Hi amrnasser
Thanks for the detailed explanation! I believe you are concerned about calibrating just the energy registers (and not the CF). And as you are using a known source to calibrate, follow the 'calibration by accurate source' description in the datasheet. However, you will have to understand that the measurement cannot be more accurate than the source itself. So, kindly set your expectations based on the source's accuracy ( in your case, how accurately you can measure the load current consumption and nominal voltage.
Say, if you need to calibrate active energy, then:
1. Assuming you don't need phase calibration, gain calibration would be the first step. That would involve setting the WGAIN register to scale the LAENERGY register reading. Always use the LAENERGY register while calibrating active energy register measurements. Equation 47 in page 41 of the RevC datasheet shows how the scaling will affect the register reading. The active energy window or line accumulation window will help you get a line cycle energy measurement (Set the number of half line cycles prior to that). Change WGAIN on the active energy window and see how the change has affected the energy measurement. Set WGAIN to desired value. This step can help you identify Wh/LSB constant. So, compare the known input with register reading and compute this constant. Equation 36 in page 39 of RevC datasheet gives the equation needed for this. You can now use this constant to convert further active energy register measurements to real world values in Wh.
2. The next step is offset calibration. This step is to set APOS register based on the error observed in the lowest signal level of the application. Page 43 of the datasheet gives a very good example to find APOS value based on your measurements. Use the active energy window of the software to set APOS. This step improves the accuracy at lower current inputs.
I think this is a good starting point for you to try calibration and see if you get reliable results from your setup. Once you finish these steps, you will gain some understanding of how to look for relevant details in the datasheet and user guide to perform calibration of CF and other measurements as well. Let me know if you have further doubts.
Regards
hmani