Rockwell Automation T8472 Trusted TMR 120V ac Isolated Output Module - Manual (Page 24)

Trusted
TM
Module T8472
Issue 13 Sep 11 PD-T8472 24
5. Fault Finding and Maintenance
5.1. Fault Reporting
Output module faults are reported to the user through visual indicators on the front panel of the module
and through status variables which may be automatically monitored in the application programs and
external system communications interfaces.
There are generally two types of faults that must be remedied by the user: external wiring and module
faults. External wiring faults require corrective action in the field to repair the fault condition. Module
faults require replacement of the output module.
5.2. Field Wiring Faults
By measuring the output channel voltage and current, the module automatically detects field-wiring and
load faults. When a field signal fails open circuit, short circuit or there is no field supply voltage
connected, the output status indicator will display the configured LED mode, the corresponding output
state will be reported and the line fault status for that channel will be set to ‘1’. All other output
channels will be unaffected, except in the case of common cause wiring and supply voltage faults in
the field.
The field output voltage and current variables can be monitored to determine the actual operating
conditions of each output channel. This additional information assists the user in determining the
specific type of wiring fault.
Once the specific field-wiring fault has been identified and corrected, the output status variables and
output status indicator will display the normal on/off status of the field device.
Note that short circuits are only detected when the output is energized.
5.3. Module Faults
Extensive diagnostics provide the automatic detection of module faults. The TMR architecture of the
output module and the diagnostics performed ensure the validity of all critical circuits. Using the TMR
architecture provides a Fault Tolerant method to withstand the first fault occurrence on the module and
continue normal output controls without interruption in the system or process. Faults are reported to
the user through the Healthy status indicators on the front panel of the module and through the INFO
and HKEEPING variables. Under normal operations all three Healthy Indicators are green. When a
fault occurs, one of the Healthy Indicators will be flashing red. It is recommended that this condition is
investigated and if the fault is within the module, it should be replaced.
Module replacement activities depend on the type of spare module configuration chosen when the
system was configured and installed. The module may be configured with a Dedicated ‘Companion’
Slot or with a Smart Slot for a spare replacement module.
5.4. Companion Slot
For a Companion Slot configuration, two adjacent slots in a Chassis are configured for the same input
module function. One slot is the primary slot and the other a unique secondary (also known as ‘spare’
or ‘hot-repair’) slot. The two slots are joined at the rear of the Chassis with a double-wide I/O Interface
Cable that connects both slots to common field wiring terminations. During normal operations, the
primary slot contains the active module as indicated by the Active indicator on the front panel of the