Vector fluxgate magnetometer for high operation temperatures up to 250 °C

Vector fluxgate sensors have to operate at high temperatures for various applications. In drilling processes with greater drilling depths fluxgate sensors and corresponding electronic circuits are required to operate in a high temperature environment of up to 250 °C for a prolonged period of time. We present an accordant three-axis vector fluxgate system consisting of three single Vacquier-type fluxgate sensors and the signal processing electronics. The high temperature stability is achieved by selecting appropriate materials, mainly for the fluxgate core. The electronic circuits are built using commercially available silicon-on-insulator processed active and appropriate passive devices. The sensor system was characterized in a high temperature environment (up to 250 °C) by evaluating sensitivity, noise, crosstalk, excitation current amplitude and bandwidth. We found a system sensitivity of 28 kV/T (at room temperature) with an acceptably low temperature coefficient of 6.8 × 10−4 °C−1 and a room temperature flux density noise of 43 pT/(Hz)1/2 at 1 kHz. At 250 °C the noise values decrease by approximately 50%.