Functions; Process Values - Siemens SITRANS F Operating Instructions Manual

Functions

In the following the main functionalities of the device are described in detail.
For overview of all functions and parameters, refer to the parameter tables in the appendix
"LUI menu structure" (Page 189).
8.1

Process values

The process values are cyclically updated every 10 ms (100 Hz update rate) synchronous
with the DSP update cycle.
Process value parameters
The process values
● Massflow *
● Volumeflow *
● Corrected volumeflow
● Density *
● Process media temperature
● Fraction A (massflow or volumeflow)
● Fraction B (massflow or volumeflow)
● Fraction A %
● Fraction B %
Only the process variables listed above with * are available to be allocated to the 4-20 mA
1)
output on Channel 1. Other process variables are available through HART and all of
Channels 2 to 4.
Process value derivations
The front-end of the FCS430 flowmeter measures time and derives the values of certain
process variables from those measurements. The time period of vibration of the two
measuring tubes is inversely proportional to their frequency, which is used to determine
density. The average difference in phase of the two measuring tubes is dependent upon the
mass flowrate of the process medium. In this measurement context, phase difference is
expressed not in degrees of rotation but as an absolute time measurement. For this reason
the result of zero offset correction is displayed in µs, being the unit of the true measurement.
The process variables are interrelated and derived in the following fashions:
SITRANS FC430 with HART
Operating Instructions, 03/2012, A5E03361511-01
are:
1)
8
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