Research on the Orthogonal Fundamental Mode Fluxgate Sensor Circuit

Abstract

Currently, magnetic fluxgate circuits used for magnetic field measurements mostly adopt parallel excitation second harmonic generation. The magnetic fluxgate developed by this method cannot possess both low noise and high bandwidth at the same time. The orthogonal fundamental mode fluxgate is used in this paper: the excitation magnetic field is orthogonal to the magnetic field to be measured, and the external magnetic field is detected by measuring the voltage signal in the pick-up coil. The excitation magnetic field changes with the parallel excitation second harmonic method while the direction of the excitation magnetic field does not change in the orthogonal fundamental mode scheme, which can effectively reduce the influence of Barkhausen noise. The magnetic fluxgate circuit is designed based on the orthogonal fundamental mode scheme and its performance indexes are tested. The range of the magnetic fluxgate is ±100000 nT, the sensitivity is $100~\mu \text{V}$ /nT, the output noise is 8.9 pT/rt(Hz)@1 Hz, and the bandwidth is DC-15 kHz. The orthogonal fundamental mode fluxgate improves the bandwidth performance while enabling low-noise magnetic field measurements in practical applications.

Keywords

• Low noise fluxgate
• orthogonal fundamental mode
• Barkhausen noise