
Re: Cummulative value calculation using PI Expression
rickyjoerescar Jun 6, 2016 6:10 AM (in response to MDA_Nuclear)I recommend using PI System Explorer for this. Create an analysis and the syntax goes like this.
Prevval(temp,'*') + temp
you would need to map it to another tag to store the data. Once the analysis is running you will just display the tag on your processbook and dataset is not needed anymore. Also, I foresee that using dataset would not fit the job since you are looking at adding real time values at a certain interval.

Re: Cummulative value calculation using PI Expression
tmcmanus Jun 6, 2016 3:27 PM (in response to rickyjoerescar)1 of 1 people found this helpfulSome great points here:
1) Using an Analysis (which will store the calculations in an output tag) will let very easily trend the "Cumulative" tag alongside the original very easily
2) Using an Analysis will allow you to control the output time stamps, and will make for a more seamless realtime usage
We have plenty of great resources to help get you up to speed with AF Analytics if you're unfamiliar with these  here is one of our free online courses that can help you get started  Configuring Analytics with PI AF
I'd also strongly recommend checking out our other free courses, such as the Visualization ones to see what might be helpful for you Learn PI
And lastly, we have a pretty stocked OSIsoftLearning  YouTube channel which can help to review when accomplishing specific tasks


Re: Cummulative value calculation using PI Expression
leonard Jun 6, 2016 8:30 PM (in response to MDA_Nuclear)2 of 2 people found this helpfulHi Glory,
If you don't have Analysis. You can use a PI performance eq or dataset in processbook using the TagTot function:
 Expression: Tagtot('yourPItag', '*24h','*') *24 . This is a sliding Windows calculation (24h until now). 24 is the conversion factor for yourpitag which have unit/hr as engineering unit, 1440 for unit/mn and 86400 for unit/s. Check out the PIperformanceEq document for this function.
Cheers.

Re: Cummulative value calculation using PI Expression
MDA_Nuclear Jun 18, 2016 11:17 AM (in response to MDA_Nuclear)Thanks for all your help! Problem solved.

Re: Cummulative value calculation using PI Expression
gachen Jun 20, 2016 6:47 PM (in response to MDA_Nuclear)This is from another thread that I just responded to, but I thought it may be helpful here too:
I just want to add that in general, we discourage the use of PI Calculation Data Sets in PI ProcessBook, in favor of configuring an analogous AF Analysis, PE Equation or Totalizer point. There are several reasons for this:
 PI ProcessBook Calculation Data Sets need to be recalculated with every refresh. If using one of the other options above, then the calculations are calculated once, and stored into a point. This should improve performance, especially for potentially expensive calculations. If you have many ProcessBook connections all running the same calculation, it can be a big hit on PI Data Archive's archive subsystem performance, because archive subsystem will need to calculate the result individually for each connection. However, storing the results in a point means archive subsystem only needs to retrieve alreadycalculated events.
 Storing the values in a point is much more scalable: the results can then be shared amongst different ProcessBook displays, as well as different clients, without needing each individual client to calculate the result independently.
 Storing the values in a point also give you the history of the calculations.