A Tale of Two Tags

It was the best of times it was the worst of times…

Sorry, just couldn’t resist.

I have two tags pulled from the same CLX controller.

Both are historical tags.

Both change once per hour.

One is updating in the database once per hour.

The other is updating in the database once every 10 seconds, with the same value.

Both are set as Default scan class.

Both are set as Default Historical scan class.

Can you point me where to look?

Something is obviously different, but I just don’t see it.



You want to look at the scan classes for this one. When you use our historian you setup a scan class for history which is the rate to log data. By default our Default Historical scan class is a 10 second scan class. Keep in mind that we only log data when it changes. So even if they have the same scan class nothing gets put into the db until it changes.

Let me send support some screen shots.

It is easier to paste them into an email…



Sounds good.

I’d say it must either be the (historical) deadband, or the “max executions between storing”.

If the deaband is 0, or max execs is set to 1, it would cause it to log every exec, which for the default historical deadband, is 10 seconds.