Research Of 3-axis Fluxgate Magnetometer Based On STM32

Fluxgate magnetometer is a magnetic sensor device designed on the relevant principle of fluxgate,which can be widely applied in geophysical exploration,space environment exploration and geomagnetic navigation.Magnetic prospecting technology is one of the most effective means,especially in the field of mineral resources exploration.This paper analyzes the recent development status of fluxgate sensors,and studies the key technologies of fluxgate magnetometer design,selection of frequency of probe excitation signal and method of extraction of effective sensing signal.According to theory analysis and practical tests,4.74 KHz is selected as the excitation signal frequency.Besides,second harmonic method is applied to extract an effective sensing signal.On this basis,the 3-axis FGM_V1 fluxgate magnetometer was designed to realize the fluxgate magnetometer system based on STM32 microcontroller.The main work is as follows: 1.Design of the system's hardware circuit.The circuit mentioned above includes the power circuit,STM32 main control circuit,excitation circuit,sensing circuit and auxiliary circuit which consists of STM32 minimum system and communication circuit.The minimum system mainly takes responsibility for the debugging of the previous software program.The communication testing circuit is designed for later program downloading and serial communication.2.The design of the system software.Using software to output excitation square wave which contains fixed frequency and duty cycle.The output signal of the sensing circuit for A/D sampling has also been realized.Communication through the serial port with the host computer has finally been achieved.3.Tests and analysis for the output waveforms of each functional module in detail.In order to collect the data of the magnetic field data,the related test was performed separately in the zero magnetic field and the actual environmental magnetic field.The instrument's noise,volume,power consumption,3-axis steering and other aspects are analyzed.It has also been compared with a high-precision Magson fluxgate magnetometer.The FGM_V1 fluxgate magnetometer realized in the paper achieves the design requirements.The 3-axis noise is less than 0.5mV;Compared with the previous version,Its volume is reduced by 40%;The actual test power consumption is only 0.35 W.The instrument can also sense the change of the direction of magnetic field sensitively.This system has the characteristics of small size and low power consumption which meets the design expectations and has practical value in application.