Magnetic sensor based on giant magneto-impedance effect using the self-regulating technology on the bias magnetic field

The bias magnetic field is generally used to set properly the operating point of the magnetic sensor based on the giant magneto-impedance effect (GMI sensor) as the GMI profile exhibits a nonlinear and unipolar dependence on the applied external magnetic field. However, the changes in sensing direction or position of the GMI sensor will induce a fluctuation in the output voltage signal by varying the bias magnetic field due to the uniform geomagnetic field without any magnetic shield. A scalar field GMI sensor using the self-regulating technology on the bias magnetic field is developed in order to overcome the output fluctuation. The self-regulating technology based on the principle of the feedback control can self-regulate the bias magnetic field so as to keep it in the initial state. The mathematical model and the detailed structure of the self-regulating system (SRS), and the structure of the magnetic detector are also investigated. It is demonstrated that the variation in the bias magnetic field can be effectively suppressed by the SRS and a relatively high stability is achieved in the output of the GMI sensor. It is suitable for the GMI sensor to be used in moving platforms such as vehicles, robots and portable instruments.