Rockwell Automation 1762-IT4 Thermocouple/mV Input Module - Manual (Page 72)

Publication 1762-UM002A-EN-P - July 2002
4-4 Diagnostics and Troubleshooting
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
Non-critical vs. Critical
Module Errors 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.
Critical module errors are conditions that may prevent normal or
recoverable operation of the system. When these types of errors
occur, the system typically leaves the run or program mode of
operation until the error can be dealt with. Critical module errors are
indicated in Table 4.3 Extended Error Codes on page 4-6.
Module Error Definition
Table Analog module errors are expressed in two fields as four-digit Hex
format with the most significant digit as “don’t care” and irrelevant.
The two fields are “Module Error” and “Extended Error Information”.
The structure of the module error data is shown below.
Module Error Field
The purpose of the module error field is to classify module errors into
three distinct groups, as described in the table below. The type of
error determines what kind of information exists in the extended error
information field. These types of module errors are typically reported
Table 4.1 Module Error Table
“Don’t Care” Bits Module Error Extended Error Information
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Hex Digit 4 Hex Digit 3 Hex Digit 2 Hex Digit 1