Siemens SITRANS FC330, Руководство по эксплуатации, Страница: 191 / 280

Depending on application, you should furthermore ensure the following:
● Liquid application
Ensure that the sensor is filled with liquid and liquid only.
Air or gas bubbles in the liquid cause instability and can result in measurement errors.
Flush the pipe systems and the sensor for several minutes at maximum flowrate to remove
any air bubbles which may be present.
Note
The liquid must be homogeneous in order to measure with high accuracy. If the liquid
contains solid particles of greater density than the liquid, then these solids can settle,
especially at low flow rates, which will cause instability in the sensor and lead to
measurement errors.
For pastes or process fluids with suspended solids always orient the sensor vertically with
flow in upward direction to maintain solids suspension.
● Gas application
Ensure that the gas pressure/temperature conditions contain sufficient superheat to prevent
dewing or precipitation. If the gas contains vapor or droplets then these may precipitate,
causing instability.
Step 2: Performing a zero point adjustment
The second step in the troubleshooting procedure is to zero point adjust the device. For further
information on zero point adjustment, see Commissioning (Page 81).
Step 3: Calculating the measurement error
The result of the zero point adjustment will show you if the zero point was set under good and
stable conditions.
The lower the obtained value of the parameter Zero point standard deviation, the lower is the
achievable measuring error. For a well-installed flowmeter, the Zero point standard deviation
corresponds to the specified zero point stability for the sensor size, see Performance
(Page 195).
The parameter Zero point standard deviation is located in the Maintenance & Diagnostics menu
in SIMATIC PDM.
Calculating the measurement error
● The error curve is plotted from the formula:
E = ± (Cal)
2
+
z x 100
qm
( )
2
E = Error [%]
Z = Zero point [kg/h]
qm = Mass flow [kg/h]
Cal. = Calibrated flow accuracy: 0.10 or 0.2
Diagnostics and troubleshooting
10.3 Operation troubleshooting
SITRANS FC330
Operating Instructions, 01/2019, A5E44030648-AB
191