DMTA-10022-01EN, Rev. C, January 2015
Chapter 10
176
In general, set the main bang blank just beyond the point at which the gage hangs up,
and then proceed to test with the transducer both coupled to and uncoupled from the
test material in order to ensure accurate measurements.
In mode 1, however, the length of the main bang blank determines the minimum
thickness that can be measured, and must therefore be positioned with care after
selecting the initial gain level (see Figure 10-9 on page 176). When the main bang
blank is too short, the instrument hangs up on the excitation pulse and readings are
not possible. When the main bang blank is too long, the minimum measurable
thickness is unnecessarily restricted. When using immersion transducers, ensure that
the main bang blank is always set before the interface echo from the shortest water
path.
Figure 10-9 Main bang blank position for mode 1
In mode 2 and mode 3, the setting of the main bang blank is not critical if set to some
point between the end of the excitation pulse and the interface echo (see Figure 10-10
on page 177).
Initial pulse
Main bang blank
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