Computer Busses

19

Fieldbus

19.1 Introduction

Field buses are special local area networks that are dedicated to data acquisition and the control of sensors and actuators. They typically run over low-cost twisted pair cable. They differ from many traditional LANs (such as Ethernet) in that they are optimised for the exchange of short point-to-point status and command messages. There are many Fieldbus standards that exist, each developed for a specific purpose.

The potential market for Fieldbus equipment is enormous. Figure 19.1 shows an estimate of sales over time. It can be seen that the expected market in 2003 is over 50%. Instrumentation interfaces have evolved from 3–15PSI transmitters, to 4–20 mA analogue interfaces, now to serial interfaces (typically either ...