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articles:nist_traceability [2019/06/12 22:32]
rrandall [Conclusion]
articles:nist_traceability [2020/04/24 08:01] (current)
rrandall [An "unbroken chain of calibrations" to what?]
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 a. calibrated or verified, or both, at specified intervals, or prior to use, against measurement standards __traceable to international or national measurement standards; when no such standards exist, the basis used for calibration or verification shall be retained as documented information__;//"​ a. calibrated or verified, or both, at specified intervals, or prior to use, against measurement standards __traceable to international or national measurement standards; when no such standards exist, the basis used for calibration or verification shall be retained as documented information__;//"​
 </​WRAP>​ </​WRAP>​
-Unfortunately,​ the language in ISO 9001:2015 & AS9100:2016 (Rev. D) is extremely antiquated in stating its requirements for "​measurement traceability"​. In contrast, ISO 17025:2017 is much more modern and technically correct in stating:\\+Unfortunately,​ the language in ISO 9001:2015 & AS9100:2016 (Rev. D) is extremely antiquated in stating its requirements for "​measurement traceability"​. ​And, unfortunately,​ similar antiquated language appears in U.S. Regulations. For example, 21 CFR 820.72 states: 
 + 
 +<WRAP center round box 80%>​**TITLE 21--FOOD AND DRUGS** \\ 
 +CHAPTER I--FOOD AND DRUG ADMINISTRATION \\ 
 +DEPARTMENT OF HEALTH AND HUMAN SERVICES \\ 
 +SUBCHAPTER H--MEDICAL DEVICES \\ 
 +PART 820 -- QUALITY SYSTEM REGULATION \\ 
 + 
 +Subpart G--Production and Process Controls \\ 
 + 
 +Sec. 820.72 Inspection, measuring, and test equipment. \\ 
 +(b) (1) Calibration standards. Calibration standards used for inspection, measuring, and test equipment shall be __traceable to national or international standards__. If national or international standards are not practical or available, the manufacturer shall use an independent reproducible standard. If no applicable standard exists, the manufacturer shall establish and maintain an in-house standard.</​WRAP>​ 
 + 
 +In contrast, ISO 17025:2017 is much more modern and technically correct in stating:\\
 <WRAP center round box 80%> <WRAP center round box 80%>
 **ISO 17025:2017, “General requirements for the competence of testing and calibration laboratories”** \\ **ISO 17025:2017, “General requirements for the competence of testing and calibration laboratories”** \\
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 [[http://​www.isobudgets.com/​measurement-traceability-complying-iso-17025-requirements/​|{{ :​articles:​measurement-traceability-pyramid-600px.jpg?​direct }}]] [[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, contrary to the antiquated language of ISO 9001:2015 & AS9100:​2016,​ it is possible to “bypass” the National Metrology Institutes (NMIs) to obtain traceability to SI units. Using the example of DC volts, [[https://​www.fluke.com|Fluke]],​ a world leader in the field of metrology, 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.+I describe the above pyramid as "//​typical//"​ because, contrary to the antiquated language of ISO 9001:2015 & AS9100:​2016,​ it is possible to “bypass” the National Metrology Institutes (NMIs) to obtain traceability ​directly ​to SI units. Using the example of DC volts, [[https://​www.fluke.com|Fluke]],​ a world leader in the field of metrology, 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
 + 
 +Also, while not strictly speaking a National Metrology Institute (NMI), the [[https://​www.bipm.org|"​Bureau International des Poids et Mesures"​ (BIPM)]] offers [[https://​www.bipm.org/​en/​bipm-services/​|calibration & Measurement services]] (with traceability to SI Units) to its [[https://​www.bipm.org/​en/​about-us/​member-states/​|Member States]]. In that instance, the BIPM would serve as equivalent to a NMI. 
 + 
 +Transcat has an excellent White Paper on this topic at: [[https://​www.transcat.com/​calibration-resources/​white-papers/​what-is-measurement-traceability]].
 ===== What are SI Units? ===== ===== What are SI Units? =====
 {{ :​articles:​2018-si.png?​direct&​130|}} {{ :​articles:​2018-si.png?​direct&​130|}}
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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]]. ​ 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]]. ​
  
-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]]).+==== Legal Metrology ==== 
 + 
 +Fluke performs this comparison ​described above 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 NIST as holding ​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]]). 
 ===== What are "​International Standards"?​ ===== ===== 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: \\+While ISO 9001:2015, AS9100:2016 (Rev. D) and ISO 17025:2017 all mention "​International Standards", ​none of them define what this means. Fortunately,​ 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), defines this term. 
 + 
 +<WRAP center round box 80%> 
 +**International Measurement Standard** \\ 
 +//measurement standard recognized by signatories to an international agreement and intended to serve worldwide// \\ 
 +\\ 
 +EXAMPLE 1   The international prototype ​of the kilogram. 
 + 
 +EXAMPLE 2   ​Chorionic Gonadotrophin,​ World Health Organization (WHO) 4th international standard 1999, 75/589, 650 International Units per ampoule. 
 + 
 +EXAMPLE 3   ​VSMOW2 (Vienna Standard Mean Ocean Water) distributed by the International Atomic Energy Agency (IAEA) for differential stable isotope amount-of- substance ratio measurements. 
 + 
 +---- 
 +Source: 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
 +</​WRAP>​ 
 + 
 + 
 + 
 + 
 + 
 + 
 + 
 + 
 +I am aware of only four (4) "​international ​standards" ​(as opposed to SI //units//); three of which are listed as examples in the definition shown above. However, there are probably others. Those that I am aware of include: \\
 \\ \\
 **1 - The international prototype of the kilogram (OBSOLETE as of May 20, 2019)** \\ **1 - The international prototype of the kilogram (OBSOLETE as of May 20, 2019)** \\
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 The only SI unit "​physical artifact"​ (i.e., not defined by a fundamental,​ natural constant), the international prototype kilogram (IPK), was certified in 1889, and consists of a cylinder of platinum-iridium. The IPK is maintained by the [[https://​www.bipm.org/​en/​publications/​si-brochure/​kilogram.html|BIPM]]. The only SI unit "​physical artifact"​ (i.e., not defined by a fundamental,​ natural constant), the international prototype kilogram (IPK), was certified in 1889, and consists of a cylinder of platinum-iridium. The IPK is maintained by the [[https://​www.bipm.org/​en/​publications/​si-brochure/​kilogram.html|BIPM]].
  
-<​note>​Because the IPKs stability has been a matter of significant concern, during November 2018, the world’s measurement experts voted and unanimously approved a revision of the SI that establishes a measurement system entirely based on physical constants of nature. The changes took effect on [[http://​www.worldmetrologyday.org|World Metrology Day]], May 20, 2019; which  commemorates the anniversary of the signing of the Metre Convention in 1875. See [[https://​www.theverge.com/​2018/​11/​13/​18087002/​kilogram-new-definition-kg-metric-unit-ipk-measurement|The Kilogram is Dead; Long Live the Kilogram]]</​note>​+<​note>​Because the IPKs stability has been a matter of significant concern, during November 2018, the world’s measurement experts voted and unanimously approved a revision of the SI that establishes a measurement system entirely based on physical constants of nature. The changes took effect on [[http://​www.worldmetrologyday.org|World Metrology Day]], May 20, 2019; which commemorates the anniversary of the signing of the Metre Convention in 1875. See [[https://​www.theverge.com/​2018/​11/​13/​18087002/​kilogram-new-definition-kg-metric-unit-ipk-measurement|The Kilogram is Dead; Long Live the Kilogram]]</​note>​
 **2 - Chorionic Gonadotrophin (Biological standard)** \\ **2 - Chorionic Gonadotrophin (Biological standard)** \\
 Defined by the [[http://​apps.who.int/​iris/​bitstream/​handle/​10665/​70154/​WHO_BS_09.2107_eng.pdf|World Health Organization (WHO)]] in the 4th international standard 1999, as 75/589, 650 International Units per ampoule. Defined by the [[http://​apps.who.int/​iris/​bitstream/​handle/​10665/​70154/​WHO_BS_09.2107_eng.pdf|World Health Organization (WHO)]] in the 4th international standard 1999, as 75/589, 650 International Units per ampoule.
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 **3 & 4 - VSMOW2 (Vienna Standard Mean Ocean Water) & SLAP2 (Standard Light Antarctic Precipitation)** \\ **3 & 4 - VSMOW2 (Vienna Standard Mean Ocean Water) & SLAP2 (Standard Light Antarctic Precipitation)** \\
 Distributed by the [[https://​nucleus.iaea.org/​rpst/​ReferenceProducts/​ReferenceMaterials/​Stable_Isotopes/​2H18O-water-samples/​VSMOW2.htm|"​International Atomic Energy Agency"​ (IAEA)]] for differential stable isotope amount-of-substance ratio measurements,​ the [[http://​www-naweb.iaea.org/​NAALIHL/​docs/​ref_mat/​InfoSheet-VSMOW2-SLAP2.pdf|VSMOW2 & SLAP2 reference material standards]] are used in producing the triple point of water (see the BIPM "​[[https://​www.bipm.org/​utils/​common/​pdf/​ITS-90/​Guide_ITS-90_2_2_TPW-2018.pdf|Guide to the Realization of the ITS-90 - Triple Point of Water]]"​) with the smallest amount of uncertainty. Distributed by the [[https://​nucleus.iaea.org/​rpst/​ReferenceProducts/​ReferenceMaterials/​Stable_Isotopes/​2H18O-water-samples/​VSMOW2.htm|"​International Atomic Energy Agency"​ (IAEA)]] for differential stable isotope amount-of-substance ratio measurements,​ the [[http://​www-naweb.iaea.org/​NAALIHL/​docs/​ref_mat/​InfoSheet-VSMOW2-SLAP2.pdf|VSMOW2 & SLAP2 reference material standards]] are used in producing the triple point of water (see the BIPM "​[[https://​www.bipm.org/​utils/​common/​pdf/​ITS-90/​Guide_ITS-90_2_2_TPW-2018.pdf|Guide to the Realization of the ITS-90 - Triple Point of Water]]"​) with the smallest amount of uncertainty.
-===== Conclusion ​=====+===== Traceability to Organizations,​ rather than SI Units =====
  
-Specifying that a calibration service provider __must__ supply "NIST Traceable"​ calibration certifications not only reveals a lack of understanding "​metrological traceability",​ it ignores the reality that many calibrations,​ whether from NMIs (e.g., the [[https://​www.nrc-cnrc.gc.ca/​eng/​solutions/​advisory/​calibration_index.html|NRC]] in Canada, [[http://​www.cenam.mx/​eng/​|CENAM]] in Mexico, [[https://​www.ptb.de/​cms/​en.html|PTB]] in Germany,) or accredited commercial metrology laboratories,​ may be traceable to SI units through other means (e.g., intrinsic measurement standards).+The US Federal Aviation Administration,​ "​[[https://​www.faa.gov/​documentLibrary/​media/​Order/​6200.4G.pdf|FAA National Policy - Order 6200.4G]]"​ (dated 03/08/10) states: 
 + 
 +<WRAP center round box 80%> 
 +**FAA National Policy - Order 6200.4G** \\ 
 +Appendix 2 - Definitions \\ 
 +h. Calibration Standard - a device or instrument used as a basis to calibrate measure, gage, test, inspect, or otherwise examine basic accuracy values. The standard has a higher order of accuracy than the examined item and is __traceable to the National Institute of Standards and Technology (NIST)__.</​WRAP>​ 
 + 
 + 
 +Specifying that a calibration service provider __must__ supply "NIST Traceable"​ calibration certifications, which this policy essentially requires, ​not only reveals a lack of understanding "​metrological traceability",​ it ignores the reality that many calibrations,​ whether from NMIs (e.g., the [[https://​www.nrc-cnrc.gc.ca/​eng/​solutions/​advisory/​calibration_index.html|NRC]] in Canada, [[http://​www.cenam.mx/​eng/​|CENAM]] in Mexico, [[https://​www.ptb.de/​cms/​en.html|PTB]] in Germany,) or accredited commercial metrology laboratories,​ may be traceable to SI units through other means (e.g., intrinsic measurement standards).
  
 This is politely pointed out by the [[https://​ilac.org|ILAC – International Laboratory Accreditation Cooperation"​]]. This is politely pointed out by the [[https://​ilac.org|ILAC – International Laboratory Accreditation Cooperation"​]].
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 Source: [[https://​ilac.org/?​ddownload=840|ILAC-P10:​01/​2013,​ "ILAC Policy on the Traceability of Measurement Results"​]]" ​ Source: [[https://​ilac.org/?​ddownload=840|ILAC-P10:​01/​2013,​ "ILAC Policy on the Traceability of Measurement Results"​]]" ​
 </​WRAP>​ </​WRAP>​
 +===== Conclusion =====
  
 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. 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.
 +
 +NIST, for example, is a non-regulatory agency of the United States Department of Commerce. When the US Government was "shut down" during 1995, 2013, 2018, and 2019, NIST operations were suspended. So if your company had measurement standards at NIST awaiting calibration,​ or if you outsourced calibration to a metrology lab who had its measurement standards at NIST, then the length of time associated with the government "​shutdown"​ was added to the delay in receiving those instruments. These government "​shutdowns"​ create a "​ripple effect"​ throughout industry.
 +
 +To avoid this, standards writing bodies and regulatory agencies should gain a better understanding of "​metrological traceability"​ and allow other NMIs and/or accredited commercial metrology laboratories to be utilized in providing metrological traceability to SI units. In particular, these bodies should promote international consistency of measurements through adopting the recommendations of the [[https://​ilac.org/​latest_ilac_news/​joint-bipm-oiml-iso-and-ilac-declaration-on-metrological-traceability-signed/​|"​Joint BIPM, OIML, ISO and ILAC Declaration on Metrological Traceability"​]].
 +
 +----
 +
 +For more information visit: [[https://​us.flukecal.com/​literature/​about-calibration]]