Variable reactance position detector
AssigneeGSI Lumonics Corporation
InventorMichael B. Nussbaum
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Abstract
A position sensor comprises a capacitive transducer and an inductor connected in series with the transducer. The transducer is a differential capacitor whose total admittance is essentially independent of changes in the sensed position. The total capacitance and inductance resonate at the fundamental frequency of a generator that provides a drive voltage and the resulting voltage across the sensor is thus substantially greater than the drive voltage. This increases the current through the transducer, and consequently increases the sensitivity of the sensor.
Claims7
A position sensor for monitoring the position of an object, said sensor comprising:
- A. a transducer comprising first and second electrically reactive sensing elements whose relative impedances vary inversely as a function of the position of the object, the sum of the the admittances of said sensing elements being essentially invariant;
- B. a reactive element that resonates with the parallel combination of said sensing elements at a resonant frequency;
- C. a drive circuit;
- 1. providing an electrical output current at said resonant frequency, and;
- 2. connected to pass the output current through the series combination of the reactive element and said parallel combination;
- and
- D. an output circuit responsive to the relative currents passing through the sensing elements.
Dependencies are inferred from the claim text.