Preface Preface to the fourth edition In this fourth edition of the Instrumentation Reference Book we have attempted to maintain the one-volume scheme with which we began while expanding the work to match the current view of the automation practitioner in the process industries. In the process industries, practitioners are now required to have knowledge and skills far outside the "instrumenta- tion and control" area. Typically, automation practitioners have been required to be familiar with enterprise organiza- tion and integration, so the instruments and control systems under their purview can easily transfer and receive needed information and instructions from anywhere throughout the extended enterprise. They have needed substantially more experience in programming and use of computers and, since the first edition of this work was published, an entirely new subdiscipline of automation has been created: industrial networking. In fact, the very name of the profession has changed. Wide Web has made it possible for any standard anywhere to be located and purchase or, in some cases, read online free, so it has not been necessary to cross-reference stan- dards liberally in this work. The editor wants to thank all the new contributors, attrib- uted and not, for their advice, suggestions, and corrections. He fondly wishes that he has caught all the typographical errors, but knows that is unlikely. Last, the Editor wants to thank his several editors at Butterworth-Heinemann for their patience, as well as Michael Forster, the publisher. --W. H. Boyes Maple Valley, Washington 2002 Preface to the Second edition E. B. Jones's writings on instrument technology go back at least to 1953. He was something of a pioneer in producing