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Last Good Value from PI

Within our plant, we use the PI as our main plant historian. We can access process history using PI datalink to import the data into excel. There was a situation last week where I was attempting to create a dashboard view of the process.

Unfortunatly one of the tags I needed to use is not reliable and regularly shows a bad value. The value is unlikely to change much and it will come back again. What I wanted to do was take the 'last good value' and use that in the calculation.

I think that the following excel formula allows me to do this:


Note this will only work for non negative values. For other values, the >0 part will need to be changed.

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