Excitation efficiency of fluxgate sensors

Among ferromagnetic sensors, fluxgates are the most resistant to field shocks. In order to achieve low perming, the peak amplitude of the fluxgate excitation current must be high. The fluxgate excitation efficiency (Ip-p/Irms) can be increased by judicious tuning. This paper describes a simplified analytical solution for the non-linear fluxgate excitation circuit which is very different to the solution for a free-running tank circuit. The experimental results show a surprising effect: high excitation efficiency is achieved only at certain frequencies.