《BS-5775-0-1993 ISO-31-0-1992.pdf》由会员分享，可在线阅读，更多相关《BS-5775-0-1993 ISO-31-0-1992.pdf（24页珍藏版）》请在三一文库上搜索。
1、BRITISH STANDARD BS 5775-0: 1993 ISO 31-0:1992 Specification for Quantities, units and symbols Part 0: General principles UDC 389.15/.16:006.72 Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 10:01:10 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5775-0:1993 This British Standard, having been
2、 prepared under the direction of the Systems Department Steering Committee, was published under the authority of the Standards Board and comes into effect on 15 July 1993 BSI 12-1999 First published February 1982 Second edition July 1993 The following BSI references relate to the work on this standa
3、rd: Committee reference S/1 Draft for comment 90/51778 DC ISBN 0 580 22194 6 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Systems Department Steering Committee (S/-) to Technical Committee S/1, upon which the following bodies were rep
4、resented: Chartered Institution of Building Services Engineers Department of Trade and Industry (National Physical Laboratory) Department of Trade and Industry (National Weights and Measures Laboratory) EEA (the Association of Electronics, Telecommunications and Business Equipment Industries) Instit
5、ute of Physics Institute of Trading Standards Administration Institution of Chemical Engineers Institution of Electrical Engineers Institution of Mechanical Engineers Institution of Structural Engineers Royal Society Royal Society of Chemistry Schools Mathematics Project Society of Chemical Industry
6、 Amendments issued since publication Amd. No.DateComments Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 10:01:10 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5775-0:1993 BSI 12-1999i Contents Page Committees responsibleInside front cover National forewordii 1Scope1 2Quantities and units1 3
7、Recommendations for printing symbols and numbers7 Annex A (informative) Guide to terms used in names for physical quantities11 Annex B (informative) Guide to the rounding of numbers14 Annex C (informative) International organizations in the field of quantities and units15 Table 1 SI base units4 Tabl
8、e 2 SI derived units with special names, including SI supplementary units5 Table 3 SI derived units with special names admitted for reasons of safeguarding human health5 Table 4 SI prefixes6 Table 5 Units used with the SI7 Table 6 Units used with the SI, whose values in SI units are obtained experim
9、entally7 List of referencesInside back cover Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 10:01:10 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5775-0:1993 ii BSI 12-1999 National foreword This Part of BS 5775 has been prepared under the direction of the Systems Department Steering Commit
10、tee. It is identical with ISO 31-0:1992 Quantities and units Part 0: General principles, published by the International Organization for Standardization (ISO). ISO 31-0 was prepared by Technical Committee ISO/TC 12 “Quantities, units, symbols, conversion factors” with the active participation and ap
11、proval of the UK. This Part of BS 5775 supersedes BS 5775-0:1982, which is withdrawn. The principal changes made in this revised version are as follows: a) new tables of SI base units, SI derived units, SI prefixes and some other recognized units have been added; b) a new subclause (2.3.3) on the un
12、it “one” has been added; c) a new Annex C on international organizations in the field of quantities and units has been added. BS 5775 comprises the following Parts, each of which is identical with the corresponding Part of ISO 31. Part 0: General principles; Part 1: Space and time; Part 2: Periodic
13、and related phenomena; Part 3: Mechanics; Part 4: Heat; Part 5: Electricity and magnetism; Part 6: Light and related electromagnetic radiations; Part 7: Acoustics; Part 8: Physical chemistry and molecular physics; Part 9: Atomic and nuclear physics; Part 10: Nuclear reactions and ionizing radiations
14、; Part 11: Mathematical signs and symbols for use in the physical sciences and technology; Part 12: Characteristic numbers; Part 13: Solid state physics. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their co
15、rrect application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Cross-reference International StandardCorresponding British Standard ISO 2955:1983BS 6430:1983 Method for representing SI and other units in information processing systems with limited ch
16、aracter sets (Identical) Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 18, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the am
17、endment table on the inside front cover. Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 10:01:10 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5775-0:1993 BSI 12-19991 1 Scope This part of ISO 31 gives general information about principles concerning physical quantities, equations, quantity a
18、nd unit symbols, and coherent unit systems, especially the International System of Units, SI. The principles laid down in this part of ISO 31 are intended for general use within the various fields of science and technology and as a general introduction to the other parts of ISO 31. 2 Quantities and
19、units 2.1 Physical quantity, unit and numerical value In ISO 31 only physical quantities used for the quantitative description of physical phenomena are treated. Conventional scales, such as the Beaufort scale, Richter scale and colour intensity scales, and quantities expressed as the results of con
20、ventional tests, e.g. corrosion resistance, are not treated here, neither are currencies nor information contents. Physical quantities may be grouped together into categories of quantities which are mutually comparable. Lengths, diameters, distances, heights, wavelengths and so on would constitute s
21、uch a category. Mutually comparable quantities are called “quantities of the same kind”. If a particular example of a quantity from such a category is chosen as a reference quantity called the unit, then any other quantity from this category can be expressed in terms of this unit, as a product of th
22、is unit and a number. This number is called the numerical value of the quantity expressed in this unit. EXAMPLE The wavelength of one of the sodium lines is = 5,896 107m Here is the symbol for the physical quantity wavelength; m is the symbol for the unit of length, the metre; and 5,896 107 is the n
23、umerical value of the wavelength expressed in metres. In formal treatments of quantities and units, this relation may be expressed in the form A = A A where A is the symbol for the physical quantity, A the symbol for the unit and A symbolizes the numerical value of the quantity A expressed in the un
24、it A. For vectors and tensors the components are quantities which may be expressed as described above. If a quantity is expressed in another unit which is k times the first unit, then the new numerical value becomes 1/k times the first numerical value; the physical quantity, which is the product of
25、the numerical value and the unit, is thus independent of the unit. EXAMPLE Changing the unit for the wavelength from the metre to the nanometre, which is 109 times the metre, leads to a numerical value which is 109 times the numerical value of the quantity expressed in metres. Thus, = 5,896 107m = 5
26、,896 107 109nm = 589,6 nm REMARK ON NOTATION FOR NUMERICAL VALUES It is essential to distinguish between the quantity itself and the numerical value of the quantity expressed in a particular unit. The numerical value of a quantity expressed in a particular unit could be indicated by placing braces (
27、curly brackets) around the quantity symbol and using the unit as a subscript. It is, however, preferable to indicate the numerical value explicitly as the ratio of the quantity to the unit. EXAMPLE /nm = 589,6 NOTE 1This notation is particularly useful in graphs and in the headings of columns in tab
28、les. 2.2 Quantities and equations 2.2.1 Mathematical operations with quantities Two or more physical quantities cannot be added or subtracted unless they belong to the same category of mutually comparable quantities. Physical quantities are multiplied or divided by one another according to the rules
29、 of algebra; the product or the quotient of two quantities, A and B, satisfies the relations AB = A B A B Thus, the product A B is the numerical value AB of the quantity AB, and the product A B is the unit AB of the quantity AB. Similarly, the quotient A/B is the numerical value A/B of the quantity
30、A/B, and the quotient A/B is the unit A/B of the quantity A/B. A B - - A B - A B - -= Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 10:01:10 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5775-0:1993 2 BSI 12-1999 EXAMPLE The speed v of a particle in uniform motion is given by v = l/t where
31、l is the distance travelled in the time-interval t. Thus, if the particle travels a distance l = 6 m in the time-interval t = 2 s, the speed v is equal to The arguments of exponential, logarithmic and trigonometric functions, etc., are numbers, numerical values or combinations of dimension one of qu
32、antities (see 2.2.6). EXAMPLES exp(W/kT), In(p/kPa), sin , sin(t) NOTE 2The ratio of two quantities of the same kind and any function of that ratio, such as the logarithm of the ratio, are different quantities. 2.2.2 Equations between quantities and equations between numerical values Two types of eq
33、uation are used in science and technology: equations between quantities, in which a letter symbol denotes the physical quantity (i.e. numerical value unit), and equations between numerical values. Equations between numerical values depend on the choice of units, whereas equations between quantities
34、have the advantage of being independent of this choice. Therefore the use of equations between quantities should normally be preferred. EXAMPLE A simple equation between quantities is v = l/t as given in 2.2.1. Using, for example, kilometres per hour, metres and seconds as the units for velocity, le
35、ngth and time, respectively, we may derive the following equation between numerical values: vkm/h= 3,6lm/ts The number 3,6 which occurs in this equation results from the particular units chosen; with other choices it would generally be different. If in this equation the subscripts indicating the uni
36、t symbols are omitted, one obtains v = 3,6l/t an equation between numerical values which is no longer independent of the choice of units and is therefore not recommended for use. If, nevertheless, equations between numerical values are used, the units shall be clearly stated in the same context. 2.2
37、.3 Empirical constants An empirical relation is often expressed in the form of an equation between the numerical values of certain physical quantities. Such a relation depends on the units in which the various physical quantities are expressed. An empirical relation between numerical values can be t
38、ransformed into an equation between physical quantities, containing one or more empirical constants. Such an equation between physical quantities has the advantage that the form of the equation is independent of the choice of the units. The numerical values of the empirical constants occurring in su
39、ch an equation depend, however, on the units in which they are expressed, as is the case with other physical quantities. EXAMPLE The results of measuring the length l and the periodic time T at a certain station, for each of several pendulums, can be represented by one quantity equation T = C l1/2 w
40、here the empirical constant C is found to be C = 2,006 s/m1/2 (Theory shows that C = 2;g1/2, where g is the local acceleration of free fall.) 2.2.4 Numerical factors in quantity equations Equations between quantities sometimes contain numerical factors. These numerical factors depend on the definiti
41、ons chosen for the quantities occurring in the equations. EXAMPLES 1 The kinetic energy Ek of a particle of mass m and speed v is 2 The capacitance C of a sphere of radius r in a medium of permittivity is C = 4;r 2.2.5 Systems of quantities and equations between quantities; base quantities and deriv
42、ed quantities Physical quantities are related to one another through equations that express laws of nature or define new quantities. For the purpose of defining unit systems and introducing the concept of dimensions, it is convenient to consider some quantities as mutually independent, i.e. to regar
43、d these as base quantities, in terms of which the other quantities can be defined or expressed by means of equations; the latter quantities are called derived quantities. v l t - - 6 m 2 s - -3 m s - -= Ek 1 2 - -mv2= Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 10:01:10 GMT+00:00 2006, Un
44、controlled Copy, (c) BSI BS 5775-0:1993 BSI 12-19993 It is a matter of choice how many and which quantities are considered to be base quantities. The whole set of physical quantities included in ISO 31 is considered as being founded on seven base quantities: length, mass, time, electric current, the
45、rmodynamic temperature, amount of substance and luminous intensity. In the field of mechanics a system of quantities and equations founded on three base quantities is generally used. In ISO 31-3, the base quantities used are length, mass and time. In the field of electricity and magnetism a system o
46、f quantities and equations founded on four base quantities is generally used. In ISO 31-5, the base quantities used are length, mass, time and electric current. In the same field, however, systems founded on only three base quantities, length, mass and time, in particular the “Gaussian” or symmetric
47、 system, have been widely used. (See ISO 31-5:1992, Annex A.) 2.2.6 Dimension of a quantity Any quantity Q can be expressed in terms of other quantities by means of an equation. The expression may consist of a sum of terms. Each of these terms can be expressed as a product of powers of base quantiti
48、es A, B, C, . from a chosen set, sometimes multiplied by a numerical factor , i.e. ABC., where the set of exponents (, , , .) is the same for each term. The dimension of the quantity Q is then expressed by the dimensional product dim Q = ABC. where A, B, C, . denote the dimensions of the base quanti
49、ties A, B, C, ., and where , , , . are called the dimensional exponents. A quantity all of whose dimensional exponents are equal to zero is often called a dimensionless quantity. Its dimensional product or dimension is A0B0C0. = 1. Such a quantity of dimension one is expressed as a number. EXAMPLE If the dimensions of the three base quantities length, mass and time are denoted by L, M an