Hello,

I have a short question. I've create a totalizer tag with help from these manual: https://techsupport.osisoft.com/Troubleshooting/KB/KB00793

Looks fine for the totalization for one day. But why do I have to multiplicate with the conversion factor of 24? What should I choose for one month? The calculation should divide the Time by the TimeStamp of each Snapshot... ( e.g. kg/h * (TimeStamp2[h] - TimeStamp1[h])

Without these conversion factor the calculated value is much too small. With 24 it looks good.

In my opinion the calculation for one day or one month should be the same with the exception that the final value is writen by bod('*') or bom('*') ... or are I'm wrong?

Thanks for any help!

Hi Tobias,

If this is a new setup, I'd highly recommend using Asset Analytics rather than a PI Totalizer. Asset Analytics is a feature provided in the PI AF Server. For reference: OSIsoft: How to Setup Expression Analyses with PI AF [PI AF 2014- v2.6.0.5843] - YouTube

The setup would be straightforward, the function would be TagTot() and you would need to multiply by the conversion factor in this specific case 24.

To answer your specific question, the PI System assumes the unit of time for any rate is units/day. If you have a data point capturing a rate that is units/hours, to calculate the correct total, we need to multiply by 24.

In your example, the difference in timestamps would be represented as a unit of day so we would have:

kg/h*(T2-T1)d = kg/h*d > these units don't simplify to a total...

so we need to to do:

kg/h*(T2-T1)d *24h/d = kg/h*d*24h/d > simplifying the units out we end up with kg

It's very important to note that it doesn't matter if (T2-T1) is the fraction of a day or multiple days, we always need to use the factor which converts the rate unit of the data point to 1 day.

In the case of seconds we would multiply by 86440, minutes 1440 and hours 24.

Let us know if this isn't clear.

Thanks,

Seb