A portable low noise low frequency three-axis search coil magnetometer

The design of a three-axis search coil magnetometer is described which has noise characteristics that are close to or better than comparable superconductor magnetometers over the 20Hz to 2000Hz range. The sensor coils and electronic conditioning equipment weighs less than 14Kg and can be transported by one person in a 46cm × 46cm × 15cm instrumentation case. The sensing elements consist of three concentric circular coils. The coil signals are processed to provide two outputs: one proportional to frequency, one independent of frequency. Laboratory tests verified that predicted and actual performance agreed quite closely.