| 摘要 |
PROBLEM TO BE SOLVED: To provide a method and a detector for detecting a paint film defective position for a buried paint-coated steel pipe capable of restraining an influence of a low frequency region limitation in signal propagation to detect a signal stably and highly sensitively. SOLUTION: The signal of an M line signal generator 10 is amplified by an electric power amplifier 3 to be impressed between the buried steel pipe 1 and an installed electrode. A probe 6 is made to travel on a ground surface along a longitudinal direction of the buried steel pipe 1 to detect a potential difference between wheel electrodes 6a, 6b. A reference signal of the pattern same to that of a signal applied with a frequency band limitation equivalent to that of the signal of the M line signal generator 10 received in a propagation route is output from a reference signal generator 11'. A mutual correlation of the potential differences between wheel electrodes 6a, 6b and the reference signal is computed by a correlation processing part, a peak value therein is adopted as a representative value of the potential differences, and computing processing is performed using the representative value. An S/N ratio is remarkably improved by this manner. COPYRIGHT: (C)2005,JPO&NCIPI
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