ABB SmartMedia SM2000, Дополнение к руководству пользователя

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Videographic Recorders
SM1000 and SM2000 2 Math Configuration
IM/SM2000ADV Issue 7 17
Mass Flow – Derived density correction
This method uses a preset table of temperature and density
values to define the correction, which is calculated as follows:
Qmd = Qc x density correction
Mass Flow – Measured Density Correction
Qmm = Qc x input from density meter.
Where a3 is the input from an external density meter.
2.10.2 Ideal Gas Flow
Gas flow is usually measured using a differential pressure device
across orifice plates and wedges.
Corrections can be applied to compensate for variations in
temperature and pressure – see Fig. 2.13.
Where , the square root extraction and scaling can be
achieved on the DP device or on the input set up of the recorder.
Let m1 = constant 1 x a3
Qc = m2 = a1 x constant2 x a2/m1
Note. Input a3 is the actual product temperature input (as
a2 in previous examples) but with the density correction
applied using a custom linearizer – see Section 4.9.1 of the
User Guide (IM/SM1000 or IM/SM2000).
Note. With all of the above calculations the engineering
range should allow for the extremes of all the input variables.
m3
a1 a3 scaling factor
× ×
m2
----------------------------------------------------------- =
m3
a1 a3 m2
⁄ ×
m2
------------------------------- =
Fig. 2.13 Temperature and Pressure Compensation
Note. The engineering range should allow for the extremes
of all the input variables.
Q
P
ref
x T
A
x Q
T
ref
x P
A
Q
c
= Corrected Volumetric Flow
Ideal Gas Flow
P
A
T
A
Q = Volumetric uncorrected flow
T
ref
= Reference temperature in K or ºR
T
A
= Actual temperature in K or ºR
P
ref
= Reference pressure in Absolute
P
A
= Actual pressure in Absolute
Q K h =