Programmable Controllers in Process Control Applications

The capability of the special-purpose computer called the programmable controller (PC) has been increased to the point where it has to be considered a viable alternate when selecting a controller to perform operational logic functions in chemical control applications. Guidelines used in the application of PC´s in process control are described. The advent of the PC in chemical process applications provides new challenges for the manufacturer, application engineer, and user. What position in the control family hierarchy (e. g., relay sequencers, logic, microcomputers, direct digital control, mini-computers, etc.) the PC presently holds is defined.