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Measurement uncertainty
The result of a measurement is complete only when accompanied by a quantitative statement of its uncertainty. This measurement uncertainty reflects the incomplete knowledge of the measurand and allows to assess the reliability, the comparability or a risk associated with the measurement result. In metrology, the specification of the uncertainty is essential, e.g. to achieve traceability to the underlying SI unit.
The „Guide to the Expression of Uncertainty in Measurement“ (GUM) offers universally applicable rules for evaluating measurement uncertainties , and is an internationally recognized guide today. Thus, the GUM enables expressions of uncertainty to be consistent and internationally transferable – which is a basis for trade and the economy.
Practical support
PTB Working Group 8.42 offers practical support in the field of measurement uncertainty. Statistical issues in line with and beyond the GUM are dealt with in consultations with PTB staff and in collaborations, in research activities (see WG 8.42) and through participation in Committees. To support the assessment of uncertainties according to the rules of the GUM, the Working Group offers Advanced Training. Software Applications facilitate the implementation of these evaluations.
In addition, the Working Group supports legal metrology regarding statistical questions (in the PTB-AK "Statistics for metrology and verification“ and in the Working Group for Metrology and Verification "Test Centers and Sampling Procedures") and develops sampling procedures and plans for the implementation of Section 35 of the new Measures and Verification Ordinance in agreement with the German verification authorities (see Sampling procedures in legal metrology).
Advanced training measures
PTB Working Group 8.42 regularly offers advanced training, seminars and other events in the field of measurement uncertainty. These promote the application of the GUM and its supplements and improve the understanding of methods for evaluating measurement uncertainty as well as their applicability.
PTB-Seminar “Practical aspects of evaluating measurement uncertainty”
Training course ”Introduction to evaluating measurement uncertainty according to the rules of the GUM”
- Externally organized by the German Calibration Service DKD for its members: 22nd Sept. 2022, 29th Jan. 2019, 22nd March 2017, nearly every 2 years in Berlin
- For PTB staff: at least twice each year in Berlin and Braunschweig and on inquiry
To improve the quality, efficiency and dissemination of measurement uncertainty training, the Mathmet activity MU Training developed freely available training material. For example, PTB developed the following video with partners:
The coverage factor k explained –
From standard uncertainty u to expanded uncertainty UThe coverage factor k explained –
From standard uncertainty u to expanded uncertainty U
From standard uncertainty u to expanded uncertainty U
From standard uncertainty u to expanded uncertainty U
Software
A number of software applications are available for evaluating uncertainties according to the rules of the GUM. Some of these applications include:
- GUM Workbench
- QMSys GUM Software
- GUMsim
- MSL Uncertainty Calculator, GUM Tree Calculator, Excel add-in,R library
- NIST Uncertainty Machine (including User's Manual)
- NPL's Software to support GUM Supplements 1 and 2
- METAS UncLib An advanced Measurement Uncertainty Calculator
- LNE-MCM software for a simple and validated implementation of GUM Supplement (Publikation)
- Python uncertainties package
A comprehensive, up-to-date list of software to evaluate uncertainty as well as their characteristics was developed by the consortium of the activity MU Training and is freely available at the website.
Committees
- JCGM WG 1 - Working Group on the Expression of Uncertainty in Measurement (GUM) (Metrology organization / international)
- AGME Arbeitsausschuss Prüfstellen und Stichprobenverfahren (Working Committee "Test Centers and Sampling Test Procedures) (Legal metrology / national)
- PTB Arbeitskreis Statistik für das Mess- und Eichwesen (PTB-AK "Statistics for measures and verification legislation) (Legal metrology / national)
- VDI/VDE Fachausschuss Eignung von Prüfprozessen (Technical Committee "Suitability of testing procedures) (Standardization / national)
- Review of and statement for guidelines like
- VDA 5 "Mess- und Prüfprozess - Eignung, Planung und Management“ (Gelbband 2020)
- DKD-R 5-1 "Kalibrierung von Widerstandthermometern" (2019)
- JCGM GUM-6 „Developing and using measurement models“ (JCGM 103 CD 2018)
- DKD-R 5-8 "Kalibrierung von Hygrometern zur direkten Erfassung der relativen Feuchte" (2018)
- DKD-R 10-8 "Statische Kalibrierung von Kalibriereinrichtungen für Drehmomentschlüsseln" (2017)
- Revision JCGM 100 „Guide to the Expression of Uncertainty in Measurement” (JCGM_100201X_CD 2014)
Literature
- GUM-documents to evaluate measurements:
- JCGM 100:2008 Guide to the expression of Uncertainty in Measurement
- JCGM 104:2009 An introduction to the GUM and related documents
- JCGM 101:2008 Propagation of distributions using Monte Carlo method - Suppl.1 to the GUM
- JCGM 102:2011 Extension to any number of output quantities - Suppl. 2 to the GUM
- JCGM 106:2012 The role of measurement uncertainty in conformity assessment
- JCGM GUM-6:2020 Developing and using measurement models
- PTB statement regarding systematic errors in the calculation of uncertainty in measurements (2019)
- VIM - International Vocabulary of Metrology
Publications
- Publications related to the evaluation of measurement uncertainty of the Working Group 8.42 "Data Analysis and Measurement Uncertainty"