Gas- and Steam Flowcomputer
DigiFlow 515
Operating Manual
12
Example No. 1:
With an orifice plate the flow shall be measured in the range of 0-2,000 m
3
/h, what to a Measuring range rela-
tionship of 10:1 corresponds. The two transmitters are spanned as follows:
Transmitter 1:
0 600m
3
/h
Transmitter 2:
0 2,000m
3
/h
In range up to 600m
3
/h Transmitter 1 is used, at flow rates above 600m
3
/h transmitter 2 is used. Since D.P.
transmitters are accurate over a 3:1 range, then the system will provide reliable readings between 200 and
2000 m
3
/h, which is a 10:1 range.
6.1.1 Parameter setting of the flow calculator:
For the correct function of the flow calculator the following parameters must be entered:
•
k
F
k–factor of flow measuring instruments with frequency output
•
S
Vb
/S
V
Span (for analog flowmeters)
•
T
b
Reference
temperature
•
p
b
Reference
pressure
•
d
Specific gravity of the gas
The flow calculator gets the signals for flow, pressure and temperature. In dependence of the chosen gas
equation the compressibility factor is taken into account and the density calculates.
Which parameters are to be entered, can be looked up in chapters 5.4.
6.1.1.1 Programming the Span as Mass
It is possible to enter the measuring range of the flow measuring instrument as mass flow. The computer will
then calculate the span as:
S
S
Vb
M
b
=
ρ
[
9
]
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