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• International unit

Creation and development of the metric system of measures

The metric system of measures was created at the end of the 18th century. in France, when the development of trade industry urgently required the replacement of many units of length and mass, chosen arbitrarily, by single, unified units, which became the meter and kilogram.

Initially, the meter was defined as 1/40,000,000 of the Paris meridian, and the kilogram was defined as the mass of 1 cubic decimeter of water at a temperature of 4 C, i.e. the units were based on natural standards. This was one of the most important features of the metric system, which determined its progressive significance. The second important advantage was the decimal subdivision of units, corresponding to the accepted system of calculation, and a single way of forming their names (by including the appropriate prefix in the name: kilo, hecto, deca, centi and milli), which eliminated complex conversions of one unit to another and eliminated confusion in titles.

The metric system of measures has become the basis for the unification of units throughout the world.

However, in subsequent years, the metric system of measures in its original form (m, kg, m, ml ar and six decimal prefixes) could not satisfy the demands of developing science and technology. Therefore, each branch of knowledge chose units and systems of units that were convenient for itself. So, in physics, the centimeter - gram - second (CGS) system was followed; in technology, a system with basic units has found wide distribution: meter - kilogram-force - second (MKGSS); in theoretical electrical engineering, several systems of units derived from the CGS system began to be used one after another; in heat engineering, systems were adopted based, on the one hand, on the centimeter, gram and second, on the other hand, on the meter, kilogram and second with the addition of a unit of temperature - degrees Celsius and off-system units of the amount of heat - calories, kilocalories, etc. . In addition, many other non-systemic units have found application: for example, units of work and energy - kilowatt-hour and liter-atmosphere, pressure units - millimeter of mercury, millimeter of water, bar, etc. As a result, a significant number of metric systems of units were formed, some of them covering certain relatively narrow branches of technology, and many non-systemic units, the definitions of which were based on metric units.

Their simultaneous application in certain areas led to the clogging of many calculation formulas with numerical coefficients not equal to unity, which greatly complicated the calculations. For example, in engineering, it has become common to use kilograms to measure the mass of the ISS system unit, and kilogram-force to measure the force of the MKGSS system unit. This seemed convenient from the point of view that the numerical values ​​of the mass (in kilograms) and its weight, i.e. the forces of attraction to the Earth (in kilogram-forces) turned out to be equal (with an accuracy sufficient for most practical cases). However, the consequence of equating the values ​​of essentially heterogeneous quantities was the appearance in many formulas of the numerical coefficient 9.806 65 (rounded 9.81) and the confusion of the concepts of mass and weight, which gave rise to many misunderstandings and errors.

Such a variety of units and the associated inconveniences gave rise to the idea of ​​creating a universal system of units. physical quantities for all branches of science and technology, which could replace all existing systems and individual off-system units. As a result of the work of international metrological organizations, such a system was developed and received the name of the International System of Units with the abbreviation SI (International System). The SI was adopted by the XI General Conference on Weights and Measures (CGPM) in 1960 as modern form metric system.

Characteristics of the International System of Units

The universality of the SI is ensured by the fact that the seven basic units underlying it are units of physical quantities that reflect the basic properties of the material world and make it possible to form derived units for any physical quantities in all branches of science and technology. The same purpose is served by additional units necessary for the formation of derived units depending on the plane and solid angles. The advantage of the SI over other systems of units is the principle of constructing the system itself: the SI is built for a certain system of physical quantities that make it possible to represent physical phenomena in the form of mathematical equations; some of the physical quantities are taken as basic and through them all the rest are expressed - derived physical quantities. For the main quantities, units are established, the size of which is agreed upon at the international level, and for the remaining quantities, derived units are formed. The system of units constructed in this way and the units included in it are called coherent, since the condition is met that the ratios between the numerical values ​​of quantities expressed in SI units do not contain coefficients that are different from those included in the initially chosen equations connecting the quantities. The coherence of SI units in their application makes it possible to simplify calculation formulas to a minimum by freeing them from conversion factors.

The SI eliminated the plurality of units for expressing quantities of the same kind. So, for example, instead of a large number units of pressure used in practice, the unit of pressure in SI is only one unit - the pascal.

The establishment of its own unit for each physical quantity made it possible to distinguish between the concepts of mass (SI unit - kilogram) and force (SI unit - Newton). The concept of mass should be used in all cases when we mean the property of a body or substance that characterizes their inertia and ability to create a gravitational field, the concept of weight - in cases where we mean the force arising from interaction with the gravitational field.

Definition of basic units. And it is possible with a high degree of accuracy, which ultimately not only improves the accuracy of measurements, but also ensures their unity. This is achieved by "materialization" of units in the form of standards and transfer from them to working measuring instruments with the help of a set of exemplary measuring instruments.

The international system of units, due to its advantages, has become widespread in the world. At present, it is difficult to name a country that would not implement the SI, would be at the stage of implementation or would not make a decision on the implementation of the SI. Thus, countries that previously used the English system of measures (England, Australia, Canada, the USA, etc.) also adopted the SI.

Consider the structure of the construction of the International System of Units. Table 1.1 shows the basic and additional SI units.

SI derived units are formed from basic and supplementary units. SI derived units with special names (Table 1.2) can also be used to form other SI derived units.

Due to the fact that the range of values ​​of most measured physical quantities can now be very significant and it is inconvenient to use only SI units, since the measurement results in too large or small numerical values, the SI provides for the use of decimal multiples and fractions of SI units , which are formed with the help of multipliers and prefixes given in Table 1.3.

International unit

On October 6, 1956, the International Committee of Weights and Measures considered the recommendation of the commission on the system of units and made the following important decision, completing the work on establishing the International System of Units of Measurement:

"The International Committee for Weights and Measures, Having regard to the task received from the Ninth General Conference on Weights and Measures in its Resolution 6, concerning the establishment of a practical system of units of measurement which could be adopted by all countries signatory to the Metric Convention; having regard to all documents , received from 21 countries responding to the survey proposed by the Ninth General Conference on Weights and Measures, taking into account Resolution 6 of the Ninth General Conference on Weights and Measures establishing the choice of base units for the future system, recommends:

1) to be called the "International System of Units" a system based on the base units adopted by the Tenth General Conference, which are as follows;

2) that the units of this system listed in the following table apply, without prejudice to other units that may be added subsequently."

At its session in 1958, the International Committee for Weights and Measures discussed and decided on a symbol for the abbreviation of the name "International System of Units". A symbol consisting of two letters SI (the initial letters of the words System International) was adopted.

In October 1958, the International Committee of Legal Metrology adopted the following resolution on the issue of the International System of Units:

metric system measure weight

"The International Committee of Legal Metrology, meeting in plenary session on October 7, 1958 in Paris, announces its accession to the resolution of the International Committee of Weights and Measures on the establishment of an international system of units of measurement (SI).

The main units of this system are:

meter - kilogram-second-ampere-degree Kelvin-candle.

In October 1960, the issue of the International System of Units was considered at the Eleventh General Conference on Weights and Measures.

On this issue, the conference adopted the following resolution:

"The Eleventh General Conference on Weights and Measures, Bearing in mind Resolution 6 of the Tenth General Conference on Weights and Measures, in which it adopted six units as the basis for the establishment of a practical system of measurement for international relations, Bearing in mind Resolution 3 adopted by the International Committee of Measures and weights in 1956, and taking into account the recommendations adopted by the International Committee of Weights and Measures in 1958, relating to the abbreviation of the name of the system and to prefixes for the formation of multiples and submultiples, decides:

1. Assign the name "International System of Units" to the system based on six basic units;

2. Set the international abbreviation for this system "SI";

3. Form the names of multiple and submultiple units using the following prefixes:

4. Use the following units in this system without prejudice to what other units may be added in the future:

The adoption of the International System of Units was an important progressive act that summed up a large long-term preparatory work in this direction and summarizing the experience of scientific and technical circles different countries and international organizations in metrology, standardization, physics and electrical engineering.

The decisions of the General Conference and the International Committee for Weights and Measures on the International System of Units are taken into account in the recommendations of the International Organization for Standardization (ISO) on units of measurement and are already reflected in the legislative provisions on units and in the unit standards of some countries.

In 1958, the GDR approved a new Regulation on units of measurement, built on the basis of the International System of Units.

In 1960, in the government regulation on the units of measurement of the Hungarian People's Republic based on the International System of Units.

State standards of the USSR for units 1955-1958. were built on the basis of the system of units adopted by the International Committee for Weights and Measures as the International System of Units.

In 1961 the Committee of Standards, Measures and measuring instruments under the Council of Ministers of the USSR approved GOST 9867 - 61 "International System of Units", which establishes the preferred use of this system in all areas of science and technology and in teaching.

In 1961, by government decree, the International System of Units was legalized in France and in 1962 in Czechoslovakia.

The international system of units was reflected in the recommendations of the International Union of Pure and Applied Physics, adopted by the International Electrotechnical Commission and a number of other international organizations.

In 1964, the International System of Units formed the basis of the "Table of Units of Legal Measurement" of the Democratic Republic of Vietnam.

Between 1962 and 1965 in a number of countries, laws have been issued to adopt the International System of Units as mandatory or preferred, and standards for SI units.

In 1965, in accordance with the instructions of the XII General Conference on Weights and Measures, the International Bureau of Weights and Measures conducted a survey on the status of the adoption of the SI in countries that had acceded to the Metric Convention.

13 countries have adopted the SI as mandatory or preferred.

In 10 countries, the use of the International System of Units has been admitted and preparations are underway to revise laws in order to give a legal, mandatory character to this system in this country.

In 7 countries, SI is admitted as optional.

At the end of 1962, a new recommendation of the International Commission on Radiological Units and Measurements (ICRU) was published, devoted to quantities and units in the field of ionizing radiation. Unlike the previous recommendations of this commission, which were mainly devoted to special (non-systemic) units for measuring ionizing radiation, the new recommendation includes a table in which the units of the International System are placed in the first place for all quantities.

At the seventh session of the International Committee of Legal Metrology, which took place on October 14-16, 1964, which included representatives of 34 countries that signed the intergovernmental convention establishing the International Organization of Legal Metrology, the following resolution was adopted on the implementation of the SI:

"The International Committee of Legal Metrology, taking into account the need for the rapid spread of the International System of Units of SI, recommends the preferred use of these SI units in all measurements and in all measuring laboratories.

In particular, in temporary international recommendations. adopted and disseminated by the International Conference of Legal Metrology, these units should preferably be used for the calibration of measuring apparatus and instruments to which these recommendations apply.

Other units permitted by these recommendations are only temporarily permitted and should be avoided as soon as possible."

The International Committee of Legal Metrology has established a rapporteur secretariat on Units of Measurement whose task is to develop a model draft legislation on units of measurement based on the International System of Units. Austria has taken over the rapporteur secretariat for this topic.

Benefits of the International System

The international system is universal. It covers all areas of physical phenomena, all branches of technology and the national economy. The international system of units organically includes such private systems that have long been widespread and deeply rooted in technology, such as the metric system of measures and the system of practical electrical and magnetic units (ampere, volt, weber, etc.). Only the system that included these units could claim recognition as universal and international.

The units of the International System are for the most part quite convenient in size, and the most important of them have practical names of their own.

The construction of the International System corresponds to the modern level of metrology. This includes the optimal choice of basic units, and in particular their number and size; consistency (coherence) of derived units; rationalized form of electromagnetism equations; the formation of multiples and submultiples by means of decimal prefixes.

As a result, various physical quantities in the International System, as a rule, have different dimensions. This makes a full-fledged dimensional analysis possible, preventing misunderstandings, for example, when checking calculations. Dimension indicators in SI are integer, not fractional, which simplifies the expression of derived units through basic ones and, in general, operating with dimensions. The coefficients 4n and 2n are present in those and only those equations of electromagnetism that relate to fields with spherical or cylindrical symmetry. The method of decimal prefixes, inherited from the metric system, makes it possible to cover huge ranges of changes in physical quantities and ensures that the SI complies with the decimal system.

The international system is inherently flexible. It allows the use of a certain number of non-systemic units.

SI is a living and developing system. The number of basic units can be further increased if necessary to cover any additional area of ​​phenomena. In the future, it is also possible that some of the regulatory rules in force in the SI will be relaxed.

The international system, as its very name says, is intended to become the only system of units of physical quantities universally used. The unification of units is a long overdue necessity. Already, the SI has made numerous systems of units unnecessary.

The international system of units is adopted by more than 130 countries around the world.

The International System of Units is recognized by many influential international organizations, including the United Nations Educational, Scientific and Cultural Organization (UNESCO). Among those who recognized the SI are the International Organization for Standardization (ISO), the International Organization of Legal Metrology (OIML), the International Electrotechnical Commission (IEC), the International Union of Pure and Applied Physics, etc.

Bibliography

1. Burdun, Vlasov A.D., Murin B.P. Units of physical quantities in science and technology, 1990

2. Ershov V.S. Implementation of the International System of Units, 1986.

3. Kamke D, Kremer K. Physical bases of units of measurement, 1980.

4. Novosiltsev. On the history of the basic SI units, 1975.

5. Chertov A.G. Physical quantities (Terminology, definitions, designations, dimensions), 1990.

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In 1795, the Law on New Measures and Weights was passed in France, which established a single unit of length - meter, equal to ten millionths of a quarter of the arc of the meridian passing through Paris. Hence the name of the system - metric.

A platinum rod one meter long and of a very strange shape was chosen as the standard of the meter. Now the size of all rulers, one meter long, had to correspond to this standard.

Units installed:

- liter as a measure of the capacity of liquid and granular bodies, equal to 1000 cubic meters. centimeters and containing 1 kg of water (at 4 ° heat Celsius),

- gram as a unit of weight (the weight of pure water at a temperature of 4 degrees Celsius in the volume of a cube with an edge of 0.01 m),

- ar as a unit of area (the area of ​​a square with a side of 10 m),

- second as a unit of time (1/86400 of a mean solar day).

Later, the basic unit of mass became kilogram. The prototype of this unit was a platinum weight, which was placed under glass flasks and the air was pumped out - so that dust would not get in and the weight would not increase!

The prototypes of the meter and kilogram are still kept in the National Archives of France and are called "Meter Archive" and "Kilogram Archive" respectively.

There were different measures before, but an important advantage of the Metric system of measures was its decimality, since submultiple and multiple units, according to the accepted rules, were formed in accordance with the decimal count using decimal factors, which correspond to the prefixes deci, - centi, - milli, - deca, - hecto- and kilo-.

Currently, the metric system of measures is adopted in Russia and in most countries of the world. But there are other systems as well. For example, the English system of measures, in which the foot, pound and second are taken as the main units.

It is interesting that in all countries there are familiar packaging for different foods and drinks. In Russia, for example, milk and juices are usually packaged in liter bags. And large glass jars - entirely three-liter!

Remember: on professional drawings, the dimensions (dimensions) of products are signed in millimeters. Even if these are very large products, like cars!

Volkswagen Cady.

Citroen Berlingo.

Ferrari 360.

The newest book of facts. Volume 3 [Physics, chemistry and technology. History and archeology. Miscellaneous] Kondrashov Anatoly Pavlovich

When was the metric system introduced in Russia?

The metric, or decimal, system of measures is a set of units of physical quantities, which is based on a unit of length - a meter. This system was developed in France during the revolution of 1789-1794. At the suggestion of a commission of the largest French scientists, one ten-millionth part of a quarter of the length of the Paris meridian was accepted as a unit of length - a meter. This decision was due to the desire to base the metric system of measures on an easily reproducible "natural" unit of length, associated with a practically unchanged object of nature. The decree on the introduction of the metric system of measures in France was adopted on April 7, 1795. In 1799, a platinum prototype of the meter was made and approved. Dimensions, names and definitions of other units of the metric system of measures have been chosen so that it does not wear national character and can be applied in all countries. The metric system of measures acquired a truly international character in 1875, when 17 countries, including Russia, signed the Meter Convention to ensure international unity and improve the metric system. The metric system of measures was approved for use in Russia (optionally) by the law of June 4, 1899, the draft of which was developed by D. I. Mendeleev. It was introduced as a mandatory decree of the Council of People's Commissars of the RSFSR of September 14, 1918, and for the USSR - by a decree of the Council of People's Commissars of the USSR of July 21, 1925.