Importance

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Abstract

A variable differential transformer system (10), both linear and rotary (L/RVDT) includes a primary coil (12) drive by a primary drive (20) having a triangle wave generator whose frequency is set by an external frequency control (R.sub.osc and C.sub.osc) which includes compensation for gain temperature error. Secondary coils (14, 16) have a common connection for balanced loading with an input stage arrangement (R7, R8, R9, R10) providing low common mode range and a way to differentiate between normal operation and coil faults detected by a fault detection network (28). Synchronous demodulation (22) extracts both magnitude and direction from the secondary coil signals. Electronic calibration (24) is shown which compensates for sensor offset and gain. Sensor offset calibration is accomplished by adding a percentage of the synchronous demodulation reference wave form to the differential secondary signal. A filter network (26) averages the synchronous demodulated signal in order to extract the DC component of the wave form. A dual function output amplifier (30) provides a means of reporting the analog sensor output and the occurrence of a sensing element fault with sufficient drive current to interface with external loads. A variable rotary core assembly (18) and a variable linear core assembly (18') are shown which allow axial adjustment of the core relative to the coils to provide offset temperature error compensation.

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