The book PLCs and SCADA has been written for the students of Electronics/Instrumentation Engineering and undergraduate and postgraduate courses who are studying Programmable Logic Controllers. It is also helpful for the professional engineers who have basic knowledge of operation and control of PLCs and for the new engineer embarking on an exciting career in electronics design and control. This book provides a comprehensive theoretical, yet practical, look at all aspects of PLCs and their associated devices and systems. The principal objective of the book is to provide an introduction to various PLC concepts and to develop a foundation that can be used as basis for research and further study in this field.