PURPOSE: To grasp defect characteristic exactly and quantitatively by extracting feature quantity set in advance from a defect detection signal of a magnet sensor array and detecting defect position.
CONSTITUTION: A detected body 30 is magnetized by a direct current electric magnet 10 and magnetic flux leaks from a defect part, which is detected by a magnetic sensor array 21 and the defect detection signal is amplified with an n channel type amplifier 50. A length meter 60 generates a relative position signals of the detected body 30, the electric magnet 10 and the array 21. The defect detection signal and the relative position signal are digitized respectively by an A/D converter 70 and input in a central processing unit 80. The unit 80 detects the defect position from the relative position signal, From the defect detection signal, maximum and minimum values and their signal wave shaped as the feature quantity are extracted and from the maximum and the minimum values, defect depth is presumed from the zero cross point of the signal wave shape, defect size is presumed. In this way, the defect characteristic of the detected body 30 is grasped exactly and quantitatively.
OGAWA SHIGEKI
KUWANO HIROKI
Next Patent: JPS5172787