Zero Point Adjustment - Siemens SITRANS F Operating Instructions Manual

Zero point adjustment

In the following the automatic zero point adjustment function is described in detail.
NOTICE
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 LUI (Page 72) or PDM (Page 87) for more details.
NOTICE
Change of parameters during zero point adjustment
Do not change any other parameter during the zero point adjustment procedure.
Automatic zero point adjustment
SITRANS FC430 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 massflow 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
SITRANS FC430 with HART
Operating Instructions, 03/2012, A5E03361511-01
x is an instantaneous flow value sampled
i
N
in the time domain
∑
x
i
N = Number of samples during zero point
=
i 1
≡
x
adjustment
N
C
215