appareillage des méthodes telluriques

OBS: L'appareillage des méthodes telluriques (...) se compose d'électrodes non-polarisables, digitalisés, de câble et d'un système de chronométrage par radios. La profondeur d'investigation peut être très grande.

OBS: Since the currents cannot be measured directly, it is necessary to measure the potential gradients between electrodes planted on surface or possibly in drill holes (...) non-polarizing electrodes should be used to reduce erratic potentials at the soil contact; lead plates, which are fairly inert chemically, are often employed instead. The electrodes are connected to an amplifier which will drive a strip chart or magnetic tape recorder. If specific frequencies are of interest, various bandpass and reject filters are incorporated in the amplifier section. Also, static potentials between the electrodes, which may be several hundred millivolts, must be balanced out; this is done with a potentiometer, or capacitance input, the latter having a time constant considerably longer than the maximum period to be recorded.