Electrostatic position-measuring transducer
First Claim
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1. A transducer having a plurality of measurement cycles comprising:
- a. two relatively movable elements, each said element having a surface positiond in spaced opposition to a surface of the other element;
b. two sets of first electrodes fixed on the surface of one of said elements, each first electrode having a base portion and a finger portion extending from said base portion in a direction transverse to the path of relative movement of said elements, the finger portions of each set of first electrodes being uniformly spaced one measurement cycle apart, and the finger portions of one set of first electrodes being interdigitated at one-half cycle spacing with the finger portions of the other set of first electrodes;
c. two sets of second electrodes fixed on the surface of the other said elements, each set of second electrodes having finger portions extending in a direction transverse to said path and spaced approximately one cycle apart opposing the finger portions of said sets of first electrodes, the finger portions of one set of second electrodes being uniformly interdigitated with the finger portions of the other set of second electrodes;
d. first and second coupling electrodes fixed on the surface of said other of said elements, said coupling electrodes respectively opposing and capacitively coupling with the base portions of said two sets of first electrodes;
e. means for electrically interconnecting each set of second electrodes, respectively, and for connecting said sets of second electrodes in an external circuit; and
f. means for connecting said first and second coupling electrodes in a external circuit.
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Abstract
Two relatively movable, spaced elements having electrostatically coupled sets of uniformly spaced interdigitated electrodes form a precision, high gain linear or angular position-measuring transducer. Coupling electrodes on one element capacitively couple to portions of the electrodes on the other element so that electrical connections to external excitation and detection circuitry need be made to only one of the two elements. The shape and dimensions of the electrodes can be arranged to reduce or eliminate undesired impedance variations, capacitive coupling and unwanted harmonic coupling wave frequency components.
73 Citations
17 Claims
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1. A transducer having a plurality of measurement cycles comprising:
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a. two relatively movable elements, each said element having a surface positiond in spaced opposition to a surface of the other element; b. two sets of first electrodes fixed on the surface of one of said elements, each first electrode having a base portion and a finger portion extending from said base portion in a direction transverse to the path of relative movement of said elements, the finger portions of each set of first electrodes being uniformly spaced one measurement cycle apart, and the finger portions of one set of first electrodes being interdigitated at one-half cycle spacing with the finger portions of the other set of first electrodes; c. two sets of second electrodes fixed on the surface of the other said elements, each set of second electrodes having finger portions extending in a direction transverse to said path and spaced approximately one cycle apart opposing the finger portions of said sets of first electrodes, the finger portions of one set of second electrodes being uniformly interdigitated with the finger portions of the other set of second electrodes; d. first and second coupling electrodes fixed on the surface of said other of said elements, said coupling electrodes respectively opposing and capacitively coupling with the base portions of said two sets of first electrodes; e. means for electrically interconnecting each set of second electrodes, respectively, and for connecting said sets of second electrodes in an external circuit; and f. means for connecting said first and second coupling electrodes in a external circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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Specification