| 摘要 |
An electrically conducting lead for use in locating at ground level the presence of a joint or other discontinuity in an underground pipeline 13, comprises a loop of cable to extend along the pipeline 13 past the joint (14, 15, figure 1) to be detected. The loop comprises a length of single cable 8 and a length of co-axial cable 9. The single cable 8 is, in use, connected to the output of a signal generator and receiver and the inner core 10 of the coaxial cable 9 is, in use, connected to the input of the signal generator and receiver. The outer part of cable 9 serves as a screen for the return signal and is, in use, connected to ground at its near end. The loop may be housed in a flexible protective sleeve 12 of insulating material. <IMAGE> |
