Development Of Fluxgate_based Instrument For NMR Geomagnetic Field Measurement

Nuclear magnetic resonance (NMR) technology is one of the world’s only method ofgeophysical exploration of groundwater which can be directly detected with high resolution, highwater efficiency, rich information and interpretation only, and so on. In recent years, NMRtechnology in the detection of underground water, the dam seepage prevention, the mine/tunneldisaster water obtained widely used advanced detection, etc.NMR technology in the application needs to know the local geomagnetic field intensity andgeomagnetic inclination of geomagnetic information, which requires a three-componentmagnetic measuring device, because the market supply of flux-gate magnetometer isn’t on therequirements of the nuclear magnetic resonance instrument design, cannot be achieved with theseamless joint between NMR to find water meter, and can’t satisfy the three-component magneticfield intensity and dip angle of the double demand, can’t meet in the mine tunnel under thecondition of high electromagnetic interference, such as magnetic survey requirements. And theintensity of magnetic field will directly affect the accurate measurement instrument of theexcitation pulse from the accurate setting, which in turn affect the accuracy of the detectionresults. So, high reliability, high precision magnetic measurement device is the key to ensure thereliable work of the NMR water meter.The research purpose of this paper is to develop a three-component flux-gate magnetometerto meet the demand of NMR magnetic survey of water meter. Firstly, paper introduces the singlecomponent flux-gate sensor, the basic principle of three-component flux-gate sensor, andtheoretically discusses the working principle of magnetic flux gate inside the sensor and thevarious parameters on its performance, the influence of the flux-gate sensor drive circuit design,analog signal processing circuit, sampling circuit, finally completed the flux-gate magnetometer.And build the calibration test platform, the resolution and precision of the system calibration,and the system stability, test evaluation. The precision of the magnetic measurement system as awhole, is30nT,for the larmor frequency is1Hz.The accuracy of the magnetic angle is1°.