How to ensure EMC performance of I/O modules in humid environments?

Ensuring the EMC performance of I/O modules in humid environments requires attention to insulation, corrosion, and condensation. First, modules should have a high protection rating, such as IP65 or higher, to prevent direct moisture intrusion. The PCB must be coated with a conformal coating with good moisture resistance, especially in high-voltage areas and high-impedance circuits, to prevent increased leakage current and insulation degradation that could lead to EMC performance deterioration. All connectors should be models with rubber sealing rings. The surface treatment of the metal casing should be corrosion-resistant to prevent increased grounding impedance due to rust, which could affect shielding effectiveness.

In circuit design, the impedance values of high-impedance nodes should be appropriately reduced to decrease sensitivity to surface contamination. For applications where condensation may occur, heating circuits can be added inside the module, or a breathable but waterproof membrane can be used. In terms of testing, in addition to routine EMC testing, damp heat cycling testing is necessary to verify the stability of insulation resistance, withstand voltage, and EMC performance in humid environments. Modules operating in humid environments for extended periods should have their appearance and electrical performance checked regularly.