Capacitance sensing system using multiple capacitances to sense rotary motion
AssigneeCambridge Technology, Inc.
InventorBruce E. Rohr
Life of this patent
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Abstract
A capacitance sensing system for sensing the rotary position of a rotating shaft, particularly one having limited rotary motion. The system uses at least four capacitances comprising fixed capacitance plate members, one of which is preferably made of four arcuate segments enclosing the shaft and the other of which is a ring member enclosing the shaft and displaced therefrom along the shaft. A dielectric member is attached to the shaft between the fixed plate members. The capacitance value of the four capacitances change as the shaft rotates in such a manner that the capacitance changes produce an output voltage which represents the rotary position of the shaft, which output voltage is insensitive to radial motions of the shaft.
Claims9
A detection system for determining the angular position of a rotating element, said system comprising
- at least two capacitance means including
- a first capacitance plate member comprising at least four arcuate segments enclosing said rotating element;
- a second capacitive plate ring member enclosing said rotating element and displaced from said first capacitive plate member along the length of said rotating element;
- a dielectric member fixedly mounted on said rotating element between said first and second capacitive plate members so as to form at least a first capacitance having a capacitance value Ca and at least a second capacitance having a capacitance value Cb, said capacitance values varying oppositely, one increasing and the other decreasing as said rotating element rotates;
- and
- measurement circuit means including at least said first and second capacitances and output circuit means responsive at least to the difference between said first and second capacitance values to provide an output representing the angular position of said rotating element.
Dependencies are inferred from the claim text.