Metrication and SI Units

PEDIATRICS ◽  
1980 ◽  
Vol 65 (3) ◽  
pp. 659-664
Author(s):  
Arno R. Hohn ◽  
Alfred B. Amler ◽  
Paul S. Bergeson ◽  
Harvey R. Gold ◽  
Stewart L. Griggs ◽  
...  
Keyword(s):  
United States ◽  
International System ◽  
The United States ◽  
International Standards ◽  
Reference Laboratory ◽  
Royal Decree ◽  
Weights And Measures ◽  
International System Of Units ◽  
System Of Units ◽  
Metre Convention

Because of the increasing international use of the SI system (International System of Units) in medicine, the Committee on Hospital Care has written this statement to familiarize pediatricians with this concept. The current state of the system, its derivation, purported advantages, and controversial aspects are described; and the Committee has made specific recommendations for consideration regarding its future use and development. BACKGROUND The British Imperial System of Weights used in the United States today derives from a variety of ancient cultures. A Roman contribution is the use of the awkward number 12 as a base. Royal decree established the yard as the distance from the tip of the nose to the end of the thumb of King Henry I. The inch was based on the size of three grains of barley "dry and round." Equally illogically derived units evolved to eventually form the irrational English "system."1 The metric system with its "base-10" or "decimal" system derived its units of mass and volume from its units of length, thus correlating its basic units to each other. The need for further refinement of metrics and a single worldwide and interdisciplinary system of measurements led to the development of the International System of Units (le Systeme International d'Unités) with the international abbreviation "SI." This is sometimes referred to as "the modern metric system" and is said to complete the process of metrication.2 Seventeen countries, including the United States, signed the Metre Convention in 1870. This led to the establishment of the International Bureau of Weights and Measures at Sèvres, France, which acts as an international standards reference laboratory and as the permanent secretariat for the Metre Convention.

Dimensions of plane and solid angles and their units in the International System of Units (SI)

2020 ◽  
pp. 26-32
Author(s):  
M. I. Kalinin ◽  
L. K. Isaev ◽  
F. V. Bulygin
Keyword(s):  
Solid Angle ◽  
International System ◽  
International Committee ◽  
Plane Angle ◽  
Arc Length ◽  
Weights And Measures ◽  
International System Of Units ◽  
System Of Units ◽  
In Series ◽  
Solid Angles

The situation that has developed in the International System of Units (SI) as a result of adopting the recommendation of the International Committee of Weights and Measures (CIPM) in 1980, which proposed to consider plane and solid angles as dimensionless derived quantities, is analyzed. It is shown that the basis for such a solution was a misunderstanding of the mathematical formula relating the arc length of a circle with its radius and corresponding central angle, as well as of the expansions of trigonometric functions in series. From the analysis presented in the article, it follows that a plane angle does not depend on any of the SI quantities and should be assigned to the base quantities, and its unit, the radian, should be added to the base SI units. A solid angle, in this case, turns out to be a derived quantity of a plane angle. Its unit, the steradian, is a coherent derived unit equal to the square radian.

scholarly journals Adapting the International System of Units to the twenty-first century

2011 ◽  
Vol 369 (1953) ◽  
pp. 3907-3924 ◽  
Author(s):  
Ian M. Mills ◽  
Peter J. Mohr ◽  
Terry J. Quinn ◽  
Barry N. Taylor ◽  
Edwin R. Williams
Keyword(s):  
International System ◽  
International Committee ◽  
First Century ◽  
Weights And Measures ◽  
International System Of Units ◽  
System Of Units ◽  
Elementary Charge ◽  
Magnetic Constant ◽  
Base Units ◽  
New Si

We review the proposal of the International Committee for Weights and Measures (Comité International des Poids et Mesures, CIPM), currently being considered by the General Conference on Weights and Measures (Conférences Générales des Poids et Mesures, CGPM), to revise the International System of Units (Le Système International d'Unitès, SI). The proposal includes new definitions for four of the seven base units of the SI, and a new form of words to present the definitions of all the units. The objective of the proposed changes is to adopt definitions referenced to constants of nature, taken in the widest sense, so that the definitions may be based on what are believed to be true invariants. In particular, whereas in the current SI the kilogram, ampere, kelvin and mole are linked to exact numerical values of the mass of the international prototype of the kilogram, the magnetic constant (permeability of vacuum), the triple-point temperature of water and the molar mass of carbon-12, respectively, in the new SI these units are linked to exact numerical values of the Planck constant, the elementary charge, the Boltzmann constant and the Avogadro constant, respectively. The new wording used expresses the definitions in a simple and unambiguous manner without the need for the distinction between base and derived units. The importance of relations among the fundamental constants to the definitions, and the importance of establishing a mise en pratique for the realization of each definition, are also discussed.

scholarly journals World Metrology Day, 20 May 2018

2018 ◽  
Vol 40 (2) ◽  
pp. 31-31
Keyword(s):  
International System ◽  
Science And Technology ◽  
Measurement Methods ◽  
Weights And Measures ◽  
International System Of Units ◽  
System Of Units ◽  
Measurement Science ◽  
To Come ◽  
Quantum Phenomena

Abstract The theme for World Metrology Day 2018 is Constant evolution of the International System of Units. This theme was chosen because in November 2018, the General Conference on Weights and Measures is expected to agree one of the largest changes to the International System of Units (the SI) since its inception. The proposed changes are based on the results of research into new measurement methods that have used quantum phenomena as the basis for standards that are fundamental.  The SI will be based on a set of definitions each linked to the laws of physics and have the advantage of being able to embrace further improvements in measurement science and technology to meet the needs of future users for many years to come.

Metre Convention Is a Root International System of Units

2021 ◽  
pp. 549-557
Author(s):  
Džanina Omićević ◽  
Dževad Krdžalić ◽  
Esad Vrce
Keyword(s):  
International System ◽  
International System Of Units ◽  
System Of Units ◽  
Metre Convention

Bye-Bye, IPK!

2019 ◽  
Vol 41 (2) ◽  
pp. 53-54
Author(s):  
Daniel Rabinovich
Keyword(s):  
Electric Current ◽  
International System ◽  
Golf Ball ◽  
Weights And Measures ◽  
Units Of Measurement ◽  
International System Of Units ◽  
System Of Units ◽  
Utmost Care ◽  
Physical Quantities

Abstract The International Prototype Kilogram, after 130 years of dutiful service, is finally retiring. The IPK, a golf ball-sized cylinder made of a special platinum-iridium alloy (90:10), was introduced in 1889 at the first General Conference on Weights and Measures (CGPM) near Paris to define the unit of mass using an artifact fabricated with the utmost care and precision available at the time. New units were subsequently adopted for other physical quantities such as electric current (the ampere) and temperature (the kelvin), and the increasing need for a more cohesive set of units of measurement led to the implementation of the International System of Units (SI) in 1960.

scholarly journals The Proposed New SI: Consequences For Mass Metrology

ACTA IMEKO ◽  
2014 ◽  
Vol 3 (2) ◽  
pp. 3 ◽  
Author(s):  
Roman Schwartz ◽  
Michael Borys
Keyword(s):  
International System ◽  
Weights And Measures ◽  
International System Of Units ◽  
System Of Units ◽  
Future Revision ◽  
New Si

At its 24<sup>th</sup> meeting in October 2011 the General Conference on Weights and Measures (CGPM) adopted a Resolution on the possible future revision of the International System of Units (SI). This paper provides an overview of the proposed changes to the SI, the focus being on the proposed redefinition of the kilogram and possible consequences for mass metrology.<br />

scholarly journals Quantity Calculus, Fundamental Constants, and SI Units

2018 ◽  
Vol 123 ◽  
Author(s):  
Barry N. Taylor
Keyword(s):  
International System ◽  
Fundamental Constants ◽  
Weights And Measures ◽  
International System Of Units ◽  
Si Units ◽  
System Of Units ◽  
Revised Si ◽  
Base Units ◽  
New Si

A revised International System of Units (SI) is expected to be established by the 26th General Conference on Weights and Measures when it convenes in November 2018 and to be put into practice starting on 20 May 2019, World Metrology Day. In consequence, the article published in this journal in 2011, “The Current SI Seen from the Perspective of the Proposed New SI,” is updated in this paper, which provides an opportunity to again demonstrate the usefulness of the quantity calculus in dealing with quantities and units. The quantity calculus and the seven defining constants of the current and revised SI are reviewed, and expressions for the seven current and revised SI base units are given. Relationships between the magnitudes of revised and current SI units and expressions for the numerical values of current SI defining constants expressed in revised SI units are also obtained using the quantity calculus.

scholarly journals New SI and precision measurements: an interview with Tianchu Li

2020 ◽  
Vol 7 (12) ◽  
pp. 1837-1840
Author(s):  
Jin Wang
Keyword(s):  
International System ◽  
Precision Measurements ◽  
Weights And Measures ◽  
Frequency Standards ◽  
System Of Units ◽  
Constant E ◽  
Most Significant Change ◽  
History Of ◽  
Metre Convention ◽  
New Si

Abstract On 13–16 November 2018, the 26th General Conference of Weights and Measures (CGPM) was held in Paris. The conference adopted Resolution A on ‘Revision of the International System of Units (SI).’ According to Resolution A: four of the SI basic units, namely kilograms, amps, kelvin and mole, are defined by the Planck constant h, the basic charge constant e, the Boltzmann constant k and the Avogadro constant NA, respectively. This establishes the basic quantities and units in SI on a series of constants. The new SI was officially launched on 20 May 2019. This is the most significant change and a milestone in the history of metrology since the Metre Convention was signed in 20 May 1875. Professor Tianchu Li, an academician of the Chinese Academy of Engineering, has been working on time and frequency standards for 37 years. In this interview, Prof. Li reviews the quantization and constant evolutions of the second and meter, and introduces the redefinitions of ampere, kelvin, kilogram and mole, and their significance for precision measurements.

scholarly journals The greatest recognition to the scientist Nikola Tesla: Award of the unit for magnetic induction (T) in the international system of units (SI)

2006 ◽  
Vol 3 (2) ◽  
pp. 217-222 ◽  
Author(s):  
Gordana Spaic ◽  
Srdjan Spiridonovic
Keyword(s):  
Magnetic Induction ◽  
International System ◽  
International Committee ◽  
Weights And Measures ◽  
International System Of Units ◽  
Nikola Tesla ◽  
System Of Units ◽  
Electricity And Magnetism ◽  
The Way

The paper describes the reasons and results that led to the greatest recognition that a scientist can achieve, his name Tesla given to a unit in the field of electricity and magnetism in the International System of Units (SI). The difficulties on the way from a proposal to its final adoption through different Technical and Experts Committees of the International Electro technical Commission (IEC) and of the International Committee on Weights and Measures are described. Some examples for the usage of the "tesla" unit are mentioned.

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