USA as Represented by Secretary of the Navy

Gregory Kaminski

Michael A Deeds

A movable capacitive sensing component and plural stationary capacitive sensing components are similarly constructed and are located together. The movable capacitive sensing component includes two interdigitated electrode elements at least one of which moves in accordance with displacement of an object. The stationary capacitive sensing components includes two interdigitated electrode elements that do not move, and differ from each other in terms of relative displacement between the fixed electrode elements. The movable capacitive sensing component measures a capacitance value. Another capacitance value is estimated, from the capacitance values measured by the stationary capacitive sensing components, for the displacement indicated by the movable capacitive sensing component's measured capacitance value. The actual displacement of the object is found by subtracting the respective capacitance values and converting this result to displacement, or by converting the respective capacitance values to displacement and subtracting the respective displacement values.

Environmentally compensated capacitive sensor

A printed wiring board includes an input conditioner having a plurality of analog dc inputs and a plurality of analog dc outputs; a switching circuit having an analog dc output, the switching circuit being connected to the plurality of analog dc outputs of the input conditioner; a sample and hold converter having an analog dc output, the sample and hold converter being connected to the analog dc output of the switching circuit; an A/D converter having a digital output, the A/D converter being connected to the analog dc output of the sample and hold converter; a microprocessor connected to the digital output of the A/D converter; a timer circuit connected to the microprocessor; a random access memory connected to the microprocessor; and a VME interface connected to the microprocessor. The printed wiring board further comprises an ac multiplexer; a plurality of rms to dc converters connected to the ac multiplexer, the rms to dc converters being connected to the switching circuit; a zero crossing detector connected to the ac multiplexer; a phase detector connected to the zero crossing detector and to the microprocessor; a filter connected to one of the outputs of the zero crossing detector; and a frequency measurement circuit connected to the filter and to the microprocessor.

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Waldorf, MD, United States of America

Gregory Kaminski