We are using KM34Z256 MCU in the product to measure the energy. 24-bit sigma-delta ADC is used for 3-phase current sampling and 16-bit SAR is used for 3-phase voltage sampling. Now the product meet class 0.2% current /0.2% voltage /0.5% active energy accuracy with default FW function blocks and basic calibration.
Is it possible to meet 0.2% active energy in this setup? What are the critical issues should be considered?