GB638732A - Improvements in and relating to the measurement of the thickness of electrically insulating material - Google Patents

Abstract

638,732. Locating conductors. BRITISH INSULATED CALLENDER'S CABLES, Ltd., POOLE, J. H., LEWIS, S. E., and TAYLOR, R. C. April 8, 1948, Nos. 9897/48, 11411/48 and 7227/49. [Class 37] [Also in Group XXXVIII] Apparatus for measuring the thickness of insulating material, comprises two conductors spaced apart by the material to be measured, and placed in the gap of a magnetic circuit which is coupled with a coil, so that flux obtained by energizing the coil produces in the loop consisting of the two conductors an E.M.F. whose magnitude is dependent on the width of the loop ; alternatively, the flux may be produced by supplying current to the loop, and the E.M.F. in the coupled coil measured. As shown, Fig. 1, for measuring the eccentricity of the conductor 7 of an insulated cable 6, two external conductors 8, 9 located in insulating blocks 10, 11 are used, held against the cable by springs 12, 13. The E.M.F's produced-in the two loops formed by inner conductor 7 with each outer conductor 8, 9 are compared in a measuring circuit (Fig. 2, not shown), and the difference indicates the eccentricity of the cable conductor 7. Alternatively, each loop may be fed with A.C. in opposition, and the E.M.F. induced in the coil 2 measured. For determining the eccentricity in two perpendicular directions, the apparatus may be duplicated, Fig. 4, with the gauging conductors 8, 9 located approximately symmetrical to both magnetic fields. A.C. in phase quadrature is supplied to each pair of loops 7, 8a, 9a and 7, 8b, 9b, (Fig. 5), from two oscillators Oa, Ob, the unbalance voltage being collected by coupling coils 2a, 2b and added together to show the overall eccentricities on a meter 19. In a further embodiment, Fig. 6, the cable 22 is located by an adjustable guide member 24, so that the E.M.F. induced in the loop comprising a fixed conductor 23 and the cable conductor 21 by energizing a coupling coil 27 is indicative of the position of the cable conductor 21 in a plane parallel to the pole faces.