Differential to single-ended conversion circuit for a magnetic wheel speed sensor

An apparatus for developing a series of voltage pulses that are developed during rotation of a wheel comprising;

• a magnetic sensor associated with said wheel and having a pick-up coil with first and second coil outputs and means for causing an alternating differential voltage to be generated in said pick-up coil when said wheel rotates relative to said sensor;
• an input circuit including first and second input lines connected respectively to said first and second coil outputs of the pick-up coil for receiving said differential voltage;
• rectification means coupled to said first and second input lines and having first and second rectified outputs, said rectification means providing full wave rectification of said differential voltage on said first and second input lines respectively as said first and second rectified outputs;
• a difference amplifier having a positive input coupled to the first rectified out, put and a negative input coupled to the second rectified output and having an output for producing a single-ended voltage output in response to said inputs;
• and
• an adaptive threshold circuit coupled to the output of said difference amplifier for producing said series of voltage pulses in response to the single-ended voltage output.

A method for converting a differential voltage produced by a sensor in response to rotation of a wheel to a single-ended voltage, comprising:

• generating said differential voltage in response to the rotation of said wheel;
• receiving said differential voltage with first and second input lines of an input circuit;
• rectifying the differential voltage received from said first and second input lines and producing first and second rectified outputs;
• buffering said first and second rectified outputs of said differential voltage;
• measuring the difference between said first and second rectified outputs of said differential voltage to produce a single-ended voltage;
• and
• processing said single-ended voltage to obtain rotational speed information.