Safety Manager Safety Manual - Tuv-fs.com

3 – Safety Manager fault detection and response
An important advantage of input validation is that it can be implemented for input
values of which the validity cannot be guaranteed. Furthermore, the invalid input
can be exactly identified. This allows the implementation of effective correction
strategies of only the affected part of the process.
Common function block
A last option is to create a common function block, e.g. square root. The function
block validates the operand(s) and only performs the intended function if the
operands are valid. Otherwise a predefined value is returned. An additional
function block output should be provided which indicates if the calculation result
is valid or not. This output signal can be used for the implementation of corrective
actions in the application (see Figure 8 on page 36).
Figure 8 Square-root function with validity check in function block
Transmitter
Function block
Process
value
Alarm/
Annunciation
36 Release 131, Issue 4.2