Signal conditioning circuit for L/R VDT sensors
AssigneeUnited Technologies Corporation
InventorGary A. McCorkle
Life of this patent
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Abstract
A highly accurate signal conditioning circuit for use with a linear/rotary variable differential transformer (L/R VDT) operating in a unipolar mode is disclosed. The circuit may be utilized for ratiometric comparison of L/R VDT primary coil peak excitation and L/R VDT secondary coil peak response. Unique peak detectors are used for detecting both primary and secondary peak values. The circuit may include an oscillator having R and C elements in a tank circuit which also includes the L/R VDT primary coil. Offset errors may be determined externally by providing for a momentary shutdown of the oscillator to permit the measurement of DC components to the signal conditioner and excitation DC outputs, by external means.
Claims4
Signal conditioning circuitry for providing an output signal indicative of L/R VDT primary coil excitation waveform voltage amplitude and for providing an output signal indicative of the voltage across a selected one of the L/R VDT's secondary coils and therefore indicative of L/R VDT displacement on one side of the null only, comprising:
- a first linear slope peak detector, responsive to a present rectified signal value of the primary coil excitation voltage amplitude for comparing said primary's present rectified signal value to a stored first peak detector output signal indicative of the peak amplitude of a past rectified signal value of said primary excitation and for changing said stored first peak detector output signal value to correspond to and be indicative of said present primary rectified signal value;
- and
- a second linear slope peak detector responsive to a present rectified signal value of the selected secondary coil's voltage amplitude for comparing said present secondary rectified signal value to a stored second peak detector output signal indicative of the peak amplitude of a past secondary rectified signal value and for changing said stored second peak detector output signal value to correspond to and be indicative of said present rectified signal value.
A unipolar L/R VDT driver/signal conditioning circuit driven by a unipolar DC source, comprising:
- oscillator means, responsive to a DC source for providing a sine wave output signal for driving the primary coil of the L/R VDT, said oscillator means having a tank circuit having said primary coil as an inductive element;
- first rectifier means, responsive to said sine wave output signal for rectifying said sine wave output signal and providing a first rectified signal indicative of the present magnitude of said sine wave output signal;
- first peak detector means, responsive to said first rectified signal for comparing the peak amplitude of said rectified signal magnitude to a stored first peak detector output signal magnitude indicative of the peak amplitude of a past rectified signal magnitude and for changing said stored output signal magnitude to correspond to and be indicative of said present magnitude;
- second rectifier means, responsive to the secondary output signal of the L/R VDT secondary coil coupled from said primary coil and indicative of the position of the core of the L/R VDT, for rectifying said secondary output signal and providing a second rectified signal indicative of the present position of said core;
- and
- second peak detector means, responsive to said second rectified signal for comparing the peak amplitude of said rectified signal magnitude to a stored second peak detector output signal magnitude indicative of the peak amplitude of a past rectified signal magnitude and for changing said stored output signal magnitude to correspond to and be indicative of said present position.
Dependencies are inferred from the claim text.