Rockwell Automation T7485 ICS Regent+Plus Isolated Guarded Output Modules User Manual
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Isolated Guarded Digital Output Module (T7485)
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performed on each switch to eliminate the effects of AC phase
on the test.
When two isolated Guarded output modules are wired in
parallel for fault tolerance, the output circuit testing is non-
coincident between the modules and the test pulses do not
disturb the load in either the on or off state.
When an output switch is tested, the test pulse duration is
nominally 125 msec, and is insufficient to affect the state of
most field loads. The output circuit test interval will range
from 1 to 60 seconds, depending on the quantity of I/O
configured in the system.
If an output switch doesn’t change state when tested, an
output switch fault is detected. An output switch failure is
annunciated as a module fault. An I/O module fault is
indicated by the module FAULT LED on the module, the red
I/O fault LEDs on the processor modules and the system
control relay fault bit for the module assembly and slot.
Output Fuse Monitoring
For each output, the voltage at the fuse terminal is monitored
and the optically coupled signal is sensed by the FPGAs. If a
fuse blows, the corresponding output’s blown fuse LED is
illuminated on the front of the module and a module fault is
also indicated.
There are three instances when a blown fuse will not be
detected. These are described below.
1)
For DC voltage applications, the positive side of the
field power source must be connected to the “IN”
terminal and the load must be connected to the fused
“OUT” terminal for proper blown fuse detection.
2)
If dual modules are wired in parallel for fault tolerance,
when an output is on and only one of the two modules’
fuse blows, the blown fuse is not detected. This effect
will not normally occur, because if an output load short
circuit occurs, both modules’ fuse should blow.
3)
When an output is fully connected to a load and power
source, and the output is in the off state, if the field
power supply is not powered (i.e. the power source’s
Note: