Patent ID: 6674279
Filing Date: 2004-01-06
Classification: G01D,G01P

Abstract:
A variable attenuation circuit for adaptively attenuating an alternating differential voltage produced from a magnetic sensor in response to rotation of a wheel, comprising:an input circuit for receiving an input alternating differential voltage from a magnetic sensor via first and second input lines, said input circuit including an RC filter coupled to said first and second input lines for attenuating high frequency signals; a voltage to current converter circuit for converting the input alternating differential voltage to a differential current signal, wherein the voltage to current converter circuit has an input coupled to the input circuit, and the input has a constant input impedance; variable attenuation circuitry for selectively attenuating said differential current signal; a current to voltage converter circuit for converting the attenuated differential current to a voltage signal; a comparator for comparing the voltage signal to a threshold: an initial threshold circuit for setting an initial threshold for a comparison by the comparator, wherein the initial threshold circuit generates an initial threshold that varies proportional to internal resistance of the current to voltage converter circuit; a controller for controlling when the initial threshold voltage will be applied as an input to the comparator; and an output for providing the output voltage within a preferred voltage range.