Rockwell Automation 1790P-4R0 CompactBlock LDX I/O RTD/Resistance Input Module - Manual (Page 48)

Publication 1790-UM002A-EN-P
4-4 Diagnostics and Troubleshooting
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 broken input conditions.
Non-critical module errors are typically recoverable. Channel errors
(over-range or under-range errors) are non-critical. Non-critical error
conditions are indicated in the module input data table.
Out-of-Range Detection
When the input signal 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 4.
Possible causes for an out-of-range condition include:
•
The temperature is too hot or too cold for the RTD being used.
•
The wrong RTD is being used for the input type selected, or for the
configuration that you have programmed.
•
The input device is faulty.
•
The signal input from the input device is beyond the scaling range.
Open-Wire Detection
The module performs an open-circuit input test on all channels on each
scan. Whenever an open-circuit condition occurs, the overrange input bit
for that channel is set in input data word 4.
Possible causes of a broken input condition include:
•
the input device is broken
•
a wire is loose or cut
•
the input device is not installed on the configured channel
•
an RTD is internally shorted
•
an RTD is not installed correctly
Module Error Definition Table
RTD/resistance module errors are expressed on a channel basis in input
read word 4. The structure of the status data is shown in the following
table.