How can the grounding of the FTU chassis meet EMC requirements?

Chassis grounding is critical in FTU EMC design, requiring a low-impedance discharge path. A combination of multi-point and single-point grounding is employed. The metal chassis is continuously conductive on all six sides, with beryllium copper springs at the joints, achieving a contact resistance of less than 10mΩ. The chassis is connected to the grounding post via a low-impedance copper strip (25mm²), with a grounding resistance of less than 0.1Ω. The internal PCB is connected to the chassis via metal supports, each using serrated washers to ensure contact. Cable shielding is connected to the chassis via a 360° crimping method. On the PCB, digital ground and analog ground are connected to the chassis via 100nF/2kV capacitors. This grounding system allows for rapid discharge of electrostatic discharge current, with a lightning surge impedance of less than 1Ω, meeting IEC 61000-4-2 Level 4 electrostatic discharge (contact discharge 8kV) and IEC 61000-4-5 surge test requirements.