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How to set AF Attribute values as stepped or not stepped regardless of PI Point property "step"

Question asked by ChristophRose on Mar 6, 2020
Latest reply on Mar 24, 2020 by Roger Palmen

I have Data stored in PI Points. In AF (and PI Vision) I need to treat that data as stepped in some cases and as non-stepped in other cases.

 

I thought that this could be set using the value retrieval method "By Time".

Usually this is set as automatic. Looking at the documentation this means:

AutomaticA continuous point (step attribute = 0) is treated as Interpolated, whereas a discrete point (step attribute = 1) is treated as At or Before.

This would suggest that setting it to "At or Before" on a non-stepped PI Point would return the values as if it was stepped, while setting it to "Interpolated" on a stepped-PI Point would return the values as if they not stepped.

 

This does not work.

 

The one workaround I've found is using a Formula Data Reference that references another Attribute and set the stepped/not stepped flag for the result of the Formula Data Reference. While this works, from what I understand this creates a lot of unneccessary calculations having to be done during every access to the values.

 

What is the use case for the Value retrieval methods After, At or After, Automatic, Before, Interpolated for PI Points?

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