I recently became aware of the buffer lag known issue describe here if you are running buffer 126.96.36.199: PI Event pipe data updates getting delayed
Also, have you tried turning debug on for the equation using the PI ACE Wizard and examining the message log. You should be able to see values arriving and the ACE equation calculating. Does the equation use a large lag factor? I think the default is five seconds. Is it natural or periodic scheduled?
>I have plotted one of the output tag and its corresponding calculation.
Could you tell us which do you use for getting corresponding calculation?
AF formula? Dataset or analysis with output tag?
PI ACE calculates the results by snapshot values.
On the other hand, if you use dataset or formula, these are calculated with compressed values.
So differences can be seen.
For avoiding incorrect calculation results by the row data is not coming, it is good to use event trigger (Natural) by PI ACE rather than periodic.