The ultrasonic thickness measurement is a technique intended for the meaurement of the thickness of a piece made of uniform material. This technique is particularly useful:

• when you have to measure the thickness at points distant from the edge of the piece;
• when there is the need to measure the thickness at points where it is not possible to access to both the outer surfaces of the workpiece.

The principle of operation of this type of technique is the same as the SONAR: a ultrasonic pulse is emitted and the instrument detects the delay of the returning echo; Knowing the speed of sound in the medium, it is possible to calculate the distance from the surface which reflected the sound pulse.