Q: How to implement EMC mitigation for IoT devices in industrial environments (EMC immunity)?
Answer
Industrial EMC immunity requirements (IEC 61000-4 series): (1) ESD immunity (61000-4-2): add TVS diodes on all external connectors. (2) Radiated RF immunity (61000-4-3): 10 V/m for most industrial environments. Shield enclosure + filtering on all cables entering the enclosure. (3) Fast transient burst (61000-4-4): add TVS + 100 nF cap + 1 kV rated optocoupler on all signal lines. (4) Surge immunity (61000-4-5): add TVS on power and long data cables (2-20 kV). (5) Conducted RF immunity (61000-4-6): add EMI filter on all cables >1 m. (6) Voltage dip/interruption (61000-4-11): use hold-up capacitor or UPS for critical processes. Design approach: (1) Use shielded enclosure for all industrial products. (2) Isolate communication ports (RS-485 USB Ethernet) with optocouplers and TVS. (3) Use industrial-grade components rated for immunity. (4) Filter all cables at the enclosure entry point. (5) Implement watchdog and recovery for transient upset conditions.
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