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--- articles:nist_traceability [2018/12/14 12:33] – [What are SI Units?] rrandall
+++ articles:nist_traceability [2019/01/25 09:25] – [An "unbroken chain of calibrations" to what?] rrandall
@@ Line 62: / Line 62: @@
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 [[http://www.isobudgets.com/measurement-traceability-complying-iso-17025-requirements/|{{ :articles:measurement-traceability-pyramid-600px.jpg?direct }}]]
+I describe the above pyramid as "//typical//" because it is not a requirement to obtain traceability to SI units through a National Metrological Institute (NMI).
 ===== What are SI Units? =====
 {{ :articles:2018-si.png?direct&130|}}
-The "[[https://www.bipm.org/en/measurement-units/|International System of Units]]" (//Système International d'Unités//, with the international abbreviation SI) consists of 7 base units that define 22 derived units. With the exception of the kilogram, the base SI units are derived from intrinsic (i.e., invariant) constants of nature, such as the speed of light in vacuum and the [[https://en.wikipedia.org/wiki/Boltzmann_constant|Boltzmann constant]] (which serves as the basis for the Kelvin temperature scale). According to Dr. Chris Sutton, "[[https://www.sciencelearn.org.nz/resources/1872-non-si-units|the SI system of units allows for complete coverage of all scientific measurements]]". \\
+The "[[https://www.bipm.org/en/measurement-units/|International System of Units]]" (//Système International d'Unités//, with the international abbreviation SI) consists of 7 base units that define 22 derived units. With the exception of the kilogram, the base SI units are all derived from intrinsic (i.e., invariant) constants of nature, such as the speed of light in vacuum and the [[https://en.wikipedia.org/wiki/Boltzmann_constant|Boltzmann constant]] (which serves as the basis for the Kelvin temperature scale). According to Dr. Chris Sutton, "[[https://www.sciencelearn.org.nz/resources/1872-non-si-units|the SI system of units allows for complete coverage of all scientific measurements]]". \\
 The SI Units are defined in the [[https://www.bipm.org/en/publications/si-brochure/|SI Brochure]], which is published by the [[https://www.bipm.org/en/about-us/|“Bureau International des Poids et Mesures” (BIPM)]], located in France.