On sounding, the digital SAS 1000 terrameter sends down direct current into the earth subsurface through the pair of steel current electrodes, while the established subsurface potential difference across the subsurface under investigation is measured by the terrameter through the steel potential electrodes.
For each sounding, the terrameter
computes and displays a mean digital value of the apparent resistivity of the subsurface under investigation using the
theory that the measured potential difference as given by [5] and [6] is