What are the common fieldbus protocols used in industrial instrumentation?

Common fieldbus protocols include: Foundation Fieldbus (process industries, intrinsically safe option), Profibus (factory automation, high speed), Modbus (simple, widely supported, RTU and TCP versions), DeviceNet (CAN-based, industrial automation), CANopen (motion control, embedded systems), AS-Interface (sensors/actuators, simple wiring), EtherNet/IP (Industrial Ethernet, high speed), and PROFINET (Siemens Industrial Ethernet). Selection criteria include: application type, speed requirements, cable length, number of devices, intrinsic safety needs, and existing infrastructure. Modern trend is toward Industrial Ethernet variants.