My gateway is running Ignition 7.9.6 on Win7 x64
I have 2 OPC tags set to grab timer preset and accumulated values on our default 1 sec driven scan class. These 2 OPC tags are updating each second as expected in the designer.
Now I have created a second expression tag that is set up to grab the difference between these 2 values and essentially give me a countdown of the process on the plant floor. This tag is set up on the same default 1 sec driven scan class.
The expression tag does not evaluate as expected. Sometimes this value doesn’t update for 20-30 seconds but it does not give an error. I have checked out the default scan class execution info on the gateway web interface, and it shows that the default scan class is executing each second without delay.
The issue is intermittent, but seems to start happening after the gateway has been running for a while. We had the issue on our main ignition server and recently migrated the gateway to another machine. The issue went away for about 3 weeks, but is present again so I would imagine it’s something caused by our configuration.
One thing that we’ve noticed that seems to coincide with the scan class evaluation issues we’re having is that historical data is missing from trends. We have had to set the “validate scan class executions” parameter to false on all of our easy charts to mitigate this, but I would rather be able to find the root cause of the issue than use workarounds.
Can anyone suggest ways to troubleshoot this?