Easy Chart Intermittently Displaying Tag Historian Data

We’re using Ignition 7.9.1

The issue we have is Ignition sometimes decides not to display tag data in the Easy Chart.

An example is posted below. When watching the green line, you can see it travel all the way across the chart as it should. I have bound a table to the window showing the tag data for the same tag and bound to the start and end date of my Easy chart:

Now, when I adjust the time frame a little bit, I will get periodic instances of the line disappearing on the chart all-together. I don’t imagine there is anything wrong with the query as the table data still shows as it should. As you can imagine, it’s pretty hard to rely on trending data when this happens:

I have also noticed this issue on things like when I’m using the run condition to show a digital signal in a trend on pumps. Quite often, the trend shows that the pump was not running when indeed, it was.

Does anyone have any suggestions on how to resolve this? I can take more screenshots if necessary if clarification is required.

Thanks in advance for the help!

What happens if you set ‘Validate Scan Class Executions’ false in the easy chart’s advanced properties?
You might be running into the Historian’s (moderately aggressive) stale value detection, which is by default a 2x multiplier of the historical scan class. You can also check the size of the sqlth_sce table, eg:
SELECT COUNT(*) FROM sqlth_sce

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Oh, man. You’re a lifesaver. Thanks very much!

As soon as I flip that, the trend populates the missing data.

This is a problem I’ve struggled with since my very early days with using EasyChart component. It seems that there are combinations of tag history settings, and chart settings that under certain circumstances will result in a trace(s) not showing up, or partially showing up.

Is there a deep dive document somewhere that I can cubby away to pull out everytime I use the EasyChart, because apparently I’ve not figured it out even after trying several attempts at trial/error with mostly the EasyChart’s Tag History Settings (TH Res, TH Res Mode, Allow Interpolation, Validate, Ignore Bad, Bypass Cache) and the History settings in the individual Tag Editor (Hist SC, Deadband, Value Mode, Max time between records)

I think the thing that results in a blank trace given the selection of certain timeframes is just leaving the Max Time between records in it’s default setting (Unlimited), particularly for discrete values that don’t change that often, like setpoints, or numbers of units running, etc. I don’t see the “Last Change” time tag property update even if I force the historian to record the value say, every 10 seconds, which makes sense to me…if the tag value didn’t change according to the deadband and scanclass settings. If I zoom in to the point level on EasyChart, I think the visibility is there…or if you dig up the tag data in the tag historian tables.

So in summary, the lesson to me has been it’s a lot more complex and dimensional then at first blush…so don’t expect to be able to just drag a tag to an EasyChart, and it automagically show up in every time frame you select to view it. It may not happen if you haven’t addressed all three of the settings areas mentioned above…EasyChart Tag History properties, Tag History properties, and Scanclass properties, and they’re all working together to deliver what you expect.

Note to self: RTFM and coalesce the knowledge of all three of these areas.