ABB 2600T Series Instruction Manual page 95

2 6 0 0 T S E R I E S | P R E S S U R E T R A N S M I T T E R S | O I/ 2 6 6/ F F - E N R E V. E
If the status of IN_LO is unusable and IN is usable and greater than RANGE_LO, then g should be set to one. If the status of IN is
unusable, and IN_LO is usable and less than RANGE_HI, then g should be set to zero. In each case the PV should have a status of
Good until the condition no longer applies. Otherwise, the status of IN_LO is used for the PV if g is less than 0.5, while IN is used for
g greater than or equal to 0.5. An optional internal hysteresis may be used to calculate the status switching point.
Six constants are used for the three auxiliary inputs. Each has a BIAS_IN_i and a GAIN_IN_i. The output has a BIAS and a GAIN static
constant. For the inputs, the bias is added and the gain is applied to the sum. The result is an internal value called t_i in the function
equations. The equation for each auxiliary input is the following:
t_i = (IN_i + BIAS_IN_i) * GAIN_IN_i
The flow compensation functions have limits on the amount of compensation applied to the PV, to assure graceful degradation if
an auxiliary input is unstable. The internal limited value is f.
Equations
Algorythm type
Flow Compensation Linear
Flow Compensation Square Root
Flow Compensation Approximate
BTU Flow
Traditional Multiply Divide
Average
Traditional Summer
Fourth Order Polynomial
Simple HTG Compensated Level
Description
Used for density compensation of Volume flow
Usually:
– IN_1 is pressure – (t_1)
– IN_2 is temperature – (t_2)
– IN_3 is the compressibility factor Z – (t_3)
Both IN_1 and IN_2 would be connected to the same
temperature
NOTE:
– The Square Root of the third power can be achieved
connecting the input to IN and IN_1.
– The Square Root of the fifth power can be achieved
connecting the input to IN, IN_1, IN_3.
– IN_1 is the inlet temperature
– IN_2 is the outlet temperature
All inputs except IN_LO (not used) are linked together OUT= (PV + t_1
– The PV is the tank base pressure
– IN_1 is the top pressure – (t_1)
– IN_2 is the density correction pressure – (t_2)
– GAIN is the height of the density tap
Function
OUT= {f · PV · GAIN + BIAS}
t_1
Where f = is limited
t_2
OUT= {f · PV · GAIN + BIAS}
√
t_1
Where f = for Volumetric Flow is limited
t_2 · t_3
For the calculation of the Volumetric Flow t_3 = Z
The compressibility factor Z can be set writing into
the IN_3 a constant value Z or can be calculated by a
previous block linked in the IN_3.
OUT= {f · PV · GAIN + BIAS}
√
t_1 · t_3
Where f = for Volumetric Flow is limited
t_2
In case it would be necessary produce the Mass Flow,
the compressibility factor Z must be set as into the
1
IN_3 as
Z
OUT= {f · PV · GAIN + BIAS}
√
Where f = is limited
t_1 · t_2 · t_3
2
OUT= {f · PV · GAIN + BIAS}
Where f = t_1 – t_2 is limited
OUT= {f · PV · GAIN + BIAS}
t_1
Where f = + t_3 is limited
t_2
PV + t _ 1 + t _ 2 + t _ 3
OUT= · GAIN + BIAS
f
f= number of inputs used in computation
OUT= (PV + t_1 + t_2 + t_3) · GAIN + BIAS
+ t_2 + t_3 ) · GAIN + BIAS
2 3 4
PV – t_1
OUT= · GAIN + BIAS
PV – t_2
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