Computers of various degrees of sophistication and size have become indispensable elements of the modern world. They are being used by customers of all sizes from the single-family home to the largest industrial or business organization. These computers are affected by the quality of electrical power in ways different from the traditional users of electrical energy such as motors and furnaces. Power interruptions and other disturbances which have only minor effects on the performance of a machine tool can completely invalidate the output of a computer or even result in damage or destruction of this sensitive electronic device. Fortunately, ways of minimizing such problems have been developed. Some of these preventive measures especially line voltage regulation and continuity of service are done by the utility but most can be provided within the premises of the owner of the computer and are best done there. Many problems met in the past have been solved by more adequate design of the computer apparatus itself.
It is important to recognize that the computer produces information, generated numerically by low-level signals in its electronic circuitry. The input and output signals are so small that stray disturbances can significantly distort them. The output produced can be worthless or worse, misleading.
We shall consider the term "computer" here to include all types of apparatus which use encoded digital signals which are processed by digital circuitry and presented at the output either as a graphic record or as an operating control signal (such as a micro-processor being used in an energy management system).
In this section, the intention is to cover the kinds of problems that pertain to various types of computers and place them in proper perspective so that solutions can be found and the cost-effectiveness determined. The main emphasis will be on smaller systems of the types that surround us, rather than the very large computer systems that require careful engineering before installation.
