| 摘要 |
PROBLEM TO BE SOLVED: To accurately determine a coat damaged point of an embedded pipe. SOLUTION: While an AC reference signal is transmitted to the embedded pipe 10, a pair of search coils 21, 22, 23, and 24, with their mutual coil axes uniformly directed, are disposed on either side of a right overhead line 11 of the embedded pipe, and these coils are moved on the ground to detect the phase of signals induced in the search coils, thereby measuring the amount of change in the phase. In the event that there is another embedded pipe 12 crossing the embedded pipe, it is determined whether a current is detected due to electrical contact with the embedded pipe. COPYRIGHT: (C)2004,JPO&NCIPI
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