APPARATUS FOR MEASURING ELECTRICAL RESISTANCE OF ROCKS BY THE AMPLITUDE METHOD DURING GEOPHYSICAL MINERAL PROSPECTING

摘要

A device for geophysical prospecting using radiotelegraph signals comprises a magnetic field strength sensor and an electric field strength sensor each connected to a selective amplifier. The amplifiers feed a meter measuring the ratio of their output amplitudes, which corresponds to a certain value of rock electric resistance. The device is provided with means for amplifier gain adjustment control in the form of an oscillator whose frequency is equal to that of the radio transmitting station used for prospecting. The oscillator signal passes through the amplifiers during spacing intervals between radiotelegraph signals of the transmitting station. The amplifiers output stages comprise elements for comparing the voltage of the amplified signal with that of a reference signal. A drift of the amplifier gain will change the output of the comparison elements and the automatic gain control system will adjust the gain of the amplifiers.