I've created an event frame start trigger which is;
Tag1 = Preval(tag)
This works but starts only 10 minutes after the value has changed in PI. I've checked the PI data and it corresponds with when the 2nd value that PI records (compmax value on the tag is 10 minutes, with a compdev = 0). The scan rate for the tag is 1 second so should pick up the change in value within 2 seconds.
Processbook sees the tag valve change at 13:00hrs
At 13:10hrs the event frame starts
Why is there a 10 minute delay? It's as if the PI archive is waiting for the 2nd PI value to come in before it notices the change in state. I've considered changing the compmax to 10 seconds, but that will result in lots of unnecessary data points being stored in PI.
I've also tried "not(hasvaluechanged(tag)" as the trigger condition and that does the same thing.
I'm trying another trigger (see below) but as a batch takes 3 hours its a bit of along waiting game!
tag = tagval(tag,'*-10s')
Any help greatly appreciated.