Inspectioneering Journal

Advances in Hand-Held Ultrasonic Thickness Gages with Live Color Waveforms (A-Scan)

By Dan Carnevale at Danatronics Corporation. This article appears in the January/February 2009 issue of Inspectioneering Journal.


Ultrasonic thickness gages have progressed a long way since their early development in the 1960’s. The first thickness gages were large and bulky although they used the same conventional longitudinal (compressional wave) techniques still in use today.

Thickness gages are used in a wide variety of industries including refineries, power plants, process control, oil and gas, transportation, automotive and manufacturing to name a few. An Ultrasonic thickness gages are excellent devices when access to only one side is possible. Ultrasound can be used on most engineering materials such as steel, aluminum, glass, plastics, composites and rubber. Ultrasound, by its very name, means high frequency sound. In the case of conventional ultrasonic thickness gages, the sound does not pass through air. As such, a fluid, known as couplant, must be applied to the test surface much like the gel used in medical ultrasound to image babies. Also, due to the millions of cycles generated per second, ultrasound is generally not applicable to wood, concrete or porous materials due to the pres- ence of air pockets which are not conducive to the passage of sound waves. The formula to calculate one sided ultrasonic thickness measurements is as follows: T=V*t/2 where (T) is Thickness, (V) is the Acoustic sound Velocity of the test material and (t) is the transit time. We divide by 2 to represent the round trip in the test material.

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