Patent ID: 6064199
Filing Date: 2000-05-16
Classification: G01B,G01D

Abstract:
Apparatus for detecting passage between a point on a body and a reference position, comprising:a pair of magnetic field sensors disposed laterally along a direction of movement between the body and the reference position;a magnet disposed at the reference position to provide a magnetic field through the body and the pair of magnetic field sensors, the magnitude of the field passing through the body and the pair of sensors being related to the relative position between the point on the body and the reference position, each one of the sensors producing an output signal related to the magnitude of the magnetic field passing such sensor;a differencing circuit fed by the output signal produced by each one of the sensors for producing a difference signal having a peak when the point of the body is positioned between the pair of sensors;a peak detector for detecting the peak in the difference signal and for producing a peak detection signal indicating detection of such peak;a threshold circuit fed by the differencing signal for producing a gating signal when the magnitude of the difference signal exceeds a threshold level;a gate, the gating signal enables the peak detector produced peak detection signal to pass through the gate to an output of the apparatus when the gating signal indicates the magnitude of the difference signal exceeds the threshold such peak detection signal being inhibited from passing through the gate to the output of the apparatus in the absence of such gating signal; anda threshold level adjusting circuit for establishing the threshold level in accordance with the magnitude of the difference signal.