Rockwell Automation 1746-NT4 Series B,D17466.6.1 SLC 500 4-Channel Thermocouple/mV Input Module User Manual - Manual (Page 82)

Publication 1746-UM007C-EN-P - July 2004
7-4 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
•
open circuit errors
•
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 when the input type (bits 0-3 in the
channel configuration word) is invalid, or when the open circuit state
selection (bits 6 and 7) is invalid.
Open Circuit Detection
An open-circuit test is performed on all enabled channels. Whenever
an open circuit condition occurs (see possible causes listed below),
the channel LED blinks and bit 12 of the channel status word is set.
Possible causes of an open circuit include:
•
The thermocouple may be broken.
•
A thermocouple wire may be loose or cut.
•
The thermocouple may not have been installed on the
configured channel.
•
The CJC may be damaged.
If a damaged CJC termination is the cause of the detected open circuit
condition, the status LED for each channel configured for
thermocouple or CJC input blinks.
If an open-circuit is detected, the channel data word reflects input
data as defined by the open-circuit bits (6 and 7) in the channel
configuration word.