| 摘要 |
PURPOSE:To make it possible to redidly detect an internal flaw at low cost, by injecting an ultrasonic wave in an insulating spacer to be inspected and a flaw free insulating spacer coming to be a and prepared under the same condition as said spacer and comparing the reflected waves from both spacers. CONSTITUTION:The ultrasonic waves oscillated from an ultrasonic oscillator 3 is simultaneously injected in an insulating spacer A and a flow free insulating spacer B for a comparing reference from probes 1, 2. Whereupon, the reflected waves from both spacers A, B are simultaneously received by receivers 4, 5 and the outputs of both receivers 4, 5 are inputted to a differential amplifier 6. When the insulating spacer A to be inspected has no flaw, there is no difference between both reflected wave pulses by the spacer A and the flaw free insulating spacer B for the comparing standard and, therefore, no output is generated in the differential amplifier 6. Contrarily, when spacer A has an internal flaw such as void, a difference is generated between both reflected wave pulses by the amount corresponding to the reflected wave pulse at the void boundary surface and, therefore, output is generated in the differential amplifier 6 and a pulse wave form is displayed on a CRT display 7.
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