International System of Units


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International System of Units

 

In·ter·na·tion·al Sys·tem of U·nits (SI),

, Système International d'Unités (in'tĕr-na'shŭn-ăl sis'tem yū'nits, sēs-tĕm' ahn-tĕr-nahs-ē'ōn-nahl' dūn'nē-tā'),
A system of measurements, based on the metric system, adopted at the 11th General Conference on Weights and Measures of the International Organization for Standardization (1960) to cover both the coherent units (basic, supplementary, and derived units) and the decimal multiples and submultiples of these units formed by use of prefixes proposed for general international scientific and technologic use. SI proposes seven basic units: meter (m), kilogram (kg), second (s), ampere (A), kelvin (K), candela (cd), and mole (mol) for the basic quantities of length, mass, time, electric current, temperature, luminous intensity, and amount of substance, respectively; supplementary units proposed include the radian (rad) for plane angle and steradian (sr) for solid angle; derived units (for example, force, power, frequency) are stated in terms of the basic units (for example, velocity is in meters per second, m s-1). Multiples (prefixes) in descending order are: exa- (E, 1018), peta- (P, 1015), tera- (T, 1012), giga- (G, 109), mega- (M, 106), kilo- (k, 103), hecto- (h, 102), deca- (da, 101), deci- (d, 10-1), centi- (c, 10-2), milli- (m, 10-3), micro- (μ, 10-6), nano- (n, 10-9), pico- (p, 10-12), femto- (f, 10-15), atto- (a, 10-18). Proposed prefixes are zetta- (Z, 1021), yotta- (Y, 1024), zepto- (z, 10-21), and yocto- (y, 10-24).
[Fr. Système International d'Unités]

In·ter·na·tion·al Sys·tem of U·nits

(SI) (in'tĕr-nash'ŭn-ăl sis'tĕm yū'nits)
A system of measurements, based on the metric system, adopted at the 11th General Conference on Weights and Measures of the International Organization for Standardization (1960) to cover both the coherent units (basic, supplementary, and derived units) and the decimal multiples and submultiples of these units formed by use of prefixes proposed for general international scientific and technologic use. SI proposes seven basic units: meter (m), kilogram (kg), second (s), ampere (A), Kelvin (K), candela (cd), and mole (mol) for the basic quantities of length, mass, time, electric current, temperature, luminous intensity, and amount of substance; supplementary units proposed include the radian (rad) for plane angle and steradian (sr) for solid angle; derived units (e.g., force, power, frequency) are stated in terms of the basic units (e.g., velocity is in meters per second, m/sec-1). Multiples (prefixes) in descending order are: exa- (E, 1018), peta- (P, 1015), tera- (T, 1012), giga- (G, 109), mega- (M, 106), kilo- (k, 103), hecto- (h, 102), deca- (da, 101), deci- (d, 10-1), centi- (c, 10-2), milli- (m, 10-3), micro- (μ, 10-6), nano- (n, 10-9), pico- (p, 10-12), femto- (f, 10-15), and atto- (a, 10-18). The prefix zepto (z) has been proposed for 10-21.
[Fr. Système International d'Unités]

In·ter·na·tion·al Sys·tem of U·nits

(SI) (in'tĕr-nash'ŭn-ăl sis'tĕm yū'nits)
System of measurements, based on the metric, to cover both coherent units (basic, supplementary, and derived units) and the decimal multiples and submultiples of these units formed by use of prefixes proposed for general international scientific and technologic use. SI proposes seven basic units: meter (m), kilogram (kg), second (s), ampere (A), kelvin (K), candela (cd), and mole (mol) for the basic quantities of length, mass, time, electric current, temperature, luminous intensity, and amount of substance, respectively. Multiples (prefixes) in descending order are: exa- (E, 1018), peta- (P, 1015), tera- (T, 1012), giga- (G, 109), mega- (M, 106), kilo- (k, 103), hecto- (h, 102), deca- (da, 101), deci- (d, 10-1), centi- (c, 10-2), milli- (m, 10-3), micro- (μ, 10-6), nano- (n, 10-9), pico- (p, 10-12), femto- (f, 10-15), atto- (a, 10-18). Proposed prefixes are zetta- (Z, 1021), yotta- (Y, 1024), zepto- (z, 10-21), and yocto- (y, 10-24).
[Fr. Système International d'Unités]
References in periodicals archive ?
[2] Nonstandard abbreviations: IUB, International Union of Biochemistry and Molecular Biology; SI, International System of Units; CGPM, General Conference on Weights and Measures; IUPAC, International Union of Pure and Applied Chemistry; CCU, Consultative Committee for Units; CIPM, International Committee for Weights and Measures; and CCQM, Consultative Committee for Amount of Substance.
What began with defining the second using atomic clocks 50 years ago and defining the meter using the speed of light over 30 years ago will now continue for all units in the International System of Units. Four other constants play the main roles: Planck's constant h , the Avogadro constant N A , the Boltzmann constant k and the charge of the electrone.
A quick reference guide to the International System of Units (SI) is found at the back of the volume.
This method is unique in molecular genetic measurement as it is traceable to the International System of Units (SI) on the basis of counting individual DNA molecules.
Over the last three months we have seen some positive developments such as the extension of the property visa period from six months to three years and the implementation of the International System of Units, which will bring uniformity of scale to the market, Elaine Jones, CEO, Asteco Property Management, said in a statement.
A calibrator that uses the International System of Units (SI base units) of time and length to derive gas flow measurements can be considered primary technology.
The document uses both the International System of Units (SI) and customary units.
ITU would continue to be responsible for the dissemination of time signals via radiocommunication and BIPM for establishing and maintaining the second of the International System of Units (SI) and its dissemination through the reference time scale.

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