Final Report on EUROMET.T-K7: Key comparison of water triple point cells

Abstract

From 2002 to 2004 the Consultative Committee for Thermometry (CCT) carried out a Key Comparison (KC) of water triple point cells (CCT-K7). In 2005 the Regional Metrology Organization (RMO) EURAMET decided to initiate an additional KC of water triple point cells, EUROMET.T-K7, to extend the metrological equivalence to a larger number of national metrology institutes (NMIs) from the EURAMET region.The EUROMET.T-K7 comparison was carried out in 2006–2008 with the coordination of VSL and the participation of 24 EUROMET NMIs, 9 of them having participated in CCT-K7 as well (8 out of 9 used the same transfer cell they had used in CCT-K7).This report presents the results of this comparison, provides detailed information of the measurements performed by all participating laboratories and links the comparison results to the CCT-K7 comparison.Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCT, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

EURAMET.T-K7 Key Comparison of Water Triple-Point Cells

“…The associated standard uncertainty u(D i j ) required some elaboration because a distinction had to be introduced between intra-group pairs (pairs of participants belonging to the same group) and inter-group pairs (pairs of participants belonging to different groups). In both cases, u(D i j ) was calculated by linking the pair of laboratories with the shortest chain of actual measurements (see [5] for the details). The resulting table of equivalence is shown in Table 3.…”

“…The resulting table of equivalence is shown in Table 3. The robustness of this linkage mechanism was tested in [5] and further discussed in [6]; here we only remind that the link between CCT-K7 and EURAMET.T-K7 resulting from the above-mentioned assumption can be expressed by the following relationship:…”

“…In 2006-2007, in order to extend the metrological equivalence to a larger number of NMIs, another KC of water triple-point cells, EURAMET.T-K7 [5] was carried out by the EURAMET RMO. Twenty-four NMIs from the EURAMET region took part in this comparison, nine of them having participated in CCT-K7 as well.…”

“…Twenty-four NMIs from the EURAMET region took part in this comparison, nine of them having participated in CCT-K7 as well. The link between the "daughter comparison" EURAMET.T-K7 and the mother "comparison" CCT-K7 was established by using the results obtained by a selected subset of linking laboratories that participated in both comparisons: CEM, IPQ, LNE-INM/CNAM, VSL, and SMU (for the details of the linkage mechanism, see [6]). With reference to the observation made at the end of the previous paragraph, some of the linking laboratories (namely, CEM, LNE-INM/CNAM, and VSL) adopted a new national definition in EURAMET.T-K7 with respect to their definition in CCT-K7, so that new DOEs were generated among them that should replace the old equivalence established in CCT-K7 and should be used to correct both the unilateral and bilateral CCT-K7 equivalences.…”

Design and Capabilities of the Temperature Control System for the Italian Experiment Based on Precision Laser Spectroscopy for a New Determination of the Boltzmann Constant

“…A standard TPW cell is used to evaluate the resistance of C-SPRTs at the TPW temperature. For this experiment, the TPW cell is the same that was used in the recent K7 key comparison and that will be also compared to the other TPW cell involved in all the other experiments and methods for the determination of k B in Europe [11].…”