7 - Distributed control systems (DCS)

Abstract

This chapter deals with distributed control systems (DCS). DCS is the powerful and secure communication system which allows the “distribution” of control. The predecessors to DCS are multiloop type, mini computer-based units, where the I/O capacity can be increased by adding memory, but the total size is limited to the processor maximum memory size. The interface unit is the means by which the DCS transfers information to the management computer or information system; it converts the communication protocol used for the DCS to that used for the management system. In most process control applications the speed of the DCS is quite adequate, but if high speeds are necessary in selected operations, PLCs can be interfaced directly to most DCS using standard components, which make the PLC transparent to the operator. The standard functions available with DCS provide an integrated control system capable of all aspects of processes control, able to be applied to most process, either as the system stands, or with integration with other equipment, to achieve the total control requirements of any plant, and in many cases the necessary management production information. Finally, with such developments, it is essential that a careful study of all available control systems is carried out to ensure that the best suited and most cost-effective control system for the project is selected.