Abstract: The wall thickness of an object is measured on the basis of three consecutive rear wall reflections caused by an ultrasonic wave impinging on the front wall of the object. The time intervals between, on the one hand, the first and second rear wall reflections and, on the other hand, the second and third rear wall reflections are compared. In the event of correspondence of these time intervals, a "good" signal indicative of a true thickness value is produced. The system is adapted for a highly accurate wall thickness measurement, with the feasibility of providing an indication of the percentage of "good" measurements in sequence thereof.