IEEE 280-1985 (R2003) pdf free.IEEE Standard Letter Symbols for Quantities Used in Electrical Science and Electrical Engineering.
IEEE 280 covers letter symbols used to represent physical quantities in the field of electrical science and electricalengineering.These symbols are independent of the units (see ANSIIEEE Std 260-1978 [2]’) employed or specialvalues assigned.Also included are selected symbols for mathematics and for physical constants.
When the following American National Standards referred to in this standard are superseded by a revision approved bythe American National Standards Institute, the latest vision shall be used.
[1] ANSI Y10.17-1961(R1973),American National Standard Guide for Selecting Greek Letters Used as LetterSymbols for Engineering Mathematics.
[2]ANSIIEEE Std 260-1978,IEEE Standard Letter Symbols for Units of Measurement.[3] ANSI/IEEE Std 268-1982,American National Standard Metric Practice.
Letter symbols include symbols for physical quantities (quantity symbols) and symbols for the units in which thesequantities are measured (unit symbols).
A quantity symbol is in general, a single letter1(for example, I for electric current) specified as to general form oftype, and modified when appropriate by one or more subscripts or superscripts. In a given work the same letter symbol should appear throughout for the same physical quantity，regardless of the units employed or of special valuesassigned.A unit symbol is a letter or group of letters (for example, mm for millimeter), or in a few cases a special sign, that maybe used in place of the name of a unit.
Letter symbols are mainly restricted to the English and Greek alphabets.”The type families that are used for text inmodern book and journal publishing all include italic (sloping) type faces and related roman (uprighr) type faces. Theformer are used for quantity symbols, and the latter, for unit symbols—the distinctions are discussed more fully in thefollowing paragraphs.(In the context of this standard, the term roman is used simply to mean upright in contrast withsloping and carries no connotation regarding serifs, line widths, or the like.) In situations where roman and italic arenot both available, care shall be taken to avoid confusion between quantities and units. For example, an underline isfrequently used to indicate italic type, and where an underline can be provided, as in manual typewriting, this practiceis often helpful.
Unconventional type faces should generally not be used for letter symbols. Script and Old English faces, for example,are not appropriate for unit symbols. Such special faces have seen limited use for quantity symbols, but good modernpractice avoids them (see 3.3, last paragraph).IEEE 280 pdf download.