Long-time fluctuations of off-diagonal GMI-based magnetometers

This paper presents the measurement of long-time equivalent magnetic field fluctuations. It was obtained with a low noise off-diagonal GMI magnetometer. Acquisitions are conducted with a dedicated acquisition system. The GMI sensor principle and associated noise sources are reminded. Furthermore, the noise model is extended to include the impact of the very low frequency drift of the associated GMI impedance. The homemade GMI magnetometer and the used high dynamic analog to digital converter board are described. The obtained performances show a peak to peak fluctuations of 10 nTpp and a drift of 20 nT/h during 4.5 hours after a transient response. Results are compared, in real time, to a commercial flux gate magnetometer.