Siemens SITRANS FC330, Руководство по эксплуатации, Страница: 271 / 280

Zero point adjustment
D
In the following the automatic zero point adjustment function is described in detail.
Note
Preconditions
Before a zero point adjustment is initiated, the pipe must be flushed, filled and at an absolute
flowrate of zero preferably also at operating pressure and temperature. Refer to "Zero point
adjustment" via HMI (Page 86) or SIMATIC PDM (Page 102) for instructions.
Note
Change of parameters during zero point adjustment
Do not change any other parameter during the zero point adjustment procedure.
Automatic zero point adjustment
SITRANS FC330 measures and calculates the correct zero point automatically.
The automatic zero point adjustment of the flowmeter is set by the following parameters:
● Zero Point Adjustment Period
● Start Zero Point Adjustment
When zero adjust is initiated by selecting "Start Zero Point Adjustment", the mass flow values
are acquired and totalized for the configured period (Zero Point Adjustment Period). The default
zero point adjustment period (30 s.) is normally sufficient for a stable zero point measurement.
Note
Extremely low flow quantity
If the flow quantity is extremely small, extremely precise measurement is necessary. In this
case, a long zero point adjustment period can be selected for improved zero point adjustment.
Zero point calculation
During zero point adjustment, an average value is automatically calculated using the following
formula:
Zero Point Offset Value
Average of N flow values
N
x
x
N
i
i
∑
=
≡
1
x
i
is an instantaneous flow value sampled in
the time domain
N = Number of samples during zero point ad‐
justment
SITRANS FC330
Operating Instructions, 01/2019, A5E44030648-AB
271