Allen-Bradley MicroLogix 1200, User Manual, Page: 71 / 144

Publication 1762-UM002A-EN-P - July 2002
Diagnostics and Troubleshooting 4-3
Power-up Diagnostics
At module power-up, a series of internal diagnostic tests are
performed. If these diagnostic tests are not successfully completed,
the module status LED remains off and a module error is reported to
the controller.
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 pages 4-4 to 4-6 for a description of
module errors.
Over- 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 5.
Possible causes of an out-of-range condition include:
•
The temperature is too hot or too cold for the type of
thermocouple being used.
•
The wrong thermocouple is being used for the input type
selected, or for the configuration that was programmed.
•
The input device is faulty.
•
The signal input from the input device is beyond the scaling
range.
If module status
LED is: Indicated
condition: Corrective action:
On Proper Operation No action required.
Off Module Fault Cycle power. If condition persists, replace the
module. Call your local distributor or Rockwell
Automation for assistance.
AB Parts