|$ 195||$ 125||$500||$ 1,750|
|Trimble GPS||$ 65||$300||$ 1,000|
|Antenna Mount||$ 15||$60||$ 225|
The EM61 Mark II, one of the newer 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.
An Archer Field PC is included with the EM-61 for data collection. We suggest renting a GPS with this instrument.
The Geonics EM-61 Mark II 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.