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AssigneeTexas Instruments Incorporated
InventorThomas R. Maher
Estimating the term…
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.
A variable differential transformer system comprising a primary winding and first and second secondary windings interconnected to one another and having a common point therebetween, the primary winding magnetically coupled to the first and second secondary windings to form magnetic loops, a ferromagnetic sensor element movably mounted within the magnetic loops,
In a variable differential transformer system having a primary winding driven by an AC source magnetically coupled to two interconnected secondary windings having a common point therebetween to form magnetic loops and having a ferromagnetic sensor element movably mounted within the magnetic loops, and conditioning circuitry to provide an output signal an AC signal being developed at the common point of the secondary windings which is proportional to the AC drive, comprising the method steps of taking the difference between the wave forms of the two secondary windings to form a differential AC wave, deriving a synchronous demodulation reference wave form from the AC signal at the interconnection of the secondary windings and synchronously demodulating the differential AC wave using the reference wave form derived from the secondary windings to provide an output signal which proportion to the displacement of the sensor element.
In a variable differential transformer system having a primary winding driven by an AC source and magnetically coupled to two interconnected secondary windings having a common point to form magnetic loops and having a ferromagnetic sensor element movably mounted within the magnetic loops, the AC drive causing AC wave forms in the secondary windings dependent upon the position of the sensor element wherein an AC signal is developed at the common point of the secondary windings which is proportional to the AC drive developing an AC offset temperature error correction wave from the AC signal at the common point of the secondary windings and adding the AC correction wave to the AC wave forms of the secondary windings to provide correction for non-zero AC wave forms of the secondary windings occurring when the sensor element is at a selected neutral position.
Dependencies are inferred from the claim text.