CCTK7, EUROMET.TK7, EURAMET.TK7.2, K7.3 & K7.1,
COOMET.TK7 and APMP.TK7.1
MEASURAND : Temperature of triple point of water
NOMINAL VALUE : 273.16 K
Full set of degrees of equivalence D_{i} and expanded uncertainty U_{i} (k = 2), relative to the CCTK7 key comparison reference value, expressed in µK
Click here to download the Graph of Equivalence
In CCTK7 NMISA, MSL and NRC realized systematically higher temperatures, because they were the only laboratories which based their realizations on the recommendation of the Supplementary Information for the ITS90 to use water with the isotopic composition of standard mean ocean water.
Since the publication of CCTK7 results, the CIPM approved Recommendation 2 (CI2005) "Clarification of the definition of the kelvin, unit of thermodynamic temperature": see on pages 23 and 24 of the EUROMET.TK7 Final Report for detailed information on the application of this recommendation by the participants.
CCTK7, EUROMET.TK7, EURAMET.TK7.2, K7.3 & K7.1,
COOMET.TK7 and APMP.TK7.1
MEASURAND : Temperature of triple point of water
NOMINAL VALUE : 273.16 K
Full set of degrees of equivalence D_{i} and expanded uncertainty U_{i} (k = 2), relative to the CCTK7 key comparison reference value, expressed in µK
In dark blue: CCTK7 participants
In green: EUROMET.TK7 participants
In orange: EURAMET.TK7.2 participant
In braun: EURAMET.TK7.3 participant
In grey: EURAMET.TK7.1 participants
In blue: COOMET.TK7 participants
In pink: APMP.TK7.1 participant
Pairwise degrees of equivalence are computed inside CCTK7 and EUROMET.TK7 only.
Full matrix of equivalence for CCTK7
Lab i  D_{i}  U_{i} 
/ µK  / µK  
BIPM  22  90 
LNEINM  76  134 
CEM  36  85 
CENAM  27  58 
NMISA  83  150 
NMIA  51  72 
INRIM  37  58 
IPQ  18  322 
KRISS  47  115 
MSL  95  39 
NIM  11  124 
NIST  62  69 
NMIJ  32  304 
NMiVSL  6  113 
NPL  23  81 
NRC  62  52 
PTB  37  113 
SMU  47  109 
A*STAR  11  144 
UME  75  183 
VNIIM  0  94 
Results are presented under A4 printable format in Summary Results (PDF file).
Metrology area, Subfield  Thermometry, Fixed Point Cells 
Description  Comparison of water triple point cells 
Time of measurements  2011  2012 
Status  Approved for equivalence 
Final Reports of the comparisons  
Measurand  Temperature: 273.16 K 
Transfer device  Water triple point cell 
Comparison type  Key Comparison 
Consultative Committee  CCT (Consultative Committee for Thermometry) 
Conducted by  APMP (Asia Pacific Metrology Programme) 
Comments  Results published on 19 June 2018 EUROMET.TK7, EURAMET.TK7.2, EURAMET.TK7.3, EURAMET.TK7.1, COOMET.TK7 and APMP.TK7.1 results are linked to those of CCTK7 Comparison of water triple point cells

Pilot institute 
NMIJ AIST
National Metrology Institute of Japan Japan 
Contact person  T. Nakano 
Pilot laboratory  

NMIJ AIST 
National Metrology Institute of Japan, Japan, APMP 
VMISTAMEQ 
Viet Nam Metrology Institute, Directorate for Standards and Quality, Viet Nam, APMP 
This page proposes printout on A4 paper (portrait) of the comparison details (best printed out using a black and white printer).
Please, select items to be printed out, then click on "OK" :
CCTK7, EUROMET.TK7, EURAMET.TK7.2, K7.3 & K7.1,
COOMET.TK7 and APMP.TK7.1
MEASURAND : Temperature of triple point of water
NOMINAL VALUE : 273.16 K
The key comparison reference value, x_{R}, is calculated as the arithmetic mean of the results, x_{i}, from all participants, including some laboratories who made corrections for the influence of chemical impurities and isotopic composition, and some who did not. x_{R} = 22 µK (expressed as the difference from the BIPM value). The uncertainty of x_{R}, u_{R}, is calculated as the standard deviation of the mean of the data set. u_{R} = 11 µK. Because the distribution of the pooled data is multimodal, care should be taken when using this quantity for calculating confidence intervals. 
The degree of equivalence of laboratory i with respect to the key comparison reference value is given by a pair of terms: D_{i} = (x_{i}  x_{R}) and its expanded uncertainty U_{i} (k = 2), both expressed in µK. The uncertainty includes the participant's uncertainty, the comparison uncertainty and the uncertainty of the key comparison reference value. 
The degree of equivalence between two laboratories i and j is given by a pair of terms: D_{ij} = (D_{i}  D_{j}) = (x_{i}  x_{j}) and its expanded uncertainty U_{ij} (k = 2), both expressed in µK. The uncertainty includes both participants' uncertainties and twice the comparison uncertainty. 
The EUROMET reference value referred to the NMiVSL reference cell (VSL094), x_{R EUR}, and its standard uncertainty, u_{R EUR}, are computed from the weighted mean of the individual results, with the exclusion of the CMI and GUM results, as explained in Section 7.1 on page 29 of the EUROMET.TK7 Final Report: x_{R EUR} = 15.6 µK, and u_{R EUR} = 10.5 µK 
The degree of equivalence of laboratory i, participant in EUROMET.TK7, with respect to the EUROMET reference value is given by a pair of terms: D_{i}_{EUR} = x_{i}_{EUR}  x_{R EUR}, and its expanded uncertainty U_{i}_{EUR} (k = 2), both expressed in µK. 
The linkage process of EUROMET.TK7 results to those of CCTK7 is explained in Section 7.3 on page 36 of the EUROMET.TK7 Final Report. It is based on the common participation of CEM, IPQ, LNEINM, NMiVSL, and SMU in both comparisons. 
The degree of equivalence of laboratory i, participant in EUROMET.TK7, with respect to the CCTK7 key comparison reference value is given by a pair of terms: D_{i} = D_{i}_{EUR} + d_{LINK} with d_{LINK} = 64.7 µK, and its expanded uncertainty (k = 2) U_{i} = 2[(U_{i}_{EUR}/2)^{2} + (u_{LINK})^{2}]^{1/2}, with u_{LINK} = 19.7 µK, both expressed in µK. 
Pairwise degrees of equivalence are computed inside EUROMET (see Section 7.2 on page 30 of the EUROMET.TK7 Final Report). 
The linkage process of COOMET.TK7 results to those of CCTK7 is explained in Section 6 of the COOMET.TK7 Final Report. It is based on the common participation of VNIIM in both comparisons 
The degree of equivalence of laboratory i, participant in COOMET.TK7, with respect to the CCTK7 reference value is given by a pair of terms: D_{i}, and its expanded uncertainty (k = 2) U_{i}, both expressed in µK. 
No pairwise degrees of equivalence are computed inside COOMET.TK7. 
The degree of equivalence of INTiBS relative to the CCTK7 key comparison reference value is computed through the common participation of VSL in EURAMET.TK7.2 and EUROMET.TK7 (see Section 6 of the EURAMET.TK7.2 Final Report). 
The degree of equivalence of GUM relative to the CCTK7 key comparison reference value is computed through the common participation of VSL in EURAMET.TK7.3 and EUROMET.TK7 (see Sections 6 and 7 of the EURAMET.TK7.3 Final Report). 
New degrees of equivalence relative to the CCTK7 key comparison reference value are obtained in EURAMET.TK7.1 for SMU and CMI, through the common participation of SMU in EURAMET.TK7.1 and EUROMET.TK7, taking into account the change of national reference cell at SMU since the completion of EUROMET.TK7. 
The degree of equivalence of VMISTAMEQ relative to the CCTK7 key comparison reference value is computed through the common participation of NMIJ in APMP.TK7 and CCTK7 (see Section 8 of the APMP.TK7.1 Final Report). 
CCTK7, EUROMET.TK7, EURAMET.TK7.2, K7.3 & K7.1,
COOMET.TK7 and APMP.TK7.1
MEASURAND : Temperature of triple point of water
NOMINAL VALUE : 273.16 K
x_{i} : temperature difference between the national reference of laboratory i and the BIPM reference, x_{i} = T(Lab i)  T(BIPM), where T is the temperature
u_{i} : combined standard uncertainty of x_{i}
Lab i  x_{i} / µK 
u_{i} / µK 
BIPM  0  44 
LNEINM  54  66 
CEM  14  41 
CENAM  5  27 
NMISA 
105 
74 
NMIA 
29 
34 
INRIM 
15 
27 
IPQ 
40 
160 
KRISS 
69 
56 
MSL 
117 
16 
NIM 
33 
61 
NIST 
40 
33 
NMIJ 
54 
151 
NMiVSL 
16 
55 
NPL 
45 
39 
NRC 
85 
23 
PTB 
14 
56 
SMU 
69 
53 
A*STAR 
34 
71 
UME 
53 
91 
VNIIM 
22 
46 
MEASURAND : Temperature of triple point of water
NOMINAL VALUE : 273.16 K
x_{iEUR} : temperature difference between the national reference of laboratory i and the NMiVSL reference cell (VSL094), x_{i} = T(Lab i)  T(VSL094), where T is the temperature
u_{iEUR} : combined standard uncertainty of x_{iEUR}
Lab i  x_{iEUR} / µK 
u_{iEUR} / µK 
INM(RO)  3  64 
MKEH  77  69 
EIM  45  113 
MIKES  17  65 
PTB 
39 
37 
DTI 
51 
68 
JV 
146 
194 
VNIIM 
63 
52 
DZM/LPM 
10 
50 
UME 
86 
77 
DMDM 
151 
119 
BEV 
20 
174 
IPQ 
30 
80 
NML(IE) 
40 
106 
CMI 
310 
61 
GUM 
309 
75 
VMT/PFI 
62 
119 
CEM 
51 
44 
INRIM 
2 
29 
LNEINM 
16 
56 
MIRS/FELMK 
33 
25 
SMD 
44 
34 
SMU 
4 
58 
NMiVSL 
14 
28 
MEASURAND : Temperature of triple point of water
NOMINAL VALUE : 273.16 K
The comparison was performed in three stages: 1) each participating laboratory carried out comparisons of the transfer cell with its national standard cell in local conditions; 2) the transfer cells were forwarded together with measurement results to BelGIM, where they were compared with the standard BelGIM cell using its laboratory equipment; and 3) the transfer cells were sent back to laboratories, where they were compared again to the national standard cells in order to determine the stability of the transfer cells.
The measurement results of the participating laboratories are given in section 2, 3, and 4 of the COOMET.TK7 Final Report.
MEASURAND : Temperature of triple point of water
NOMINAL VALUE : 273.16 K
The measurement results of this bilateral key comparison between VSL (The Netherlands) and INTiBS (Poland), carried out in 2010, are summarized in Sections 3 and 4, on pages 5 and 6 of the EURAMET.TK7.2 Final Report.
They lead to the following numbers:
T^{INTiBS} _{Nat. Ref.}  T^{VSL} _{Nat. Ref.} = 2.9 µK and associated combined standard uncertainty (k = 1) u = 46 µK, where "Nat. Ref." stands for "National Reference".
MEASURAND : Temperature of triple point of water
NOMINAL VALUE : 273.16 K
The measurement results of this bilateral key comparison between VSL (The Netherlands) and GUM (Poland), carried out in 2011, are summarized in Sections 3 and 4, on pages 5 and 6 of the EURAMET.TK7.3 Final Report.
They lead to the following numbers:
T^{GUM} _{Nat. Ref.}  T^{VSL} _{Nat. Ref.} = 11.5 µK and associated combined standard uncertainty (k = 1) u = 60 µK, where "Nat. Ref." stands for "National Reference".
MEASURAND : Temperature of triple point of water
NOMINAL VALUE : 273.16 K
The measurement results of this bilateral key comparison between CMI (Czech Republic) and SMU (Slovakia), carried out in 2009, are summarized in Sections 2 and 3 of the EURAMET.TK7.1 Final Report.
It should be noted that SMU replaced its national reference cell with a cell with known isotopic composition after completion of key comparison EUROMET.TK7.
MEASURAND : Temperature of triple point of water
NOMINAL VALUE : 273.16 K
The measurement results of this bilateral key comparison between VMISTAMEQ (Viet Nam) and NMIJ (Japan), carried out in 2014  2015, are summarized in Sections 3 to 6 of the APMP.TK7.1 Final Report.
They lead to the following numbers:
T^{VMISTAMEQ} _{Nat. Ref. } T^{NMIJ }_{Nat. Ref. }= 19.9 µK and associated combined standard uncertainty (k = 1) u = 46.3 µK, where "Nat. Ref." stands for "National Reference".