The Residence Times Difference (RTD) Ring Fluxgate Magnetometer

The ring geometry is the most studied architecture of the fluxgate magnetometer thanks to its low noise and the possibility of multi-directional sensing. In this paper the ring geometry is studied with the Residence Times Difference (RTD) readout to exploit the advantages of both geometry and readout. The flexibility of the CoFeSiB micro-wire core has allowed for the realization of this geometry by bending a simple rod fluxgate to form the ring structure. A sensitivity comparison is presented between the ring's center and the outer region. In addition, a comparison in term of sensitivity and noise is presented here to benchmark the optimal sensing position between the centre in the closed ring and the gap in the opened ring. The results clearly show that the RTD ring fluxgate here proposed preserves the typical low noise of the closed core, but it also modifies the optimal sensing direction, which is no more the direction of the core, but the perpendicular axis at the centre of the plane of the ring. In this paper we, therefore, investigate the cross-field effect that, conventionally, is regarded as an unwanted feature to be mitigated. This is of great importance for the use of the microwire core ring flux gate in view of potential 'wearable' applications of this sensor.