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ADE7880 harmonic reading value VS digital power meter (Chroma 66202) reading result question

Question asked by Sam.S on Sep 23, 2016
Latest reply on Feb 15, 2017 by Sam.S

Dear Sir,


   Our customer use ADE7880 EVB to evaluate ADE7880 Harmonic engine performance now.


Below is our customer testing result that Chroma 66202 VS ADE7880 reading Harmonic value that base on same loading:


Chroma 66202
THD 2nd:0.0105~0.0025
THD 3rd:0.1037~0.0878
THD 4th:0.1059~ 0.0961


2nd:0.00373745~0.000877857 thd: 0.003…
3rd:0.00153494~0.000659943 thd: 0.004…
4th:0.00417805~0.00109673 thd: 0.005…


In 2nd order harmonic, the result is simular in both(Chroma 66202 and ADE7880);


But in great than 3rd and 4th order, ADE7800 reading value is small than Chroma 66202,

1. What reason can cause harmonic value is small than real value(digital power meter) when the harmonic index is great than 3rd order?

2. Dose THD procedure need to do calibration first or do some compensation calculation?

3. Have others register have to initial first before to get the harmonic related values?


PS: Our customer use below formula to calculate the THD:


THD calculation formula


Thank you!