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Manual
1 Technical Description
1.5 Functional description of the structure switches
1.5.2 Analog input signal processing freely connected (S4 = 1)
30
SIPART DR22 6DR2210
C79000-G7476-C154-03
0
0.81
Δ
p
0.25
0.49
1.00
0.09
0.3
0.7
0.5
0.9 1.0 q
Figure 1-13
Relationship between flow q and active pressure
Δ
p
To measure the flow, a choke is installed at the measuring point which constricts the pipe and
has two connections for tapping the active pressure.
If the properties of the choke and the measuring material are known to the extent that the
equation specified above can be calculated, the active pressure is a measure of the flow.
If you have chosen a certain choke, the flow can be described in the calculation state or
operation state.
q
B
=
K ·
ρ
B
·
Δ
p
or q
=
K ·
ρ
·
Δ
p
Since the density is included in the measuring result according to the above equation,
measuring errors occur when the density in the operating state differs from the value based on
the calculation of the choke. Therefore a correction factor F is introduced for the density in
operating condition.
V
B
V
F =
B
=
with
V =
1
as specific volume.
as specific volume.
In order to be able to perform the correction with the factor F, the current specific volume must
be determined first.
For the dry gases the densities change according to the laws for ideal gases:
The correction factor is then given as:
V
=
R Tp
=
1
ρ
F
=
T
B
· p
p
B
· T
with p as absolute pressure and T as absolute temperature.
Содержание 6DR2210
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Страница 3: ...SIPART DR22 6DR2210 C79000 G7476 C154 03 1 SIPART DR22 6DR2210 Edition 12 2006 Manual ...
Страница 236: ...Manual 6 Ordering data 234 SIPART DR22 6DR2210 C79000 G7476 C154 03 ...
Страница 242: ...Manual 7 Application examples for configuring the controller 240 SIPART DR22 6DR2210 C79000 G7476 C154 03 ...
Страница 260: ...Manual 9 Explanation of abbreviations 258 SIPART DR22 6DR2210 C79000 G7476 C154 03 ...
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