Switched capacitance meter reading device

Communications: electrical – Continuously variable indicating – With particular transmitter

Patent

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Details

364480, 364556, 340870020, G08C 1910

Patent

active

050309501

ABSTRACT:
An apparatus for remotely monitoring the position of a rotatable member, relative to a substrate spaced apart from the rotatable member, as the rotatable member is rotated about an axis of rotation by an axle, including an array of spaced-apart, outer electrodes delimiting a center portion, a center electrode in the center portion and first and second transistors in contact with the center electrode; each outer electrode is in contact with a transistor used to selectively connect an outer electrode to ground; the first transistor, when turned on, supplies current to the center electrode to form a charge to a capacitor formed by the center electrode, rotatable member, and predetermined outer electrode, and the second transistor, when turned on, supplies current proportional to the formed charge to a current-to-voltage converter; a clock is connected to and controls the first and second transistors, turning them on and off so that when one is off and the other is on, in a repetitive cycle; the average voltage output of the current-to-voltage converter is proportional to the capacitance formed by the center electrode, rotatable member, and the predetermined outer electrode and the converter's output is connected to a low-pass filter, the voltage output of the low-pass filter is compared to one or more fixed voltage references by a comparator, which generates an output voltage that reflects the results of the comparison and, a microprocessor scans the output of the comparator, changes the fixed reference to another value if there is more than one, selects the outer electrodes one at a time, and determines the rotational position of the rotatable member.

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