Alarm Hanging with Active Delay and Dynamic Enable

During testing over the past few days of 7.6 new alarming I am seeing a behavior that I don’t think is correct. When setting up an alarm we use different “permissive” in the enable for different alarms. When we also set the active delay to some value other than 0 we get very unexpected behavior. When alarm is set this way and the value for the tag your are alarming on is in an alarm state and the enable goes high then low in less time than that set in the active delay value then the alarm goes active and hangs there even though the alarms enable property is not true at this time.

We tested this in a just memory tags and it does the same thing. Note this behavior is not seen if the active delay value is set to a 0.

Running 7.6 rc5


Yes, I’ve been able to replicate this. As you noticed, there are basically two issues:

  1. The deadband timer doesn’t check the enabled property when it expires, so it will still fire the event.
  2. When the alarm becomes disabled, it removes its active events from the state model, which causes an inconsistency when the event from #1 comes through. I believe this gets worked out after a certain combination of the alarm going active/inactive again, or disabled/enabled, but it’s annoying.

The fixes for these will be in 7.6.2 beta 1, as 7.6.1 is already in the process of going out.

Thanks for the detailed report,