Rockwell Automation 1715-OF8I Redundant I/O System User Manual - Manual (Page 212)

212 Rockwell Automation Publication 1715-UM001C-EN-P - March 2014
Chapter 6 1715 Redundant I/O System in SIL 2 Safety Applications
Analog Output Modules
The analog output module can be used in applications where the output current
is in the range 4…20 mA during normal operation including trip/action value
and where 0 mA is the fail safe value. In these applications, one 1715-OF8I
output module is sufficient for SIL 2 requirements, two modules provide a 1oo2
level.
The analog output module is rated at SIL 2 as a fail-safe simplex module and
when used in a 1oo2 configuration as a duplex module with these features:
• Commanded values and scaling factor
The fail-safe lowest commanded value irrespective of the scaling factor is
0 mA. The application cannot change the scaling factor; it can only be
changed by an online update.
• Fail-safe guard band
The fail-safe guard is 1% (0…2 mA) and not user-configurable.
Reaction to Faults
If an output module faults, the following status information is reported:
• Module presence
• Module health and status
• Channel health and status
• Field faults
• An echo of the front panel indicators for each module
If any of the following internal conditions exist, the output module fails safe:
• An internal software error is detected
• A power feed combiner over-temperature condition is detected