I have seen this done in Processbook standard trends programmatically .I am not 100% sure if this could be done in a SQC trend.
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As far as I know, it's not possible to modify the SQC chart at this level of detail. There may be third-party plugins that provide this functionality though.
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Have you considered using the annotations feature?
In short, annotations can be added to a specific event in the Archive right from PI Processbook (through the Details and Annotations panel).
The annotation icons are displayed on the trend right above the annotated events as you can see on the screenshot below. The annotation description can be viewed either through the Details and Annotations panel or by hovering the mouse over the annotation icon on the trend.
It's definitely an option, just not as clear or "pretty" as the users would prefer. I think this is great for an immediate solution so I will look into it. The only difficultly I'm having right now is that the annotations seem to just disappear after saving them (both in ProcessBook and SMT) so I'm going to need to troubleshoot that. I would prefer to automate it when triggered by a certain event anyways so maybe it will work better that way anyhow.
I'll let you know how it goes!
I probably should have mentioned that I have Moving Average charts, not individuals charts... because I am now seeing that annotations do not show up on moving average charts. Is there a feature request in for this?
Another option would be using Trend Cursors (it will give you a vertical line, but no text notes like in annotations).
The complication is that once a Trend Cursor is placed on the trend/SQC chart, the chart will stop updating. However, it can be worked around by updating the SQC chart through the Display_DataUpdate event handler:
Private Sub Display_DataUpdate() SQCSymbol1.Cursors.RemoveAll ThisDisplay.Revert SQCSymbol1.Cursors.Add (SQCSymbol1.StartTime) End Sub
I guess that leaves the question of where the cursor timestamps come from. You could always read annotations from the SQC tags or values from another trigger tag.
This is not an elegant workaround, but it could be a solution to consider.