How can the safety capacitors of the PMS (Power Measurement System) for electrical force measurement switches balance EMC (Electrical Conformity) and metering?

In a PMS (Power Management System), safety capacitors (X and Y capacitors) provide filtering, but their leakage current can affect metering accuracy. In particular, leakage current from Y capacitors connected to protective ground can flow into the sampling ground, causing zero drift. The key to balancing EMC and metering lies in the selection of capacitors and the grounding scheme. For X capacitors (differential mode filtering), low-loss, high-stability film capacitors (such as MKP type) are used, with capacitance values typically ranging from 0.1-0.47μF, and their impact on metering is minimal. Y capacitors (common mode filtering) present a greater challenge, requiring the following measures: Select Y1-class capacitors with extremely low leakage current (e.g., 2.2nF/300VAC, leakage current <0.25mA); do not directly connect the Y capacitor between the analog ground (AGND) and chassis ground (PE) of the metering board, but instead connect them through a 100kΩ resistor in parallel with a CMZ2012A-900T common mode inductor (90μH), providing a high-frequency grounding path while blocking power frequency leakage current. Simultaneously, concentrate the Y capacitors near the power input port, away from the metering circuit. This design can control the power frequency leakage current introduced by the Y capacitor to below 10μA, the metering zero drift to less than 0.05%, and meet the EN 55032 Class B conducted emission limits.