Design Of The Low Frequency Weak Magnetic Field Measuring System Based On Fluxgate Magnetometer

Low frequency weak magnetic field measurement is of importance and role in the area of energy security,national defense and sustainable development. Now magnetic optical pumping magnetometer,atom and the proton spin precession magnetometer and SQUID magnetometer are the most commonly used instruments of weak magnetic field measurement. These instruments have achieved precision of 10-10～10-18 nT, and have been widely applied to the fields of space probe,navigation measuring,the earth's environment,archaeological research and bio-magnetic field measurement etc..Instruments of weak magnetic field measurement existed have been of the characteristics of bulky,complex and high requirements on the measurement conditions. Fluxgate magnetometer which was arising in 1930 has achieved measurement accuracy of 10-6～10-10nT and has been of the characteristics of stable performance,compact,,small power consumption,,good seismic,simple,low cost, and has been widely used. With the development of electronic technology, computer and information science, the development trend of weak magnetic field measurement is high sensitivity and stable fluxgate magnetometerThis thesis researched in depth the principle of low frequency weak magnetic fields and established a fluxgate low frequency weak magnetic field measurement system which leaded into technology of digital phase-locked amplification firstly. This system improved the time and space resolution of fluxgate probe, resolution achieved the precision of 0.05nT and dynamic range was 0.1nT～100nT, and realized simultaneous measurement of multiple probe. This thesis firstly analysis principles and methods of weak magnetic field measurement, and shows the necessity and feasibility of further improve the precision of fluxgate magnetometer. Secondly a dynamic compensation of a constant weak magnetic environment has been established based on PID control in the method of adding a magnetic shielding cavity on three-dimensional Helmholtz coil. Importantly we designed a kind of fluxgate low frequency weak magnetic field measurement system cited the principle of digital phase-locked amplifier technology. Finally the thesis summarized the structure and performance of this system and put forward areas for improvement.