Patent ID: 8089270

Claim:
Apparatus for detecting a passing magnetic article and providing a detector output signal indicative of the passing magnetic article comprising: a magnetic field transducer responsive to a magnetic field associated with the magnetic article for generating a magnetic field signal proportional to the magnetic field; a peak detector responsive to the magnetic field signal for generating a tracking signal that tracks positive and negative peaks of the magnetic field signal and for providing the detector output signal that transitions from a first signal level to a second signal level when the magnetic field signal differs from the tracking signal by more than a threshold offset amount; a peak-to-peak signal level detector responsive to the magnetic field signal for detecting a peak-to-peak signal level of the magnetic field signal; a speed determination circuit for providing a speed signal indicative of a speed of rotation of the magnetic article; and a threshold offset determination circuit responsive to the peak-to-peak signal level of the magnetic field signal and to the speed signal for establishing the threshold offset amount.