A magnetic field transducer based on closed-loop operation of magnetic sensors

A high sensitivity magnetic transducer able to sense magnetic fields from DC up to tens kHz is discussed in this paper. The system is based on a ing field coil fed by a current on the basis of the residual field, sensed by a magnetic sensor (Hall or magneto-resistive) placed in the coil center. In this way, the coil current proportionally represents the external field component along the coil axis, and it can be easily converted in a voltage signal by a series resistor. Then, a one-axis gauss meter can be readily obtained. The sensitivity and the bandwidth of the overall system are discussed by a transfer function analysis. A hardware prototype has been realized, and significant test results are shown by means of a reference magnetic field generation set-up. Useful guidelines for the overall system design are given in the paper.