I've got a dataset which is a PE calc...
If 'xzsc-4502' = "Made" then tagval('At-403a', findeq('xzsc-4502', '*', '*-4h', digstate("Not Made"))) else 'At-403a'
All it's doing is holding the value of a tag at its previous value when a valve goes closed (XZSC-4502 = made when the valve is closed). Now the valve has opened and closed several times in the past 4 hours so I would expect the dataset to return different data to what is actually being stored when the valve is closed, but all I get is "No data".
If I replace tagval('At-403a', findeq('xzsc-4502', '*', '*-4h', digstate("Not Made"))) with the nooutput() function then I get the right kind of thing just with no data when the valve is closed.
Is there a restriction on using the findeq() function within a dataset? It works in other PE's I have but not in a dataset. Is it because a dataset is evaluating data at that instance in time and therefore cannot see historical data in order to search for when the valve was last open??