GB1143243A - The testing of cables - Google Patents

Abstract

1,143,243. Photo-electric detection of foreign bodies in cable insulation. SIEMENSSCHUCKERTWERKE A.G. June 20, 1966 [June 18, 1965; Aug.23, 1965; Oct.28, 1965], No.27558/66. Heading G1A. Foreign bodies in the plastics insulation of an electric cable are detected by their attenuating affect upon a beam of radiation directed through the insulation. The beam may also be used to make simultaneous measurement of the diameter and eccentricity of the cable and the surface quality. Infrared radiation from a laser 12 is intermittently passed by chopper 14 to a beam splitting mirror 15, to provide two beams of radiation which are directed by mirrors 16 and 12 through the cable, moving longitudinally, to be received by detectors 23 and 25. The mirrors 16 and 19 are oscillated to provide a scan across the diameter of the cable and at the same time, but at a lower frequency, are moved back and forth through a 45 degree arc about the cable so as to give a complete scan of the whole cross-section of the cable. A sharp fluctuation in either of the detector signals whilst the beams are scanning the insulation indicator a foreign body, which may initiate marking of the cable. From the change in the level of the signals as the beams cross the boundary of the insulation and the core the width of the cable insulation 2 and core 1 may be determined. A further detector 27 monitors the alternating laser radiation reflected off the surface of the insulation and continuous radiation emitted by the cable to thereby indicate cable surface quality and temperature. Interference by ambient radiation is avoided by filters. By comparing the signals from detectors 25 and 23, effects due to variation in laser sensitivity are avoided.