Rockwell Automation T7480 ICS Regent+Plus Guarded Analog Output Modules - Manual (Page 8)

Guarded Analog Output Modules (T7480)
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Industrial Control Services
Figure 4. Fault Tolerant Configuration.
Field Wiring
For field wiring details, refer to PD-7901 - I/O Termination
Assembly.
Effects of Open Circuit Field Wiring
When a Guarded analog output module is controlling the
outputs (as opposed to the standby mode) an open circuit in
the field wiring connected to a load device will be detected as a
failure. This causes the controlling module to switch off,
annunciate a fault and enter the standby mode. Once in the
standby mode, all of its outputs are shunted to AGND internal
to the module, thus eliminating the open circuit and the
module’s comparators become healthy. This will have one of
two effects based upon single or dual module configuration:
Single Guarded Module Configuration
In a single guarded output configuration the module will
toggle back and forth between the controlling and standby
modes about every one or two seconds. The ON status LED on
the face of the module will turn on and off repeatedly until the
open circuit field wiring is corrected. During this time the
module FAULT status LED will also be on and the system will
report a fault for this module.