Patent ID: 6072318
Filing Date: 2000-06-06
Classification: G01D

Abstract:
A capacitive device for measuring dimension comprising:a scale equipped with an array of scale electrodes,a transducer able to be displaced parallel to and facing the scale and equipped with m=2 emitting electrodes and n receiving electrodes, said scale electrodes being arranged so when they are facing said transducer, a portion at least of each of said scale electrodes faces one of said m=2 emitting electrodes so that each of said scale electrodes is capacitively coupled to one of said emitting electrodes, and further being arranged so an area of said array of scale electrodes faces said receiving electrodes so that each receiving electrode is capacitively coupled with at least one of said scale electrodes, the coupling between said scale electrodes and said receiving electrodes depending upon the position of the transducer, said scale electrodes forming a substantially parallel arrangement in said area of the array which faces said receiving electrodes, and neighboring electrodes in said area being capacitively coupled to different emitting electrodes, the n receiving electrodes being connected electrically in such a way as to form N groups of mutually connected electrodes, N being an integer greater than or equal to two,a generator generating m=2 emission signals in phase opposition on the emitting electrodes,processing means determining with the aid of the relative values of N measuring signals received on the N groups of receiving electrodes a numerical result representing the position of the transducer along the scale, wherein said processing means comprises a primary counting device that provides the high order bits of the numerical result with the aid of a first algorithm and a secondary precision device providing the low order bits of the numerical result with the aid of a second algorithm, and the N measuring signals form a system in which the phase progresses regularly by .lambda./N from one measuring signal to another.