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• Hydraulics 4th ed., Per. and add. Tutorial and workshop for academic undergraduate, Eduard Mikhailovich Kartashov. The textbook outlines the main physico-mechanical properties of liquids, the questions of hydrostatics and hydrodynamics, given the foundations of the theory of hydrodynamic similarity and mathematical modeling ...

Units of physical quantities

Unit of measurement of physical quantity - The physical amount of fixed size, which is conditionally assigned a numerical value equal to one, and used for the quantitative expression of homogeneous physical quantities.

Example - 1 m - a unit of length; 1 C - a unit of time; 1 A is the unit of power of electric current.

System of units of physical quantities - A combination of basic and derivative units of physical quantities formed in accordance with the principles adopted for a given system of physical quantities.

Reference. Historically, the first system of units of physical quantities was adopted in 1791. The National Assembly of France is a metric system of measures.
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She was not yet a system of units in a modern sense, but included units of lengths, areas, volumes, compatibility and weight, which were based on two units: meter and kilogram.

In 1832 ᴦ. German mathematician K. Gauss proposed a methodology for building a system of units as a totality of basic and derivatives. He built a system of units in which three arbitrary, independent units - lengths, masses and time were taken as the basis. All other units could be determined using these three. Such a system of units associated with a certain way with three main, Gauss called the absolute system. For the main units he accepted a millimeter, milligrams and a second.

In the future, with the development of science and technology, a number of systems of units of physical quantities, built on the principle proposed by Gauss, based on the metric system of measures, but differ from each other by the main units are appeared.

Consider the most important systems of units of physical quantities.

SGS system. The system of units of physical values \u200b\u200bof SGS, in which the main units are centimeter as a unit of length, grams as a unit of mass and second as a unit of time, was set in 1881 ᴦ.

MKGSS system. The use of a kilogram as a unit of weight, and subsequently as a unit of force in general, led at the end of the XIX century to the formation of a system of units of physical quantities with three main units: a meter - a unit of length, a kilogram-force - a unit of strength and second - a unit of time.

MKSA system. The foundations of this system were proposed in 1901 ᴦ. Italian scientist Georgie. The main units of the MKS system are meter, kilogram, second and amp.

The presence of a number of systems of units of physical quantities, as well as a significant number of non-system units, inconvenience associated with recalculation during the transition from one system of units to another, required unification of units of measurements. The growth of scientific and technical and economic relations between different countries caused it is extremely important to include such a unification internationally.

A unified system of units of physical quantities was required, practically comfortable and embracing various measurement areas. At the same time, it had to preserve the principle of coherence (equality unit of proportionality coefficient in the equations of communication between physical quantities).

The current "international units' system" (SI - system international) was adopted by the one-General Conference on measures and weighs in 1960. The system of SI is the only system of units of physical quantities, which is accepted and used in most countries of the world.

On the territory of our country, the SI system is valid from 1.01.1982 ᴦ. In accordance with GOST 8.417-81''GSI. Units of physical quantities. The system C consists of seven basic, two additional and a number of derivatives of units (Tables 1.1 and 1.2).

The unit of derivative of the physical size of the system of units is formed in accordance with the equation that binds it either with the main units or with the basic and already defined derivatives.

Table 1.1 - Basic and Additional Units System System

Physical quantity	unit of measurement
Name	Dimension	Recommended designation	Name	Designation
Russian	International
O S N O V N S E
Length	L.	L.	meter	M.	M.
Weight	M.	M.	kilogram	kg	kg.
Time	T.	T.	second	from	S.
Electric current power	I.	I.	ampere	BUT	A.
Thermodynamic temperature	Θ	T.	Kelvin	TO	TO
Number of substances	N.	N, υ	mole	mole	MOL.
The power of light	J.	J.	Kandela	CD	CD
D o p o l n and t el b n s e
Flat corner	-	-	radian	glad	RAD.
Corner	-	-	Steradian	cf.	Sr.

Table 1.2 - Some derivative units of SI system having a special name

Physical quantity	unit of measurement
Name	Dimension	Name	Designation	Expression
Frequency	T -1.	hertz	Hz	S -1.
Strength, weight	LMT -2.	Newton	N.	m kg s -2
Pressure, mechanical voltage	L -1 MT -2	pascal	PA	M -1 KG S -2
Energy, Working Number of Heat	L 2 MT -2	joule	J.	m 2 kg s -2
Power	L 2 MT -3	watt	T.	m 2 kg s -3
Number of electricity	TI	pendant	CL	SA
Electrical Voltage, Potential	L 2 MT -3 i -1	volt	IN	M 2 KG S -3 A -1
Electrical capacity	L -2 M -1 T 4 I 2	farad	F.	M -2 KG -1 S 4 A 2
Electrical resistance	L 2 MT -3 i -2	Oh.	Oh.	m 2 kg s -3 a -2

The equation of communication between values \u200b\u200breflects the relationship between values \u200b\u200bdue to the law of nature, in which physical quantities are understood under the letter symbols. For example, the equation reflects an existing speed dependence. V. from the way l. and time t.. From the above example, it can be seen that it is extremely important for measuring the speed to measure the length of the journey and time, for ĸᴏᴛᴏᴩᴏᴇ this path passed.

System Unit of Physical Size (System Unit) - a unit of physical quantity, which is included in the adopted system of units.

All main, derivatives, multiple and dolle units are systemic. For example: 1 m; 1 m / s; 1 km; 1 nm.

Introduced Unit of Physical (Intimated unit) is an unit of physical quantity that is not incorporated into any of the adopted systems of units.

Introduced units are divided into four types:

- allowed on a par with units, for example: a unit of mass - ton; Flat angle units - degrees, minute of second; Unit of volume - liter, etc.;

- allowable to use in special areasTo which include: units of length (in astronomy) - Astronomical unit, parsec, light year; an optical force unit (in optics) - diopter; Energy unit (in physics) - electron-volt;

- temporarily allowed to use Along with the units of SI, for example: in marine navigation - sea mile; In jewelry case, the unit of mass - carat, etc.
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These units must be seized in accordance with international agreements;

- seized from useThese include a pressure unit - a millimeter of a mercury pillar; Power unit - horsepower, etc.

There are multiple and dolly units of physical quantity.

Multiple unit(multiple unit) - a unit of physical quantity, for an integer number of times a large system or non-systemic unit.

Examples:

- unit of length 1 km \u003d 10 3 m, ᴛ.ᴇ. multiple meter;

- the frequency unit of 1 MHz (megahertz) \u003d 10 6 Hz is a multiple hertz;

- A unit of activity of radionuclides of 1 MBK (megabeckequer) \u003d 10 6 BC Pasta Becker.

Dolly unit of physical quantity (dolly unit) - a unit of physical quantity, for an integer time a smaller system or incoming unit.

Example - a unit of length 1 nm (nanometer) \u003d 10 -9 m and a unit of time 1 μs (microsuekunda) \u003d 10 -6 C are dolly respectively from the meter and a second.

Table 1.3 shows the consoles for the formation of multiple and dolly units C.

Size Unit of Physical Size(Unit size) - quantitative determination of a unit of physical quantity reproducible or stored measuring means.

The unit size stored by subordinate standards or measurement workers must be set to the national primary standard. In this case, there must be several comparison steps (through secondary and working standards).

Table 1.3 - multipliers and consoles for the formation of decimal multiple and dolle units and their names

Multiple	Console	Designation of the console	Factor	Console	Designation of the console
Between-national	Russian	International	Russian
10 18	ex	E.	E.	10- 1	deci	D.	D.
10 15	Peta	R	P	10- 2	Santi	from	from
10 12	Tera	T.	T.	10- 3	Milli	M.	M.
10 9	Giga	G.	G.	10- 6	micro	μ	MK
10 6	mega	M.	M.	10- 9	Nano	N.	N.
10 3	kilo	K.	to	10 -12	pico	P.	P
10 2	hecto	H.	G.	10 -15	Femto	F.	F.
10 1	dese	DA	Yes	10 -18	Atto	but	but

Units of physical quantities are concepts and types. Classification and features of the category "Units of Physical Values" 2017, 2018.

State security system
Unity of measurements

Units of physical quantities

GOST 8.417-81

(ST SEV 1052-78)

State Committee of the USSR on Standards

Moscow

Designed State Committee of the USSR on standards Performers Yu.V. Tarbeyev , Dr. tech. sciences; K.P. Shirokov, Dr. tech. sciences; PN Selivanov, Cand. tehn sciences; ON THE. Yeruhin Made State Committee of the USSR on Standards Member of the State Standard L.K. Isaev Approved and enacted Resolution of the State Committee of the USSR on the standards of March 19, 1981 No. 1449

State Standard of the SSR Union

State system for ensuring uniformity of measurements Units Physical Values State System for Ensuring The Uniformity of Measurements. UNITS OF PHYSICAL QUANTITS

GOST 8.417-81 (ST SEV 1052-78)

Decree of the State Committee of the USSR on the standards of March 19, 1981 No. 1449, the deadline is established

Since 01.01 1982

This standard establishes units of physical quantities (hereinafter - units) used in the USSR, their names, designations and rules for the application of these units The standard does not apply to units used in scientific research and when publishing their results, if they do not consider and do not use the results Measurements of specific physical quantities, as well as on units of quantities estimated by conditional scales *. * Under the conditional scales are understood, for example, Rockwell and Vickers hardness scales, photosensitivity of photographic materials. The standard corresponds to ST SEV 1052-78 in terms of the general provisions, units of the international system, units that are not included in SI, the rules for the formation of decimal multiples and dolly units, as well as their names and designations, the rules for writing the designations of units, the rules for the formation of coherent derivatives of SI units ( See Reference Appendix 4).

1. GENERAL PROVISIONS

1.1. It is subject to mandatory use of the units of the international system of units *, as well as decimal multiple and dollars from them (see Section 2 of this standard). * International Unit system (International Abbreviated Name - Si, in Russian Transcription - SI), was adopted in 1960 by the XI General Conference on Measures and Weighs (GKMV) and clarified on subsequent GKMV. 1.2. It is allowed to apply on a par with units according to claim 1.1 units that are not included in C, in accordance with PP. 3.1 and 3.2, their combinations with SI units, as well as some of those who are widely used in practice decimal multiples and dollars from the above units. 1.3. It is temporarily allowed to apply on a par with units of claim 1.1 units that are not included in C, in accordance with paragraph 3.3, as well as some of those who have spread to the practice of multiples and dollars from them, combinations of these units with si, decimal, multiple and dollane from They are with units of claim 3.1. 1.4. In the newly developed or revised documentation, as well as publications, the values \u200b\u200bshould be expressed in units of SI, decimal, multiple and dollars from them and (or) in units allowed to use in accordance with paragraph 1.2. It is also allowed in the specified documentation to apply units according to claim 3.3, the period of seizure of which will be established in accordance with international agreements. 1.5. In the newly approved regulatory and technical documentation for measuring instruments, their graduation should be provided in units of C, decimal multiple and dollars from them or in units allowed to use in accordance with clause 1.2. 1.6. The newly developed regulatory and technical documentation on methods and means of calibration should include verification of measuring instruments, progressive in newly administered units. 1.7. SI units established by this standard, and units allowed to use PP. 3.1 and 3.2, should be applied in the learning processes of all educational institutions, textbooks and textbooks. 1.8. Revision of the regulatory, technical, design, technological and other technical documentation, which uses units that are not provided for in this standard, as well as bringing into compliance with PP. 1.1 and 1.2 of this standard of measuring instruments, graded in units to be seized, are carried out in accordance with paragraph 3.4 of this standard. 1.9. With legal relations on cooperation with foreign countries, with the participation in the activities of international organizations, as well as in the exporting products supplied with export products (including transport and consumer containers) of technical and other documentation, international designations of units are used. In the documentation for export products, if this documentation does not go abroad, the Russian designations of units are allowed to apply. (New edition, change No. 1). 1.10. In the regulatory and technical design, technological and other technical documentation on various types of products and products used only in the USSR, preferably Russian designations of units are used. At the same time, regardless of which the designations of units are used in the documentation for measuring instruments, when specifying units of physical quantities on signs, scales and panels of these measuring instruments, international designations of units are used. (New edition, change No. 2). 1.11. In print editions, it is allowed to apply either international or Russian units. At the same time, the use of both types of designations in the same edition is not allowed, with the exception of publications on units of physical quantities.

2. Units of the International System

2.1. The main units of C are given in Table. one.

Table 1

Value
Name	Dimension	Name	Designation		Definition
			international
Length					The meter is the length of the path passing by light in vacuo for the time interval 1/299792458 S [XVII GKMV (1983), resolution 1].
Weight		kilogram			Kilogram is a mass unit equal to the mass of the international prototype kilogram [I GKMV (1889) and III GKMV (1901 g)]
Time					Second is a time equal to 9192631770 Radiation periods corresponding to the transition between two ultra-thin levels of the main state of the Cesium atom-133 [XIII GKMV (1967), resolution 1]
Electric current power					The amp is the power equal to the power of an unchanged current, which, when passing along two parallel straight-line conductors of the infinite length and a negligible area of \u200b\u200bthe circular cross section, located in a vacuum at a distance of 1 m one from the other, would cause a length of 1 m in each portion of the interaction, equal 2 × 10 -7 N [MKMV (1946), resolution 2, approved by IX GKMV (1948)]
Thermodynamic temperature					Kelvin is a unit of thermodynamic temperature equal to 1/273,16 parts of the thermodynamic temperature of the triple point of water [x III GKMV (1967), resolution 4]
Number of substances					Mol is the amount of a substance of the system containing as many structural elements as containing atoms in carbon-12 weighing 0.012 kg. When applied, praying structural elements should be specified and can be atoms, molecules, ions, electrons and other particles or specified particle groups [XIV GKMV (1971), resolution 3]
The power of light					Candela is an power equal to the power of light in a given direction of the source emitting monochromatic radiation with a frequency of 540 × 10 12 Hz, the energy force of which in this direction is 1/683 W / SR [XVI GKMV (1979), resolution 3]
Notes: 1. In addition to the temperature of Kelvin (designation T.) It is also allowed to use the Celsius temperature (designation T.) determined by the expression T. = T. - T. 0, where T. 0 \u003d 273.15 K, by definition. The Kelvin temperature is expressed in Kelvin, Celsius temperature - in degrees Celsius (the designation of international and Russian ° C). In size, degrees Celsius is equal to Kelvin. 2. The interval or difference of Kelvin temperatures are expressed in Kelvin. The interval or temperature difference Celsius is allowed to express both in Kelvin and in degrees Celsius. 3. The designation of the international practical temperature in the international practical temperature scale of 1968, if it is necessary to distinguish between the thermodynamic temperature, is formed by adding to the designation of the thermodynamic, the temperature of the index "68" (for example, T. 68 or T. 68). 4. The unity of light measurements is ensured in accordance with GOST 8.023-83.

(Modified edition, change No. 2, 3). 2.2. Additional units of C are given in Table. 2.

table 2

Name of magnitude
	Name	Designation		Definition
		international
Flat corner				Radine has an angle between two circle radius, the length of the arc between which is equal to the radius
Solid angle	steradian			Steeradian is a bodied corner with a vertex in the center of the sphere, cutting on the surface of the sphere area equal to the square of the square with a side of the radius of the sphere

(Modified edition, change No. 3). 2.3. The derivatives of the SI units should be formed from the basic and additional units of the SI according to the rules for the formation of coherent derivatives (see required application 1). Derivatives of SI units having special names can also be used to form other derivatives of SI units. Derivative units that have special names, and examples of other derivatives of units are shown in Table. 3 - 5. Note. Electric and magnetic units of C should be formed in accordance with the rationalized form of the electromagnetic field equations.

Table 3.

Examples of derivatives of SI units whose names are formed from the names of the main and additional units

Value
Name	Dimension	Name	Designation
			international
Area		square meter
Volume, capacity		cubic meter
Speed		meter per second
Angular velocity		radian per second
Acceleration		meter for a second squared
Angular acceleration		radian for a second squared
Wave number		meter in minus of the first degree
Density		kilogram on cubic meter
Specific volume		cubic meter per kilogram
		ampere per square meter
		ampere per meter
Molar concentration		mole on a cubic meter
Flow of ionizing particles		second degree
Flow density particle		second in minus first degree - meter in minus second degree
Brightness		candela per square meter

Table 4.

Derivatives of SI units having special names

Value
Name	Dimension	Name	Designation		Expression through basic and additional, units
			international
Frequency
Strength, weight
Pressure, mechanical voltage, elastic module
Energy, work, amount of heat					m 2 × kg × s -2
Power, energy flow					m 2 × kg × s -3
Electric charge (number of electricity)
Electrical Voltage, Electric Potential, Electric Potential Difference, Electrical Force					m 2 × kg × s -3 × a -1
Electrical capacity	L -2 M -1 T 4 I 2				m -2 × kg -1 × s 4 × a 2
					m 2 × kg × s -3 × a -2
Electrical conductivity	L -2 M -1 T 3 I 2				m -2 × kg -1 × s 3 × a 2
Magnetic Induction Flow, Magnetic Flow					m 2 × kg × s -2 × a -1
Magnetic Flow Density, Magnetic Induction					kG × S -2 × A -1
Inductance, mutual inductance					m 2 × kg × s -2 × a -2
Light flow
Light					m -2 × CD × SR
Nuclide activity in a radioactive source (radionuclide activity)		beckel
Absorbed dose of radiation, Kerma, indicator of the absorbed dose (absorbed dose of ionizing radiation)
Equivalent dose of radiation

(Modified edition, change No. 3).

Table 5.

Examples of derivatives of SI units whose names are formed using special items shown in Table. four

Value
Name	Dimension	Name	Designation		Expression through the main and additional units
			international
Moment of power		newton-meter			m 2 × kg × s -2
Surface tension		Newton on meter
Dynamic viscosity		pascal Soon			m -1 × kg × s -1
		cubic meter pendant
Electrical displacement		square meter pendant
		volt on meter			m × kg × s -3 × a -1
Absolute dielectric constant	L -3 M -1 × T 4 I 2	farad on meter			m -3 × kg -1 × s 4 × a 2
Absolute magnetic permeability		henry per meter			m × kg × s -2 × a -2
Specific energy		joule per kilogram
System heat capacity, system entropy		joule on Kelvin			m 2 × kg × s -2 × k -1
Specific heat, specific entropy		joule on kilogram Celvin		J / (kg × k)	m 2 × s -2 × k -1
Surface power flow density		watt per square meter
Thermal conductivity		watt on meter-koblenn			m × kg × s -3 × k -1
		joule on Mol			m 2 × kg × s -2 × mol -1
Molar entropy, molar heat capacity	L 2 MT -2 Q -1 N -1	joule on Mol Celvin		J / (mol × k)	m 2 × kg × s -2 × k -1 × mol -1
		watt on Steradian			m 2 × kg × s -3 × sr -1
Exposure dose (X-ray and gamma radiation)		pendant per kilogram
Power absorbed dose		gray per second

3. Units that are not included in C

3.1. Units listed in Table. 6, allowed to be applied without limitation on a par with units of C. 3.2. Without limit time, the relative and logarithmic units are allowed to use relative and logarithmic units with the exception of the unit (see paragraph 3.3). 3.3. Units shown in Table. 7, temporarily allowed to apply before adoption of relevant international solutions. 3.4. The units whose relations with SI units are given in the reference application 2 are removed from circulation within the time limits provided by the programs for transition activities to the SI units developed in accordance with RD 50-160-79. 3.5. Based on the sectors of the national economy, the use of units not provided for in this Standard, by introducing them to industry standards in coordination with Gosstandart.

Table 6.

Introduction units allowed to use on a par with units

Name of magnitude					Note
	Name	Designation		SO ratio
		international
Weight
	atomic unit of mass			1,66057 × 10 -27 × kg (approximately)
Time 1.
				86400 S.
Flat corner				(P / 180) RAD \u003d 1,745329 ... × 10 -2 × RAD
				(P / 10800) RAD \u003d 2,908882 ... × 10 -4 RAD
				(P / 648000) RAD \u003d 4,848137 ... 10 -6 RAD
Volume, capacity
Length	astronomical unit			1,49598 × 10 11 m (approximately)
	light year			9,4605 × 10 15 m (approximately)
				3,0857 × 10 16 m (approximately)
Optical power	diopter
Area
Energy	electron-volt			1,60219 × 10 -19 j (approximately)
Full power	volt-ampere
Reactive power
Mechanical stress	newton per square millimeter
1 It is also allowed to apply other units that have gained widespread, for example a week, month, year, century, millennium, and the like. 2 It is allowed to apply the name "Gon" 3 is not recommended for accurate measurements. With the ability to displace the designation L with the number 1, the designation L is allowed. Note. Time units (minute, hour, day), flat angle (degree, minute, second), astronomical unit, light year, diopter and atomic mass unit is not allowed to apply with consoles

(Modified edition, change No. 3).

Table 7.

Units temporarily allowed to use

Name of magnitude					Note
	Name	Designation		SO ratio
		international
Length	nautical mile			1852 m (exactly)	In marine navigation
Acceleration					In gravimetry
Weight				2 × 10 -4 kg (exactly)	For precious stones and pearls
Linear density				10 -6 kg / m (exactly)	In the textile industry
Speed					In marine navigation
Rotation frequency	turnover per second
	turnover per minute			1/60 S -1 \u003d 0,016 (6) S -1
Pressure
Natural logarithm of the dimensionless ratio of physical quantity for the same physical size adopted for the original					1 NP \u003d 0.8686 ... B \u003d \u003d 8,686 ... DB

(Modified edition, change No. 3).

4. Rules for the formation of decimal multiple and dolly units, as well as their names and designations

4.1. Decimal multiple and dollane units, as well as their names and designations, should be formed using multipliers and consoles shown in Table. eight.

Table 8.

Farmers and consoles for the formation of decimal multiple and dolle units and their names

Factor	Console	Designation of the console		Factor	Console	Designation of the console
		international				international

4.2. Joining the name of two or more consoles in a row is not allowed. For example, instead of the name of the microcrofrad unit, picoparad should be written. Notes: 1 Due to the fact that the name of the main unit - a kilogram comprises the "kilo" console, for the formation of multiple and dolly units of mass, a dolly unit of gram is used (0.001 kg, kg), and the consoles must be attached to the word "gram", for example, Milligram (MG, mg) instead of microcilograms (M KG, ICCG). 2. The dolly unit of mass - "gram" is allowed to be applied and without attaching the console. 4.3. The prefix or its designation should be written in a unit with the name of the unit to which it joins, or, accordingly, with its designation. 4.4. If the unit is formed as a product or relationship of units, the prefix should be attached to the name of the first unit included in the work or in relation. It is allowed to use the console in the second multiplier of the work or in the denominator only at substantive cases when such units are widespread and the transition to units formed in accordance with the first part of the item is associated with great difficulties, for example: a ton-kilometer (T × km; t × km), watt per square centimeter (W / CM 2; W / cm 2), volts per centimeter (V / CM; V / cm), ampere per square millimeter (A / MM 2; A / mm 2). 4.5. The names of multiple and dollane units from the unit erected into a degree should be formed by attaching the console to the name of the source unit, for example, to form the names of a multiple or a dollar unit from a unit of a square meter, which is a second degree of a number of length - meters, the prefix should be attached To the name of this last unit: a square kilometer, a square centimeter, etc. 4.6. The designations of multiple and dolly units from the unit erected into a degree should be formed by adding the corresponding indicator to the designation of multiple or dollar from this unit, and the indicator means the construction of a multiple or dollar unit (along with the prefix). Examples: 1. 5 km 2 \u003d 5 (10 3 m) 2 \u003d 5 × 10 6 m 2. 2. 250 cm 3 / s \u003d 250 (10 -2 m) 3 / (1 S) \u003d 250 × 10 -6 m 3 / s. 3. 0.002 cm -1 \u003d 0.002 (10 -2 m) -1 \u003d 0.002 × 100 m -1 \u003d 0.2 m -1. 4.7. Recommendations for the selection of decimal multiple and dolly units are shown in the reference application 3.

5. Rules for writing designations of units

5.1. To write values \u200b\u200bof values, apply the designations of units with letters or special signs (... °, ... ¢, ... ¢ ¢), and two types of letter notation are installed: international (using Latin or Greek alphabet letters) and Russians (using the letters of the Russian alphabet) . The units set as standard are given in Table. 1 - 7. International and Russian designations of relative and logarithmic units are as follows: percentage (%), PROMILL (O / O), a million share (RR M, MUD -1), Bel (B), Decibel (DB, DB), Oktawa (- , Oct), Decade (-, Dec), background (phon, background). 5.2. The alphabetic designations of units must be printed by direct font. In the notation of units, the point as a sign of reduction does not put. 5.3. The designations of units should be applied after numeric: values \u200b\u200bof values \u200b\u200band placed in a string with them (without transfer to the next string). There should be a space between the last digit number and the designation of the unit, equal to the minimum distance between the words, which is defined for each type and size of the font according to GOST 2.304-81. Exceptions are notation in the form of a sign raised above the string (clause 5.1), before which do not leave the space. (Modified edition, change No. 3). 5.4. If there is a decimal fraction in the numerical value of the value, the units designation should be placed after all numbers. 5.5. When specifying values \u200b\u200bof values \u200b\u200bwith limit deviations, numeric values \u200b\u200bshould be concluded with limit deviations in brackets and designations of the unit after brackets or to put out the designations of units after the numerical value of the value and after its limit deviation. 5.6. It is allowed to apply the designations of units in the headlines of the graph and in the names of the strings (sides) of the tables. Examples:

Nominal flow. M 3 / H	Upper testimony limit, m 3		Price division of the extreme right roller, M 3, no more
100, 160, 250, 400, 600 and 1000
2500, 4000, 6000 and 10000
True Power, KW
Overall dimensions, mm:
length
width
height
Pitch, mm.
Luxury, MM.

5.7. It is allowed to apply the designations of units in the explanations of the designations of values \u200b\u200bto formulas. Placing the designations of units in one row with formulas expressing the dependencies between the values \u200b\u200bor between their numerical values \u200b\u200bpresented in the letter form is not allowed. 5.8. The alphabetic designations of units included in the work should be separated by dots on the midline, as signs of multiplication *. * In typewritten texts it is allowed not to raise the point. Convenient designations of units included in the work, separating spaces, if it does not lead to a misunderstanding. 5.9. In the letter notation of the relationship of units as a sign of division, only one trait should be applied: oblique or horizontal. It is allowed to apply the designations of units in the form of a product of the designations of units, erected to degree (positive and negative) **. ** If for one of the units included in the ratio, the designation is established in the form of a negative degree (for example, S -1, M -1, to -1; C -1, M -1, K -1), apply oblique or horizontal trait not allowed. 5.10. When applying the oblique feature of the units in the numerator and the denominator should be placed in the string, the product of the designations of units in the denominator should be included in the brackets. 5.11. When specifying a derivative of a unit consisting of two or more units, it is not allowed to combine alphabetic designations and names of units, i.e. For one units, give designations, and for others - names. Note. It is allowed to apply the combinations of special signs ... °, ... ¢, ... ¢ ¢,% and o / oo with letternal designations of units, for example ... ° / s, etc.

ATTACHMENT 1

Mandatory

Rules for the formation of coherent derivatives of units

Coherent derivatives of units (hereinafter - derivative units) of the international system, as a rule, form with the help of the simplest equations of communication between the values \u200b\u200b(defining equations) in which the numerical coefficients are equal to 1. To form derivatives of units of magnitude in the communication equations, they are taken equal to units of C. Example. The velocity unit is formed using an equation that determines the speed of a straight and evenly moving point

V. = s / T.,

Where V. - speed; S. - the length of the traveled path; T. - time movement time. Substitution instead S. and T. their units si gives

[v.] = [s.]/[t.] \u003d 1 m / s.

Consequently, the unit of SI is a meter per second. It is equal to the speed of a straightforward and evenly moving point, at which this point for the time 1 S moves to a distance of 1 m. If the communication equation contains a numerical coefficient other than 1, then for the formation of a coherent derivative unit to the right-hand side, the values \u200b\u200bare substituted with values \u200b\u200bin units of C, which gives the number 1. Example to the coefficient to the coefficient. If an equation is used to form an energy unit

Where E. - kinetic energy; m - mass of material point; V. - the speed of the point, then the coherent unit of the energy of the C form, for example, as follows:

Consequently, the energy unit is a Joule (equal to Newton meter). In the examples given, it is equal to the kinetic energy of the body with a mass of 2 kg moving at a speed of 1 m / s, or a body weighing 1 kg moving at speeds

ATTACHMENT 2

Reference

The ratio of some non-system units with si units

Name of magnitude					Note
	Name	Designation		SO ratio
		international
Length	angstrom
	x-unit			1,00206 × 10 -13 m (approximately)
Area
Weight
Solid angle	square degree			3,0462 ... × 10 -4 SR
Strength, weight
	kilogram-power			9,80665 N (exactly)
	kilopond
	gram-power			9,83665 × 10 -3 N (exactly)
	ton-power			9806.65 N (exactly)
Pressure	kilogram-power per square centimeter			98066.5 RA (for sure)
	kilopond per square centimeter
	millimeter water column		mm waters. Art.	9,80665 RA (exactly)
	millimeter mercury pillar		mm RT. Art.
Voltage (mechanical)	kilogram-power per square millimeter			9,80665 × 10 6 RA (exactly)
	kilopond per square millimeter			9,80665 × 10 6 RA (exactly)
Work, Energy
Power	horsepower
Dynamic viscosity
Kinematic viscosity
	om-square millimeter per meter		Om × mm 2 / m
Magnetic flow	maxwell
Magnetic induction
	gPLBERT			(10/4 p) a \u003d 0,795775 ... and
Magnetic field tension				(10 3 / p) a / m \u003d 79,5775 ... a / m
The amount of heat, thermodynamic potential (internal energy, enthalpy, isochloro-isothermal potential), heat of phase transformation, heat of chemical reaction	calorie (interddet)			4,1858 J (exactly)
	thermochemical calorie			4,1840 j (approximately)
	calorie 15-degree			4,1855 J (approximately)
Absorbed dose of radiation
Equivalent radiation dose, equivalent dose rate
Exposure dose of photon radiation (exposure dose of gamma and x-ray radiation)				2.58 × 10 -4 C / KG (exactly)
Nuclide activity in the radioactive source				3,700 × 10 10 bq (exactly)
Length
Angle of rotation				2 P RAD \u003d 6,28 ... RAD
Magnethodific power, the difference of magnetic potentials	amperworth
Brightness
Area

Modified edition, meas. Number 3.

ATTACHMENT 3

Reference

1. The selection of a decimal multiple or a dollar unit from a unit is dictated primarily by the convenience of its use. From the variety of multiple and dollane units that can be formed using consoles, choose a unit leading to numerical values \u200b\u200bof the value acceptable in practice. In principle, multiple and dollane units are chosen in such a way that the numeric values \u200b\u200bof the values \u200b\u200bare in the range from 0.1 to 1000. 1.1. In some cases, it is advisable to apply the same multiple or dollar unit, even if numeric values \u200b\u200bare out of range from 0.1 to 1000, for example, in the tables of numerical values \u200b\u200bfor one value or when comparing these values \u200b\u200bin the same text. 1.2. In some areas, one and the same multiple or dolly unit are always used. For example, in the drawings used in mechanical engineering, linear dimensions are always expressed in millimeters. 2. In tab. 1 of this Annex are presented to the use of multiples and dollane units from SI units. Presented in table. 1 multiple and dollane units from SI units for this physical quantity should not be considered exhaustive, as they may not cover the ranges of physical quantities in developing and newly emerging areas of science and technology. Nevertheless, the recommended multiple and dollane units from the SI units contribute to the uniformity of the presentation of the values \u200b\u200bof physical quantities belonging to various fields of technology. In the same table, there were also widespread multiple and dolly units from units applied on a par with units. 3. For values \u200b\u200bnot covered by Table. 1, you should use multiple and dolle units selected in accordance with clause 1 of this application. 4. To reduce the probability of errors in calculating decimal, multiple and dollane units are recommended to substitute only to the final result, and in the process of calculations, all values \u200b\u200bto express in units of C, replacing the console of the degrees of the number 10. 5. In Table. 2 of this Annexer shows the propagation of a unit of some logarithmic quantities.

Table 1

Name of magnitude	Designations
	units S.		units that are not incoming and si	multiple and dollars from units that are not included in si
Part I. Space and time
Flat corner	rAD; Rady (radians)	m RAD; MKRD	... ° (degree) ... (Minute) ... "(second)
Solid angle	sR; CP (Steeradian)
Length	m; m (meter)		... ° (degree) ... ¢ (minute) ... ² (second)
Area
Volume, capacity			l (L); l (liter)
Time	s; C (second)		d; SUT (day) min; Min (minute)
Speed
Acceleration	m / S 2; m / s 2
Part II. Periodic and related phenomena
	Hz; Hz (Hertz)
Rotation frequency			min -1; Min -1
Part III. Mechanics
Weight	kg; kg (kilogram)		t; T (ton)
Linear density	kg / m; kg / m	mg / m; mg / M. or g / km; g / km.
Density	kg / m 3; kg / m 3	Mg / m 3; Mg / m 3 kg / dm 3; kg / dm 3 g / cm 3; g / cm 3	t / M 3; T / m 3 or kg / l; kg / l	g / ML; g / ml
Number of traffic	kg × m / s; kg × m / s
Moment moment	kg × m 2 / s; kg × m 2 / s
Moment of inertia (dynamic moment of inertia)	kG × m 2, kg × m 2
Strength, weight	N; N (Newton)
Moment of power	N × m; N × M.	Mn × m; MN × M. kn × m; KN × M. mn × m; MN × M. m n × m; MKN × M.
Pressure	Ra; Pa (Pascal)	m RA; ICPA
Voltage
Dynamic viscosity	Ra × s; PA × S.	mPA × s; MPa × S.
Kinematic viscosity	m 2 / s; m 2 / s	mM 2 / S; mm 2 / s
Surface tension		mn / m; MN / M.
Energy, work	J; J (Joule)		(electron-volt)	Gev; GeV MEV; MeV KEV; keV
Power	W; W (watt)
Part IV. Heat
Temperature	TO; K (Kelvin)
Temperature coefficient
Warmth, the amount of heat
Heat flow
Thermal conductivity
Heat transfer coefficient	W / (m 2 × k)
Heat capacity		kj / k; KJ / K.
Specific heat	J / (kg × k)	kj / (kg × k); KJ / (kg × K)
Entropy		kj / k; KJ / K.
Specific entropy	J / (kg × k)	kj / (kg × k); KJ / (kg × k)
Specific heat	J / kg; J / kg	MJ / KG; MJ / kg kj / kg; KJ / kg
Specific heat transformation	J / kg; J / kg	MJ / KG; MJ / kg kj / kg; KJ / kg
Part V. Electricity and magnetism
Electric current (electric current)	A; A (Ampere)
Electric charge (number of electricity)	FROM; CL (pendant)
Electric charge spatial density	C / M 3; CL / m 3	C / MM 3; CL / mm 3 Ms / m 3; Μl / m 3 C / s M 3; CL / cm 3 kC / M 3; Kl / m 3 m C / M 3; μl / m 3 m C / M 3; μKl / m 3
Electric charge surface density	C / M 2, CL / m 2	Ms / m 2; Μl / m 2 C / MM 2; CL / mm 2 With / s m 2; CL / cm 2 kc / m 2; Kl / m 2 m C / M 2; μl / m 2 m C / M 2; μKl / m 2
Electric field tension		MV / M; MV / M. kv / m; KV / M. V / Mm; In / mm. V / cm; V / see mV / M; MV / M. m v / m; MKV / M.
Electrical Voltage, Electric Potential, Electric Potential Difference, Electrical Force	V, in (Volt)
Electrical displacement	C / M 2; CL / m 2	With / s m 2; CL / cm 2 kc / cm 2; CCL / cm 2 m C / M 2; μl / m 2 m C / M 2, μKl / m 2
Flow of electrical displacement
Electrical capacity	F, F (Farad)
Absolute dielectric permeability, electric constant		m F / M, ICF / M nF / M, NF / M pF / M, PF / M
Polarizedness	C / M 2, CL / m 2	C / s M 2, CL / cm 2 kc / m 2; Kl / m 2 m C / M 2, μl / m 2 m C / M 2; μKl / m 2
Electric moment dipole	C × M, CL × m
Electric current density	A / m 2, a / m 2	Ma / m 2, Ma / m 2 A / mm 2, a / mm 2 A / C m 2, a / cm 2 kA / M 2, ka / m 2,
Linear electric current density		ka / m; ka / m A / mm; A / mm. A / s m; A / cm
Magnetic field tension		ka / m; ka / m A / MM; A / mm. A / CM; A / cm
Magnethodific power, the difference of magnetic potentials
Magnetic induction, magnetic flux density	T; TL (Tesla)
Magnetic flow	WB, WB (Weber)
Magnetic vector potential	T × m; TL × M.	kt × m; KTL × M.
Inductance, mutual inductance	N; GN (Henry)
Absolute magnetic permeability, magnetic constant		m n / m; ICGN / M. nH / m; NGN / M.
Magnetic moment	A × m 2; A m 2.
Magnetization		ka / m; ka / m A / mm; A / mm.
Magnetic polarization
Electrical resistance
Electrical conductivity	S; CM (Siemens)
Specific electrical resistance	W × m; Om × M.	G w × m; Gom × M. M w × m; Mom × M. k W × m; com × m W × cm; Om × cm m w × m; Mom × M. m w × m; MKOM × M. n w × m; NOM × M.
Specific electrical conductivity		MS / M; MSM / M. ks / m; KSM / M.
Reluctance
Magnetic conductivity
Impedance
Module of full resistance
Reactance
Active resistance
Admittance
Module full conductivity
Reactive conductivity
Conductance
Active power
Reactive power
Full power			V × A, in × a
Part VI. Light and associated electromagnetic radiation
Wavelength
Wave number
Energy radiation
Radiation stream, radiation power
Energy power of light (radiation strength)	W / sr; W / cf.
Energy Brightness (Bindness)	W / (SR × m 2); W / (cf × m 2)
Energy illumination (irradiated)	W / m 2; W / m 2
Energy luminosity (nerd)	W / m 2; W / m 2
The power of light
Light flow	lm; lm (lumen)
Light energy	lm × s; LM × S.		lM × H; LM × C.
Brightness	cD / M 2; CD / m 2
Luminosity	lM / M 2; lm / m 2
Light	l x; LC (Suite)
Light exposure	lX × S; LK × S.
Light Equivalent Radiation Flow	lM / W; LM / W.
Part VII. Acoustics
Period
Frequency of the periodic process
Wavelength
Sound pressure		m RA; ICPA
Speed \u200b\u200bof particle fluctuations		mM / S; mm / S.
Speed \u200b\u200bspeed	m 3 / s; m 3 / s
Sound speed
Sound Energy Stream, Sound Power
Sound intensity	W / m 2; W / m 2	mW / M 2; MW / m 2 m w / m 2; μW / m 2 pW / M 2; PVT / m 2
Specific speaker	PA × S / M; PA × S / M
Acoustic resistance	PA × S / M 3; PA × s / m 3
Mechanical resistance	N × s / m; N × s / m
Equivalent absorption area with surface or subject
Reverb time
Part VIII Physical Chemistry and Molecular Physics
Number of substances	mol; Mole (mole)	kmol; Colol mMOL; mmol m mol; Mkmol.
Molar mass	kg / mol; kg / mol	g / mol; g / mol
Molar volume	m 3 / Moi; m 3 / mol	dM 3 / MOL; dm 3 / mol cm 3 / mol; cm 3 / mol	l / MOL; l / mol
Molar inner energy	J / mol; J / Mol.	kj / mol; KJ / Mol
Molar enthalpy	J / mol; J / Mol.	kj / mol; KJ / Mol
Chemical potential	J / mol; J / Mol.	kj / mol; KJ / Mol
Chemical affinity	J / mol; J / Mol.	kj / mol; KJ / Mol
Molar heat capacity	J / (mol × k); J / (mol × k)
Molar entropy	J / (mol × k); J / (mol × k)
Molar concentration	mOL / M 3; Mol / m 3	kMOL / M 3; Komol / m 3 mOL / DM 3; mol / dm 3	mol / 1; Mol / L.
Specific adsorption	mol / kg; Mol / kg	mMOL / KG; mmol / kg
Teterolution	M 2 / s; m 2 / s
Part IX. Ionizing radiation
Absorbed dose of radiation, Kerma, indicator of the absorbed dose (absorbed dose of ionizing radiation)	Gy; GR (Gray)	m G y; μgr
Nuclide activity in a radioactive source (radionuclide activity)	Bq; BK (Becquer)

(Modified edition, change No. 3).

table 2

Name of logarithmic size	Designation Unit	The initial value of the magnitude
Sound pressure level
Sound power level
Sound intensity level
Power level difference
Strengthening, weakening
Attenuation coefficient

ATTACHMENT 4

Reference

Information details of GOST 8.417-81 ST SEV 1052-78

1. Sections 1 - 3 (PP. 3.1 and 3.2); 4, 5 and mandatory Appendix 1 to GOST 8.417-81 correspond to sections 1 - 5 and annex to ST SEV 1052-78. 2. Reference application 3 to GOST 8.417-81 complies with the information application to ST SEV 1052-78.

Measurements

The modern stage of scientific and technological progress is characterized by an intensive increase in interest in measurements. Increasing interest in the measurement is due to the fact that they play more and more significant, and sometimes a decisive role in the decision, both the fundamental problems of knowledge and practical problems of scientific and technological progress, social problems increase the effectiveness of all social beneficial activities. Measurements are the main process of obtaining objective information on the properties of various material objects associated with human practical activities. For example, about the suitability of any detail on its size we can judge only after measurements of these sizes.

Measure - This is the process of obtaining objective information reflecting the actual, and not intended material, scientific and technical potential of society, the achieved level of social production, etc. On the information received by measurements, decisions are based on economic development authorities at all levels.

All enterprises whose activities are associated with the development, testing, production, control of products, with the operation of transport and communications, with health care, etc., conduct an innumerable amount of measurements. Based on measurement results, specific solutions are accepted.

In the diagram shown in Fig. 1.1, the main elements are shown logically interconnected during measurements.

Measurements are based on the comparison of the same properties of material objects. For properties, with a quantitative comparison of which physical methods are used, a unified generalized concept is established - a physical value.

According to GOST 16263. physical quantity - This is a property, in common with a qualitative relation to many physical objects (physical systems, their states and what is happening in them processes), but in quantitatively individual for each object. Individuality in a quantitative relationship should be understood in the sense that the property may be for a single object at a certain number of times greater than or less than for another.

Physical values \u200b\u200binclude: length, weight, time, electrical values \u200b\u200b(current, voltage, etc.), pressure, speed, etc.

Fig.1.1. Scheme of the main elements involved in measurements

But the smell is not a physical value, as it is installed using subjective sensations.

The definition of "physical quantity" can be supported by an example. Take two objects: the rolling bearing of the domestic vacuum cleaner and the rolling bearing of carriage wheels. The qualitative properties of them are the same, and quantitative different. So the diameter of the outer ring of the rolling bearing of the carriage wheels is many times more than a similar diameter of the bearing of the vacuum cleaner. Similarly, it can be judged about the quantitative ratio of mass and other properties. But for this you need to know the value of physical quantity. Assess the physical value in the form of a certain number of units adopted for it. For example, the value of the mass of the rolling bearing of carriages 8 kg, the radius of the globe is 6378 km, the diameter of the opening is 0.5 mm.

GOST 16263 leads a number of definitions associated with the concept of "physical value".

True meaning of physical quantity - This is the value of a physical value that would ideally reflect the corresponding property of the object in a qualitative and quantitative relationship. It is the limit to which the value of the physical quantity is approaching with an increase in measurement accuracy.

It is impossible to determine the experimentally true value of the physical quantity, it remains an unknown experimentator. In this regard, if necessary (for example, when checking measurement tools), instead of the true value of the physical size, its actual value is used.

Value value of physical quantity - This is the meaning of the physical value found by experimentally and so approaching the true value, which for this purpose can be used instead.

When the actual value of the physical value, the verification of measurement tools should be carried out on exemplary measures and instruments whose errors can be neglected.

With technical measurements, the value of the physical quantity found with the permissible error is taken for the actual value.

Basic physical amount - This is a physical quantity in the system and conditionally adopted as an independent of other values \u200b\u200bof this system. For example, in the system, the main physical quantities independent of others are the length l., weight m.Time t. and etc.

Derivative physical value - The physical quantity in the system and determined through the main values \u200b\u200bof this system. For example, speed v. Determined in the general case by the equation:

V \u003d DL / DT, (1.1)

where l. - distance; T. - time.

Another example. The mechanical force in the same system is determined by the equation:

F \u003d M * A, (1.2)

where m. - weight; a. - Acceleration caused by the action of force F.

Measure for quantitative comparison of the same properties of objects unit of physical size - The physical value that by definition is assigned a numeric value equal to one. Units of physical quantities are assigned a complete and abbreviated symbolic designation - dimension. For example, a mass - kilogram (kg), time - second (C), length - meter (M), force - Newton (H).

The above definitions of the physical quantity and its value allow you to determine the measurement as finding the physical value of the experimental way with the help of special technical means (GOST 16263).

This definition is fair both for the simplest cases when, applying a ruler with divisions to the part, compare its size with a unit of length, stored ruler, or when using the device compare the size of the value converted to the movement of the pointer, with a unit, a stored scale of this device, so And for more complex - when using the measuring system (to measure multiple values \u200b\u200bat the same time).

For a more complete disclosure of the concept of "measurement" knowledge of one of its essence is not enough. It is necessary to identify those conditions that are compliance with which is mandatory when performing measurements. These conditions can be formulated, based on metrological practice, summarizing its requirements, as well as based on the definition of the concept of "measured physical value":

measurements are possible, provided that the qualitative definition of the property is established, which allows to distinguish it from other properties (i.e., when the physical size is highlighted among others);

the unit is defined to determine the value;

it is possible to materialize (play or storing) units;

saving unchanged unit size (within the established accuracy) minimum during the measurement period.

If at least one of these conditions is broken, measurements are impracticable. The above conditions can serve as the basis, firstly, when considering the content of the concept of "measurement", secondly, when conducting a clear boundary between measurement and other types of quantitative assessments. From the term "measurement" there is a term "measure", which is widely used in practice. However, incorrect terms are often used: "measure", "measure", "measure", "simulating", which are not fitted into the system of metrological terms.

In technical literature on measurements or measurements, sometimes you can read about the measurement processes or dependencies. The process cannot be measured. Measure physical quantities that characterize them. For example, it is impossible to say: "Measure the item". It should be clarified which physical quantities characteristic of details are subject to measurement (length, diameter, mass, hardness, etc.). The same applies to processes, including high-speed, as well as dependencies between physical quantities.

Thus, if the dependence of the decrease in body length from the temperature change, the measured values \u200b\u200bwill increment the temperature and elongation of the body, by the values \u200b\u200bof which the specified dependence is calculated.

These calculations can be carried out using a computer associated with the measurement means, but this does not mean that the dependence is measured (it is calculated). When using the so-called statistical measurement tools (in fast-tracting processes), such, for example, expressions, such as: "Measurement of the rms of the random process voltage", "Measurement of the probability distribution density", etc.

It should be noted that not all physical quantities can be reproduced with the specified dimensions and are directly comparable to themselves like. Such values \u200b\u200binclude, for example, temperature, hardness of materials, etc. In this case, the application of natural (reference) scales comes in as follows. Objects and phenomena with some homogeneous properties are in a natural sequential series so that each item in this series of this property will be greater than that of the previous one and less than the subsequent. Next, choose several members of the row and take them for samples. Selected samples are formed by the scale (staircase) of the reference points to match the items or phenomena to the filed by the property. Examples of reference scales are the mineralogical scale of hardness, the wind power scale in the "Balary points".

A significant disadvantage of such scales consists in an arbitrary size of the intervals between the reference points and the inability to refine the size of the physical size inside the interval.

In this regard, the measuring technique provides preference to functional scales, in the construction of which the functional dependence of any physical quantity is used, convenient for direct measurement, from the measured physical quantity. Most often, this dependence is linear. As an example, the temperature scale can be brought, for example, Celsius. When constructing a scale, reference points are used, which are attributed to certain temperatures, for example, ice melting point (0,000 ° C), water boiling point (100,000 ° C), and the like. In the intervals between the temperatures of reference points, interpolation is carried out using certain temperature transducers - mercury thermometers, thermocouples, platinum resistance thermometers. In this case, the measured temperature is converted into the movement of the end of the mercury column, in the EMF thermocouple or to the resistance of the platinum resistor.

Specialist in the field of metrology M.F. Malikov, to solve metrological problems, proposed to divide all measurements into two groups, calling them "laboratory" and "technical".

TO laboratory Such measurements include the errors of the resulting results of which are estimated in the process of measurement themselves, and each result corresponds to its estimate of the error. TO technical M.F. Malikov took such measurements, the possible errors of the results of which are studied in advance and are determined, so that in the process of measurements themselves are no longer evaluated.

Laboratory - these are measurements carried out, as a rule, with fundamental studies. Characteristic is the desire to ensure higher accuracy of measurement results. From here, the specific features of laboratory measurements are followed: it is desirable from the measurement tools used to extract all the accuracy to which they are capable; It is advisable to exclude (or reduce) random errors of each measurement result, for which multiple measurements are carried out, the results of which are mathematically treated with the selected method; It is desirable to exclude (or reduce) systematic errors of each measurement result, for which special measurement methods use. In this regard, the main feature of laboratory measurements is the estimation of the error of each individual measurement result during the measurement themselves.

Technical measurements are the main mass of measurements carried out in the national economy. A distinctive feature of the technical dimensions is that they are carried out on specially designed, pre-studied and certified methods for performing measurements.

In the future, we will concern only technical measurements and under the term "measurements" will be understood "Technical dimensions".

Measurements are based on the comparison of the same properties of material objects. For properties, with a quantitative comparison of which physical methods are used, a unified generalized concept is established in metrology - a physical value. Physical quantity- property, in general, in a qualitative attitude of many physical objects, but in quantitatively individual for each object, for example, length, weight, electrical conductivity and heat capacity of bodies, gas pressure in the vessel, etc. But the smell is not a physical value, as it is installed With the help of subjective sensations.

Measure for quantitative comparison of the same properties of objects unit of physical quantity - The physical value that by agreement is assigned a numerical value equal to 1. The units of physical quantities are assigned a complete and abbreviated symbol designation - dimension. For example, a mass - kilogram (kg), time - second (C), length - meter (M), force - Newton (H).

The value of the physical size - An assessment of the physical quantity in the form of a certain number of units adopted for it - characterizes the quantitative individuality of objects. For example, the diameter of the opening is 0.5 mm, the radius of the globe is 6378 km, the speed of the runner is 8 m / s, the speed of light is 3 10 5 m / s.

Measure It is called the foundation of the physical value with the help of special technical means. For example, measuring the shaft diameter with a caliper or micrometer, fluid temperature - a thermometer, gas pressure to a pressure gauge or a vacuum. The value of physical quantity x ^, The resulting measurement is determined by the formula x ^ \u003d ai Where but- numerical value (size) of physical quantity; And - a unit of physical quantity.

Since the values \u200b\u200bof physical quantities find an experimental way, they contain measurement errors. In this regard, there is a true and actual meaning of physical quantities. True value - The value of the physical quantity that the corresponding property of the object is ideally reflects in a qualitative and quantitative relationship. It is the limit to which the value of the physical quantity is approaching with an increase in measurement accuracy.

Value value - The value of the physical quantity found by experimentally and is so close to the true value, which for a specific purpose can be used instead. This value varies depending on the required measurement accuracy. With technical measurements, the value of the physical quantity found with the permissible error is taken for the actual value.

Measurement error There is a deviation of the measurement result from the true value of the measured value. Absolute errorthey call the measurement error, expressed in units of the measured value: Oh = x ^ - x, Where x- True value of the measured value. Relative error - The ratio of the absolute measurement error to the true meaning of physical quantity: 6 \u003d ah / x. The relative error can also be expressed as a percentage.

Since the true measurement value remains unknown, in practice you can find only an approximate estimate of the measurement error. At the same time, instead of the true value, the actual value of the physical quantity obtained during the measurement of the same value with higher accuracy is taken. For example, the error of measuring linear dimensions of the caliper is ± 0.1 mm, and micrometer - ± 0.004 mm.

Measurement accuracy can be quantified as the reverse value of the relative error module. For example, if the measurement error is ± 0.01, the measurement accuracy is 100.