| 摘要 |
PURPOSE:To contrive improved evaluation accuracy of defect detection, by supplying magnetic exciting currents of different frequencies to a sensor coil and correcting by the specified one detecting signal the other detecting signal. CONSTITUTION:The primary coil of a detector 14 is excited magnetically by HF and LF currents from HF and LF oscillators 11, 12 and change of eddy- current due to a flaw of the specimen is detected by the secondary coil of the detector 14, and detected for their waves by synchronous detector 21 and 22 which are synchronized with the generators 11, 12 respectively. Further, by a multiplier 23 and a detecting output corresponding to a distance between detector 14 by a detecting signal of HF and specimen subject to flaw detection, a detecting output of the detecting signal of LF is corrected and thus, change of eddy current immune from change of distance between the detector 14 and the specimen is determined for improvement of evaluation accuracy of flaw detection. |
