Improvements Of JPM-1Proton Precession Magnetometer

Proton precession magnetometer is the instrument that makes use of Larmorprecession effect of hydrogen proton in the geomagnetic field to measure themagnetic field. The proton magnetometer has the advantages of small volume, highaccuracy and simple operation, which is widely used in geological survey and mineralresources exploration、 geomagnetic observation、 volcanic and earthquakeobservation、sunken ship detection and other fields. At present, the measurementaccuracy of domestic magnetometer is general close to1nT with single function.While the foreign one’s accuracy is near to0.2nT, with abundant extended functions,used easily but the exorbitant price also limits its application. Therefore, it plays anactive role for our magnetic prospecting career to overcome technical difficulties anddevelop advanced domestic magnetometers with proprietary intellectual propertyrights.Participating in the development of JPM-1type proton precession magnetometer,the author find that this system have realized Real-time display of proton precessionsignals and the measured results, but poor temperature stability, lacking storagespaces and inconvenient data management still exist. In this paper, some improvementmethods of JPM-1magnetometer are discussed in order to improve the accuracy ofmeasurement system, expand system storage space and rich instrument function,proceeding from Oven Controlled Crystal Oscillators module、FAT32file systembased on SD card、parallel A/D data acquisition、charge management、 auxiliaryswitch module and so on.First of all, the function and working principle of the JPM-1type ProtonMagnetometer are introduced. According to the goals of the development andcommercial limit of Magnetometer with high sensitivity and stability, thedisadvantages of JPM-1Magnetometer have been analyzed and the correspondingimprovements have been put forward. Secondly, the functions both on the hardware circuit and on the software system have been improved. By analyzing the referencefrequency effect on the accuracy of frequency measurement and the method of usingthe Constant-temperature Crystal Oscillator as the frequency reference is put forwardin order to improve the temperature stability of the measurement result; The parallelAnalog-to-Digital Converter, Battery Charging Management Circuit, Auxiliary Switchcircuit have been added in order to complete the monitoring on the powerconsumption of power supply management, make the system power efficiency andimprove the hardware part of the system function more perfect. In order to enhancethe system storage capacity and study the Larmor signal more easily, the FAT32filesystem based on SD card is established. At the same time, we design procedures ofAuxiliary Switch, Current monitoring and Signal acquisition to fix the improvementof hardware circuit. Finally, each module and the whole system have been testedsuccessfully. The results show that the OCXO’s temperature stability is higher thannormal crystal’s. effectively improving the accuracy of the frequency standards; SDcard module enhances Magnetometer’s storage space greatly and the file systembrings convenience to the data management; The use of parallel AD module makesMagnetometer’s acquisition in multi-channel and enhances the sampling efficiently;Charging Management module makes the battery charged effectively and safely;Auxiliary Switch module can make Magnetometer work in normal or low powerconsumption mode which improves the efficiency of the battery.Changes in temperature of25degrees, the results show that the measurementresults of the common crystal oscillator offset6nt crystal. The offset of OCXO isclose to zero. At the same time, the2G SD card can store nearly2000completedomain signal, these improvements will greatly improve the performance and thefunction of the system.