How to balance explosion protection and EMC considerations for I/O modules?

For I/O modules used in explosion-proof environments, their EMC design must be closely integrated with explosion-proof safety requirements. Explosion-proof requirements limit energy, and intrinsically safe circuits prevent the ignition of explosive gases by electrical sparks through voltage limiting, current limiting, and energy storage control. This requires that protective devices such as TVS diodes and varistors not only meet EMC requirements but also their parameters must satisfy intrinsic safety certification requirements; for example, their energy storage must be below a certain value. Explosion-proof enclosures are typically thick and heavy, providing good shielding, but attention must be paid to the shielding continuity of cable entry devices.

Explosion-proof standards may restrict grounding methods, such as requiring a grounding resistance of less than 1 ohm, which is consistent with the low-impedance grounding requirements of EMC. For modules used in increased safety applications, the creepage distances and clearances of their internal circuits must be increased, which may affect the layout of high-frequency circuits and the parasitic parameters of filters. All signals entering the explosion-proof area must be isolated by safety barriers, which themselves are also filtering and isolation devices. During the design process, EMC and explosion-proof certification must be carried out simultaneously, selecting devices and structures that meet both requirements. The final product needs to pass dual certification: explosion-proof certification and EMC certification to ensure safe and reliable operation in hazardous environments.