Research Of High Accuracy Digital Magnetometer System Based On Fluxgate Magnetic Technique

Fluxgate magnetometer is a very high expertise and which has broad prospect. It is primarily used to detect weak magnetic field information, such as environmental monitoring of the magnetic field, geomagnetic field research, exploration of oil field and mineral resources, materials nondestructive testing, weapons detection, magnetic field measurements of the universe and other aspects.The traditional fluxgate magnetometers often uses mechanical structure and analog circuit design, thus, resulting in relatively large size and easily affected by the environment, anti-interference ability is poor. With the rapid development of the material technology and the electronic information technology, especially the rapid development of the MEMS (Micro-electromechanical System) technology and the integrated circuit technology, makes the miniaturization, digitization of the fluxgate magnetometer become possible. Today, fluxgate magnetometers are with more compact structure, smaller size, lighter weight, better antiknock characteristic, which not only can greatly reduce the environmental impact on the system, but also reduce power consumption and improve the system's accuracy and stability. Through study and research, this paper has done the following work:Firstly, begin with the overview about the magnetic field measurement methods, this paper introduces the classification and production technology of fluxgate probe. By analyzing the transformer effect and the mathematical model of fluxgate, we clarified the working principle of fluxgate.Secondly, based on the fluxgate technology and ATmega8L and ATmegal28L microcontroller, we designed a high accuracy digital magnetometer system, which set complex signal acquisition, automatic debugging, LCD display, man-machine interactive operation and other functions in one.Thirdly, in system design details, this paper put forward a digital excitation method,which uses the MCU create a digital square-wave excitation signal to drive the fluxgate probe directly. In this way, the excitation signal is frequency adjustable, thus, it can reduce the system error caused by the otherness of the fluxgate probe, and it also can improve the stability issues of the traditional RC analog excitation circuit. By replacing complex harmonic circuit by peak detection approach, the design of circuit is simplified and power consumption is reduced. In addition, the method of automatic temperature compensation is studied and the temperature compensating circuit is added to reduce the temperature drift.Finally, we sent some intact assembled fluxgate magnetometers to the CSIC Yichang magnetism measuring and testing stations to test the performance of the system. Test results indicate that the system can work steady in the bad environment with insolation, drench, moist and high or low temperature. In addition, it can easily reach the 1nT level measurement precision and achieve the desired design specification.