1 - Overview

Abstract

This chapter introduces fundamentals and historical background of data communications technology. Data communication is the transfer of information from one point to another. Data refers to information that is represented by a sequence of zeros and ones; the same sort of data that is handled by computers. Many communications systems handle analog data, such as telephone system, radio, and television. Modern instrumentation is wholly concerned with the transfer of digital data. This chapter discusses the need for standards in the data communications industry in terms of the physical transfer of information, and the way in which data is handled. The chapter takes a look at data communications as they apply to instrumentation and control systems. It also describes the basic principles of all communication systems, and explains the role of standards and protocols. The open systems interconnection (OSI) model of communication layers, as well as the important physical standards, is elaborated. Furthermore, the chapter explains the purpose of instrumentation and control system. Four most important control devices, namely, DCS, PLCs, smart instruments, and PCs are discussed in detail.