Rockwell Automation 1715-OF8I Redundant I/O System User Manual - Manual (Page 279)

Rockwell Automation Publication 1715-UM001C-EN-P - March 2014 279
1715-IB16D Digital Input Module Diagnostics Appendix C
Closed Switch/On Condition
If SW1 is closed, then current only flows through R2, so to calculate the voltage
present at the input module, use the R2 value of 3.9 kRtotal
Figure 76 - Closed Switch/On Condition
Shield
(if used)
Terminal
Blocks
OV
20 Ω
100 Ω
50 mA
4.99k Ω
Termination
Assembly
+24V dc
R1
R2
45678
Solution For Voltage
5.1K 
SW1
3.9k
15k
Solution For Voltage 45681