Scanclass and deadband : modifiy in live


Is it possible to modify the scanclass and or the deadband of an SLQTags in realtime ?

What we need to do is to change SC and/or DB for some SQLTags when the user want to have a deeper look at some special events.

Thanks for your help

Not if the tag provider is internal. If the tag provider is a database driving provider you can since the tags are stored in the SQL database.


There are a few different things you can try.

  1. Driven Scanclasses - If the tags that you want to occasionally view more quickly can be organized into groups, the driven scan class lets you control the rate off of a trigger tag. There is a fast and a slow rate. The slow rate would be your normal rate, and then the fast would be whatever you wanted, and then you could trigger it off of a simple static db tag.

  2. Write to the deadband property of the tag - it is possible to write to most properties of tags. You can use [tt]system.tag.writeToTag(“Path/To/Tag.Deadband”, 0.01)[/tt]
    This will change the deadband, but note that right now it will also cause the tag to reload. Not usually a big deal, but it will probably blink bad quality for a second. We can probably update this property to be a “runtime property” in the future, that is- one that can be updated without a reload.

Hope this helps,

Colby, Travis,

Nice. I’ll try this. I think having the SC as a “runtime property” should be a good new for us. I’ll try driven SC.

Another “plus” would be to have an “ante mortem”. In this case, some tags only are in the ante mortm list. When a fault occur, tags values are store for a short time : 30s before the event and 30s after (both should be parameters).