Hi everyone!

I was following AN-1171 (Rev.A) to calibrate ADE7880 until I stop at:

(Page 8 of 16)

If you do the maths exactly as it appear the result is **3507.270118** (Rounded to 3507 = 0xDB3)

Now I take ADE7880 datasheet (Rev.A) to see if I'm missing something and I stop again at:

(Page 66 of 104)

Different way to calculate same register ... which one is the correct way? Why so different formulas?

I insist trying and use first equation result to calculate "n" with the second one and I get -4,050119. As datasheet says "(...)where n is a positive or negative integer(...)":

- If I round to -4, CFxDEN is 3125 (3507 - 3125 = 382)
- If I round to -5, CFxDEN is 31250 (3507 - 31250 = -27743)

Its a big difference no matter which one I choose (i know I can adjust CF later but .. I want to establish a nice accuracy from base first)

Resuming, please throw me light over CFxDEN calculations!

Thanks in advance and best regards,

CieNTi

CieNTi: Added documents revisions and formulas pages for better reference

Hi CieNTi

The value of n' decides how much energy is assigned to 1 LSB in the energy registers, say if you wish to have it in KWh(n=3) or Wh(n=0). The decision of fixing this value of 'n' will depend upon the CFxDEN and meter constant and that is the relation in the datasheet. For a particular meter constant and CFxDEN calculated, the value of 'n' can only be so much. If you need a different value of 'n', adjust the CFxDEN computations to make that possible. Or if you don't care about 'n', you need not worry about the formula in the datasheet and simply follow the flow in the App Note.

Regards

hmani