Patent ID: 8295025

Claim:
A controller for driving an excitation current through an excitation coil of a magnetostrictive ultrasonic device, the controller comprising: A source of a periodic signal having a controllable frequency; a driver responsive to said periodic signal and configured to cause an excitation current to flow through the excitation coil commensurate with said periodic signal; a current sensor in series with the excitation coil, operative to output a current-sense signal proportional to the current flowing through the excitation coil; A high pass filter, receptive to said current sense signal and operative to output a high-pass filtered version thereof; a first peak detector, receptive to said current sense signal and operative to output a first peak signal, proportional to the periodic peak value thereof; a second peak detector, receptive to said high-pass filtered version and operative to output a second peak signal, proportional to the periodic peak value thereof; and a digital processor, operative— to receive said first and second peak signals and to periodically sample them, obtaining corresponding sample function values, and— to control the frequency of said periodic signal so that each of said sample function values differs from a corresponding given optimum function value by less than a given threshold value.