Abstract
We have further lowered the white noise of an orthogonal fluxgate to about 0.3 pT/√Hz @ 8 Hz. So far, this is the lowest noise reported for a fluxgate magnetometer. The noise reduction was achieved by introducing a JFET input stage, embedded directly to the sensor head, allowing for high common-mode rejection and negligible loading of the resonant circuit. The origin of the noise was investigated by correlation measurements and we concluded that, at least in the white noise region, we observe the magnetic noise of the sensor, with about 0.1 pT/√Hz white noise contribution by the electronics. We were finally able to obtain sensor noise floor below 1 pT/√Hz @ 1 Hz also in a feedback-compensated closed-loop. Closed-loop operation allows for higher magnetometer stability and operation in Earth’s magnetic field without deteriorating its noise performance.
Highlights
We have further lowered the white noise of an orthogonal fluxgate to about 0.3 pT/ Hz @ 8 Hz
This is the lowest noise reported for a fluxgate magnetometer
The orthogonal fluxgate sensors based on magnetic microwires, when operated in fundamental mode with DC bias,1,2 show perspective for sub pT-level vectorial magnetic sensors at roomtemperature
Summary
The orthogonal fluxgate sensors based on magnetic microwires, when operated in fundamental mode with DC bias,1,2 show perspective for sub pT-level vectorial magnetic sensors at roomtemperature. The noise reduction was achieved by introducing a JFET input stage, embedded directly to the sensor head, allowing for high common-mode rejection and negligible loading of the resonant circuit. √ able to √achieve about 0.8 pT/ Hz noise density at 1 Hz and 0.8 pT/ Hz noise floor with an open-loop operated magnetometer.5 The electronic unit consisted of a multichannel DDS, a stable current source for magnetic wire excitation8 and two independent pickup preamplifiers and demodulators - see Fig. 1c.
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