Metal detectors work by transmitting an electromagnetic field from the search coil into the ground.
Any metal objects (targets) within the electromagnetic field will become energized and retransmit an electromagnetic field of their own. The detector’s search coil receives the retransmitted field and alerts the user by producing a target response.
Minelab metal detectors are capable of discriminating between different target types and can be set to ignore unwanted targets.
While metal detectors are generally highly efficient in terms of depth of response. A deep metal detector may occasionally be needed for areas with very deep sediment and / or long history of settlement.