A transmitted ultrasonic pulse is sent through paint and metal and is reflected by the rear wall. The returning echo reverberates in the metal and only a small part of the echo returns through the coating. The time between the small echoes gives us the time of the echo within the metal. This time is in direct connection to the material thickness. The underwater ultrasonic material thickness meter interprets the recurring echoes automatically and calculates the thickness of the material. A minimum of three echoes is checked each time by the automatic measurement verification (AMV) system.