Metrology of Electrical Quantities

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• TOPIC 1

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Convention of the Metre

• 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.

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Convention of the Metre

• 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.

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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.
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Pavillon de Breteuil
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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.

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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).
  

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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

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Renowned metrological institutions

• NPL National Physical Laboratory, Teddington,
  United Kingdom
• PTB PhysikalischTechnische Bundesanstalt,
• Braunschweig and Berlin, Germany

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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.

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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.

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International prototyp of the kilogram
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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.

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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.

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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.

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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.

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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.

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SI derived units

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

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

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Decimal multiples and sub-multiples of SI units
SI 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
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Decimal multiples and sub-multiples of SI units
SI 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
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Decimal multiples and sub-multiples of SI units
SI 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
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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.
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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.
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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.
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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.
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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.