50
If there are problems with your measurement SN can
be improved by:
•
Surface of pipe: Remove paint or rust
• Coupling grease: Use sufficient coupling grease
(Magnalube).
• Alignment of transducers: Make sure the trans
-
ducers are mounted as suggested by QStar UFM.
Make sure that center of transducers touches the
pipe sufficiently (might be a problem with very
small pipes). You can check the oscilloscope
while mounting the transducers.
• Make sure the transducers are not mounted on
welding seams.
• Make sure to remove air from liquid.
•
Choose another mounting position (for example,
vertical pipe).
• Make sure to provide sufficient straight run.
• Make sure that signal cables are not disturbed
by power cables.
• Pumps and motors (with frequency inverters)
generate electric noise and should be avoided.
• Use Z-mode rather than V-mode to reduce path
length and therefore to increase signal strength.
•
Try V-mode rather than W-mode.
•
Use stronger transducers, for example, –F05
instead of –F10 or –F10 instead of –F21.
Sharpness of Signals
QStar UFM uses coded signals to make sure to detect
signals in case of noise. Coded means QStar UFM makes
phase shifts within a signal package.
Figure 70
shows a sharp signal. You can see approxi
-
mately 5 waves followed by a phase shift and other waves.
FIGURE 70:
Sharpness of signals
Figure 71 shows diffused signals. There is basically no
phase shift. This might result in undetected signals.
FIGURE 71:
Diffuse Signals
i
QStar UFM is able to handle diffused signals
until a certain limit. Nevertheless sharp signals
should be the goal.
If there are problems, the sharpness can be increased by:
• Choosing different signal sequence
•
Using other mounting mode
•
Using different transducer
•
Improving pipe surface: Removing paint and/
or rust
• Making sure to use sufficient amount of coupling
grease (Magnalube)
• Aligning of transducers: Make sure that transduc
-
ers are mounted as suggested and that the center
of transducers touches the pipe sufficiently (might
be problem at very small pipes). You can check
the oscilloscope while mounting the transducers.
• Making sure that transducers are not blocked by
welding seams
•
Choosing a different location for measurement
To select a different signal sequence, enter the diagnostic
menu (Diag) and press button on the right of parameter
SendCode. Usually the signal sequences 3-Barker 5 or
4-Barker 7 are expected to bring best performance. You
can try different sequences and check influence in diag
-