GB1312241A - Differential capacitor - Google Patents

Abstract

1312241 Displacement transducers G O NORRIE 29 April 1970 [31 Jan 1969] 5347/69 Heading G1N A differential capacitor for measuring linear or angular displacement comprises two fixed electrodes 11, 12 (Fig. 1) and a pick-up electrode 15 whose coupling with the individual fixed electrode is varied by laterial displacement of it or of a screen Fig. 8, (not shown), the two fixed electrodes 11, 12 co-extending in the direction of movement 14. The fixed electrodes are separated by an obligue gap 13 and the voltage on the pick-up electrode 15, when the plates 11, 12 are connected to an AC supply, is adjusted by additional, fixed, longitudinal plates 18, 23 each with its own AC voltage, coupled to moving electrode 15 via adjustable screws 22, 25. Alternative ways of utilizing the correcting plates 18, 23 are described. The gap may have a zig-zag configuration 60 (Fig. 3) and the fixed plates or, as shown, the moving plate may be duplicated, the two plates 58, 59 being spaced 90 degrees apart relative to the cyclic zig-zag shape. One of the correcting plates may alternatively be a differential capacitor, 52, 53, 54 of the same type, giving a coarse displacement measurement over the complete displacement range. In another embodiment (Fig. 6) the fixed electrodes 100, 101 are formed on the inside of a cylindrical shell 97 co-operating with an axially movable pick-up electrode 96. Similar embodiments for measuring angular displacement are also described.