Leased Tags and Alarms


In my project i want to alert the maintenance people when some equipment have ran more than X hours. So i was thinking to have the running hours tags (from the PLC) in IGNITION, and put alarms.

The problem is that i’m doing this to 700 machines and i don’t want to saturate the OPC connection. I’m going to use the “leased” scan class to this tags (606024*1000 ms on slow rate and 1000 ms on fast rate) so only when the maintenance people see the running hours interface, the tags will be updated at fast rate.

The questions are:

  • When only 1 tag is in use, the whole scan class (and his tags) are subscribed? (I’m using IGNITION 7.2.3 and 7.1.8 )
  • If I’m using alarms in this tags, It always will run at fast rate? or the alarm configuration doesn’t implicate to pass to fast rate?

Thanks in advance.

Leased scan classes evaluate on a per tag basis. So if you have multiple tags but are only looking at one, that one is the only tag polling. The driven mode scan class is all or nothing. The leased is per tag.

The alarm configuration doesn’t make it run at the fast rate. The scan class will dictate when SQLTags evaluates alerts.

Just wanted to clarify that leased scan classes do treat the lease on a per-tag basis as of Ignition 7.2.

Previous to that version, however, leased scan classes operated as you described, where a single tag being subscribed would cause the whole scan class to run at the fast rate.