Analog Input Function Block - Siemens SITRANS P DS III Operating Instructions Manual

Operator control functions via PROFIBUS
7.1 Communications structure for PROFIBUS PA
7.1.5

Analog input function block

The analog input function block is part of the standard functions of transmitters. The
following figure shows the processing of the measured values up to the output.
M Incoming measured value from the pressure transducer
i
block
OUT Output (value, status)
Figure 7-5 Function groups of the analog input function block
Functional principle
The incoming measurement value from the pressure transducer block - or a simulated value
prescribed through the simulation switch - is subject to another normalization (measured
value scaling) and a projection onto the output range through output scaling (application-
specific measured value).
Afterwards, the signal is filtered (damping) and check for being within preset limit values.
There is always an upper and lower warning and alarm limit available.
If the measured value has the status "Bad", the shutdown logic may output a safety preset
value: This may be the last usable measured value or a preset substitute value.
Using the target mode selected in the mode and status editor you can choose between
output of the automatically collected measured value (AUTO setting) or a manually preset
simulation value (MAN setting). If the function block is out of order (O/S setting) then the
safety preset is always output.
104
MAN Manual
O/S Out of Service
AUTO Automatic
SITRANS P DS III with PROFIBUS PA
Operating Instructions, 06/2013, A5E00053276-07