Rockwell Automation T7411F ICS Regent+Plus Monitored Digital input Modules, Field powered (Type F) - Manual (Page 19)

Monitored Digital Input Modules, Type F (T7411F, T7418F)
P D - 7 0 2 7 M a r - 0 6
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short or open circuit (or there is no line monitor device
installed) the Fault Name status is off.
The status of the Name and Fault Name input variables are
summarized in Table 3 for the various field input conditions.
Table 3. Input Status for Field Input Conditions.
With Line Monitor Device
Installed
Without Line Monitor
Device Installed
Field Input
Condition Name Fault Name Name Fault Name
Switch Open OFF ON OFF OFF
Switch Closed ON ON ON OFF
Open Circuit OFF OFF Same as Switch Open
Short Circuit ON OFF Same as Switch Closed
Programming Dual Fault Tolerant Monitored Inputs
To program fault tolerant configurations using dual
monitored input modules, ladder logic is used to check the
status of the inputs and the system control relays (that report
a faulted I/O module) and provide a voted input value. Two
examples are shown below.
Normally Energized Inputs
Figure 12 shows a ladder logic rung that would be suited for
normally energized inputs that de-energize to trip.
Figure 12. Dual Voting for Normally Energized Inputs.
In this example, IN1A and IN1B represent the input
variables from two redundant monitored input modules.
IO01U01 and IO01U02 are the system control relays that
report a fault for the monitored input modules (one installed
in slot 1 of chassis 1 and the other in slot 1 of chassis 2). The
variable IN1VOTE is a shared control relay that will