Siemens SITRANS LR250 Operating Instructions Manual page 265

How an Analog Input Function Block works
The AIFB provides a linear conversion to any desired units.
1. The AIFB Input value is the processed output value of the Transducer Block, in Transducer
Block units.
2. The user selects the desired AIFB output units and scaling is applied.
3. Damping may be applied based on a time constant provided by the user. See Damping
(Page 239) for details.
4. The status of the input value from the Transducer Block is checked. If the status is Bad, a
Fail-safe condition occurs. The output is determined by the setting for Failsafe Mode.
5. Actual Mode (2.6.2.) allows the entire AI block to be overridden by a Manual Output value.
See Actual Mode (2.6.2.) for details.
6. The value is checked against the user-defined warning and alarm limits. The upper and lower
limits are defined in units corresponding to the Output range, and a limit hysteresis can be
used to adjust the sensitivity. See Alarms and Warnings (2.6.7.) for details.
7. The output value (OUT) is communicated via cyclic data transfer.
SITRANS LR250 (PROFIBUS PA)
Operating Instructions, 08/2014, A5E32221386-AC
Appendix B: PROFIBUS PA profile structure
B.2 Block Model
263