| 摘要 |
PURPOSE:To distinguish a flaw signal from a noise signal accurately by arranging two detecting parts before and behind in the relative moving direction to a material to be examined and detecting change directions and points of time of detected signal waveforms obtained from these detecting parts. CONSTITUTION:A probe 6 provided with three detecting coils 9 and 10 is so constituted that it can be moved relatively to the material to be examined. When a flaw existing on the material to be examined comes, the probe 6 generates a flaw detection signal 36, and this signal 36 has a rise section 36a, a top part 36b, a fall section 36c, a valley part 36d, and a rerise section 36e. It is discriminated in a waveform collating circuit whether this output signal meets preliminarily determined set conditions or not. Simultaneously, it is discriminated whether a time t1 of the rise section 36a, a time t2 of the fall section, and a time t3 of the rerise section are matched to preliminarily determined prescribed times or not. These discriminating means are provided to detect correctly the flaw signal in distinction from confusing signals even if they have magnifications and periods approximating those of the flaw signal. |
