METHOD AND DEVICE FOR DETECTING DAMAGED POSITION OF PAINT FILM OF BURIED STEEL PIPE

摘要

PROBLEM TO BE SOLVED: To provide a method for improving the S/N ratio of a signal and for accurately and positively detecting the damaged position of a paint film and a device suited for executing the method. ;SOLUTION: An M-series modulation signal being subjected to phase modulation of a multiplier 3 is amplified by a power amplifier 3 and is applied, as voltage, between a buried steel pipe 1 and a grounded electrode 4. In this state, a prospecting machine 6 is moved on a ground surface along the pipe-axis direction of the buried steel pipe. A pair of axle electrodes 6a and 6b are provided in forward and backward directions in the prospecting machine 6 and detect the potential of the ground surface in contact. A mutual correlation with the potential difference of the ground being detected is obtained with a signal with the same pattern as the output of the multiplier 3 from a multiplier 17 as a reference signal. Then, the damaged position of the paint film of the buried steel pipe is detected from the change in the representative value due to the move of the prospecting machine 6 with the mutually correlated peak value as a representative value.;COPYRIGHT: (C)1999,JPO