Major noise reduction in the eddy-current sensor for DC and low-frequency magnetic fields

A major improvement in the sensitivity of an eddy-current sensor is described. This was achieved as a result of internal noise reduction by a supplementary heat treatment of the ferromagnetic core. Its present sensitivity of 0.1 nT and its simple construction make this eddy-current magnetometer a real competitor with other similar devices, e.g., the flux-gate magnetometer.