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5 Performing a correlation measurement
Performing a correlation measurement
5.3.3
Zoom
The “zoom” function allows you
to enlarge areas of the correla-
tion function.
Select “zoom” with the
arrow
keys
.
The
“right” arrow key
en-
larges the mode of curve.
Position bar 1 below the cor
-
relation function shows which
part of the entire pipe length is
displayed.
The
“left” arrow key
displays
the entire correlation function
again.
Note:
Subjective evaluation of the form of the cross cor-
relation function (CCF) is particularly important when
applying the correlation procedure. The knowledge
required for this cannot be taught as a theory; practi-
cal experience is essential.
The
measurement is based on the value marked in
the CCF and on the
pipe data you have entered. The
CCF represents, in simple terms, the time relation-
ship in terms of quality of the two sounds recorded
by the two microphones to each other.
It is impossible to distinguish between the (sought)
leak sounds and the background noise. The mea
-
surement may not always, therefore, indicate a
leak; sources of background noise can also be
detected!
If there is “no“ noise present, a random measure
-
ment will be calculated. In such cases you should
look for other connection points for the microphones
where the leak noise can be picked up much more
clearly.
