Design of a GMI magnetic sensor based on longitudinal excitation

Abstract

In this article, we develop a micro magnetic sensor found on the Fe-based amorphous ribbon with longitudinal stimulation with the recognition that the micro magnetic sensor has the characteristics of good linearity, high sensitivity, high repeatability and low cost. The characteristics of Fe-based materials and the longitudinal driving mode are presented. The structure of the GMI sensing element, the principle of the conditioning circuit, the properties of the bias magnetic field, the effects of the excitation frequency of pulsed current and the length ratio of the ribbon versus the coil are also investigated. The GMI sensing element is made up of a 12-mm-long, 2-mm-wide and 20-μm-thick Fe-based amorphous ribbon, a bobbin and a 0.08-mm diameter enamel wire of 100 turns exhibiting giant magneto-impedance ratio. The bias magnetic field is provided by the permanent magnet NdFeB to shift the working points to the linear part of the impedance characteristics. The full measurement range of the magnetic field detection is ±2.5 Oe, and the sensitivity achieves 400 mV/Oe.