Study On Calibration Of Proton Magnetometer

Proton magnetometer is a measuring apparatus of earth’s magnetic field, which is designed by proton precessing characteristics and controlled by electronic circuit. It becomes the most widely used magnetometer in geological prospecting, magnetic field observation, mineral search and other fields by virtue of high accuracy, easy to carry, conveniently repaired. As a commercial product, we need to discuss the technical index to evaluate the performance of apparatus.Proton magnetometer works easily, the current in copper coil can stimulate strong magnetic field, protons in liquid which is equipped in sensor are polarized in queue. When the polarized field suddenly disappears, protons will make a Larmor precession movement in the earth’s magnetic field. By the time, proton magnetic moment is cutting the induction coil and producing a Larmor signal. Finally, calculate the earth’s magnetic field by signal frequency.In order to obtain the performance index of proton magnetometer, meanwhile, to guide the research on development of proton magnetometer, the paper theoretically analyzed several performance indices of proton magnetometer, including sensitivity, accuracy, dynamic range, temperature drift, etc. Design experiment, first level measurement of high accuracy GSM-19 type OVERHAUSER magnetometer and JOM-2 type OVERHAUSER magnetometer which is designed by our laboratory. Calculate the standard deviation eliminated diurnal variation of synchronous measurement data. The sensitivity in time domain of JOM-2 is 0.08 n T, the sensitivity in frequency domain of JOM-2 is 0.32 n T/√. Discuss the factors which affect the accuracy of proton magnetometers, experiments show that the accuracy of JPM-2 type proton magnetometer is 0.26 n T, the magnetometer exhibits good consistency. According to the classical Helmholtz coils model, propose squared Helmholtz coils and circular gradient coils, experiments show that the magnetic field range of JPM-2 type proton magnetometer is 30000-120000 n T. Discuss the influence of environmental temperature on the proton magnetometer measurements. Measure at Changchun distant area respectively in summer and winter, after calculation, the temperature drift of JPM-2 type proton magnetometer is 0.0714 n T/℃.