Low Offset Orthogonal Fluxgate Operating in Fundamental Mode

摘要

A method is presented for canceling offset of an orthogonal fluxgate operating in the fundamental mode with dc biased excitation. Offset occurs under the influence of the magnetic anisotropy that is inherent in a wire core. When both the excitation current and dc bias polarities are either positive or negative, the absolute value of the offset is the same but the signs are contrary. The offset can therefore be removed by changing polarities of both excitation current and dc bias periodically to take the mean value. This method can also reduce the input-output hysteresis. Experimental results are shown for a sensor head consisting of a 15-mm-long cobalt-based amorphous wire of 120 mum in diameter and a 300-turn sensing coil formed on the wire.