Hello Ignition community,
I have a question regarding reference tags. I commonly use UDTs containing reference tags (linked to OPC tags) to animate Perspective screens. Occasionally, during development or while testing specific tags, I temporarily change the UI reference tag to a memory tag (by overriding the data type) to assign values for testing purposes. Once testing is complete, I edit the tag again to remove the override and revert it to a reference tag. However, when I do this, the tag returns as a reference tag but with an "Uncertain" quality.
I wanted to know if this behavior is normal or if there is something that can be done to prevent the tag from being in the "Uncertain" state. Any insights would be greatly appreciated!
Just to get it out of the way, are you certain that it was working properly in the first place? Have you seen this behavior across multiple times?
I've had UDTs where I start with memory tags and selectively "enable" parts of them as reference OPC tags to work with PLC tags that aren't are ungrouped and vary from instrument to instrument. I don't recall ever seeing issues switching between memory and reference OPC tags, though this was a few years ago.
Hi Zbinder, thank you for your input. Yes, I'm certain that it was functioning correctly from the beginning. I wanted to add that I conducted a few more specific tests and believe I've narrowed down the occurrence of this "Uncertain" value to cases where the original tag, to which the reference tag points, does not change its value.
To explain, I have a tag "tag1" (which could be memory, OPC, or expression, etc.) and a reference tag ("tag2") within a UDT that points to "tag1". I perform an override on "tag2," changing it to a memory tag. I then either modify its value or leave it as is. Afterwards, I revert the override on "tag2," turning it back into a reference tag. At this point, "tag2" ends up in an "Uncertain" state. However, if I change the value of "tag1," "tag2" refreshes its value and aligns with "tag1."
Apologies, I'm mixing up my terms. The tags that I was using were being converted between OPC/memory tags, not reference tags. Maybe there is a bug that specifically affects reference tags. Sounds like you see this behavior regardless of what type the source tag is?
What version of Ignition are you running? I'm on 8.1.35 and can't recreate the behavior with a memory and reference/memory tag. I'm wondering if manually restarting the tag on the right click menu would have any effect for you.
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Well, I've conducted more tests and noticed that this "Uncertain" quality behavior seems to occur only in the Ignition 8.1.44 instance running in a container within AWS. I performed the same tests on other Ignition instances (versions 8.1.44 and 8.1.47) running in Docker containers on my local machine, and the results were as expected: when the tag is reverted to a reference tag, it correctly inherits the value of the original tag.
I think I’ll open a ticket regarding this behavior to investigate its root cause.