07.12.2016
In order to maintain the international recognition of national standards and of the testing and calibration certificates issued by the national metrology institutes, regular participation in international comparison measurements is required within the scope of the mutual agreement of the Comité International des Poids et Mesures (CIPM) (CIPM MRA [1]). In the field of mass determination, the international comparison measurement CCM.M-K7 was therefore prepared and carried out under the leadership of the Comité Consultatif pour la Masse et les Grandeurs Apparentées (CCM) in 2014 and 2015.
In order to maintain the international recognition of national standards and of the testing and calibration certificates issued by the national metrology institutes, regular participation in international comparison measurements is required within the scope of the mutual agreement of the Comité International des Poids et Mesures (CIPM) (CIPM MRA [1]). In the field of mass determination, the international comparison measurement CCM.M-K7 was therefore prepared and carried out under the leadership of the Comité Consultatif pour la Masse et les Grandeurs Apparentées (CCM) in 2014 and 2015. The pilot laboratory in charge of the comparison was the national metrology institute of the Republic of Korea (KRISS) – with the support of PTB. The CCM nominated a total of ten national metrology institutes as participants. These were divided into two groups. Then, a set of weights with the nominal values
5 kg, 100 g, 10 g, 5 g and 500 mg as transfer standards was circulated within each group. To check the stability of the transfer standards, the mass of each of them was determined at the pilot laboratory before and after the measurements were taken by the participants. After all the participants had finished their measurements, the results were evaluated by means of a Monte Carlo method [2, 3] and a final report was written. In the results, the corrections were taken into account which had been determined for the national prototypes of the kilogram by the Bureau International des Poids et Mesures (BIPM) within the scope of the last calibration campaign with the international prototype of the kilogram [4]. When determining the mass of the transfer standards at PTB, expanded measurement uncertainties (k = 2) in a range from 0.0004 mg (for 500 mg, rel. standard uncertainty 4.0 × 10-7) to 0.112 mg (for 5 kg, rel. standard uncertainty 1.1 × 10-8) were achieved. Figure 1 shows, for example, the agreement of the participants' results with the reference values for the nominal values 100 g and 500 mg. All of PTB's results are in agreement with the reference values within the uncertainty ranges determined for a confidence interval of 95 %.
a)
b)
Figure 1: Difference between the participants' results and the reference value (DoE: Degrees of Equivalence) and their expanded measurement uncertainty (k = 2) for the transfer standards with the nominal values a) 100 g and b) 500 mg [5].
References:
[1] 
http://www.bipm.org/en/cipm-mra/cipm-mra-documents/
[2] Cox, M. G.: The evaluation of key comparison data. Metrologia 39 (2002), pp. 589-59
[3] Joint Committee for Guides in Metrology (JCGM): Evaluation of measurement data – Supplement 1 to the “Guide to the expression of uncertainty in measurement” – Propagation of distributions using a Monte Carlo method. JCGM 101 1st edn 2008, Joint Committee for Guides in Metrology, Sèvres, 90 pages
[4] Stock, M.; Barat, P.; Davis, R.; Picard, A.; Milton, M. J. T.: Calibration campaign against the international prototype of the kilogram in anticipation of the redefinition of the kilogram part I: comparison of the international prototype with its official copies. Metrologia 52 (2015), pp. 310–316
[5] Lee, S. et al.: The final report for CCM.M-K7: Key comparison of 5 kg, 100 g, 10 g, 5 g and 500 mg stainless steel mass standards. Metrologia 54 (2017) 07001, 23 pages
Contact person:
Dr. Michael Borys, FB 1.8, AG 1.81, E-Mail: 
michael.borys(at)ptb.de