| 摘要 |
PURPOSE:To prevent the erroneous judgment caused by a surface--echo by providing a surface-echo-judging-value setting circuit and a surface-echo judging circuit, and setting a defect gate and a defect judging value in response to the height and the position of the surface echo. CONSTITUTION:When the flaw of a body under test 6 is detected, defect gates 38 are set 18 on the entire range of a plate thickness. The obtained defect echo 33 is compared with a judging value 39 in a surface-echo judging circuit 16. When the surface echo is partially high and exceeds the judging value, a surface-echo judged result 36 is made ON. The defect gate 38 is set at the short value with the defect-gate setting circuit 18. When the defect echo 33 obtained with the defect gate 38 is judged with the surface-echo judging circuit 16 again, the echo 33 is smaller than the judging value 39. Therefore, the judged result 36 is made OFF, and the ' defect gate 38 is returned into the original state. Thereafter, the flaw detection is started. When the height of the surface echo is normal, the defect gate 38 does not exceed the surface echo judging value 39. Therefore, the defect gate 38 does not become short. |
