Temperature Dependence of Offset and Sensitivity in Orthogonal Fluxgate Operated in Fundamental Mode

Orthogonal fluxgate in fundamental mode has low noise output but its offset is often very large. A method has been proposed to compensate the offset consisting in periodical switching of the dc bias of the excitation and subtraction of the signal obtained with positive and negative dc bias. This method has been already proved to effectively suppress the offset, however no investigation has been made for the temperature drift of the offset. In this paper we show that this method can be used also to compensate the drift of the offset for a wide temperature range: compensated output shows about 120 nT maximum variation of the offset in -90 degrees C to +90 degrees C temperature range, making orthogonal fluxgate in fundamental mode competitive to cheap parallel fluxgate. Moreover the dependence of the open loop sensitivity on the temperature is also investigated: no substantial drop of the sensitivity is observed in the same temperature range.