26
Metal detectors work due to the fact that metal is conductive. Metal detectors create an electromagnetic field, which penetrates the ground.
When the coil senses a change in this field (caused by a metal object) it sends a signal back to the control box which then alerts the operator. Metal detectors react to the size, shape and composition of objects. Typically, the larger the object, the deeper it can be detected.
The
The frequency of a detector is the number of times a signal is transmitted into the ground and received back, per second (measured in Hertz - Hz).