The industrial field bus

Several national and international bodies are trying to create a field bus standard. Broadly, the aim is to define a `low-level´ local area network (LAN) suitable for interconnecting simple sensors and actuators in both factories and process plants. The activity most relevant to Europe and the UK is that of the International Electrotechnical Commission (IEC) under the auspices of Technical Committee No.65, Sub-committee 65C, working group 6 (IEC 65C/WG6). The functional requirements outlined by this group include features that go towards defining the term `low-level´ in relation to field bus as opposed to `high-level´ communications systems such as MAP and miniMAP. Major field bus features include: bit serial digital communication; capability for at least 30 nodes on a basic system; interconnection of dumb or low intelligence devices only; short messages; and capable of moderate distances (1500 metres)