Siemens 6DR2410, Руководство пользователя

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Manual 1 Technical Description
1.5 Functional Description
1.5.8 Complex Functions (Arithmetic blocks c, d, h)
SIPART DR24 6DR2410
C79000-G7476-C153-03
59
F
=
ρ
ρ
B

=
V
B
V

with V
=
1
ρ
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.
P
abs.A
V
B
q Flow
ρ
Density
Δ
p Active pressure
p Pressure
Â
Temperature (
_
C)
T Temperature (K)
V Specific volume
K Flow coefficient
R Gas constant
F Correction factor f (p, T)
Indices :
A Start
E End
B Calculation state
abs Absolute variable
m Ground
v Volume
V
m
3
/kg
Correction range
P
abs.A
to P
abs.E
Range of the pressure transmitter
Â
A
to
Â
E
Range of the temperature transmitter
Â
A
Â
B
Â
E
_
C
Â
P
abs.E
P
abs.B
P
abs.
bar
Figure 1--27 Display of the correction range
This gives for the corrected flow
q
=
F ·K ·
ρ
B

·
Δ
p

=
K ·
ρ
B

·
Δ
p

·
T
B
· p
P
B
· T

The factor contained in the formula K ·
ρ
B

is already taken into account in the measurement
of the active pressure and can therefore be ignored by the computer.