| 摘要 |
PROBLEM TO BE SOLVED: To reduce the influence of a disturbance noise and grounding resistance between a detection electrode and the ground surface so as to enhance precision, in a paint film damaged position detecting method for a steel pipe using correlation processing relating to voltage impression for pseudo-random signals and detected signals. SOLUTION: A peak value of a correlation result is detected (15) by storing a detected digital data array (11) comprising detected signals converted in order by an AC converter 10 by an amount corresponding to one cycle of pseudo- random signals, and by conducting parallelly with a high speed correlation processings (13, 14) for finding product-sum calculation in all the corresponding positions, while shifting (16) the corresponding of two data array elements between a reference digital data array (12) having a pattern the same at preliminarily prepared pseudo-random signals and the detected digital data array (11) by one cycle of the false random signals.
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