An ultrasonic thickness gauge is a small, computerized instrument that measures the thickness of material using high frequency sound waves or ultrasound. Placed against one side of the material, its transducer, a small probe, generates an ultrasonic burst that echoes back when hitting the other side of the material.
The velocity of the sound in the test material is a key factor in calculating thickness using a simple mathematical formula programmed into the gauge. To arrive at the material's thickness, velocity (speed of sound in the specific material) is multiplied by half the time it took the sound to travel through the material and return.
Ultrasonic thickness gauges measure all types of engineering and building materials, including metals, plastics, ceramics and rubber. The type of gauge and transducers used depends on the type and thickness of material. Corrosion gauges, with dual transducers, detect the thickness remaining in metal pipes or tanks that have internal corrosion. Precision gauges with single element transducers, used for all other materials, are extremely accurate. The level of accuracy delivered with any gauge depends on several factors, such as correct calibration, consistency of sound velocity through the material and roughness or curvature of the material's surface.