The frequency difference translator: An improvement in airborne techniques for measuring the Earth's total magnetic field gradient

Improvements in Airborne techniques for the measurement of the Earth's total magnetic field gradient using optically pumped magnetometers are discussed. These techniques involve fast and accurate measurements of small frequency differences and are applicable to a large class of transducers which have for an output a frequency varying with the input variable. Description and design details are given of a newly developed analog instrument which allows a continuous read-out of frequency difference with a resolution of better than 0.01 Hz.