Ultrasonic signal processing system including a flaw gate

Abstract

An ultrasonic signal processing system that includes flaw gates that process signals from an inspection transducer is disclosed. The flaw gates operate in pairs where each pair is dedicated to a time window corresponding to, for example, flaw depth or transducer angle. The time window for a pair of flaw gates is indicated by a channel code produced by a timing control unit. One flaw gate in each pair processes incoming digitized transducer signals during a scan to produce reflector indications while the other gate in each pair transfers data from a previous different position scan to a main computer. The main computer determines flaw locations from the reflector indications and transducer positions provided by the flaw gate. The flaw gates each adjust reflector indication location signals for changes in distance between an immersed ultrasonic wave inspection transducer and the surface of the material being inspected as well as record the location of the inspection transducer at the time of each indication detection. The flaw gates produce the indication by comparing the digitized transducer signal waveform with a threshold curve where an indication is an excursion of the signal waveform above the threshold. The flaw gates each contain a comparator that indicates when the window is open and activates a waveform memory that automatically stores the digitized transducer signals during the window.