I'm doing daily logging data for daily report and for the daily flow calculation, I'm doing those step:
1- When Timer1 = 11h55 -> Daily_Volume = (Actual_Volume - Yesterday_Volume)
2- When Timer2 = 11h56 -> Yesterday_Volume = (Actual_Volume )
3- When Timer3 = 11h58 -> Log to database Daily Volume
The problem is that when you restart the application or the PC, the calculation tag "Yesterday volume" reset to the last saved value.
Exemple 2012-01-01 last saved application changes,
- 2012-01-01 my Actual_Volume = 1000 USGal moved to my Yesterday_Volume.
- 2012-01-02 my Actual_Volume (1100 USGal) - Yesterday_Volume (1000 USGal) = Daily_Volume (1000 USGal) move the Actual_Volume to Yesterday_Volume.
- 2012-01-03 my Actual_Volume (1200 USGal) - Yesterday_Volume (1100 USGal) = Daily_Volume (100 USGal)
...
We've got a power shutdown or any PC reboot. On the 2013-01-01
- 2013-01-01 my Actual_Volume (19000 USGal) - Yesterday_Volume (1000 USGal) = Daily_Volume (18000 USGal) move the Actual_Volume to Yesterday_Volume.
- 2013-01-02 my Actual_Volume (19100 USGal) - Yesterday_Volume (19000 USGal) = Daily_Volume (100 USGal) move the Actual_Volume to Yesterday_Volume.
Those values reset to the last application saved value cause bad data in my daily, monthly, yearly reports. How can we retain calculation tag value to avoid those reset problem?