HVAC Control in the New Millennium.pdf - HVAC.Amickracing

Control Technology, Microelectronics and Nanotechnologysmaller, after which came tubes which were somewhat larger.The arrival of the transistor produced a sensational reduction insize. The transistor itself is a spot of semi-conducting material. Thismaterial is not as good a conductor as metal, but it is better than aninsulator like plastic or rubber.When it contains certain impurities in its structure, this semiconductorcan act as an amplifier and switching device. These impuritiescan be very small.The first transistors that were manufactured had an initial size ofabout one cubic centimeter. Several levels of miniaturization werequickly achieved.Transistors were then combined into logic units. These electroniccircuits consists of 20 to 100 components arranged as sets of logic gatesfor AND, OR and NOT functions. They were built on a chip of siliconabout a centimeter square. These chips have grown to where they arenow the heart of just about every electronic device including watchesand the largest computers.Miniaturization did not stop when it came to etching completecircuits on a chip. Using techniques known as large-scale integration(LSI), hundreds, thousands and even millions of individual units wereamassed on one chip of semi-conductor material.Still the process of miniaturization continues into the future. Thebuilding units of computers are getting smaller and smaller, shrinkinginto the infinities of the molecular world.Computer ApplicationsThe outcome of these reductions in cost and size, and the hugeincreases in memory capacity and reliability, allow computing circuits tobe widely used in areas which would have been inconceivable before theadvent of microprocessors. Many areas of special-purpose computingwhich have been available at high cost and with only marginal reliabilityin the past have also become cheaply available.Computers have the capacity to read and store text, graphics andeven human retina signatures and fingerprints. They can also recognizethe human voice and understand spoken words and phrases. They alsohave the ability to communicate with the user by drawing diagrams orpictures on CRT screens and also by the use of synthetic speech and©2001 by The Fairmont Press, Inc. All rights reserved.