Automatic weld flaw detector

An automatic weld-flaw detecting apparatus, which comprises a probe movable along a welded member for applying and detecting ultrasonic waves, a memory for memorizing the amplitude of the echoes, a comparator coupled to the memory and the probe for repeatedly comparing an echo amplitude after each movement of the probe for a unit distance with the content of the memory and applying the larger of the compared amplitude to the memory, said memory memorizing only the larger of the compared amplitudes, a source of clock pulses, a counting circuit responsive to the distance of movement of said probe, a first counter set for counting clock pulses over a period of time corresponding to the time a beam of ultrasonic wave from the probe takes to reach a weld portion and its echo returns to said probe, a second counter coupled to the first counter and adapted to commence in response to said first counter having counted clock pulses up to the set value and stop counting in response to the content of said counting circuit, a gate circuit opened only between the stop and start of clock pulses from said second counter, an A-D converter responsive to said probe for applying the echo amplitude of the flaw into said comparator upon receiving control of said gate circuit, a latch memory circuit responsive to said comparator and said counting circuit for memorizing the contents of said counting circuit at the time of memory of the maximum flaw echo amplitude by said memory and a recorder for recording each of the contents of said latch memory circuit, and the memory circuit, and whereby it is made possible automatically to record a maximum value of flaw echo amplitude in a weld portion and the distance between the probe and the weld portion during each scan by said probe.