GB1464973A - Capacitive wire gauge - Google Patents

Abstract

1464973 Monitoring cross-section of wires electrically ADE CORP 27 Feb 1974 [15 March 1973] 8942/74 Heading G1N In an arrangement for gauging the crosssectional configuration of an electrically conductive wire W by positioning the wire W within a tubular sensing electrode 4 and monitoring the capacitance therebetween a conductive guard 8 is provided to mitigate the effects of stray capacitance existing in the environment. The sensing electrode 4 together with end electrodes 6, for reducing fringe capacitance field effects, are mounted on a quartz tube, Fig. 1 (not shown) and together with guard 8 are connected to A.C. supply 20 via diode circuits 16, 14 whereby the same instantaneous potential is applied thereto. In order to monitor the capacitance a balancing capacitor 18 of capacitance equal to that which would exist between electrode 4 and wire W when the latter is of the required cross-section is employed. If when the wire to be tested is positioned within or passes through the electrode 4 varies from this crosssection so that the capacitance between it and electrode 4 changes charge is built up at the junctions 15. This charge is conducted to ground through a pair of low pass filters 32, 36 and 34, 38 and D.C. current meters 26, 28. The average current through the meters gives an indication of the difference in capacitance between balancing capacitor 18 and sensing electrode 4 and wire W and hence the cross-sectional configuration of the wire W. Only one meter may be used and a linearizing circuit may be provided at the meter inputs. A grounded shield 10 may also be provided, the diode circuit 14 and balancing capacitor 18 being located within the guard 8 and the remaining components within shield 10 so that they are not affected by stray capacitances. Alternatively the junctions 15 may be connected by shielded cables to the meters &c. positioned at a remote location.