Rockwell Automation 1747-L40 SLC 500 Fixed Hardware Style - Manual (Page 99)

Chapter 8
Troubleshooting
8–8
The following will assist you in troubleshooting your input modules.
Input Circuit Operation
An input circuit responds to an input signal in the following manner:
1. An input filter removes false signals due to contact bounce or electrical
interference.
2. Optical isolation protects the backplane circuits by isolating logic circuits
from input signals.
3. Logic circuits process the signal.
4. An input LED turns on or off indicating the status of the corresponding
input device.
Input
Input
Conditioning
Optical
Isolation
Logic Circuits Processor
LED
5. The processor receives the input status for use in processing the program
logic.
Troubleshooting Your Input
Modules