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Signal quality
The signal quality or Q value is displayed in window M04. It indicates the level of the detected
signal. The Q value is indicated by numbers from 00 to 99. 00 represents the weakest detected
signal whereas 99 represents the maximum. The position of the sensors should be adjusted until
the detected signal quality is as strong as possible.
Total time and delta time
The total transit time and the total transit time difference, which are displayed in window M04, are
further factors for the measurement accuracy. The measurement calculations in the flow meter
are based on these two parameters. Therefore, if the total transit time difference varies greatly, it
means that the detected signal quality is too poor. This may be the result of poor pipe installation
conditions, inadequate sensor installation or incorrect parameter entry. In general, the variation
of the total transit time difference should be less than ±20 %. Only if the pipe diameter is too small
or the velocity too low, the variation can be larger.
Transit time ratio
The transit time ratio indicates whether the mounting distance of the sensors is accurate. The
normal transit time ratio should be 100 ±3 % when properly installed. Check this in window M04.
If the transit time ratio exceeds 100 ±3 %, a check is required:
•
whether the parameters (pipe outside diameter, wall thickness, pipe material, lining,
etc.) have been entered correctly,
•
whether the mounting distance of the sensors corresponds to the display in window
M14,
•
whether the sensors are correctly positioned on the pipe,
•
whether the shape of the pipe is distorted or deformed.
6.2.4
Warnings
The pipe parameters must be entered accurately or the flow meter will not work properly.
•
During installation, apply enough coupling gel to mount the sensors to the pipe wall.
While checking the signal strength and Q value, slowly move the sensors across the
mounting location until the strongest signal and maximum Q value are reached. Note
that the larger the pipe diameter, the more the sensors need to be moved.
•
Check that the mounting distance matches the indication in window M14 and that the
sensors are mounted centrally on the pipe on the same pipe size.
•
Pay special attention to pipes with seams as such pipes are usually uneven. If the
signal strength is always displayed as 0.00, this means that no signal is detected.
Therefore, it is necessary to check whether the parameters (including all pipe
parameters) have been entered correctly. Check that the sensor mounting method is
correct, the pipe is not worn and the lining is not too thick. Make sure that there is
actually fluid in the pipe or that the sensors are not too close to a valve or manifold
and that there are not too many air bubbles in the fluid, etc. If still no signal is
detected, the measuring location must be changed.
© PCE Instruments
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