Foundation Fieldbus (FF) and Profibus are the two most universal serial data
bus formats that have been developed for interfacing between a central processor
and smart sensing devices in a process control system. The Foundation
Fieldbus is primarily used in the United States and the Profibus format is primarily
used in Europe. Efforts are being made for a universal acceptance of one
bus system. At present, process control equipment are being manufactured for
one system or the other; global acceptance of equipment standards would be preferred.
Aserial data bus is a single pair of twisted copper wires and enables communication
between a central processing computer and many monitoring points
and actuators when smart sensors are used. This is shown in Fig. 13.12.
Although initially more expensive than direct lead connections, the advantages
of the serial bus are minimal bus cost and installation labor. The system replaces
all the leads to all the monitoring points by one pair of leads, new units can be
added to the bus with no extra wiring, a plug and play feature is provided,
giving faster control, and programming that is the same for all systems. Higher
accuracies are obtained than using analog and more powerful diagnostics are
available. As the cost of integration and development lowers, the bus system with
its features will become more cost effective than the present systems.