Patent GB-1532675-A (GB)
Title: Method and apparatus for monitoring the function in ultrasonics testing of tubes and bars
IPC: G01S7/52
Filed: 1976-10-01
Abstract: 1532675 Ultrasonic flaw detectors KRAUTKRAMER GmbH and MANNESMANNROHREN-WERKE AG 1 Oct 1976 40910/76 Heading G1G The operational function of one or more transmitters, receivers and/or amplifiers used for ultrasonic testing of pipes and bars for material flaws is monitored by amplifying the output signals from the or each receiver which result from reception of scatter sonic signals from the surface of the pipe or bar, and detecting reduction of the amplified stray signals below a predetermined level to signal operational failure. As described with reference to Fig. 7 (not shown), a single transmitting-receiving transducer has two output channels one connected to a flow monitoring channel including an amplifier and the other connected to a scatter signal monitoring channel including a second amplifier, the gain of this latter amplifier being higher than that of the first amplifier. In a modification as described with reference to Fig. 9 (not shown), the output of a single transmitting-receiving transducer is connected to an amplifier whose output is connected to a first flaw monitoring channel and a second scatter signal monitoring channel which includes additional amplifier stages for detecting the scatter signals. In a further modification as described with reference to Fig. 11 (not shown), the output of the single  transducer is connected to a logarithmic amplifier whose output is applied to a monitor system on which two different limit values are set, one for flaw signals and the other for scatter signals. In a two-transducer system as described with reference to Fig. 8 (not shown), one transducer acts as a transmitter-receiver and the other as a receiver. The receiver transducer detects flaw signals whereas the transmitter-receiver transducer detects the scatter signals and has its output connected to a scatter signal monitoring channel including an amplifier. As shown in Fig. 10, this arrangement is modified by having both transducers 1a, 1b acting on transmitter-receivers, and in a first cycle causing the transducer 1b to act as a transmitter-receiver and the second transducer 1a to act as a receiver only so that flaw signals from receiver 1a are monitored in the channel comprising amplifier 8 and monitor 10 and scatter signals received from transducer 1b are monitored in the channel comprising amplifier 9 and monitor 11, and in a second cycle causing the transducer 1a to act as a transmitter-receiver so that scatter signals received from transducer 1a are monitored in the channel comprising amplifier 8, amplifier stages 13 and monitor 11. In a modification of this arrangement, Fig. 12 (not shown), the amplifier 8 is replaced by a logarithmic amplifier whose output is applied to a monitor on which two different limit values are set, one for flaw signals and the other for scatter signals. As described with reference to Fig. 13 (not shown), to prevent an operational breakdown signal  being provided for spurious reductions of the scatter signals, a counter is connected to the output(s) of the scatter signal monitoring channel(s) and provides a breakdown signal only when a predetermined number of scatter signal reductions have been detected. A multiple transducer embodiment is described with reference to Fig. 14 (not shown).