Three-dimension micro magnetic detector based on GMI effect

The giant magneto-impedance (GMI) effect of amorphous wire was analyzed theoretically. The amorphous wire had strong GMI effect in the stimulation of sharp pulse of 680 kHz and 18 mV. A pulse generator was designed to provide high frequency pulse to a magnetic impedance (MI) element. The induced voltage on the pickup coil wound on the amorphous wire was sampled and held with a detect circuit using analog switch. A stable magnetic sensor was constructed. A three-dimension micro magnetic field detector was designed with a central controller MSP430F449. High stability and sensitivity were obtained in the MI sensor with the detect circuit. Experiment results showed that the resolution of the detector was 1nT in the full scale of ±2 Oe and the detector worked stably from the room temperature to about 80 ℃. A small ferromagnetic target was detected by the three-dimension detector in laboratory environment without magnetic shielding. The target moving direction was ascertained with the wave shape of axis parallel in that direction.