Patent ID: 8988070
Filing Date: 2015-03-24
Classification: G01V

Abstract:
1. A pulse-induction type metal detector comprising: (a) a transmitter coil; (b) means to energize said transmitter coil with a current wave form whose trailing edge reverses polarity after crossing zero and returns rapidly to zero, after the portion of said waveform with reversed polarity has reached a predetermined amplitude; (c) a receiver coil; (d) means to amplify and process signals captured by said receiver coil, using at least three signal sampling intervals to derive a first and a second time constant, using signals captured during sampling intervals one and two to derive said first time constant, and using signals captured during sampling intervals two and three to derive said second time constant; (e) means to derive the algebraic difference between said first and second time constants, and (f) means to regulate the amplitude of said reversed-polarity portion of said current wave form, based on the algebraic difference between said first and second time constants.