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ADe7880 power register reading

Question asked by ooben on Apr 16, 2013
Latest reply on Apr 26, 2013 by hmani

I am working with ADE 7880 evb now. The inputs for three channel are all 110 v AC and 100 mA at 50 Hz and voltages and currents are all in phase. there is no harmonic component. Now, I got reading for phase A:


AWATT: 0x26364

AVA: 0x263D4


FWATT: 0x98D64

FVA: 0x98D4A

FVAR: 0x158


AVRMS: 0x126048

AIRMS: 0x1092C0


FVRMS: 0x125EA1

FIRMS: 0x10A39F


questions are:

1. why FWATT not equal to AWATT and FVA != AVA?

2. how should I interpret FWATT (and FVA and FVAR) register value as human understandable reading?

3. ADE7880 datasheet gives S = V * I, but here AVA not equal to AVRMS*AIRMS ? Also, FVA not equal to FVRMS*FIRMS.




Note,  approximately, AVRMS = FVRMS and AIRMS =  FIRMS as expected. when I convert those values to the real voltage and current, I multiply them by voltage and current coefficient factors, for example: AVRMS * V_factor = 0x126048 * 9.396*10^-5 = 113.1556v , which is fine comparing to 110 v input. AIRMS * I_factor = 0x1092C0 * 9.387*10^-8 = 0.10196 A, comparing to 100 mA input.