Physics:ISO 1
ISO 1 is an international standard set by the International Organization for Standardization that specifies the standard reference temperature for geometrical product specification and verification. The temperature is fixed at 20 degrees Celsius (°C), which exactly equals both 293.15 kelvin (K) and 68 degrees Fahrenheit (°F).[1]
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 this temperature was used in ISO recommendation number 1 in 1951.[2] It soon replaced worldwide other reference temperatures for length measurements that manufacturers of precision equipment had used, 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.
It was the first ISO standard, issued originally as ISO/R 1, an ISO Recommendation.[3]
See also
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Lists of ISOs | Succeeded by ISO 2 |
References
- ↑ "ISO 1:2016 - Geometrical product specifications (GPS) -- Standard reference temperature for the specification of geometrical and dimensional properties". Iso.org. 2016-08-26. http://www.iso.org/iso/home/store/catalogue_ics/catalogue_detail_ics.htm?csnumber=67630.
- ↑ 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.
- ↑ Tranchard, Sandrine (2017-02-23). "ISO celebrates 70 years". https://www.iso.org/cms/render/live/en/sites/isoorg/contents/news/2017/02/Ref2163.html.
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