How can isolation devices for power measurement switches (PMS) improve immunity to interference?

In PMS (Power Management System), using isolation devices (such as optocouplers, digital isolators, and isolation amplifiers) can break ground loops and block common-mode noise conduction, effectively improving system immunity. Selection and application considerations: For digital signal isolation (such as switching signals, SPI), select according to speed requirements: for low speeds (<100kbps), use optocouplers (such as TLP181); for high speeds (>1Mbps), use magnetically coupled digital isolators (such as ADuM1401). For analog signal isolation (such as sampling), use isolation amplifiers (such as ADuM4190) or isolated ADCs (such as ADuM7701).

The isolation voltage of the isolation device should meet system safety requirements (such as 3000Vrms). Power supply isolation is equally important; a separate isolated power supply module (such as DC/DC) should be provided for the isolation side. During layout, the isolation device should be connected across the PCB's isolation strip, completely separating the primary and secondary circuits, including the ground plane. The width of the isolation strip should typically meet safety creepage distance requirements (such as 8mm/300V). By using isolation appropriately, the impact of ground potential difference and common-mode noise can be minimized, and the system can easily pass immunity tests such as EFT and surge.