How do you design fieldbus segments for intrinsically safe hazardous area applications?

Fieldbus IS design: entity concept (barrier plus cable plus devices calculated to prevent ignition), select IS barrier (certified for specific fieldbus, appropriate voltage/current limits), calculate segment parameters (cable capacitance and inductance vs barrier limits, device consumption), design topology (trunk-spur maintaining IS parameters), specify cable (fieldbus Type A with known parameters), select devices (FISCO or entity certified), ground per manufacturer requirements (single point typically), and document calculations. FISCO (Fieldbus Intrinsically Safe Concept) simplifies calculation with interchangeable certified components. Zone considerations: Zone 1 vs Zone 0 affects device selection. Verify installation matches design calculations. Commission with calibrated test equipment. Maintain documentation for inspection.