What are the advantages of fieldbus systems over traditional 4-20 mA wiring?

Fieldbus advantages: reduced wiring costs (one cable carries multiple device signals), bidirectional digital communication (configuration, diagnostics, multiple variables), improved accuracy (no analog conversion errors), advanced diagnostics (device health information), interoperability (devices from different vendors on same network), control in the field (PID blocks in field devices reduce controller loading), simplified commissioning (auto-detection, loop checking), and reduced marshalling (home-run cables to junction boxes). Disadvantages include higher initial engineering cost, steeper learning curve, and dependency on network health. Fieldbus is optimal for large installations with many control loops.