How can the interference immunity of the concentrator metering module be improved?

Insufficient immunity of the concentrator metering module (including metering chip, reference, and ADC) can cause output fluctuations under electromagnetic interference. Improving immunity requires comprehensive hardening of the power supply, reference, interface, and PCB. For the power supply, independent LC filters (PBZ1608E600Z0T + capacitor) and LDO regulation are used for the analog and digital power supplies of the metering chip, respectively. A low-noise, high PSRR reference source (such as REF5025) is used for the reference voltage, and it is fully decoupled with capacitors (1μF + 0.1μF), and covered with a shield if necessary. A 22Ω resistor or PBZ1005B-501Z0T ferrite bead is connected in series on the digital interface (SPI) line. On the PCB, a complete ground plane is maintained below the chip, and the analog section is surrounded by a ground guard ring. On the software side, digital filtering and outlier removal are implemented. After hardening, the metering module can maintain stable output under IEC 61000-4-4 EFT level 4 interference, with an error variation of less than 0.1%.