Signification and Use of A-scan Images
© ElektroPhysik
QuintSonic 7
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A proper reference signal always consists of a positive pulse (P). This pulse almost reaches the
positive maximum (approx. 95%). It is followed by a smaller negative pulse (N), followed by a flat
reverberation time (A). The complete signal curve should represent a smooth progression without
sudden jumps or sharp bends (Note: Here, it is not referred to the small steps caused by the
restricted graphics resolution).
7.2.2
Raw measuring signal
Example a raw measuring signal A-scan image
This is an example of an A-scan image generated and stored in the background if a measuring
signal has been taken. This kind of A-scan image will be generated at any launch of a measuring
procedure, irrespective of whether the coupling to the measuring object has been successful or
not. It exactly reflects the representation of the measuring signal received by the ultrasonic sensor
head. A-scan profiles are not uniform but strongly depend on the properties of the object to be
measured as well as on the coupling performance. The above figure shows an example for a
measuring signal. As with the reference signal, the signal profile should be smooth without jumps
or sharp bends. There are no further requirements for a proper A-scan image.
The above A-scan image does not allow to deduce any statements with respect to the position of
the layer interfaces. This is because the individual echoes overlap and thus would result in a totally
misleading overall image. In this A-scan image, a maximum pulse does not inevitably represent the
position of an echo. Echoes are often located in zones of low intensity or even in zero passages.
If measurement has been accidentally launched by pushing the sensor sleeve and the sensor was
clean and has been held into the air, the A-scan image that results from this action will be identical
with the reference A-scan image.
Please note that the A-scan image of the measuring signal is of no significance for the user, it only
serves for servicing purposes. It is only mentioned in this manual for the sake of completeness and
to enhance the understanding of the overall context.