AS-Interface is considered the ideal protocol for networking discrete automated valves and instruments in the process industries. This easy to install protocol economically networks up to 62 field devices onto a single pair of wires that delivers both signal and power. Interfacing conveniently to most popular PLCs and DCS systems, it may be used in both general purpose and hazardous areas with explosion proofing, nonincendive equipment and nonincendive field wiring protection concepts.

DeviceNet may be used with both discrete and analog applications. It interfaces conveniently into most Rockwell/Allen Bradley and many other DCS/PLC systems integrating up to 63 devices on a 4-wire trunk network carrying power on two wires and communication on the remaining pair. Used in both general purpose and hazardous areas with explosion proofing and nonincendive equipment protection concepts, DeviceNet is suitable for the process industries as well as factory automation.

Foundation Fieldbus has become the de facto standard for networking analog process instrumentation. Designed for use in the process industries, Foundation Fieldbus offers multi-drop capabilities (typically up to 16 devices per network), long trunk length and compatibility with intrinsically safe circuits. Featuring an object oriented block structure for convenient PID loop configuration and true control in the field, Foundation Fieldbus also promises to enhance process performance, reduce set-up time and enable instrument diagnostics.

Available as Profibus DP (Distributed Peripherals) or PA (Process Automation) this protocol has become well accepted for both discrete and analog applications. Profibus DP features High speed data access capable of handling time critical functions while dramatically cutting wiring and commissioning costs. PA is recommended for process applications where intrinsically safe protection concepts must be used.

Traditionally used for integrating I/O back planes into legacy DCS systems, Modbus may be used to network up to 32 analog or discrete devices on a 4-wire network. Because of it’s universal acceptance, this protocol is recommended where legacy systems are prevalent and other protocols may not be readily adapted.

Hart is widely used in the process industries to monitor and configure analog process instrumentation. Hart has a very strong following and has helped many plants enhance their process performance, by reducing set-up time and enabling instrument diagnostics.