I have a realtime OPC tag KWH_TOTAL, which I am storing in a Historical Transaction Group at a rate of 5minutes.
Then I have created another SQL Query tag ‘KWH_DAILY’ to look at the KWH_TOTAL from my previously created Transaction Group (SELECT LAST(KWH_TOTAL) FROM kwh_table;).
Lastly, I subtract the two in a an expression tag called KWH ( KWH_TOTAL - KWH_DAILY).
Now this KWH expression tag, I want this to be an incremental tag, rather than JUST the difference between the two Tags? How do I make this tag (or whatever approach) to have the KWH only count up, based on the subtraction?