GPI QME05, Руководство пользователя, Страница: 51 / 60

51
nostic data (SigQ, see Troubleshooting: Oscilloscope
Menu of QStar UFM ) as well as visually in oscilloscope.
Separating Signals (small pipes)
When measuring at small pipes (<1.9 in.) the distances
between the received signals become smaller. In the
worst case, signals might interfere as shown in Figure
72 Interfering signals.
FIGURE 72: Interfering Signals
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t1w
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In this case, there are not only the desired signal within
the measuring window but also the interfering pipe wall
signal and also a part of the W-mode signal.
i
QStar UFM uses sophisticated algorithms to
separate desired signals from interfering signals.
These algorithms are mainly applied when having
the auto window function activated. But especially
when measuring at very small pipes interference
might occur anyway. In that case the user can
separate signals (in order to filter out the desired
signal) manually in the oscilloscope mode.
If interference does occur:
• Use W-Mode rather than V-mode (first counter-
measure)
• Use Z-Mode rather than V-mode (when W-mode
does not work)
• Deactivate Auto-Window and use ZOOM function/
shift function (arrow buttons) to kick out disturbing
signals of the measuring window.
• Use different signal sequence, for example,
3-Barker5 or 1Puls rather than 4-Barker 7
• Use transducer working at higher frequency
(F21 rather than F10) to get sharper signals.
When using F21 (2MHz) instead of F10 (1MHz)
the signals become half as wide (half of time)
which makes it easier to separate signals.
FIGURE 73: Separated Signals
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time
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Window
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Window
Deactivate the auto-window in order to separate signals
manually. Always check the measured speed of sound
of the separated signal. When the (separated) desired
signal is within the measuring window, the speed of sound
(parameter vS in diagnostic menu) should be within
+/- 20% of the expected speed of sound (for example,
when measuring water at 68° F speed of sound should
be within 1400-1500 ft/s). If vS exceeds the expected
values you most likely have separated the wrong signal
(example, pipe wall signal, then vS is showing speed of
sound of pipe material).
Activate/Deactivate Auto-Window
When in main menu “Flow 1”, choose OSZ to enter the
oscilloscope menu.
Determine whether to use auto window or not. In case
of problems with measurement we recommend to try
without auto window first.
Choose “NO”
Display shows distinguished signals (UP and DOWN) in
the oscilloscope.
Press DIAG and OSZ again to activate auto window.
Answer with YES. Check if position of ultrasonic signals
have been changed. Check if value for delay has been
changed. If yes, use auto window for your measurement.
Auto window is activated when you say YES and when
you leave oscilloscope mode. To deactivate auto window
enter oscilloscope mode again and answer with NO).