In order to detect internal discontinuity in the material, ultrasonic pulse-waves are introduced. The sound waves generated by an ultrasound transducer are launched into the material being tested. As the sound travels through the material, reflections or echoes occur at the back surface. Any internal discontinuity will reflect the sound wave and generate a signal into the receiver. The time lags of the echoes are measured in order to determine the thickness of the material and the distance to the discontinuity in the product.
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