I’m trying to figure out the best way to access tag history in a derived/reference/expression tag. For example, say tagA is an opc tag and it’s storing history. I want the value of tagB to be calculated from tagA’s history (tagB might be the average of tagA over 1 week, the exact value of tagA 24 hrs ago, etc.).
The only way I can think of accomplishing this is to make tagB an expression tag that uses the Advanced/RunScript function that runs a jython script that uses the system.tag.queryTagHistory function. I’m worried this method will be too inefficient to use on a large scale (say 1000’s of tagB’s).
Does anyone have a recommendation?
Thanks,
Levi