The EM61 Mark II, one of the newest instruments from GEONICS, is a time-domain metal detector which detects both ferrous and non-ferrous metals. A powerful transmitter generates a pulsed primary magnetic field in the earth, which induces eddy currents in nearby metallic objects. The eddy current decay produces a secondary magnetic field measured by the receiver coil.
Detects a single 200-litre (55 gal) drum at a depth of over 3 meters beneath the instrument, yet is relatively insensitive to nearby cultural interference, such as fences, buildings and power lines
Response is a single, sharply defined peak, greatly facilitating quick and accurate location of the target
Depth of the target can usually be estimated from the width of the response