I have a total of 32 PI Tags that I need to add together. I was wondering if it is a good idea to use all 32 Tags in one Performance Equation or to break it up into 4 groups of 8?
In terms of PE performance, I wouldn't expect this to be an issue. However, keep in mind that if only 1 of the tags being summed has a "bad" value such as I/O Timeout, etc. Then the entire calculation will fail and write "Calc Failed" as the value. You would need to determine what you would like to happen if a tag has a bad value. Do you have a default value you want to use? Or just not include it in the total sum.
You might need to implement something like:
(If BadVal('Tag1') Then 0 Else 'Tag1') + (If BadVal('Tag2') Then 0 Else 'Tag2') ...
You can imagine this would become quite a long PE expression.
Are you using PI AF? This sounds like a perfect application for a Rollup Calculation.
Hope this helps!
- Adam Fink
Thanks for the insight. I didn't consider the case if the points might be bad.
These points are alarm points, so if it was a bad value, I think those if statements you mentioned will be important in determining if we are getting bad values. The Rollup Calculation in PI AF sounds great for this purpose, but I am calling a lot of PI Tags that aren't in the AF Structure and I thought it would have been better to just use Performance Equations.
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