Low power portable DC magnetometer

The authors describe a low-power-consumption, portable DC field magnetometer which employs a relatively new sensor. Power is saved owing to the selection of a thin ferromagnetic amorphous material for the sensor core. In addition, the use of a sensor core excitation current consisting of a square-waveform carrier whose amplitude modulation by another square wave permits on-and-off operation leads to the economic utilization of power in the electronic circuitry. The magnetometer is operated by six type-AA 1.5-V cells connected so as to supply ±4.5 V. The power consumption is 60 mW; two thirds of this is applied to the excitation coils of the sensor. The sensitivity of the magnetometer is 1 nTs for a 0.2-Hz bandwidth and can be increased to 0.1 nTs with a 1-Hz bandwidth by using sensors with relatively thin cores of properly heat-treated MuMetal or Molypermalloy