Profibus System Integration PDF 4.03MB - Schneider Electric

Fieldbus OverviewIntroductionThis section provides a brief overview of the available fieldbus solutions, beforeproceeding to architecture selection.Three Instrumentation buses may be used in process applications: HART, ProfibusPA or Foundation Fieldbus. Before the use of instrumentation buses, it wasnecessary to purchase a field instrument specific to range of process variables(traditional 4-20 mA interface).HART OverviewHART ("Highway Addressable Remote Transducer") is a communication protocoldesigned for industrial process measurement and control applications. HART is thebest overall solution for obtaining value-added device and diagnostic information indigital form while retaining compatibility with legacy 4-20 mA automation architectures.HART is called a hybrid protocol because it combines analogue and digitalcommunication. It can communicate a single variable using a 4-20 mA analog signal,while also communicating added information on a digital signal. The ability to carrythis added digital information is the basis of HART's key benefits. Examples of thisadditional digital information include Device Status & Diagnostic Alerts, ProcessVariables & Units, Loop Current & % Range, Basic Configuration Parameters,Manufacturer & Device Tag.HART is currently the world's most broadly supported protocol for the processindustry. Almost 600 HART-based products are available from different vendors.FOUNDATION Fieldbus OverviewFOUNDATION fieldbus was designed specifically to address the needs of processautomation including providing safe and effective real time process control on the bus.Two related implementations of FOUNDATION fieldbus have been introduced, eachmeeting different needs within the process automation environment. These twoimplementations use different physical media and communication speeds.• FF H1 mainly connects to field devices. It provides communication and powerover standard twisted-pair wiring• FF HSE (High Speed Ethernet) works at 10 or 100 Mbit/sec and generallyconnects input / output subsystems. Currently, FF HSE does not provide powerover the cable.15