in the probe outputs signals in the maximum amplitude value, and the high-resolution ADC is used for accurately collecting the amplitude value generated by induction, thereby providing effective precision guarantee when the subsequent integral operation is carried out, carrying out integral collection in the whole period on the induction signals generated by the polarization frequency, and carrying out normalization processing on the time integral value of the collected period, so as to ensure that the difference of the amplitude value generated by each frequency can be clearly distinguished, by the above, the utility model discloses can each module hardware advantage of make full use of guarantee magnetic field measurement's precision.
2. The utility model discloses a magnetic field measuring device does not need the tuned circuit to carry out signal frequency selection and amplification, need not lock amplifier circuit and high gain amplifier circuit and enlargies faint larmor signal, need not high accuracy frequency measurement circuit and measures larmor signal frequency, for patent application CN201010147845, this application need not class C power amplifier, resonance amplifier circuit (because the utility model discloses by so based on the polarization resonance of proton, the oscillation high frequency signal of its polarization proton only need a few KHZ frequencies about can, the event need not to set up class C power amplifier in frequency generation circuit, the signal receiving terminal of its probe also need not to set up amplifier circuit), direct current pulse generator, frequency meter etc, and the probe constitutes simplyr, greatly reduced hardware cost and small, measuring means is simple and easy.
3. The measuring device of the utility model can receive induction signals while the polarized coil is positioned through the signal sending and signal receiving double-coil magnetic field measuring probe, thereby achieving the synchronous acquisition mode, reducing the cost and complexity of the probe, and realizing the synchronous and quick high-precision measurement of magnetic field frequency (namely, determining the frequency while polarizing); in addition, in the aspect of quickly determining the magnetic field frequency, when the magnetic field frequency is determined, a frequency sweeping mode from coarse to fine can be preferentially used for multiple times so as to further reduce the measurement time, quickly locate the measured magnetic field frequency and further improve the measurement efficiency on the basis of synchronous online measurement of the magnetic field frequency.
Drawings
The features and advantages of the invention will be more clearly understood by reference to the accompanying drawings, which are schematic and should not be understood as imposing any limitation on the invention, in which:
fig. 1 is the system structure block diagram of the medium-frequency resonance polarization synchronous magnetic field measuring device of the present invention.
Fig. 2 is a diagram of the internal coil winding of the probe in the magnetic field measuring device of the present invention.
Detailed Description
The following detailed description of the embodiments of the present invention is provided with reference to the accompanying drawings and examples. The following examples are intended to illustrate the invention, but are not intended to limit the scope of the invention.
In order to make the above objects, features and advantages of the present invention more comprehensible, embodiments of the present invention are described in detail below with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The present invention can be embodied in many different forms other than those specifically described herein, and it will be apparent to those skilled in the art that similar modifications can be made without departing from the spirit and scope of the invention, and it is therefore not to be limited to the specific embodiments disclosed below.
In the prior art, because protons in the magnetic field measurement probe perform larmor precession under the action of a magnetic field of an external environment, the precession frequency and the magnetic field are in a corresponding proportional relationship, and the magnetic field is generated by polarizing an internal coil, so that the magnetic field acts on the protons to generate magnetic moments when the protons precess.
The traditional mode is the direct current power supply polarization, and the utility model discloses a measuring device uses the square wave polarization of certain frequency, and its measuring device's theory of operation does: the proton generates nuclear magnetic resonance under the action of an external magnetic field, and because of frequency polarization, the probe can continuously polarize the proton and can be polarized again in the relaxation process, and meanwhile, the frequency polarization can generate an alternating magnetic field in the coil, so that the nuclear magnetic resonance imaging device has stronger electromotive force, increases the signal amplitude in two aspects, and reduces the difficulty in measuring a micro signal. Experiments prove that when the precession frequency generated by an external magnetic field to protons is the same as the polarization frequency, the external magnetic field strength and the internal polarization magnetic field are superposed in a resonance mode, the internal proton polarization proportion is greatly improved, the signal amplitude generated by the proton precession cutting coil is the largest, the relaxation time is the longest, and based on the phenomenon, the corresponding polarization frequency can be extracted by identifying the signal amplitude, and finally the external magnetic field is measured.
As shown in fig. 1-2, the magnetic field measuring device of the present invention mainly comprises a twin-coil magnetic field measuring probe, a polarization circuit, a high-precision frequency generation circuit, a high-resolution ADC acquisition circuit, and an MCU processor, wherein the working modes of the respective components are described as follows:
1) a probe: the probe uses a specially-made proton magnetic field measuring probe, the probe comprises a polarization coil and a receiving coil, the polarization coil is connected with the polarization coil, the receiving coil is connected with an ADC acquisition circuit, the internal resistance of the parameters of the polarization coil is 10 omega, the inductance is 30mH, the parameters of the receiving coil for induction are the same as those of the polarization coil, the polarization coil is subjected to constant voltage polarization by current of about 1A, and simultaneously, induced electromotive force generated by the receiving coil is subjected to signal acquisition.
As shown in fig. 2, the polarized coil and the receiving coil in the dual-coil magnetic field measuring probe are completely isolated, the polarized coil and the receiving coil form a dual coil and are sealed in kerosene, proton polarization and induced electromotive force signal acquisition can be synchronously performed, and an additional class-c power amplifier and a resonance amplifying circuit are not required to be respectively installed at the input end and the output end of the dual-coil probe.
2) A polarization circuit: the 12V linear voltage-stabilizing source is used as a polarization circuit to carry out constant voltage driving, the required frequency is generated by controlling the switch circuit, the same voltage peak value flows through the polarization coil when the frequency is polarized, and the differentiation caused by unstable voltage is eliminated so as to adapt to the measurement of the magnetic field frequency. In addition, the polarization signal is preferably a square wave signal, thereby reducing the difficulty of signal control.
The polarization circuit provides the driving force for the probe polarization, and the coil is under different voltage polarization circumstances, and produced magnetic field intensity is inequality, and this causes follow-up received signal amplitude to gather and itself to have the differentiation, consequently need to polarize with the constant voltage drive, and polarization coil supply voltage need keep invariable to eliminate the measuring error that the driving source caused.
3) A frequency generation circuit: the high-precision frequency generation circuit provides a frequency source for the polarization circuit, because the utility model discloses a polarize the proton, so its signal frequency of occurrence is at 800HZ ~ 4000HZMeanwhile, the resolution of the measuring magnetic field needs to reach 0.01nT, and the corresponding frequency precision needs to reach 10-4The magnitude order meets the judgment of frequency fineness, a DDS generator or a CPLD can be used for generating high-precision frequency, the CPLD is preferentially used as a frequency generating circuit, a crystal oscillator with lower temperature drift is required to be used, the CPLD frequency generation precision is high, the real-time performance is strong, and the polarization frequency can be accurately controlled.
4) ADC acquisition circuit: the ADS1271 is used for collecting the received signals, the ADC has 24-bit resolution, the highest sampling rate is 128ksps, and the received signals can be collected with high precision. The high-resolution ADC acquisition circuit can acquire signals after resonance is received by the probe receiving coil by using the ADC, and the whole system judges the frequency of the integral amplitude of the received signals, so that the ADC needs to have high resolution to effectively distinguish the tiny differentiation of amplitude change. Which can eliminate the need for a pre-installed signal amplifier.
Furthermore, in order to improve the measurement precision, 5 periods can be sent by each frequency through integral of the whole period of the received signal, integral acquisition is carried out on the 5 whole periods, normalization processing is carried out, the anti-interference capability can be effectively improved, the size of each frequency normalization value can be clearly distinguished, and the maximum corresponding frequency value is extracted. When the frequency scanning frequency is scanned according to 20Hz, 0.1Hz and 0.0001Hz in sequence, each frequency is 5 periods, and the complete measurement time is about 1.85s, so that the magnetic field value can be rapidly obtained.
5) The MCU processor: the MCU processor adopts STM32F4 series single-chip microcomputer to control all circuit parts, and simultaneously carries out integration and normalization on ADC acquisition data, and controls the dichotomy of polarization frequency to carry out scanning in a thickness mode step by step so as to quickly and effectively extract corresponding magnetic field frequency, and simultaneously carries out integration calculation on signals converted and output by the ADC to judge actual magnetic field frequency.
In summary, the above embodiments are tested, and under different magnetic field environments in different regions, the integral acquisition with different polarization frequencies is performed, when the external magnetic field frequency is the same as the polarization frequency, the maximum signal amplitude is obtained, and when the frequency is different, the amplitude is obviously reduced, so that the signal amplitude can be effectively and clearly distinguished, and thus, the external magnetic field value is obtained, and the purpose of rapidly and accurately measuring the magnetic field is achieved.
For further explanation, the advantages of the magnetic field measuring device of the present invention are described in detail below for the main working procedures of the present invention: the MCU processor sends a required frequency signal for polarizing the protons through the frequency generation circuit, the frequency drives the polarization circuit to send a wave to the probe polarization coil, and ADC data acquisition is carried out while the frequency is sent so as to achieve synchronous whole-period acquisition. And the MCU processor receives the data acquired by the ADC for integration, and calculates the final effective amplitude. In order to locate the magnetic field frequency quickly, a frequency-by-frequency scanning mode is adopted, that is, the frequency polarization is carried out one by one in the global magnetic field range, the amplitude is recorded simultaneously, and the coarse frequency scanning is carried out firstly, and then the fine frequency scanning is carried out. After the high-resolution ADC is used for collecting, the whole period is collected, the frequencies are different, so that the integrated values are differentiated, in order to eliminate the differentiation and improve the accuracy, time normalization needs to be carried out on signal integrated values generated by all the frequencies, namely, the integrated values are averaged over the collected time, the normalized values are compared, and a rough frequency interval is finally determined.
When the MCU processor controls the polarization frequencies of the fine frequency and the coarse frequency to be polarized one by one, the fine frequency scanning and the coarse frequency scanning have the same measuring mode, except that the scanning frequency is measured in a determined coarse frequency region again in a fine measuring mode (such as a conventional dichotomy measuring mode), and finally the corresponding frequency value is determined, namely the corresponding frequency value of the external environment magnetic field. Because final frequency precision is higher, if according to minimum precision from small to big when frequency scanning one by one, then need consume a large amount of time and just can confirm final frequency (nevertheless every frequency send the cycle not too big), consequently the utility model discloses use the hierarchical formula automatic frequency sweep mode of using by thickness to thin many times through the cooperation under the synchronous on-line measuring mode based on twin coil probe to quick automatic determination magnetic field frequency.
Fig. 2 shows a winding diagram of the winding interior of the probe coil, the medium inside the probe can be kerosene containing a large amount of protons (or other conventional media containing a large amount of protons), the polarizing coil is completely the same as the receiving coil, and preferably, each coil is wound in a reverse direction in a shape like a '8', on one hand, induced voltage generated when the polarizing coil polarizes itself can be reduced, and simultaneously induced electromotive force generated by the receiving coil under the action of a magnetic field can be superposed, so that a received signal is enhanced, and thereby, the geological magnetic field frequency is measured.
Through the utility model discloses a synchronous magnetic field measuring device, can adopt the measurement mode of same frequency resonance polarization synchronous collection to carry out the high accuracy measurement, high accuracy frequency generation circuit and high resolution ADC circuit all realize more easily on hardware, and need not electric capacity resonant circuit, need not to carry out the lock phase to the frequency drift among the traditional mode, owing to be the collection to the amplitude integral, only need increase the integral time, also need not lock phase amplifier circuit and high gain amplifier circuit and amplify weak larmor signal and high accuracy frequency measurement circuit measures larmor signal frequency, consequently, can effectively reduce the complexity of hardware design, reduce the difference of measuring between the instrument; in data processing and frequency measurement, due to integral amplitude measurement, external interference can be effectively eliminated, the signal-to-noise ratio and the dynamic range are improved, and the measurement precision is increased; the event the utility model discloses using the resonance frequency polarization mode based on proton, can effectively improving the discernment degree in the less region in magnetic field, making can accurately measure the change magnetic field value in the less region of magnetic field change, its hardware is with low costs, small, and measurement of efficiency is high.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
Claims (7)
1. A same-frequency resonance polarization synchronous magnetic field measuring device is characterized in that the magnetic field measuring device comprises a probe, a polarization circuit, a high-precision frequency generation circuit, a high-resolution ADC acquisition circuit and an MCU processor;
the probe is a proton magnetic field measuring probe, and comprises a polarizing coil and a receiving coil, wherein the polarizing coil is connected with a polarizing circuit, and the receiving coil is connected with an ADC (analog-to-digital converter) acquisition circuit;
the polarization circuit is driven by a linear voltage stabilizing source at constant voltage, and generates a square wave signal with required polarization frequency by controlling the switch circuit so as to polarize protons in the probe through the polarization coil;
the frequency generating circuit generates a signal with the frequency of 800 HZ-4000 HZ;
the ADC acquisition circuit is used for carrying out ADC data acquisition on the received signals of the receiving coil;
the MCU processor is respectively connected with the frequency generation circuit and the ADC acquisition circuit, sends a required frequency signal for polarizing the protons through the frequency generation circuit to drive the polarization circuit to send a wave to a polarization coil in the probe, and simultaneously carries out ADC data acquisition and integral calculation while sending the frequency signal so as to achieve synchronous whole-period acquisition, calculate effective amplitude, and finally determine the magnetic field frequency through the polarization frequency corresponding to the maximum amplitude.
2. The same-frequency resonance polarization synchronous magnetic field measurement device as in claim 1, wherein the parameters of the receiving coil and the polarization coil are the same, and the coils are wound in a reverse direction in a shape like a figure 8.
3. The same-frequency resonance polarization synchronous magnetic field measurement device according to claim 2, wherein the polarization coil and the receiving coil are sealed in kerosene medium inside the probe.
4. The same-frequency resonance polarization synchronous magnetic field measurement device according to claim 1, wherein a DDS generator or a CPLD is used as a frequency generation circuit in the frequency generation circuit, the MCU processor is an STM32F4 series single chip microcomputer, and the constant voltage of the linear voltage stabilization source is 12V.
5. The same-frequency resonance polarization synchronous magnetic field measurement device according to claim 1, wherein the ADC acquisition circuit specifically acquires signals using ADS 1271.
6. The same-frequency resonance polarization synchronous magnetic field measurement device according to claim 1, wherein no tuning amplifier circuit is required to be arranged between the receiving coil and the ADC acquisition circuit.
7. The same-frequency resonance polarization synchronous magnetic field measurement device according to claim 1, wherein the square wave signal generated by the polarization circuit is replaced by a sine wave signal.
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