Use of Magnetic Circuits for Toroidal GMI Current Sensors

In this paper, the approach of using magnetic circuits in giant magneto-impedance (GMI) current sensors is introduced for the first time in order to reduce the impact of magnetic disturbances on the sensor response. The studied current sensor had a toroidal structure. The GMI sensitive element circled the conductor carrying the measured current. The way to use a magnetic circuit in this configuration was established, and the rules of design and implementation were defined and validated by the simulation and by the measurements. The theoretical idea was to place the sensitive element on the surface of a magnetic circuit. However, in practical conditions, both simulation and measurement have demonstrated that a magnetic circuit must be placed at each side of the sensitive element, if the idea is to prevent from the effect of the different types of magnetic disturbances.