Abstract: As an ultrasonic transducer is continuously rotated about a pipe which is fed axially through a water-filled cavity, it sends sufficient periodic pulses to the pipe to cover essentially the entire pipe surface. The transducer also receives reflections from the outside and inside walls of the pipe from which information about pipe qualities is derived. A thickness processor module employs precision peak detectors in various circuits, including one in which flaw conditions are compared on successive rotation of the transducer in order to verify the presence of a flaw before an alarm is indicated. The thickness processor module may also provide display information about maximum and minimum values, average values, and eccentricity. In addition to the precision peak detector, there is also provided a rate of change filter which monitors rate of change of wall information and detects flaws by any major rate of change.