Formula symbol
DIN 1304 part 1-8 | |
---|---|
title | Formula symbol |
Regulates | Formula symbols, formula set 1: 1994 General formula symbols 2: 1989 Meteorology and geophysics 3: 2006 Generation, transport and distribution of electrical energy 5: 1989 Fluid mechanics 6: 1992 Electrical communications engineering 7: 1991 Electrical machines 8: 1994 Converters with semiconductor components |
Publishing year | from 1989 |
Formula symbols (also: size symbols ) are symbols that are used to denote physical quantities . According to DIN 1304 ("Formula symbol") and ISO / IEC 80000 ("Sizes and units"), a formula symbol consists of a basic symbol and, if necessary, of subsidiary symbols, e.g. B. Indices . The basic characters are Latin and Greek upper and lower case letters. Subsidiary characters are letters, numbers or special characters (e.g. *, ', ~, ^). Basic characters consisting of several letters are not permitted, except for parameters ( sizes of the dimension number ) such as B. the Reynolds number .
The formula symbols are occasionally based on English or Latin technical terms. For example, a force is often referred to by the symbol , which is derived from the English force or the Latin fortitudo .
In accordance with DIN 1304 and DIN 1313 ("sizes"), the basic characters must be set in italics in print . DIN 1338 ("Formula notation and typesetting") recommends a font with serifs . Such a font prevents, for example, the confusion of the capital I ( ) with the small l ( ).
Application examples
- means: The electrical resistance is equal to the electrical voltage divided by the electrical current strength .
- means: The energy is equal to the mass times the square of the speed of light .
Formula symbols can only consist of one basic symbol - as shown in the previous examples - or they can contain additional symbols to further define the size. Examples of electrical voltage are:
- : AC and DC components of a voltage
- : Peak value and rms value for sinusoidal alternating voltage
- : Real part in complex notation
Frequently used special characters in connection with formula symbols
meaning | presentation | example |
---|---|---|
Unit of measurement of a size | square brackets around the symbol of the relevant size | |
Peak value | Circumflex, "roof" | |
amount | Amount bars | |
Average | Overline | |
Expected value | angle brackets | |
Quantity transformed into another frame of reference | apostrophe | |
first (second) derivative according to location | one (two) apostrophe (s) | |
first (second) derivative with respect to time | one (two) point (s) above the symbol | |
complex conjugation | superscript asterisk | |
Vectors | Arrow or bold face | |
Matrices | Underline or bold type | |
Transposition | superscript "T" | |
Adjoint | superscript cross |
See also
swell
- German Institute for Standardization : DIN 1304 formula symbols; General formula symbols. Beuth-Verlag, 1994.
- EN ISO 80000 : 2013 Sizes and units.