Tag Change Script Missing Triggers


I have a tag change script that is occasionally missing triggers. I watched it miss three in a row earlier today but I didn’t see anything differently happening on the PLC. There doesn’t seem to be any kind of pattern to the misses.

This is on a system running Ignition 7.6.7 with Java 7u71. The script is currently set to watch 25 tags (but will probably be watching closer to 75 once everything’s online). The OPC server is Pro Server Ex by Pro-face using OPC-DA. The scan cycle for the OPC tag in the Pro-Face software is 500ms.

The script is watching a “CycleComplete” bit in the PLC that turns on for one second (using a timer) and then off. The Ignition tag is on a scan class of 250ms. It seems like one second should be long enough to trigger though.

Does anyone have suggestions on what I could try to resolve this?

I can confirm that the OPC server’s monitor showed the bit toggle but this wasn’t reflected by the Ignition tag. The scan class’s data mode is “Read.”

It might be interesting to enable SQLTags History for this tag so the next time the script doesn’t trigger you can go back and look at the history and see if there’s any gaps in the data or a value you don’t expect at the time the script didn’t trigger.

I also just created a new connection to the same OPC server and moved only that particular UDT tag member to it. I’m not sure if that helps or not. It’s been good so far but the problem is intermittent so I don’t want to say it’s resolved yet.