The Ohm Mapper is a capacitively-coupled resistivity system designed to measure subsurface resistivity in areas with high surface resistivity where exploration using traditional galvanically-coupled (DC) resistivity systems is impractical.
The Ohm Mapper consists of an ungrounded dipole transmitter and receiver. The operating principle is relatively simple: an alternating current is capacitively coupled into the earth at a particular frequency by the alternating voltage applied to the transmitting dipole. The resulting AC voltage coupled to the receiver’s dipole is measured. This voltage will be proportional to the resistivity of the earth separating the two dipoles and the current delivered to the transmitter dipole.