I have a PI tag to which real time values are stored once a week .3 sets of values are taken for this Tag eachtime.
I need to compute avg and std dev based on a formula below to calculate Upper and Lower Tolerance limit and update these values to Upper and Lower Tolerance Tag.
But the update to the Tolerance tags needs to be done only once every 20 weeks. How can this be done using Performance equation ?
Temp tag gets value every week.3 sets of values are taken.
Upper limit = Avg(Temp tag)+Std Dev(Temp tag)
Lower limit = Avg(Temp tag)-Std Dev(Temp tag)
Currently it has Tolerance data - from now on the Tolerance data needs to be updated once after 20 weeks with the data from last 20 weeks.
How can this be done?