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Abstract

Various alternative embodiments of a multi-turn capacitive encoder device are disclosed. The device includes two members that are fixed relative to each other and that include respective capacitive electrodes that are capacitively coupled between the two members. The respective capacitive electrodes on one member act as transmitter electrodes and the respective capacitive electrodes on the other member act as receiver electrodes. One or more modulation members are relatively movable between the two fixed members to alter or modulate the capacitive coupling to correspond to the rotational or angular position of the modulation member(s). At least one of the modulation members is driven using a gear reduction system such that its angular or rotational position corresponds to a plurality of turns of the input shaft of the multi-turn encoder. A plurality of signals that depend on the capacitive coupling are used to determine the rotational or angular position of the modulation member(s) relative to the first two members. The present invention combines the elements outlined above to provide a multiturn encoder including few parts, simple assembly, a small axial dimension, and relatively high resolution and accuracy.

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First Claim