Rockwell Automation T3411 ICS Regent Monitored Digital Input Modules - Manual (Page 14)

Monitored Digital Input Modules (T3411)
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Industrial Control Services
Line Monitoring
The Monitored digital input module can perform line
monitoring of the field wiring when a suitable line monitor
device is installed across the field input switch. Two types of
line monitor devices are available to match the type of module
configuration used in the application.
Figure 8 shows a single switch connected to a single monitored
input module. This type of configuration uses the T0412 line
monitor device which contains two resistors, one in series with
the field switch and one in parallel with the field switch.
Figure 8 also applies to fault tolerant input configurations
that include redundant sensors connected to redundant input
modules.
Figure 8. Line Monitoring, Single Switch Connected to
Single Module.
For fault tolerant configurations using single sensors
connected to redundant input modules, the T0413 line
monitor device is used as shown in Figure 9. This line
monitor device includes two zener diodes, one in series with
the field switch and one in parallel with the field switch.