National Measurement Institute Collection

Tungsten carbide slip gauge blocks C016 / 2042
Tungsten carbide slip gauge blocks. These are used as a standard form of length measurement. They are precision ground (lapped) to a specific thickness and then stacked to create the required length

Copy of the Imperial Standard Pound C016 / 2048
Copy of the Imperial Standard Pound. Parliamentary Copy number 5 (P.C.5) of the Imperial Standard Pound, dated 1879. The imperial system of weights and measures was established in 1824

Interference rings as length standards C016 / 2056
Interference rings as length standards. These Fabry-Perot interferometer observations (40-centimetre path difference) are for the green line of mercury-198 (left)

Kilogram 18, UK copy of SI unit of mass C016 / 2049
Kilogram 18, UK copy of SI unit of mass. The UKs National Standard Kilogram, copy number 18 of the International Prototype, was allocated in 1889 when the standard was established

Historical standards, metre and yard C016 / 2047
Historical standards, metre and yard. The two standards here are the International Prototype Metre (iridium-platinum, standard from 1889 to 1960)

Historical length standards C016 / 2046
Historical length standards. Standards established for the yard and the metre, along with their cross-sections (right). The Henry VII Yard (1497) and the Elizabeth Yard (1588)

Bank of Weston cells C016 / 2041
Bank of Weston cells. These electrochemical cells produce a stable voltage used as a standard to calibrate voltmeters and define the SI unit for electromotive force (the volt)

Kilogram 18, UK copy of SI unit of mass C016 / 2043
Kilogram 18, UK copy of SI unit of mass. The UKs National Standard Kilogram, copy number 18 of the International Prototype, was allocated in 1889 when the standard was established

Ayrton-Jones ampere balance C016 / 2034
Ayrton-Jones ampere balance. This apparatus is used to measure a standard value for the ampere, the international (SI) unit of electric current

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