- An electrode device with multiple current electrodes configured in several different ways to produce several different responses. A typical array consists of a central electrode emitting survey current, with multiple guard electrodes above and below it. Current is sent between different guard electrodes to achieve greater or less focusing. The greater the focusing, the greater the depth of investigation. About five basic measurements are obtained in this way. This hardware focusing may be further improved by software focusing, in which the signals from the basic measurements are superimposed mathematically to ensure proper focusing in a wide range of conditions.
- electrode resistivity