The programming logic controller (PLC) is the device at the heart of most automated control systems and instrumentation in industrial practice. Many computer languages have been used to write these programs in the past, with the result that PLCs from different manufacturers are generally incompatible, and make linked application systems extremely complicated. The standards body the International Electrotechnical Commission published standard IEC 1131-3 in December 1993 in order to progress towards a compatible environment. This guide acts as a tutorial to the IEC 1131-3 standard. It describes the languages and concepts, and interprets meanings for practical implementation and application.
Robert Lewis is the UK expert on two IEC working groups defining the PLC programming language standard (IEC 1131-3) and developing a new standard for specifying reusable software function blocks for distributed industrial and manufacturing systems (IEC 1499). He is a Fellow of the IET and has been concerned with the development of control systems for a wide range of industrial applications for over 15 years. One of his particular interests is the application of graphical programming techniques to the design of industrial control software.