Patent ID: 7614878

Claim:
A magnetostrictive ultrasonic dental scaler comprising: an oscillator adapted to provide electrical signals including a current and a voltage signal; a handpiece having a tool tip which vibrates in response to the electrical signals supplied to the handpiece; and a control circuit comprising: a phase detector adapted to detect phase between current and voltage signals and to generate a phase detection signal as a function of the phase; a digital signal processor operatively connected to the phase detector, the digital signal processor configured to process the phase detection signal through a digital loop filter to generate an error signal, wherein the digital signal processor is further configured to vectorially subtract a known vector component caused by static inductance of the handpiece to obtain a frequency motional feedback signal reflective of actual motion; and a voltage controlled oscillator operatively connected to the digital signal processor, wherein the digital signal processor outputs a voltage control signal as a function of the error signal and the frequency motional feedback signal to operate the voltage controlled oscillator which in response thereto adjusts at least one of frequency and amplitude of vibrations of the tool tip.