Tag name already exists (or maybe not?)

Hello,

I am running a SCADA application with WinCC Pro V13, SP1, Upd 7.

On one particular screen, two tags suddenly started showing 0. Both tags were previously working well. All the other tags used on that screen (which are also linked to the same DB as the problem tags) are still working correctly.

I have had issues in the past where the connection failed on a tag. Deleting and re-creating the tag was the only way I could find to fix it. In those cases the tag had a fault symbol, whereas this time I show a zero.

A VAT table in the PLC (a Sinumerik 317) shows the DB values associated with the tags to be reading correctly (not 0).

In an effort to fix this, I tried to delete the old tags and create new ones. This resulted in an error on compilation, stating that these two tag names already existed. When I deleted the new tags, the compilation succeeded. Now the two tags are missing from my Tag Table.

BUT, now the screen values are working! Very strange. Next step is to add the same tags to a different screen. I cannot, because the tags are no longer in the Tag Table for that machine.

I did a search under Show All Tags. The tags are not there.

Unsure what to try next, I have restored an earlier version. The Tag Tables now look correct, as do the connections but I am back to showing 0 on the two tags.

Any thoughts on where these elusive tags (the ones that "already exist") might be found? I assume they are pointed at an incorrect location within the PLC, and thus the zeros on my screen, but I cannot find them to verify.

There are other people with access to the project, making it difficult for me to rule out the possibility that someone moved something erroneously or accidentally.

Any help would be appreciated.

Derek

Hello Derek M,

did your tags start to show 0 suddenly during runtime or during the engineering process (new start of the runtime for testing)?

Did you delete the tags in the PLC tag table/DB or the HMI tag table?

To add the tags to a new screen you could connect to the tag in the PLC directly.
Or you copy-Paste the I/O field an have a look at what happens.

You say the values on the screen show again. So if you look to which tag the I/O field is connected, the missing tag is still displayed there, just not in the HMI tag table, yes?

I have two suggestions for you:

• With the older project version there could have been an error in the runtime files.
  The course of action would be to delete the "IM" folder in the windows explorer and then to recompile the project completely.
• The Project might be corrupted (in the engineering files). In this case you should contact the the Technical Support and ask them to get it repaired. https://support.industry.siemens.com/cs/ww/en/sc/3082
  

Hello H.J.

Thank you very much! Deleting the IM folder and re-compiling brought everything back to normal.

To answer your questions, I am not sure when the tags became corrupted as it was simply noticed walking by the large display screen one day, and I deleted the tags from the HMI tag table in the WinCC SCADA project file.

But, thanks to your help, all is well again!