GB1371835A - Transducer apparatus - Google Patents

Abstract

1371835 Variable capacitor displacement transducers GEORGE SALTER & CO Ltd 7 Aug 1973 [10 Aug 1972] 37312/72 Heading G1N [Also in Division H1] A displacement transducer includes a variable capacitor formed of a fixed electrode 15, Fig. 1, and a slidable electrode 12 which can move within an insulating guide tube 14 so as to overlap a tapered portion 16 of the fixed electrode. The slidable electrode is connected to a probe 11 so that the displacement to be measured by the probe varies the overlap of the electrodes and hence varies their capacitance. An oscillator circuit 39 changes its frequency as the capacitance varies, and the taper of electrode portion 16 is chosen to give a linear relationship between frequency and displacement. A set of metal loops 46, Fig. 3, is provided which are mounted on the outer casing of the transducer and which are electrically connected thereby to the fixed electrode. By use of adjusting screws 50 the relationship between capacitance and displacement can be finely adjusted. An alternative fine adjustment may be provided by a layer of conductive paint (not shown) on the outside of the guide tube, this paint being selectively removed to give the required adjustment. The output frequency may be digitally displayed.