Intrinsic safety limits voltage, current, and capacitance in the field circuit so that even a double fault cannot release enough energy to ignite the gas. Barriers and isolators are the interface between the safe area and the hazardous area. This article summarizes the main choices and what must match on the datasheet.
Zener barriers shunt energy to ground and require a high-integrity grounding system at the barrier. Galvanic isolators separate circuits magnetically or optically and do not need a ground for the safety function in the same way, but they still need correct installation per the certificate. Pick isolators when grounding is difficult or when you need higher isolation ratings.
Compatibility must be demonstrated with a calculation or tool accepted by your project standard. Swapping a transmitter or cable without updating the assessment can invalidate the Ex i loop.
Keep cable lengths within the assessed values, use the same shield termination rules the manufacturer documented, and label each barrier with its circuit ID. After a trip or replacement, verify the loop matches the as-built record.
For detailed loop verification or training on entity calculations, HazloLabs supports intrinsic safety design and documentation.