Processing ultrasonic measurements of a rotating hollow workpiece

A method of processing a hollow workpiece including measuring the position of the wall of a hollow workpiece with respect to the rotational axis of a rotary machine, comprising:

• a) rotating said workpiece in the rotary machine;
• b) rotating a shaft angle encoder in response to the rotary machine to provide a sequence of revolution signals, one for each revolution of the workpiece, and a sequence of site signals during each revolution of the workpiece;
• c) beginning with the concurrence of one of said site signals with a first, odd one of said revolution signals and until occurrence of a second, even one of said revolution signals, and thereafter beginning with concurrence of one of said site signals with each subsequent, odd one of said revolution signals and until occurrence of the next, even one of said revolution signals, directing an ultrasonic pulse toward the surface of the workpiece in response to occurrence of each of said site signals, each of said pulses providing a first echo reflected from the outside surface of said workpiece, and a second echo, following said second echo, reflected from the internal surface of said workpiece;
• d) beginning with each, odd one of said ultrasonic pulses concurring with one of said revolution signals and the next subsequent, even one of said ultrasonic pulses, and thereafter for each odd one of said ultrasonic pulses and the next subsequent, even one of said ultrasonic pulses, providing for each pair of ultrasonic pulses a first time signal indicative of the elapsed time between said first echo and either one of said pair of pulses and a second time signal indicative of the elapsed time between receipt of said first echo and said second echo of the other one of said pair of pulses;
• e) providing, in response to each of said first time signals, an outer radius signal indicative of the distance of the outer surface of the related site from said rotational axis;
• f) providing, in response to each of said second time signals, a wall thickness signal indicative of the thickness of the workpiece wall at said site;
• and
• g) processing said workpiece in a manner dependent on the distances indicated by said outer radius signals and the thicknesses indicated by said wall thickness signals.