How can the grounding of the PMS (Power Measurement System) chassis meet EMC (Electrical Compatibility) requirements?

PMS chassis grounding is fundamental for controlling radiated emissions and improving immunity; poor grounding can lead to shielding failure and ground loops. EMC-compliant chassis grounding must adhere to the principles of "low impedance, large area, and multiple connections." First, the chassis itself should be constructed of highly conductive materials (such as galvanized steel). Electrical continuity should be ensured between parts through continuous welding or the use of electromagnetic sealing gaskets, with gap lengths less than λ/20 (approximately 50cm for 30MHz). Dedicated grounding studs should be used for the chassis grounding terminals, connected to the equipment mounting base or grounding busbar via the shortest possible braided strap or copper busbar, with a target connection impedance of <10mΩ. The shielding ground on the PCB (the point connected to the chassis) should be tightly connected to the chassis through multiple screw holes, with a recommended screw spacing of less than λ/10. For internal circuitry, the grounding terminal of the filter capacitor (Y capacitor) should be directly connected to the chassis grounding point, not the PCB ground. For floating ground systems, the chassis can be connected to the circuit ground via a high-voltage capacitor (e.g., 1nF/2kV) and a discharge resistor in parallel. A well-grounded enclosure can provide more than 40dB of shielding effectiveness, helping PMS pass the IEC 61000-4-3 10V/m radiated immunity test.