ABB 2600T Series Operating Instruction page 59

Description of the transition function
Linear
When using this function the relationship between the input
value (measured value) in % of the calibrated measurement
span and the output linear (i.e.: The input value of 0%
corresponds to an output value of 0% = 4 mA, the input value
of 100% corresponds to an output value of 100% = 20 mA).
Additional settings are not possible here.
Square root
With this function the output (in % of the measuring span) is
proportional to the square root in % of the set measuring span
(i.e.: The device outputs an analog output signal that behaves
proportionally to the flow rate). It is possible to use the
complete square root function.
Fig. 39
In order to avoid the high gains occurring in the vicinity of the
zero point, the transmitter works linear with a gradient of 1 to
an input value of 0.5% of the set measuring span, and then
continues linear to the activation point of the square root
function, adjustable between 5% and 20% of the output. This
function enables a more stable output signal close to the zero
point and avoids errors due to the high gain associated with
the square root.
The standard setting is 5% of the upper range value of the
flow.
Fig. 40
1 Square root function |
2 Activation point square root function, programmable |
3 Initial gradient = 1
For leak flow volume suppression for small input signals close
to the zero point the transmitter output is set to zero until
reaching an adjustable activation point between 0% and 20%.
This function ensures the stability for flow measurements.
The default setting is 6% of the upper range value of the flow.
Fig. 41
1 Square root function |
2 Activation pont leak flow volume suppression, programmable
266CRx, 266JRx, 266CSx, 266JSx | OI/266CXX/266JXX/HART-EN Rev. B 59