| 摘要 |
PURPOSE:To detect the back and front positions of a thick object, by providing a reflective body comprising a ferrite magnet on one surface of an article to be detected and calculating the contact position of the reflective body from the reflected echo of said reflective body. CONSTITUTION:A reflective body 3 made of a ferrite magnet is mounted on the back surface 1a of a thick steel plate 1 being an object to be detected through a contact medium such as oil or glycerine, and the front surface 1b of the thick steel plate 1 is scanned by an ultrasonic vertical probe 2. When the surface 1b of the thick steel plate 1 is scanned left and right by the ultrasonic vertical probe 2, a point where the bottom surface echo BR of the reflective body 3 comes to a peak is obtained after the echo B from the back surface of the thick steel plate 1. That is, the bottom surface echo BR becomes max. at a point where the reflective body 3 has been mounted. Therefore, it can be certainly known that the position of the probe 2 at that time is that corresponding to the reflective body 3.
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