Digital compact proton magnetometer was created for measure the geomagnetic fields, including the fields of high heterogeneity. We described design of the instrument and its principles of operation. This device is using implemented digital filtering techniques and Prony method to determine the frequency of the desired signal. The experiments were made in the fields of high heterogeneity and demonstrated the possibility of precise measurements in the fields with a gradient of up to 8 mT / m. The device can be used as a metal detector, as well as for magnetic prospecting, geological studies, etc.
Keywords: nuclear magnetic resonance, free precession, proton magnetometer, geomagnetic field, digital filtering, Prony method