ABSTRACT
An industrial network is referred to as fieldbus. A fieldbus is a digital two-way multidrop communication link between intelligent field devices. At the field level, Foundation Fieldbus H1 and PROFIBUS-PA are the fieldbuses used in process control.
A segment in a fieldbus comprises several smart sensors. The main cable is called trunk and the “drop” cables to individual devices are called spurs. Topologies used in a fieldbus system are point-to-point, bus with spurs, tree (or chicken foot), daisy chain, and mixed.
A terminator is placed on either side of a segment which acts as an impedance module and has identical characteristic impedance of the line. It prevents signal reflection and consequent communication errors.
A fieldbus is a two-level network—a field-level network and a host-level network.
A fieldbus-based system, when employed in a process plant, will result in numerous benefits at different phases like planning, installation, operation, maintenance, and renovation. There is a huge saving in installation cost, device commissioning time is greatly reduced because considerable configuration and diagnostic information is available in the fieldbus devices. A fieldbus device can be diagnosed for its problems in “in situ” condition. Complexity of central control system is greatly reduced because devices have in-built controls.
