Siemens SITRANS F C MC2, Руководство по эксплуатации, Страница: 36 / 60

Troubleshooting / FAQs
8.5 Step 4: Improving the application
SITRANS F C MC2
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Operating Instructions, 10/2009, A5E02154544-02
8.5 Step 4: Improving the application
It is not always worth wile investing time and money in improving the installation and thus the
measurement accuracy. However, it should always be checked where the zero point error
(ZERO SIGMA value) originates from.
In the following it is described how to find the causes of a high ZERO SIGMA value and how
to improve the installation.
Setting "low flow cut-off"
In order to see if the zero point becomes more stable when making changes / adjustments,
the low flow cut-off must be set to 0,0%.
This is done from the transmitter:
MASS 6000 SIFLOW FC070
Choose menu entry "Basic settings"
-> Low flow cut-off Choose PDM table
Choose input
When "low flow cut-off" has been set, it is possible to see the instability directly from the
mass flow in kg/h in the transmitter display or the online window ("View->Display")
This information can be used to troubleshoot. For example, tightening the brackets which
hold the sensor, or turning off the pump to check if vibrations from the pump are disturbing
the sensor, etc.
Incorrect installation of the sensor
● Has the sensor been correctly installed, i.e. fastened to the floor / wall or frame with good
mounting brackets as shown in the Instructions?
Especially for low flow rates, i.e. flow rates less than 10% of the maximum capacity of the
flow meter, it is important that the sensor is correctly and stably installed.
If the sensor is not correctly fixed in place, the zero point of the sensor will move, leading to
measuring errors.
Try to tighten up the sensor brackets to see whether the flow instability is reduced and now
more stable.
Vibrations and cross talk
Vibrations in the pipe system are normally generated by pumps.
Typically, cross talk is generated by two sensors positioned in close proximity in the same
pipe, or installed upon the same rail or frame.
Vibrations / cross talk have a greater or lesser effect upon the zero point stability and
therefore also the measurement accuracy.
1.
Check whether there are vibrations.
Turn off the pump and check whether the zero point stability improves, i.e. if the flow rate
fluctuation in kg/h is reduced.