Patent ID: 6040692
Filing Date: 2000-03-21
Classification: 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 first and second resistors coupled to said first and second input lines, respectively;a first current sourcing circuit coupled to said first input line for sourcing current to maintain a fixed voltage at said first input line and provide a first current, said first current sourcing circuit including a first plurality of selectable current sourcing branches for attenuating said first current;a second current sourcing circuit coupled to said second input line for sourcing current to maintain a fixed voltage at said second input line and provide a second current, said second current sourcing circuit including a second plurality of selectable current sourcing branches for attenuating said second current;switching circuitry for controlling selection of pairs of said first and second plurality of current sourcing branches so as to provide selectable amounts of current sourcing to attenuate the first and second currents;a controller for adaptively selecting combinations of said current sourcing branches to attenuate the differential first and second currents in said first and second current sourcing circuits as needed to maintain the differential current within a preferred range; andan output for providing a differential output current to achieve rotational speed information about said wheel.