Patent ID: 7701204

Claim:
In a pulse-induction-type metal detector having a transmitter coil, a receiver coil, output means and coil-excitation means providing a coil pulse, the improvement comprising: (a) means to distinguish in signal received by said receiver coil, between signal components that are caused by mutual inductance between said transmitter and receiver coils and the signal components caused by eddy currents in a target; (b) compensating means to reduce said signal components caused by mutual inductance between said transmitter and receiver coils to essentially zero; (c) means to deactivate said compensating means while the signal intercepted by said receiver coil, after said coil pulse exceeds a predetermined amplitude, and (d) means to provide an unambiguous indication of the ferrous or non-ferrous nature of the target, based on the polarity of said signal component caused by mutual inductance between said transmitter and receiver coils, while said compensating means is deactivated.