Rockwell Automation 1756-OF8I ControlLogix Eight-channel Isolated Analog I/O Modules - Manual (Page 23)

Rockwell Automation Publication 1756-UM540A-EN-P - May 2014 23
ControlLogix Isolated Analog I/O Module Features Chapter 2
Module Quality Reporting
The modules indicate the quality of channel data returned to the owner-
controller. Data quality represents accuracy. There are levels of data quality
reported via module input tags.
The following input tags indicate the level of data quality. In the tag names, x
represents the module channel number:
• I.Ch[x].Fault tag - This tag indicates that channel data can be completely
inaccurate and cannot be trusted for use in the application. If the tag is set
to 1, you cannot trust the data reported. You must troubleshoot the
module to correct the cause of the inaccuracy.
Common causes of inaccurate data include the following:
–
An overrange or underrange condition exists.
– A wire off detection condition has occurred.
– A short circuit detection condition has occurred.
• I.Ch[x].Uncertain tag - This tag indicates that channel data can be
inaccurate but it is not known to what degree of inaccuracy. We
recommend that you do not use the data for control.
If the tag is set to 1, you know the data can be inaccurate but you must
troubleshoot the module to discover what degree of inaccuracy exists.
Common causes of uncertain data include the following:
–
The channel is actively being calibrated.
– An invalid sensor offset value exists.
– The channel’s last data sample failed CRC while the most recent data
sample was valid and used.
We recommend that you monitor these tags in your program to make sure the
application is operating as expected with accurate channel input data.