Wiring Flex I/O Digital Input Modules - Allen-Bradley 1794 Reference Manual

Wiring FLEX I/O Digital
Input Modules
One-Sensor Wiring Example
Input
COM
+24V
Two-Sensor Wiring Example
Input
COM
+24V
Note 1: Both sensors are monitoring the same safety application.
The wiring diagrams in Figure 3.1 show two methods of wiring the digital
input Module. In either case, users must determine whether the use of 1 or 2
sensors is appropriate to fulfill SIL2 requirements.
Figure 3.1 ControlLogix Digital Input Module Wiring
Input 1
1794-IB16
24VDC SINK INPUT
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 0
Input 1
1794-IB16
24VDC SINK INPUT
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 0
Application logic can compare input values or states for concurrence.
Figure 3.2
Input A
The user program must also contain rungs to annunciate a fault in the event of
a sustained miscompare between two points.
Figure 3.3
Input A
Input A
Timer Done
Fault
AB Drives
Input 2
1794-IB16
24VDC SINK INPUT
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
SIL2 SENSOR
Input 2
1794-IB16
24VDC SINK INPUT
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
SENSOR
SENSOR
Input B
Input B
Input B
FLEX I/O Modules
+24V dc
Optional relay contact
to switch line voltage
for periodic automated
testing
1
1
43366
43366
Actuator
Timer
Timer preset in milliseconds to
compensate for filter time and
hardware delay differences.
Fault
Alarm to Operator
Publication 1794-RM001G-EN-P - December 2011
3-3