Performance of U-shaped Core Orthogonal Fluxgate Magnetometer

Abstract

We proposed a new method for decreasing transformer effect from excitation current to sense coil in an orthogonal fluxgate operated in the fundamental mode. The point of this method is to use a U-shaped magnetic wire core on each branch of which two identical sense coils are wound and to arrange the two coils in counter series. As a result, induced voltage is reduced by a factor of 1/3 from that observed with a single wire core. The levels of the magnetic noise and drift are reduced substantially. For example, the noise level at 10 Hz decreased from 0.5 n T/√Hz to 0.08 n T/√Hz for small excitation current 4.1 m A with 5.8 m A dc bias. The driftof the sensors is confined within the range 0.5 n T for the U-shaped F G and 1 n T for the single core F G.