| 摘要 |
PROBLEM TO BE SOLVED: To improve reliability of inspection using ultrasonic waves. SOLUTION: A monitoring gate setting circuit 7 setting a monitoring gate which monitors a signal relating to a multiple reflection echo obtained from a heat resistant resin sheet 2 is installed in an abnormality detector 6. A monitoring gate is superposed on each receiving signal given to the monitoring gate setting circuit 7. A passing signal which has passed the monitoring gate is outputted to a switch 8 which switches the connection of an output terminal of the monitoring gate setting circuit 7 with the positive terminal of a first comparator 21 or the negative terminal of a second comparator 22 or the positive terminal of a third comparator 23. A first threshold value voltage, a second threshold value voltage and a third threshold value voltage are applied to the negative terminal of the first comparator 21, the positive terminal of the second comparator 22 and the negative terminal of the third comparator 23, respectively. When a voltage of the positive terminal is higher than a voltage of the negative terminal, each of the comparators 21-23 starts an alarm unit 25, which generates an alarm.
|
