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--- articles:nist_traceability [2019/05/25 12:39] – [What are SI Units?] rrandall
+++ articles:nist_traceability [2019/11/20 07:26] – [What are "intrinsic" standards?] rrandall
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 ===== What are SI Units? =====
 {{ :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.
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 </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? =====
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 As mentioned earlier, [[https://www.fluke.com|Fluke]] owns a [[https://nvlpubs.nist.gov/nistpubs/jres/095/jresv95n3p219_A1b.pdf|Josephson voltage system]], which they can use to realize the SI Units directly for DC Volts. Even though they don't send an instrument to NIST for calibration, they [[https://www.fluke.com/en-us/learn/blog/electrical/the-volt-makes-a-stop-at-the-fluke-metrology-lab|compare their Josephson voltage system to an identical Josephson Voltage system maintained by NIST]].
+==== Legal Metrology ====
 Fluke performs this comparison because, just as the requirements for “measurement traceability” contained in ISO 9001:2015 & AS9100:2016 (Rev. D) are antiquated, so is U.S. law in this area. U.S. Law has designated that NIST holds the national standards of measurement, and NIST has defined the U.S. legal volt to be produced from its one particular Josephson voltage system, so it is the national standard. However, this is only pertinent to the area of "legal metrology" (Ref.: [[https://www.oiml.org/en/about/legal-metrology|International Organization of Legal Metrology]]).
+U.S. Regulations often require metrological traceability "to NIST". For example:
 ===== What are "International Standards"? =====
 While ISO 9001:2015, AS9100:2016 (Rev. D) and ISO 17025:2017 all mention "International Standards", I am aware of only four (4) "international standards" (as opposed to SI //units//); three of which are listed as examples in the "Bureau International des Poids et Mesures" (BIPM) [[https://www.bipm.org/utils/common/documents/jcgm/JCGM_200_2012.pdf|JCGM 200:2012, "International vocabulary of metrology – Basic and general concepts and associated terms (VIM)"]] (3rd edition), sec. 5.2, "international measurement standard". However, there are probably others. Those that I am aware of include: \\
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 </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.