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.