Damping; Transfer Function; Transfer Functions Description; Linear - ABB 266 HART Operating Instruction

Damping (DAMPING)
Pressure transmitter output signals that are noisy as a result of the process can be smoothed (damped) electrically.
The additional time constant can be set between 0 s and 60 s in increments of 0.0001 s. Damping does not affect the value
shown on the digital display as a physical unit. It only affects the parameters derived from this, such as the analog output current,
free process variable, input signal for the controller, and so on.
The damping adjustment can be performed in different ways:
– Via the the local HMI:
Enter the menu: > Device Setup > Output Scaling > Damping
Set the damping to the desired value.
– Via the Asset Vision Basic Software:
See Asset Vision Software Operating Instructions
– Via the Hand Held Terminal
See relevant operating instruction

Transfer function

The 266 Pressure Transmitter provides a selection of output functions, as follows:
– Linear for differential, gauge and absolute pressure or level measurements
– Sq. Root (x) for flow measurements using restriction type primary element, like orifice plate, integral orifice, Venturi or Dall tube
and similar.
– Sq. Root (x3) for open channel flow measurements using rectangular or trapezoidal weir
– Sq. Root (x5) for open channel flow measurements using V-notch (triangular) weir.
– Bidirectional Flow
– Custom linearization table
– Cylindrical lying tank
– Spherical tank
These output functions can be activated using a Configuration Tool (Digital LCD Integral Display, Hand Held Communicator or PC
based software as Asset Vision Basic). The transfer function can be applied to the analog signal 4 to 20 mA only or also to the
indication (in engineering units).vant operating instruction

Transfer functions description

Linear

Using this function, the relationship between the input
(measured value), expressed in % of the calibrated span and
the output is linear (i.e.: at 0% input, corresponds 0% output -
4mA, at 100% input corresponds 100% output - 20mA).
No further settings are possible here.
Figure 45: Linear output

Square root

Using the Square Root function, the output (in % of the span) is
proportional to the square root of the input signal in percentage
of the calibrated span (i.e.: the instrument gives an analog
output proportional to the rate of flow).
The possibility to have the full Square Root function is given.
To avoid the extremely high gain error with the input approaching
zero, the transmitter output is linear with the input up with a
slope of 1 up to 0.5% and then still linear with the appropriated
slope to a programmable percentage value between 10 % and
20%. This option is offer in order to ensure a more stable output
when the signal is close to zero avoiding errors due to the high
gain of the square root.
To neglect the values with the input approaching zero, the
transmitter output is zero with the input up to a programmable
percentage value between 0 % and 20%. This option is offer in
order to ensure a more stable flow measure. This option is
possible for all the listed output functions. ).vant operating
instruction
2600T Series Pressure transmitters | OI/266/HART-EN Rev. D 55