ADE7880 low accuracy in the line cycle accumulation mode while harmonic voltage is in the AC source

Hi, 

   I use ADE7880 to measure AC power energy by using line cycle accumulation mode, and get the good accuracy of xWATTHR in measuring resistance load (PF=1) and motor (PF=0.26).

  While I give the standard 110 AC source with 3-order harmonic voltage of 50% THD on the resistance load, the voltage wave is distorted to  two-peak wave and I get almost

  20% error on the xWATTHR compare with Fluke 434 meter.  Because the resistance load only, the PF is still 1 even the giving distortion voltage.

  I have no idea about what is going on in my measurement and how to explain the situation. May I have any suggestion for this issue? Thank you very much

  • 0
    •  Analog Employees 
    on Jan 17, 2020 12:38 PM

    Can you provide more information: 

    what is voltage divider values used for voltage channel. 

    Are you writing xVgain register? 

    Do you get this on all channels?

    There is a good possibility you are railing the modulator. If at 110v the input signal is somewhere near full scale of the ADC then you add on 50% thd you might be railing the input. If you can't do waveform sampling try Vpeak register to capture your peak value. 

    Dave