Noise in the tuned fluxgate

Abstract

The characteristic equation of a tuned secondary fluxgate sensor is solved analytically using the Senson-Hannaford approximation of a pure second harmonic load current. The gain and bandwidth of the parametric amplification is expressed in terms of the sensor geometry, the core magnetic properties and the excitation level, and they agree with the measurements. The output signal phase and the stability criterion are derived, and the noise properties of the tuned sensor are discussed. Measurements of the signal-to-noise ratio of tuned and untuned sensors show that sensor tuning enhances the noise.