An ultrasonic thickness gauge is a nondestructive testing (NDT) method for determining a component’s thickness by measuring the time it takes for sound to travel from the transducer through the material to the component’s back end, and then measuring the time it takes for sound to return to the transducer. The thickness is then calculated using the sound velocity through the material being examined by the gauge. An ultrasonic thickness gauge’s frequency is depending on the different applications. Two models of thickness gauge.