| 摘要 |
An ultrasonic nondestructive test system is described which includes a noise gate which is capable of immediately removing noise signals from the input signals before they reach the receiver. The system includes a search unit, a transmitter and receiver unit for displaying on a display device the defects or other discontinuities on the workpiece. The noise gate includes a delay line and a coincident circuit. The return signal from the search unit is delayed a predetermined time and compared with the input signal in the coincident circuit to pass only coincident signals after a predetermined time has passed. This is because noise is characteristically a pulse of a short time duration and much less than the return pulse input from the search unit.
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