The Larmor Frequency Measurement Module Of MRS-TEM Combined Use Groundwater Detection Instrument

With the continuous improvement of science and technology, the significance andapplication of water are stronger and stronger, however, numerous regions on earth are lackingof water source, this result in the backward of various aspects. Therefore, for the purpose ofresolving problems aforementioned, searching for a kind of ground water detections is veryimportant. As so far, MRS (Magnetic Resonance Sounding) is the only way to seek water, deepdigging is not used while detecting the location and capacity of water. TEM (TransientElectromagnetic Method) is a indirect method for water detecting and result is preferably, theadvantage is that the detection range is more extensive than MRS. MRS-TEM groundwaterdetection method is composited of the accuracy of MRS and the arrangement of TEM, thecomplementary technique of MRS and TEM is called MRS-TEM Combined Use GroundwaterDetection Instrument for short.This paper presents the Larmor frequency measurement module of Nuclear MagneticResonance (NMR) spectrometer, according to the principle of NMR water searching method,the basic known quantity is the frequency of geomagnetic field. However, the magnetic field ofeach location on earth is different, only by accurate measurement of size and frequency ofmagnetic field, the largest signal strength and effect in working process of NMR spectrometercan be obtained. Therefore, the accurate measurement of Larmor frequency is the mostvaluable development module for NMR spectrometer, quantitative results of the entireinstrument are directly decided by the measured frequency. The AMR single chipmicrocomputer (SCM) control, signal acquisition and CPLD digital signal measurement areadopted to lower computer control of the module, the Labview software is integrated in uppercomputer of NMR spectrometer in form of VI. According to research contents, the problemsneed to be solved in this paper includes: Larmor frequency measurement module integration ofNMR spectrometer, lower module hooking of NMR spectrometer bus, human-computerinterface of Labview software applied in upper computer, main control circuit development, polarized circuit development, amplification circuit development, commutation circuitdevelopment, signal processing and measurement circuit development, capacitor automationresonance method development and module structure development of Larmor frequencymeasurement module.The Larmor frequency measurement system module integrated in the entire combinationinstrument is developed in this paper, the working principle of the module is torealize the accurate measurement of Larmor frequency of geomagnetic field in formof proton precession, the precision of measurement is about0.1%.