Metrology
[2] Modern metrology has its roots in the French Revolution's political motivation to standardise units in France when a length standard taken from a natural source was proposed.
This led to the creation of the decimal-based metric system in 1795, establishing a set of standards for other types of measurements.
[3][4] This has evolved into the International System of Units (SI) as a result of a resolution at the 11th General Conference on Weights and Measures (CGPM) in 1960.
[8][9] The NMS affects how measurements are made in a country and their recognition by the international community, which has a wide-ranging impact in its society (including economics, energy, environment, health, manufacturing, industry and consumer confidence).
[12] The first record of a permanent standard was in 2900 BC, when the royal Egyptian cubit was carved from black granite.
[12] The cubit was decreed to be the length of the Pharaoh's forearm plus the width of his hand, and replica standards were given to builders.
[12] In China weights and measures had a semi religious meaning as it was used in the various crafts by the Artificers and in ritual utensils and is mentioned in the book of rites along with the steelyard balance and other tools.
With a political motivation to harmonise units throughout France, a length standard based on a natural source was proposed.
[19] Scientific metrology, through the development of the Kibble balance and the Avogadro project, has produced a value of Planck constant with low enough uncertainty to allow for a redefinition of the kilogram.
[27] By defining SI base units with respect to physical constants, and not artefacts or specific substances, they are realisable with a higher level of precision and reproducibility.
The new definitions aim to improve the SI without changing the size of any units, thus ensuring continuity with existing measurements.
[30] A standard (or etalon) is an object, system, or experiment with a defined relationship to a unit of measurement of a physical quantity.
[34] The four primary reasons for calibrations are to provide traceability, to ensure that the instrument (or standard) is consistent with other measurements, to determine accuracy, and to establish reliability.
The coverage factor of k = 2 generally indicates a 95% confidence that the measured value will fall inside the uncertainty interval.
The Metre Convention created three main international organizations to facilitate standardisation of weights and measures.
The first, the General Conference on Weights and Measures (CGPM), provided a forum for representatives of member states.
The third, the International Bureau of Weights and Measures (BIPM), provided secretarial and laboratory facilities for the CGPM and CIPM.
On the last day of this conference there was vote on the redefinition of four base units, which the International Committee for Weights and Measures (CIPM) had proposed earlier that year.
[41][42] The International Committee for Weights and Measures (French: Comité international des poids et mesures, or CIPM) is made up of eighteen (originally fourteen)[43] individuals from a member state of high scientific standing, nominated by the CGPM to advise the CGPM on administrative and technical matters.
[48] The International Organization of Legal Metrology (French: Organisation Internationale de Métrologie Légale, or OIML), is an intergovernmental organization created in 1955 to promote the global harmonisation of the legal metrology procedures facilitating international trade.
[50] The OIML publishes a number of international reports in four categories:[50] Although the OIML has no legal authority to impose its recommendations and guidelines on its member countries, it provides a standardised legal framework for those countries to assist the development of appropriate, harmonised legislation for certification and calibration.
[2] ILAC originally began as a conference in 1977 to develop international cooperation for accredited testing and calibration results to facilitate trade.
[2] An NMI provides traceability to international standards for a country, anchoring its national calibration hierarchy.
[9] BIPM maintains a comparison database and a list of calibration and measurement capabilities (CMCs) of the countries participating in the CIPM MRA.
Since the calibration laboratories are accredited, they give companies a traceability link to national metrology standards.
[2] To ensure objective and technically-credible accreditation, the bodies are independent of other national measurement system institutions.
Metrology has wide-ranging impacts on a number of sectors, including economics, energy, the environment, health, manufacturing, industry, and consumer confidence.
[11] Accurate measurement and regulation of water, fuel, food, and electricity are critical for consumer protection and promote the flow of goods and services between trading partners.
[11] Legal metrology has reduced accidental deaths and injuries with measuring devices, such as radar guns and breathalyzers, by improving their efficiency and reliability.
[67] Measuring the human body is challenging, with poor repeatability and reproducibility, and advances in metrology help develop new techniques to improve health care and reduce costs.
