i have a little problem with the following scenario:
An UDT contains an OPC-Tag and an Expression Tag, both on a Driven ScanClass.
Every 15 minutes, the ScanClass executes and reads an OPC value.
The expression tag should then make a calculation, as soon as the new value arrives.
Now, the calculated value should be stored to a database table, using an id property, timestamp and the value from the UDT.
The above has to be done for a few hundred tags (from many different plcs) at the same time.
Everything works perfect if i forget the UDT and use a Standard Transaction group for every tag, but i don’t want to maintain some hundred groups, so the idea was to use one big block group, that references the UDT (block groups seem to have no support for expressions).
Is there a way to synchronize the execution, so that the tag is read, then it is calculated and when everything is calculated stored to the db? I can’t use data change events, because in rare cases the new values might be the same as the old ones.
I hope there is an easy way to do what i wan’t, that i just don’t realize by know.