How to prevent interference in the wiring of the PMS terminal area of the power measurement switch?

The terminal area (power input, communication port, sampling terminals) of the PMS is the main channel for external interference intrusion and equipment noise radiation, making interference immunity design crucial for wiring in this area. First, the terminal area should be clearly separated from other circuit areas by a clear isolation strip, typically marked on the PCB with slots or white paint. All signal lines entering from the terminals (including power L/N) must immediately pass through filtering and protection devices, such as the common-mode inductor CMZ1211-501T and X capacitor for power lines, and the ESD protection transistor ESDSM712 and common-mode inductor CML3225A-510T for communication lines, before entering the internal circuitry.

Filtering devices should be placed close to the terminals. Second, the ground plane beneath the terminals should be intact to provide low-impedance grounding for the filtering capacitors. If the terminals have a metal casing and are connected to the chassis, a ring of grounding vias should be installed around their mounting holes. For highly sensitive sampling terminals, partial shielding can be used. Cable entry directions should be fixed to avoid parallel and close routing of input/output cables within the terminal area. By strengthening terminal area filtering, protection, and grounding, a robust "EMC defense line" can be built, attenuating external conducted interference by more than 30dB and reducing internal noise radiation by 20dB.