Detech

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. It is important to keep the detector moving.

A battery of the metal detector activates the transmitter circuit that passes electricity down through a cable in the handle to the transmitter coil. When you sweep the detector above a metal object, the magnetic field penetrates right through it and the magnetic field makes an electric current flow inside the metal object.

This flowing electric current creates another magnetic field all around the object. The magnetic field cuts through the receiver coil. The magnetic field makes electricity flow around the receiver coil and up into the receiver circuit, making a loudspeaker beeps and alerting you you've found something.