Enhanced Performance of Off-Diagonal GMI Magnetic Sensors by Using Optimized Amorphous Wire Array

Giant magnetoimpedance (GMI) sensors with off-diagonal mode have advantages of wide range, good linearity, and simple circuit. The performance of the sensor is directly affected by the number of turns of the signal pickup coil. In order to obtain amorphous wire GMI sensors with better performance, the number of turns of the signal pickup coil is usually larger. However, large pickup coils result in larger device size, which is not convenient to device miniaturization. In many conditions, small size device is needed. To achieve device miniaturization and keep the performance at the same time, increasing the cross-sectional area of the sensor is another choice. This article investigates the GMI sensor performance with varying amorphous wires. The aim is to provide a viable approach to enhance the sensor performance with miniaturized device size. We investigate the influence of the number of amorphous wires and coil turns on the performance of amorphous wire-based GMI sensors. The off-diagonal output responses of sensor with different numbers of wires were measured, and the output sensitivity and noise were compared for varying numbers of amorphous wires. The sensitivity of the sensor with a single amorphous wire is 85.23 mV/Oe, while that with eight amorphous wires reaches 266.36 mV/Oe. The noise level of the sensor with a single amorphous wire is 148.4 pT/rtHz@1 Hz, and the eight amorphous wires is 44.5 pT/rtHz@1 Hz. This work presents an approach to achieve a high-performance GMI sensor with less number of pickup coils.