Accuracy Of Density; For Liquids; For Gases - Siemens SITRANS FC720 Operating Instructions Manual

Accuracy of density

Accuracy using
water at 20 °C
as an example
Fig. 11: Schematic dependency of the maximum deviation on the mass flow
D
Q
8.4 Accuracy of density

8.4.1 For liquids

Meter size
FCS700 DN100
FCS700 DN150
FCS700 DN200
FCS700 DN100
FCS700 DN150
FCS700 DN200
Deviations possible depending on product version (meter size, type of calibration)
1)
The maximum deviation depends on the product version selected, see also Accuracy of
mass flow and density according to the order code [} 32].

8.4.2 For gases

In most applications, density at standard conditions is programmed into the transmitter
and used to calculate the standard volume flow based on mass flow.
If gas pressure is a known value, after entering a reference density, the transmitter is able
to calculate gas density from temperature and pressure as well (while assuming an ideal
gas).
Alternatively, gas density can be measured. In order to do so, it is necessary to adapt the
lower density limit value in the transmitter.
For most applications the direct measurement of the gas density will have less accuracy
as stated for liquids.
%
0.5
0
0
Q /Q
flat nom
Maximum deviation in %
Nominal mass flow in kg/h
nom
Q
m
Q
nom
Q
m
Q
flat
Transmitter
SITRANS FCT020
SITRANS FCT040
A5E52748387-AA, 2023/09
1.0
Mass flow in kg/h
Mass flow above which D
applies, in kg/h
Maximum deviation of density
in g/l (lb/ft³)
Down to 4 (0.25)
Down to 2 (0.13)
FC7x0
Accuracy
flat
1)
31 / 180