Noise Behavior of High Sensitive GMI-Based Magnetometer Relative to Conditioning Parameters

The lowest measurable magnetic field of a high sensitive magnetometer based on giant magnetoimpedance (GMI) effect will be determined by its noise level. Numerous previous works have showed that the equivalent magnetic noise level of GMI magnetometer presents a 1/f behavior at low frequencies and a white noise. Currently, performances of the magnetometer are still limited by the electronic conditioning as well as the intrinsic equivalent magnetic noise of the GMI sensor. To improve sensor performances, particularly at low frequency, we have investigated two focuses on research: 1) reduce the electronic noise of the conditioning electronic by increasing the voltage sensitivity, in units of V/T and 2) reduce the intrinsic equivalent low frequency sensor noise. As previously reported, the equivalent magnetic noise at 1 Hz can be reduced by increasing the excitation current in addition to a dc bias current. By working on these bias conditions, on the given samples, we almost 1 pT/root Hz in white noise region and 15 pT/root Hz at 1 Hz.