Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revisionPrevious revision
Next revision
Previous revision
Next revisionBoth sides next revision
articles:nist_traceability [2019/05/25 12:39] – [What are SI Units?] rrandallarticles:nist_traceability [2019/06/12 22:32] – [Conclusion] rrandall
Line 66: Line 66:
 ===== What are SI Units? ===== ===== What are SI Units? =====
 {{ :articles:2018-si.png?direct&130|}} {{ :articles:2018-si.png?direct&130|}}
-Adopted by the [[https://en.wikipedia.org/wiki/General_Conference_on_Weights_and_Measures|General Conference on Weights and Measures (CGPM)]] in 1960, 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]]". \\+Adopted by the [[https://en.wikipedia.org/wiki/General_Conference_on_Weights_and_Measures|General Conference on Weights and Measures (CGPM)]] in 1960, 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. 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. 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.
Line 79: Line 79:
 </WRAP> </WRAP>
  
-SI Units are also explained on the NIST web site at: https://www.nist.gov/pml/weights-and-measures/metric-si/si-units and in "[[https://www.nist.gov/pml/special-publication-330|NIST Special Publication 330 -  The International System of Units (SI)]]". Both NIST sources will likely be updated soon to reflect the new definitions to the SI that went into effect on May 20, 2019. The new definitions impact four of the base units: +SI Units are also explained on the NIST web site at: https://www.nist.gov/pml/weights-and-measures/metric-si/si-units and in "[[https://www.nist.gov/pml/special-publication-330|NIST Special Publication 330 -  The International System of Units (SI)]]". Both NIST sources will likely be updated soon to reflect the new definitions to the SI that went into effect on May 20, 2019. 
- +
-  * The kilogram – will be defined in terms of the Planck constant (h) +
-  * The ampere – will be defined in terms of the elementary charge (e) +
-  * The kelvin – will be defined in terms of the Boltzmann constant (k) +
-  * The mole – will be defined in terms of the Avogadro constant (NA) +
- +
-While these units remain the same //size//, the change simply //defines// them more precisely. And their usage in normal, every day life will appear as unchanged. However, the new units will impact a small number of high level calibrations. +
 ===== What are "intrinsic" standards? ===== ===== What are "intrinsic" standards? =====
  
Line 143: Line 135:
 </WRAP> </WRAP>
  
-Unless required by statute or regulation (i.e., for Legal Metrology), mandating "NIST traceability" unnecessarily "limits" the sources for metrological traceability, excluding other NMIs and/or accredited commercial metrology laboratories.+Unless required by statute or regulation (i.e., for [[https://www.oiml.org/en/about/legal-metrology|Legal Metrology]]), mandating "NIST traceability" unnecessarily "limits" the sources for metrological traceability, excluding other NMIs and/or accredited commercial metrology laboratories.