Differential-type integrating GMI magnetic sensor based on orthogonal vector lock-in amplifier

A novel differential-type magnetic sensor based on the giant magnetoimpedance (GMI) effect, integrating the impedance magnitude and phase characteristics of the amorphous wire due to varying the extern magnetic field, is presented in this paper. The sensor consists of a conditioning circuit based on orthogonal vector lock-in amplifier and differential-type amplifier, and a differential-type sensing head with double sensing elements. Besides, the characteristics of our amorphous wires and the construction of the sensing head are also described in this paper. Especially, a masterly and simple design for integrating the in-phase and quadrature output of orthogonal vector lock-in amplifier utilized in the conditioning circuit is described and analyzed in detail. Multiple measurements show that the sensitivity of the GMI magnetic sensor can achieve about 748 mV/Oe with the full measurement range of ±2.0 Oe, while the linearity error is about 0.92%FS.