Siemens SITRANS F Series Operating Instructions Manual page 128

Appendix
A.4 Flowrate Calibration
Kc Calibration
For most applications, the measured flow range produces a linear meter response.
Therefore, the Kc (slope correction) calibration is the preferred method since it only requires
a single correction factor for all the flow rates encountered.
Note
Changing the calibration can cause profound changes in flow meter operating
characteristics. Use only the most respected flow standard to obtain a correction factor. The
percentage entered must provide an accurate and consistent shift across the entire flow
range anticipated for the application.
Kc Factor
To obtain the Kc factor, compare flow total data taken simultaneously from the flow meter
and a reference meter whose accuracy meets the required standard. Allow both meters to
accumulate flow total data long enough to average out any differences due to flow fluctuation
between the two meter locations. Compare outputs of the two totalizers to determine
percentage increase (+) or decrease (-) that is necessary to produce the best average
correlation between the flow meter and the reference standard.
Selecting the Kc Factor
When the [Kc] menu cell is selected, the flow meter imposes this percentage slope
adjustment of its rate output. Output data is zeroed and corrected for the Reynolds number
(flow profile compensated); however, a percent change in the rate output is imposed based
on the data entered in this cell. The number entered by the user is evaluated into a slope
correction factor by dividing it by 100 and algebraically adding it to 1. The resulting factor is
used as a multiplier on the rate register of the instrument. Thus an entry of -3% will multiply
the rate register by 0.97, for example.
To calculate Kc:
To enter the Kc Factor
1. From the [Meter Type] menu press the <Right Arrow> key and then <ENTER>.
2. Scroll down to the [Span/Set /Cal] menu, press the <Right Arrow> key and scroll down to
3. To enable the Kc Factor press the <Right Arrow> key.
126
[Calib. Flowrate].
FST020 IP65 NEMA 4X
Operating Instructions, 02/2012, A5E03086487-05