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

System Setup.
In a basic C-scan system, shown schematically in Fig. 12 above, the search
unit is moved over the surface of the test piece in a search pattern. The
search pattern may take many forms; for example, a series of closely spaced
parallel lines, a fine raster pattern, or a spiral pattern (polar scan). Mechanical
linkage connects the search unit to x-axis and y-axis position indicators,
which in turn feed position data to the x-y plotter or facsimile device. Echo
recording systems vary; some produce a shaded-line scan with echo intensity
recorded as a variation in line shading, while others indicate flaws by an
absence of shading so that each flaw shows up as a blank space on the
display (Fig. 12) above.