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| IEC
Technical Committee 25 was established in 1935.
Its title is “Quantities and units, and their
letter symbols”. Since its subsequent merger with
TC 24 and as a committee with “horizontal”
responsibilities (i.e. covering matters of a wide-ranging
nature and applicable by many “vertical”
or product-oriented committees), it is TC 25 that is
at present in charge of all questions concerning the
SI. |
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Scope of IEC TC 25
The scope of IEC TC 25 is to prepare International Standards
on quantities and units to be used generally in electrical technology,
and to review the use of quantities and units in IEC standards.
These standards should, whenever possible, be based on the SI.
Such standards may be related to definitions, names, letter symbols
and their use, to the relations in which these quantities and
units appear, and to the signs and symbols used with them.
Close co-operation is required with IEC
TC 1: ”Terminology”, and technical liaison is
maintained in particular with the following organizations:
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BIPM
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International Bureau of Weights and Measures
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ISO/TC
12
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Quantities, units, symbols, conversion factors
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ITU
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International Telecommunication Union
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OIML
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International Organization of Legal Metrology
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Methodology of TC
25
A broad and truly international consensus has to be reached, otherwise
the IEC member countries and other international organizations would
not be in a position to adopt the fundamental concepts developed
by IEC TC 25.
In this context, the following is noteworthy: (i.e. participating
members with voting rights);
- out of more than 60 IEC member countries, 16 are P-members
of TC 25 (i.e. participating members with voting rights);
- requests for new concepts, including quantities and units and
their letter symbols, may be submitted by any TC/SC or NC of the
IEC;
- committee drafts are prepared either by the project leader
or a TC 25 Working Group in which experts from the relevant TCs/SCs
and other organizations may participate if necessary;
- NCs consult their experts in the field of TC 25 and of any
other committee concerned in parallel, and submit their collated
comments in a single document;
- the resulting draft is circulated by IEC Central Office to
all parties concerned, including other international organizations.
A popular belief that TC 25 standards reflect merely the view of
a few TC 25 experts is therefore far from the truth.
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Future publication ISO/IEC 80000, Quantities and
units
The harmonization of the following two important
publications was approved by both the Technical
Management Board of the International Organization for Standardization,
ISO, and by the IEC
Standardization Management Board:
– ISO 31: Quantities and units *
– IEC 60027: Letter symbols to be used in electrical technology.
*
The harmonized ISO/IEC 80000 will consist of 13 parts as listed
below. The information in parentheses indicates the origin of the
technical content of each part.
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80000 : |
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Part 1
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General (IEC 60027-1 and IEC 60027-3, ISO 31-0)
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Part 2
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Mathematical signs and symbols to be used in the natural
sciences and technology (IEC 60027-1, ISO 31-11)
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Part 3
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Space and time (ISO 31-1 and ISO 31-2)
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Part 4
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Mechanics (ISO 31-3)
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Part 5
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Thermodynamics (ISO 31-4)
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Part 6
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Electromagnetism ( IEC 60027-1, ISO 31-5)
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Part 7
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Light (ISO 31-6)
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Part 8
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Acoustics ( ISO 31-7)
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Part 9
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Physical chemistry and molecular physics (ISO 31-8)
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Part 10
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Atomic and nuclear physics (ISO 31-9 and ISO 31-10)
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Part 11
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Characteristic numbers (ISO 31-12)
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Part 12
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Solid state physics (ISO 31-13)
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Information science and technology (IEC 60027-2 and IEC 60027-3) |
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Part 14
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Telebiometrics related to human physiology (this is a new project that is to replace IEC 60027-7)
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It should be noted that the prefix before the number 80000 will
be either ISO or IEC, but not a double ISO/IEC prefix.
The chairman of IEC TC 25, Anders J. Thor, has pointed out that
there are four systems of writing that bridge all linguistic barriers
regardless of the alphabet used. These systems are:
- the set of mathematical signs and symbols;
- the SI;
- the symbols for chemical elements; and
- the way of writing notes for music.
The fundamental importance of ISO/IEC 80000 is obvious because
the first three systems will be given in this standard. It is only
music that will be outside the scope of the future ISO/IEC 80000.
* Copies of IEC International Standards are
available form the IEC Webstore
or from IEC National
Committees and approved sales oulets. ISO publications are available
from the ISO
Store on the ISO
website or by contacting ISO
Central Secretariat.
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