Discrete Control

Author

Kelvin T. Erickson, Missouri University of Science and TechnologyFollow

Abstract

A discrete control system mainly has discrete sensors and actuators, that is, sensors and actuators that have one of two values (e.g., on/off or open/closed). Though Ladder Diagram (LD) is the primary language of discrete control, the industry trend is toward using the IEC 61131-3 (formerly 1131-3) standard. Besides Ladder Diagram, IEC 61131-3 defines four additional languages: Function Block Diagram (FBD), Structured Text (ST), Instruction List (IL), and Sequential Function Chart (SFC). Even though Ladder Diagram was originally developed for the programmable logic controller (PLC) and Function Block Diagram (FBD) was originally developed for the distributed control system (DCS), a PLC is not limited to ladder logic and a DCS is not limited to function block. The five IEC languages apply to all platforms for implementation of discrete control.

Recommended Citation

K. T. Erickson, "Discrete Control," A Guide to the Automation Body of Knowledge, 3rd Ed., pp. 57 - 78, International Society of Automation (ISA), Sep 2018.

Department(s)

Electrical and Computer Engineering

Comments

Chapter 4

International Standard Book Number (ISBN)

978-1-941546-91-8; 978-1-5231-1915-8

Document Type

Book - Chapter

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2018 International Society of Automation (ISA), All rights reserved.

Publication Date

24 Sep 2018