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

HVAC Control in the New MillenniumMicroelectronicsThe most important single invention within the whole complex ofinventions which is today called computer technology is the transistor.Electronic tubes made the first high-speed processing possible, and thestored program led the way to the possibility of computer intelligence,but the transistor paved the way for modern computers.Tubes rely for their amplifying and switching power on a heaterelectrode which pumps electrons through a vacuum. This electrodemust be shaped out of metal and it cannot be reduced beyond a certainsize. If it gets too small, it cannot produce enough heat to activate theelectrons.The transistor relies for particular structures of a minute size whichare formed inside silicon crystals. These structures can be very small anda solid-state amplifier or switch may be based in a tiny fragment of silicon.This results in substantial reductions in the size of the functioningunit of an amplifier or computing unit.The first transistorized devices occupied less than a hundredth ofthe space of electronic tubes. Because they do not rely on heat to drivetheir electrons along, transistor devices need no warming up period andthey consume far less energy. They are also faster in operation and muchmore reliable. Transistors quickly replaced electronic tubes except forsome high-power applications.The coming of the transistor could not have been foreseen by anyof the computer pioneers, nor could its dramatic consequences havebeen anticipated. The power and speed of all-transistor computers roseto a point where they were quantitatively different from anything thatthe early computer pioneers could have contemplated.Computer memories became larger, moving from a few hundred orthousands of bits of the earliest devices to hundreds of thousands, millions,tens of millions and eventually billions of words. These massivememories, now available for low cost personal computers, began to takeon new and unexpected roles. Instead of just being heavy-duty calculators,they suddenly became information handlers as well offering hugeand progressively cheaper repositories for masses of information. Asmemory space continued to multiply, memory banks became lighter andsmaller, their processing speeds increased and costs continued to drop.The first components of the earliest computers were large andmechanical. Then came electro-magnetic relays, which were a little©2001 by The Fairmont Press, Inc. All rights reserved.