Ultrasonic Thickness Measurement (UTM)

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NDT – Ultrasonic Thickness Measurement (UTM)

Because in ultrasonic pulse-echo testing the time of travel of the pulse to a reflector is measured and displayed, it is a very simple adaptation to use this measurement as a thickness gauge. Low-cost small hand-held instruments are available, and the usual read-out is a digital display rather than an oscilloscope screen. Such thickness gauges require either calibration or a knowledge of the ultrasonic velocity in the material under test.

One of the most basic ultrasonic methods applied is using a zero-degree dual transducer probe to send an ultrasonic beam into a component and receiving the ultrasound energy bounced back from the far wall of the component. Thus, a pulse-echo technique, where the time travelled from the excitation pulse to the first echo signal is used to determine the material thickness. These tests are normally done with probe frequencies ranging from 5 to 10 MHz and can measure thicknesses from 0.7mm to 200mm, and in temperature ranges of -5 ºC to 500 ºC.