The Design Of Magnetometer Digital Board Based On CPLD

Magnetometer is an Earth's magnetic field measurement instrument based on Larmor precession effect,which with high sensitivity,small size and easy to carry features.Magnetometer is widely used in archaeological,mineral exploration,volcanic eruptions,seismic detection,underground unexploded object detection and magnetic field measurement and other fields.The Larmor precession signal is a sine wave signal,its frequency is proportional to magnetic field strength,so the measurement of the frequency of the Larmor precession signal is a key factor in the accuracy of the magnetic field measurement.Because of the high sensitivity and high precision of the frequency measurement of CPLD,this paper adopts EPM1270 CPLD and STM32F4 ARM to design the magnetometer digital board and uses high-precision temperature compensation crystal signal as the reference signal of frequency measurement.The test results show that this design greatly improved the performance of the instrument.In this paper,the significance of the research of magnetometer and its development at home and abroad are introduced,firstly.Then the working principle of the magnetometer and the basic framework of the system design is introduced,secondly.The design of the hardwares of the system are introduced,thirdly.The hardware design include the select of CPLD chip,the polarization circuit,keyboard and display circuit,A/D circuit and frequency measurement circuit and so on.Then introduced software architecture of the system,CPLD control of the external circuit and CPLD and ARM work together to achieve the measurement of magnetic field values.Finally,the magnetometer was successfully debugged and assembled into proton magnetometer and Overhauser magnetometer.On the basis of the traditional magnetometer,the magnetometer research and development by our laboratory increased the real-time clock display,automatic coordination,file storage and other functions.Experiments show that the proton magnetometer and the Overhauser magnetometer can work properly,magnetic measurement is good.The sensitivity of the proton magnetometer can reach 0.115 n T,and the sensitivity of the Overhauser magnetometer can reach 0.0512 n T,which is the leading level in China.On the basis of the magnetometer,a gradient instrument is developed,which can achieve the magnetic field gradient measurement.