Rockwell Automation 1746-NR8 SLC 500 RTD/Resistance Input Module User Manual - Manual (Page 88)

Publication 1746-UM003A-EN-P
6-4 Module Diagnostics and Troubleshooting
Channel Status LEDs (Green)
The channel LED is used to indicate channel status and related error
information contained in the channel status word. This includes conditions
such as:
•
normal operation
•
channel-related configuration errors
•
broken input circuit errors such as open- or short-circuit (RTDs only)
•
out-of-range errors
All channel errors are recoverable errors and after corrective action, normal
operation resumes.
Invalid Channel Configuration
Whenever a channel’s configuration word is improperly defined, the channel
LED blinks and bit 15 of the channel status word is set. Configuration errors
occur for the following invalid combinations:
•
Input type is a 10
Ω
Copper RTD and the excitation current is set for 0.25
mA, which is not allowed.
•
Lead R Enable bits 14 and 15 are set to 11, which is invalid.
•
Broken Input select bits 6 and 7 are set to 11, which is invalid.
•
Data format bits are set to 11, and the lower limit user-set scale is equal to
the upper limit user-set scale and not equal to 0.
Open- and Short-Circuit Detection
An open- or short-circuit test is performed on all enabled channels on each
scan. Whenever an open-circuit or short-circuit condition occurs (see possible
causes listed below), the channel LED blinks and bit 13 of the channel status
word is set.
Possible causes of an open or short circuit include:
•
The RTD or potentiometer may be broken.
•
An RTD or potentiometer wire may be loose or cut.
•
The RTD or potentiometer may not have been installed on the configured
channel.
•
The RTD may be internally shorted.
•
The RTD may be installed incorrectly.
•
Wrong RTD used for type/configuration selected.