ABSTRACTMeasuring systems with a fixed source fed with alternating current at sound frequency are used almost exclusively at the present time for a quick search for conductive zones in an environment with a high specific electrical resistivity. Owing to this fact it is useful to measure in a gradient configuration, i.e. to compare the quantities of the corresponding parameters of the field in two relatively close points oriented in the direction of the assumed change of the field. In this way we can obtain a suppression of the impact of the wider environment, since, in principle, we record the first derivative, i.e. the amount of the change only.The present article points out some possibilities of the application of the system with a fixed source in non‐magnetic environment with arbitrary resistivit