Metre Convention Is a Root International System of Units

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.

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THE INTERNATIONAL SYSTEM OF UNITS

The Mechanical Universe ◽

10.1017/cbo9780511818509.032 ◽

1985 ◽

pp. 563-564

Keyword(s):

International System ◽

International System Of Units ◽

System Of Units

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

Izmeritel`naya Tekhnika ◽

10.32446/0368-1025it.2020-10-26-32 ◽

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.

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The International System of units (SI)

10.3403/30308756 ◽

1964 ◽

Keyword(s):

International System ◽

International System Of Units ◽

System Of Units

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A quantum ampere

tm - Technisches Messen ◽

10.1515/teme-2019-0129 ◽

2020 ◽

Vol 87 (4) ◽

pp. 258-265

Author(s):

Luca Callegaro

Keyword(s):

Electric Current ◽

International System ◽

International System Of Units ◽

System Of Units ◽

Elementary Charge ◽

User Friendly

AbstractThe revision of the International System of Units (SI), implemented since 20 May 2019, has redefined the unit of electric current, the ampere ( A), linking it to a fixed value of the elementary charge. This paper discusses the new definition and the realisation of the electrical units by quantum electrical metrology standards, which every year become more and more accessible, reliable and user friendly.

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