ABB 266 Operating Instruction page 49

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
Configuration hints
The minimum configuration for having the AR working and/or moving out from the OOS needs at least the following settings:
– Set ARITH_TYPE with a valid value. It must be different by 0 and in the range 1 – 9
– If the selected ARITH_TYPE is in the range between 1-5 (limited functions), the output limits COMP_HI_LIM > COMP_LO_LIM
– The BAL_TIME must be greater than the Block Execution Time
– When the ARITH_TYPE = 6 (Average) in case of no inputs available the output will be set to NaN (Not a Number)
– Set the GAIN with value different by 0
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 =
t_2
OUT= {f · PV · GAIN + BIAS}
√
Where f =
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 pre-
vious block linked in the IN_3.
OUT= {f · PV · GAIN + BIAS}
√
Where f =
t_1 · t_3
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 =
t_1 · t_2 · t_3
OUT= {f · PV · GAIN + BIAS}
Where f = t_1 – t_2 is limited
OUT= {f · PV · GAIN + BIAS}
t_1
Where f =
t_2
OUT=
PV + t_1 + t_2 + t_3
f= number of inputs used in computation
OUT= (PV + t_1 + t_2 + t_3) · GAIN + BIAS
2
PV – t_1
OUT=
PV – t_2
2600T Series Pressure transmitters | OI/266/FF/ADD-EN Rev. B 49
is limited
for Volumetric Flow is limited
t_1
for Volumetric Flow is limited
t_2
is limited
2
+ t_3 is limited
· GAIN + BIAS
f
+ t_2 + t_3 ) · GAIN + BIAS
3 4
· GAIN + BIAS