Patent ID: 7362096

Claim:
An apparatus for measuring a return signal of a magnetostrictive sensor that detects a strain; said apparatus comprising: a magnetostrictive sensor ( 20 ) for generating a return signal in response to a strain and including noise and a DC signal and one of an in-phase signal and a quadrature signal shifted ninety degrees from said in-phase signal, each proportional to the strain detected by said sensor ( 20 ); a sensor filter ( 22 ) for receiving said return signal from said sensor ( 20 ) for removing said noise and to shift the angle of said quadrature signal by an additional angle to define a final detection angle equaling said additional angle and said ninety degrees; an amplifier mechanism ( 24 ) coupled with said sensor filter ( 22 ) to increase the strength of one of said in-phase signal and said quadrature signal for creating an output which is proportional to said strain. a first demodulator ( 26 ) coupled to said amplifier mechanism ( 24 ) to detect one of said quadrature signal at said final detection angle and said in-phase signal; an excitation source ( 18 ) for providing an excitation output to drive said sensor ( 20 ); a wave generator ( 12 ) for providing an oscillating signal at a predetermined frequency to said excitation source ( 18 ); a reference filter ( 28 ) coupled to said wave generator ( 12 ) to produce a reference output shifted by said final detection angle from said oscillating signal; a reference comparator ( 30 ) coupled with said reference filter ( 28 ) to produce a square wave output shifted from said oscillating signal by said final detection angle for triggering said first demodulator ( 26 ) to detect said quadrature signal at said final detection angle and said in-phase signal; and a processor for producing a corrected output by correlating said DC signal and one of said quadrature and in-phase signals.