User's Manual

Appendix B: PROFIBUS PA profile structure
B.2 Block Model
SITRANS LR250 (PROFIBUS PA)
222 Operating Instructions, 01/2014, A5E32221386-AB
Analog Input Function Blocks AIFB1 and AIFB2
The two AIFBs are completely independent of each other. They utilize the measurement value
output from the Transducer Block [Primary Value (PV), Secondary Value 1 (SV1), or Secondary
Value 2 (SV2)] and apply any required quality checks, scaling, and Fail-safe operation
selections. The Analog Input Function Block output supplies the measured value and associated
status information to the PROFIBUS PA network via cyclic data transfer.
B.2.1
Description of the blocks
B.2.1.1
Transducer Block function groups
The figure below shows the signal flow of measured values from the sensor through the
Transducer Block into the output value:
● Primary Value (PV): Level or Volume
● Secondary Value 1 (SV1): Level
● Secondary Value 2 (SV2): Distance
The Transducer Block implements all of the basic parameters (see diagram below), including
level to volume calculation, if that option has been selected.
Transducer Block