# How to compute the Energy values ? (ADE7880)

Question asked by p301 on Apr 30, 2014
Latest reply on May 16, 2014 by p301

Hello,

I am working with an ADE7880 and I successfully get the Current, Voltage, PowerFactor, ApparentPower and ActivePower.

I am able to compute the real values of the Current, Voltage, PowerFactor, ApparentPower and ActivePower with the values I read in the ADE's registers.

Now I try do to the same thing with the Energy. I choose to use the energy accumulation mode and my accumulation number of half periods is 10.000. As I am working with 50Hz signals the duration of my accumulation is T = 1*10000 / (50 * 2) = 100 seconds.

I know the average power I have during thoses 100 seconds but I can't figure how can I compute the value of one LSB of the xWATTHR register.

On page 49/104 of the ADE7880's datasheet it's written that "Note that line cycle active energy accumulation uses the same signal path as the active energy accumulation. The LSB size of these two methods is equivalent."

I am considering this simple case : my voltage is 0.5V and my current is 0.5A when the ADE's ADC are at full scale (I am doing simulations with a function generator as I don't have big currents available at the office).

So one LSB[Whr] = (PMAX * 1024000 * 3600 * 100[sec] / (0.5[V] * 0.5[A] * 2^27) in Watt hours ? So one LSB [J] = LSB [Whr] / 3600 ?

I hope I explained my problem correctly.