User Manual

Rockwell Automation Publication 1769-UM004B-EN-P - March 2010 77
Diagnostics and Troubleshooting Chapter 5
Channel Diagnostics
When an input channel is enabled, the module performs a diagnostic check to see
that the channel has been properly configured. In addition, the channel is tested
on every scan for configuration errors, over-range and under-range, and
open-circuit conditions.
Invalid Channel Configuration Detection
Whenever a channel configuration word is improperly defined, the module
reports an error. See page 78
through page 81 for a description of module errors.
Over-range or Under-range Detection
Whenever the data received at the channel word is out of the defined operating
range, an over-range or under-range error is indicated in input data word 7.
Possible causes of an out-of-range condition include the:
• temperature is too hot or cold for the type of thermocouple being used.
• wrong thermocouple is being used for the input type selected, or for the
configuration that was programmed.
• input device is faulty.
• signal input from the input device is beyond the scaling range.
Open-circuit Detection
On each scan, the module performs an open-circuit test on all enabled channels.
Whenever an open-circuit condition occurs, the open-circuit bit for that channel
is set in input data word 6.
Possible causes of an open circuit include:
• the input device is broken.
• a wire is loose or cut.
• the input device is not installed on the configured channel.
• a thermocouple is installed incorrectly.