Patent ID: 6025711
Filing Date: 2000-02-15
Classification: G01D,G01V

Abstract:
A proximity sensing circuit, comprising:a proximity detector having a coil, said coil having a first end and a second end;an amplifier having a first input, a second input and an output, said coil being connected between said first input and said output of said amplifier;a first source of a first waveform having a first frequency;a second source of a second waveform having a second frequency;means for combining said first and second waveforms to provide a combined waveform, said combining means being connected to said first input of said amplifier;a filter connected to said output of said amplifier to provide a first output signal;an inverter connected to said filter to provide a second output signal; andmeans, connected in signal communication with said coil for determining a distance between a metal object and said coil as a function of said first and second output signals.