Ultrasonic Method to Measure Thickness

ultrasonic instruments with a graphical LCD illustrate substrate roughness by displaying wide "peaks" when the substrate is rough and narrow "peaks" when it is smooth.

This type of display helps in measuring coating systems in which the number of layers is unknown. It presents interface information about bond strength and material densities, he adds.

Coating thickness gages that use an ultrasonic principle are becoming increasingly popular. They support or replace destructive measurement techniques for concrete, wood and plastics applications.

ultrasonic pulse-echo technique of ultrasonic gages, is used to measure the thickness of coatings on nonmetal substrates such as plastic and wood without damaging the coating.

The probe of the instrument contains an ultrasonic transducer that sends a pulse through the coating, The pulse reflects back from the substrate to the transducer and is converted into a high-frequency electrical signal. The echo waveform is digitized and analyzed to determine coating thickness. In some circumstances, individual layers in a multi-layer system can be measured.

Typical tolerance for the device is ±3%. Standard methods for the application and performance of the test are available in ASTM D 6132.