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MEASURAND : Central length of long steel gauge blocks measured by interferometry according to ISO 3650

NOMINAL VALUES : 4 gauge blocks with nominal length Lk (k = 1 to 4) from 175 mm to 900 mm including two different 500 mm gauge blocks

Degrees of equivalence, Dik and expanded uncertainty Uik (coverage factor: 2), of each laboratory i with respect to the reference value for each gauge block k

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L1 = 175 mm

L2 = 500 mm

L3 = 500 mm

L4 = 900 mm

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MEASURAND : Central length of long steel gauge blocks measured by interferometry according to ISO 3650

NOMINAL VALUES : 4 gauge blocks from 175 mm to 900 mm including two different 500 mm gauge blocks

Degrees of equivalence, Dik and expanded uncertainty Uik (coverage factor: 2), of each laboratory i with respect to the reference value for each gauge block k

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CCL-K2
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Metrology area, Sub-field Length, Dimensional Metrology
Description Long gauge blocks by interferometry
Time of measurements 1999 - 2001
Status Approved for equivalence
Final Reports of the comparisons
Metrologia, 2003, 40, Tech. Suppl., 04004
References

CCL-K2 Technical Protocol

Measurand Central length: 175 mm, 500 mm and 900 mm
Transfer device Four steel gauge blocks
Comparison type Key Comparison
Consultative Committee CCL (Consultative Committee for Length )
Conducted by CCL (Consultative Committee for Length )
Comments

CCL-K2 results were published on 10 December 2003.

Long gauge blocks by interferometry
Pilot institute NPL
National Physical Laboratory
United Kingdom
Contact person Andrew Lewis

+44 (0) 20 8943 6074
First Name Last Name
wwww@ww.www +356719836 Institute 1 Institute 1 Khmelnitskiy
Pilot laboratory
NPL

National Physical Laboratory, United Kingdom, EURAMET

INMETRO

Instituto Nacional de Metrologia, Qualidade e Tecnologia, Brazil, SIM

NIM

National Institute of Metrology, China, APMP

NIST

National Institute of Standards and Technology, United States, SIM

NMIJ AIST

National Metrology Institute of Japan, Japan, APMP

NRC

National Research Council, Canada, SIM

PTB

Physikalisch-Technische Bundesanstalt, Germany, EURAMET

SMU

Slovensky Metrologicky Ustav, Slovakia, EURAMET

VNIIM

D.I. Mendeleyev Institute for Metrology, Rosstandart, Russian Federation, COOMET

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MEASURAND : Central length of long steel gauge blocks measured by interferometry according to ISO 3650

NOMINAL VALUES : 4 gauge blocks from 175 mm to 900 mm including two different 500 mm gauge blocks

The key comparison reference value xRk for each gauge block k is obtained from the weighted mean xwk of the participants' results xik (excluding the VNIIM result for L1 = 175 mm) by adding a constant Ck chosen such that the reference value is the nominal length:

xRk = Lk = xwk + Ck

The standard uncertainties uRk of the key comparison reference values are obtained from the reported individual standard uncertainties uik, see equation 4 on page 22 of the Final Report.

For each gauge block k, the degree of equivalence of each laboratory with respect to the reference value is given by a pair of terms:
the difference Dik = (xik + Ck) - xRk = xik - xwk and its expanded uncertainty Uik (coverage factor: 2), Uik = 2(uik2 - uRk2 + uAk2)1/2.
UAk represents the artefact uncertainty which takes into account uncorrelated errors including instability of the artefact. UAk values are given in the following table:


The calculation of the degree of equivalence between two laboratories i and j is not recommended for comparisons involving several material standards, since it cannot be expressed with a single pair of terms.
It would have to be calculated separately for each gauge block k and would then be given by a pair of terms:
the difference Dijk = xik - xjk and its expanded uncertainty Uijk (coverage factor: 2), Uijk = 2(uik2 + ujk2)1/2.

 

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MEASURAND : Central length of long steel gauge blocks measured by interferometry according to ISO 3650

NOMINAL VALUES : 4 gauge blocks from 175 mm to 900 mm including two different 500 mm gauge blocks

xik : result of measurement carried out by laboratory i for gauge block with nominal length Lk expressed as the deviation from nominal length in nm
uik : combined standard uncertainty of xik reported by laboratory i

Because the SMU data is known to contain errors and is not representative of their standard measurement technique, it was decided to withdraw the data from the comparison, see page 26 of the Final Report.