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[[International Standard]] '''ISO 1''' specifies the standard reference [[temperature]] for geometrical product specification and verification to be '''20 °C''', which is equal to 293.15 K and 68 °F.<ref name="iso1">International Standard ISO 1: Geometrical Product Specifications (GPS) – Standard reference temperature for geometrical product specification and verification. [[International Organization for Standardization]], 2nd edition, 2002. (1st edition: 1975)</ref> |
[[International Standard]] '''ISO 1''' specifies the standard reference [[temperature]] for geometrical product specification and verification to be '''20 °C''', which is equal to 293.15 K and 68 °F.<ref name="iso1">International Standard ISO 1: Geometrical Product Specifications (GPS) – Standard reference temperature for geometrical product specification and verification. [[International Organization for Standardization]], 2nd edition, 2002. (1st edition: 1975)</ref> {{what}} |
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Due to [[thermal expansion]], precision [[length]] measurements need to be made at (or converted to) a defined temperature. ISO 1 helps in comparing measurements by defining such a reference temperature. The reference temperature of 20 °C was adopted by the [[CIPM]] on 15 April 1931, and became ISO recommendation number 1 in 1951.<ref>Ted Doiron: [http://nvl.nist.gov/pub/nistpubs/jres/112/1/V112.N01.A01.pdf 20 °C—A Short History of the Standard Reference Temperature for Industrial Dimensional Measurements]. Journal of Research of the National Institute of Standards and Technology, Vol. 112, No. 1, January-February 2007.</ref> It soon replaced worldwide other reference temperatures for length measurements that manufacturers of precision equipment had used before, including 0 °C, 62 °F, and 25 °C. Among the reasons for choosing 20 °C was that this was a comfortable and practical workshop temperature and that it resulted in an integer value on both the Celsius and Fahrenheit scales. |
Due to [[thermal expansion]], precision [[length]] measurements need to be made at (or converted to) a defined temperature. ISO 1 helps in comparing measurements by defining such a reference temperature. The reference temperature of 20 °C was adopted by the [[CIPM]] on 15 April 1931, and became ISO recommendation number 1 in 1951.<ref>Ted Doiron: [http://nvl.nist.gov/pub/nistpubs/jres/112/1/V112.N01.A01.pdf 20 °C—A Short History of the Standard Reference Temperature for Industrial Dimensional Measurements]. Journal of Research of the National Institute of Standards and Technology, Vol. 112, No. 1, January-February 2007.</ref> It soon replaced worldwide other reference temperatures for length measurements that manufacturers of precision equipment had used before, including 0 °C, 62 °F, and 25 °C. Among the reasons for choosing 20 °C was that this was a comfortable and practical workshop temperature and that it resulted in an integer value on both the Celsius and Fahrenheit scales. |
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Revision as of 22:52, 9 June 2009
International Standard ISO 1 specifies the standard reference temperature for geometrical product specification and verification to be 20 °C, which is equal to 293.15 K and 68 °F.[1] [clarification needed]
Due to thermal expansion, precision length measurements need to be made at (or converted to) a defined temperature. ISO 1 helps in comparing measurements by defining such a reference temperature. The reference temperature of 20 °C was adopted by the CIPM on 15 April 1931, and became ISO recommendation number 1 in 1951.[2] It soon replaced worldwide other reference temperatures for length measurements that manufacturers of precision equipment had used before, including 0 °C, 62 °F, and 25 °C. Among the reasons for choosing 20 °C was that this was a comfortable and practical workshop temperature and that it resulted in an integer value on both the Celsius and Fahrenheit scales.
References
- ^ International Standard ISO 1: Geometrical Product Specifications (GPS) – Standard reference temperature for geometrical product specification and verification. International Organization for Standardization, 2nd edition, 2002. (1st edition: 1975)
- ^ Ted Doiron: 20 °C—A Short History of the Standard Reference Temperature for Industrial Dimensional Measurements. Journal of Research of the National Institute of Standards and Technology, Vol. 112, No. 1, January-February 2007.