TOPIC 1

1. TOPIC 1

2. The Convention of the Metre is a diplomatic treaty between fifty-one nations which gives authority to the Conférence Générale des Poids et Mesures (CGPM), the Comité International des Poids et Mesures (CIPM) and the Bureau International des Poids et Mesures (BIPM) to act in matters of world metrology. Convention of the Metre

3. This particularly concerns the demand for measurement standards of ever increasing accuracy, range and diversity, and the need to demonstrate equivalence between national measurement standards. The Convention was signed in Paris in 1875 by representatives of seventeen nations. Convention of the Metre

4. Conférence Générale des Poids et Mesures Meets every four years and consists of delegates of all member states. Comité International des Poids et Mesures Consists of 18 individuals elected by CGPM. It is charged with the supervision of BIPM and the affairs of the Convention of the Metre. Bureau International des Poids et Mesures International centre for metrology. Laboratoires and offices at Sevres with an international staff of about seventy.

5. Pavillon de Breteuil

6. Convention of the Metre The CIPM has set up 10 Consultative Committees, which bring together the world's experts in their specified fields as advisers on scientific and technical matters. The chairman of each Committee is designated by, and is normally a member of, the CIPM. The members of the Committees are metrology laboratories and specialized institutes agreed by the CIPM, which send delegates of their choice.

7. Convention of the Metre • Consultative Committee for Electricity and Magnetism (CCEM), new name given in 1997 to the Consultative Committee for Electricity (CCE), set up in 1927. • Consultative Committee for Units (CCU), set up in 1964 (this committee replaced the "Commission for the System of Units" set up by the CIPM in 1954).

8. Renowned metrological institutions NIST (formerly NBS) –National Institute of Standards and Technology, Gaithersburg and Boulder, USA NRC –National Research Council, Ottawa, Canada ETL –Electrotechnical Laboratory, Tsukuba, Japan NML –National Measurement Laboratory, Lindfield, Australia

9. Renowned metrological institutions NPL –National Physical Laboratory, Teddington, United Kingdom PTB –Physikalisch–Technische Bundesanstalt, Braunschweig and Berlin, Germany

10. International System of Units (SI) The 11th CGPM (1960) adopted the name Système International d'Unités(International System of Units, abbreviation SI), for the recommended practical system of units of measurement. SI units are divided into 2 classes: base units (7) and derived units.

11. SI base units Unit of length (metre, m): The metre is the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second. Unit of mass (kilogram, kg): The kilogram is the unit of mass; it is equal to the mass of the international prototype of the kilogram.

12. International prototyp of the kilogram

13. SI base units Unit of time (second, s): The second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom.

14. SI base units Unit of electric current (ampere, A): The ampere is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 metre apart in vacuum, would produce between these conductors a force equal to 2 × 10-7 newton per metre of length.

15. SI base units Unit of thermodynamic temperature (kelvin, K): The kelvin, unit of thermodynamic temperature, is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water.

16. SI base units Unit of amount of substance (mole, mol): The mole is the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kilogram of carbon 12. When the mole is used, the elementary entities must be specified and may be atoms, molecules, ions, electrons, other particles, or specified groups of such particles.

17. SI base units Unit of luminous intensity (candela, cd): The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 × 1012 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian.

18. SI derived units Derived units are expressed algebraically in terms of base units by means of mathematical symbols of multiplication and division.

19. Examples of SI derived units expressed in terms of base units Quantity Symbol volume m3 velocity m/s mass density kg/m3 current density A/m2 magnetic field strength A/m luminance cd/m2

20. Examples of SI derived units with special names Quantity Name Symbol plane angle radian rad solid angle steradian sr frequency hertz Hz force newton N pressure pascal Pa energy, work joule J quantity of heat joule J power watt W

21. Examples of SI derived units with special names Quantity Name Symbol electric charge coulomb C electric potential volt V electric resistance ohm Ω electric conductance siemens S electric capacitance farad F inductance henry H

22. Examples of SI derived units with special names • Quantity Name Symbol • magnetic flux weber Wb • magnetic flux density tesla T • luminous flux lumen lm • illuminance lux lx • activity becquerel Bq absorbed dose gray Gy • dose equivalent sievert Sv

23. Decimal multiples and sub-multiples of SI unitsSI prefixes Factor Prefix Symbol 1024 yotta Y 1021 zetta Z 1018 exa E 1015 peta P 1012 tera T 109 giga G 106 mega M

24. Decimal multiples and sub-multiples of SI unitsSI prefixes Factor Prefix Symbol 103 kilo k 102 hecto h 101 deca da 10-1 deci d 10-2 centi c 10-3 milli m

25. Decimal multiples and sub-multiples of SI unitsSI prefixes Factor Prefix Symbol 10-6 micro µ 10-9 nano n 10-12 pico p 10-15 femto f 10-18 atto a 10-21 zepto z 10-24 yocto y

26. Measurement standards Material measures, measuring instruments, reference materials or measuring systems intended to define, realize, conserve or reproduce a unit or one or more values of a quantity to serve as a reference.

27. Measurement standards International standard is a standard recognized by an international agreement to serve internationally as the basis for assigning values to other standards of the quantity concerned. National standard is a standard recognized by a national decision to serve, in a country, as the basis for assigning values to other standards of the quantity concerned.

28. Measurement standards Primary standard is a standard that is designated or widely acknowledged as having the highest metrological qualities and whose value is accepted without reference to other standards of the same quantity. Secondary standard is a standard whose value is assigned by comparison with a primary standard of the same quantity.

29. Measurement standards Reference standard is a standard, generaly having the highest metrological quality available at a given location or in a given organization, from which measurements made there are derived. Working standard is a standard that is used routinely to calibrate or check material measures, measuring instruments or reference materials.

30. Measurement standards Transfer standard is a standard used as an intermediary to compare standards. Travelling standard is a standard, sometimes of special construction, intended for transport between different locations.