Signification and Use of A-scan Images
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QuintSonic 7
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The distance between the two coupling echoes presents the thickness of couplant layer. Make
sure not to apply an excessive amount of couplant. If the two coupling echoes follow each other
without space between each other, one can assume that the couplant layer was thin enough to
ensure efficient coupling. If the coupant layer is too thick (as it often occurs when using coupling
gel) the ultrasonic wave will risk to propagate in multiple travel paths. This may be due to various
propagation paths in the couplant causing the pulse to enlarge. As a consequence, reproducibility
of readings will be bad. To avoid such problems, it is recommended to apply only a thin layer of
couplant.
In rare cases, the problem may occur that the acoustic properties of the couplant and the top layer
of the coating system do not differ sufficiently in order to be distinguished from each other. As a
consequence, there will be no negative echo even if the coupling is good enough. In such case it is
recommended to use another couplant.
7.3.3.2
Noise floor
Example: noise floor
As the generated ultrasonic sound wave travels through the complete measuring object, not only
the acoustic properties at the layer interfaces needed for coating thickness measurement will be
represented but also the conditions in the layers themselves. Basically, no industrial coating
material is totally homogeneous. As a consequence, small reflections will occur at material
discontinuities, micro blowholes or inclusions. They will be represented as irregular course of the
zero line (noise floor). The strength of noise depends on the object to be measured. QuintSonic 7
offers several selection methods usually suppress such noise almost completely.
By means of a suitable amplitude parameter clipping choice (see section 8.3.3) adapted to the
object to be measured QuintSonic 7 enables to suppress the noise floor completely. The clipping
Noise
components