Rubber sheets and rubber coatings can be difficult to gauge with conventional mechanical thickness measurement techniques. With ultrasonic thickness gages, however, any point on the entire surface of a rubber sheet - and not just the edges - can be measured without ever having to contact the opposite side. Ultrasound waves travel through the rubber coating and reflect from the acoustic interface of the rubber and the substrate. This acoustic interface can be air, rubber-steel, rubber-composite, or other materials, as long as the outside surface of the rubber is available for probe coupling.
It is important to know the exact nature of the application since rubber coating on certain materials may require special setups in order to maintain accuracy of thickness readings.