Study On Terrestrial Magnetism Sensors Based On Amorphous Materials

With the development of geomagnetism, topography and space physics, geomag-netic navigation which is a newly passive and autonomous navigation system causes more and more people's anttention. Magnetic field sensors based on giant magneto-impedance meet the requirement of geomagnetic navigation systems for terrestrial magnetism sensors due to their high sensitivity, quick response and low power consumption. This paper works activly on the design of high-performanced magnetic field sensors based on giant magnetoimpedance in amorphous wires.Firstly, based on a phisical simplified model, Maxwell equations, Landau-Lifshitz(LL) equation and Ohm's equation is solved to obtain the electral impedance of the amorphous wire. The factors and mechanism that influence the giant magneto-impedance effect in amorphous wires can be found out from the expression of the electral impedance. Analysis results of experimental datas show the relationship between GMI ratio, magnetic sensitivity and GMI influence factors which includes externally-applied magnetic field, frequency of driving current and length of the wire, and then we find out the best working condition of an amorphous wire.Secondly, the structural design of the sensor's circuit is accomplished according to the amorphous wire's working condition. The sensor's dynamic model is built, and then output transfer function and error transfer function is worked out. Calibration is also performed in the magnetic field shield equipment.Test results show that the sensitivity of the sonsor we designed can get up to 4.865Oe/Gs.Finally, a noise analysis of the sensor we designed is presented. A noise model of the sensor's output is set up. Expressions are obtained for the output power voltage noise spectral density and equivalent input power magnetic noise spectral density. The results of spectral analysis of outputs which come from different parts of the sensor's ciucuit show that intrinsic amorphous wire magnetic noise and oscillator's noise contribute most in the output. So optimizing noise features of the wire can improve performmance of magnetic field sensors greatly.