Preparatory Notes for ASNT NDT Level III Examination - Ultrasonic Testing, UT

With ultrasonic instruments having digital echo evaluation these calculations
are naturally carried out by an integrated microprocessor and immediately
displayed so that the operator does not need to make any more timeconsuming
calculations, Fig. 55. This is of great help with weld testing
because with the calculation of the flaw depth an additional factor must be
taken into account, namely: whether the sound pulses were reflected from the
opposing wall. If this is the case then an apparent depth of the reflector is
produced by using the depth formula which is greater than the thickness T of
the test object. The ultrasonic operator must acertain whether a reflection
comes from the opposite wall and then proceed with calculating the reflector
depth, Fig. 56b.