BIPM Key Comparison Research Articles

Measurement of short gauge blocks by interferometry

Main textThis comparison piloted by CEM (ES), started in Nov 19 and concluded with some delay in February 21. Participants were CEM, PTB, SMD, METAS, INRIM and CMI.Two sets of eight gauge blocks in both steel and ceramic were circulated, covering the range 1.5 mm to 100 mm. The gauge blocks were of rectangular cross section and comply with the calibration grade K of ISO 3650 standard.Main measurand to be reported was the deviation ec of the central length lc from the nominal length ln of the gauge block. The arithmetic mean of the two values for wringing on both faces was considered as representative for ec In cases where only one face was wrung the corresponding value was reported as the result. As an auxiliary measurand the difference of the found deviations dc when the block was wrung to face A and face B, respectively, was reported.The uncertainty of measurement was evaluated according to the ISO Guide to the Expression of Uncertainty in Measurement. For efficient evaluation and subsequent assessment of CMC claims an uncertainty statement in the functional form was preferred.The key comparison reference value (KCRV) was calculated on a gauge-per-gauge basis as the weighted mean of the participants' results. The check for consistency of the comparison results with their associated uncertainties was based on Birge ratio and the degrees of equivalence for each laboratory and gauge block with respect to the KCRV were evaluated by using En values, in line with the WG-MRA-KC-report-template.Looking at the principal measurand, the central length ec, there were in total 11 values out of 96 not compatible with the final reference values, this representing the 11.4 % of the full set of results, considering both materials. With respect to the difference in central length from wringing in faces A and B, dc, there were in total 6 values not compatible with the reference value, this representing a 6.5 % of the 92 values communicated.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 https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCL, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

EURAMET Key Comparison EURAMET.M.D-K4.2020: Hydrometer calibration comparison from 600 kg/m3 to 2000 kg/m3

Main textThis report presents the results of the key comparison EURAMET.M.D-K4.2020 (EURAMET 1496) that covered the calibration of high-resolution hydrometers for liquid in the density range 600 kg/m3 to 2000 kg/m3 at the reference temperature of 20 oC. Nine laboratories participated in this key comparison, eight European national metrology institutes and one from Asia Pacific metrology: NIM from China. The participating laboratories were initially divided into two petals linked by two density laboratories: INRIM and PTB. In each petal, four similar transfer standards, hydrometers in the density range 600 kg/m3 to 2000 kg/m3 are used.The equipment used by the participants was found to have very similar characteristics. Most of the declared relative uncertainties were within the 5x10-5.The results of all participated laboratories have been linked to the CIPM key comparison CCM.D-K4 by INRIM and PTB. Discrepant results have been reported for three laboratories, which, however, do not affect their CMCs.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 https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Activity measurements of the radionuclides 99mTc, 18F and 64Cu for the POLATOM, Poland, in the ongoing comparisons BIPM.RI(II)-K4 series and KCRV update in the corresponding BIPM.RI(II)-K1 comparison

Main textIn 2016, comparisons of activity measurements of 99mTc, 18F and 64Cu using the Transfer Instrument of the International Reference System (SIRTI) took place at the National Centre for Nuclear Research, Radioisotope Centre (POLATOM, Poland). Ampoules containing about 33 kBq of 99mTc, 28 kBq of 18F and 110 kBq of 64Cu solutions were measured in the SIRTI for about 3, 5 and 1.5 half-lives, respectively. The POLATOM standardized the activity in the ampoules by 4π(LS)β–γ coincidence measurements. The comparisons, identifiers BIPM.RI(II)-K4.Tc-99m, BIPM.RI(II)-K4.F-18 and BIPM.RI(II)-K4.Cu-64, are linked to the corresponding BIPM.RI(II)-K1.Tc-99m, BIPM.RI(II)-K1.F-18 and BIPM.RI(II)-K1.Cu-64 comparisons. The BIPM.RI(II)-K1 99mTc and 18F key comparison reference values have been updated to include the latest BIPM.RI(II)-K4 linked results and degrees of equivalence for both comparison series have been evaluated.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 https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Bilateral comparison in torque transducer calibration between CENAM, Mexico and CEM, Spain, SIM.M.T-S1

Main textThe purpose of this comparison, SIM.M.T-S1, was to determine the results agreement of torque transducer calibration measurements between the two participating laboratories. The data evaluated in this comparison was the average reading and the uncertainty of the instrument under calibration for each torque target point. Clockwise and counter clockwise values were evaluated separately.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 https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Subsequent comparison of measurements of neutron source emission rate (2012) - CCRI(III)-K9.AmBe.1

Main textTo 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 https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Final report on the supplementary comparison EURAMET.AUV.V-S1

Main textThe Supplementary comparison EURAMET.AUV.V-S1 has been carried out within the framework of the CIPM MRA. The specific task of this comparison is the measurement of the magnitude and phase of the sensitivity of single-ended accelerometers in the medium frequency domain (10 to 10 000 Hz). The sensitivity is calculated as the ratio of the amplitude of the output of the accelerometer to the amplitude of the acceleration at its reference surface with secondary means in accordance with ISO 16063-21 "Methods for the calibration of vibration and shock transducers - Part 21: Vibration calibration by comparison to a reference transducer". The participating NMIs are BEV (Austria), BIM (Bulgaria), CMI (Czech Republic), IPQ (Portugal), KEBS (Kenya), METAS (Switzerland) and MIKES (Finland). BEV (Austria) was the pilot laboratory of the comparison. The measurements took place between October 2019 and February 2021. Three single-ended accelerometers were circulated. The final report includes the measurement results from the participants, information about their calibration methods, and the analysis leading to the assignation of equivalence degrees.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 https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCAUV, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Supplementary comparison for the traceability in high voltage capacitance and dissipation factor measurements (EURAMET.EM-S34)

Main textThe intercomparison consisted of calibrating the capacitance and loss factor (tan δ) of a set of reference capacitors at different voltage levels, including high voltage up to 200 kV, for frequencies between 50 Hz and 1kHz in low voltage measurements and 50 Hz in high voltage measurements.The travelling standards consisted of a set of four reference capacitors (TRC) with fixed input and grounding leads and the corresponding connection cables of the following rated characteristics:* System 1: 100 pF and rated voltage of 200 kV.* System 2: 100 pF and rated voltage of 700 V.* System 3: 500 nF and rated voltage of 10 V.* System 4: 5000 nF and rated voltage of 10 V.The coordinating laboratory was LCOE (Spain) and the participating institutes were LNE (France), VTT MIKES (Finland), RISE (Sweden), TÜBITAK UME (Türkiye), PTB (Germany) and LCOE (Spain). Participants used their best measurement procedures and setups in order to achieve their best calibration capabilities.Some of the institutes did not perform all the measurements, therefore comparison reference values are based sometimes in the results of only 4 institutes.Not all the laboratories measured at the same ambient temperature; to prevent this inconvenience and to be able to compare results, all capacitance values were corrected at 23 °C. The long drift of the high voltage capacitor of system 1, probably due to some small SF6 leakage, was also considered to calculate the CRV of each institute. Very good agreement between institutes is obtained for high voltage capacitance measurements (high voltage capacitance coefficient determination) and for low or high voltage dissipation factor measurements. Only a few low voltage measurements of capacitance are considered not compatible.Undertaking the work collaboratively through EURAMET proved to be an excellent tool to compare calibration and measurement capabilities of NMI and DI, as well as an opportunity for several institutes to improve their CMCs.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 https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Final report on GULFMET supplementary comparison of high voltage transformer measuring systems (GULFMET.EM-S6)

Main textA comparison of high voltage transformer measuring systems between SE "Ukrmetrteststandard" (Ukraine), TÜBİTAK (Turkey) and NMCC SASO (Saudi Arabia), conducted between November 2020 and December 2021. Voltage transformers ПЭТН-6/10 and НЛЛ-35 are used as the traveling standards and SE "Ukrmetrteststandard" acted as the pilot laboratory. Measurements were performed at a current from 6 kV to 35 kV at frequencies 50 Hz and 60 Hz.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 https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Final report on the supplementary comparison EURAMET.AUV.V-S2

Main textThe supplementary comparison EURAMET.AUV.V-S2 has been carried out within the framework of the CIPM MRA. The specific task of this comparison is the measurement of the magnitude and phase of the sensitivity of single-ended accelerometers in the medium frequency domain (10 Hz to 10000 Hz). The sensitivity is calculated as the ratio of the amplitude of the output of the accelerometer to the amplitude of the acceleration at its reference surface with secondary means in accordance with ISO 16063-21 "Methods for the calibration of vibration and shock transducers - Part 21: Vibration calibration by comparison to a reference transducer". The participating NMIs are BEV (Austria), and METAS (Switzerland). BEV (Austria) was the pilot laboratory of this bilateral comparison. The measurements took place between November 2021 and January 2022. A single-ended accelerometer was circulated. This report includes the measurement results, information about calibration methods, and the analysis leading to the assignation of equivalence degrees.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 https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCAUV, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Supplementary comparison study - measurement capabilities for the quantification of ethanol in water

Main textThe accurate quantification of ethanol in water is essential for forensic applications such as blood and breath alcohol testing and for commercial applications such as the assessment of alcoholic beverages.The intercomparison EURAMET.QM-S14 is part of a capacity building project named ALCOREF "Certified forensic alcohol reference materials" [1] that is running within the European Metrology Programme for Innovation and Research (EMPIR) [2]. The intercomparison should allow project partners and other interested National Metrology Institutes (NMIs) and Designated Institutes (DIs) to benchmark their analytical methods for the quantification of ethanol in water. The study plan was agreed by the European Association of National Metrology Institutes (EURAMET) Subcommittee Bio- and Organic Analysis (SCBOA) and the Organic Analysis Working Group (OAWG) of the Comité Consultatif pour la Quantité de Matière (CCQM) in February and April 2019, respectively. The intercomparison was coordinated by BAM. Two concentration levels relevant for the calibration and verification of evidential breath alcohol analysers were distributed to study participants. Fifteen institutes from 15 countries registered for the intercomparison and returned results. Participants mostly applied gas chromatography with flame ionisation detection (GC-FID) or mass spectroscopy (GC-MS), one participant used titrimetry and one participant employed a test bench for breath analyser calibration ("bubble train"). Participants did either in-house purity assessment of their commercial ethanol calibrants by Karl-Fischer titration, chromatographic methods, quantitative nuclear magnetic resonance spectroscopy (qNMR) and/or density measurements; or they used ethanol/water Certified Reference Materials (CRMs) from NMIs/DIs for calibration.CCQM OAWG agreed to use a consensus value from participants' results that utilizes the reported uncertainties as Key Comparison Reference Value (KCRV). The Gaussian Random effects model with Hierarchical Bayesian solution (HB-REM) is a reasonable approach in this case. The KCRVs and Degrees of Equivalence (DoEs) were calculated with the NIST consensus builder version 1.2 Hierarchical Bayes procedure [3].Successful participation in the interlaboratory comparison has demonstrated the capabilities in determining the mass fraction of ethanol in aqueous matrices in the range 0.1 mg/g to 8 mg/g. Fourteen out of 15 participants have successfully quantified both samples, one participant successfully quantified only the lower-level (0.6 mg/g) sample.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 https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Comparison in 50 kg Mass Standard SIM.M.M-S12

Main textThis report describes the results of the supplementary comparison SIM.M.M-S12, planned and carried out to evaluate the difference among the laboratories and the reference in the calibration of 50 kg mass standards.This comparison was undertaken by CESMEC (Chile) as pilot laboratory; CENAM (México) as support laboratory; and INACAL (Peru).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 https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

AFRIMETS key comparison (AFRIMETS.M.M-K7) of five stainless steel mass standards: 5 kg, 100 g, 10 g, 5 g and 500 mg

Main textThis key comparison is based on a decision of TCM of AFRIMETS on July 2015 in South Africa. TCM agreed that NIS-Egypt will pilot this comparison by providing the technical support and contributing to the link to the CCM comparison. The comparison consisted of one set of five stainless steel mass standards with nominal values: 5 kg, 100 g, 10 g, 5 g and 500 mg. These masses are owned by the LPEE-LNM and chosen to be the transfer mass standards. The pilot laboratory (NIS) measured the volume and the magnetic properties of the standards before the circulation and had reported these values to the participants. The pilot laboratory has also verified the stability of all travelling standards for one year.Six laboratories measured the set of travelling standards between September 2018 and December 2019.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 https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Supplementary comparison for the traceability of AC high voltage reference measuring systems up to 200 kV (EURAMET.EM-S33)

Main textThe intercomparison consisted of calibrating a High Voltage Travelling Reference Measuring System, TRMS, using peak and rms voltage values, at the frequency of 50 Hz and with voltages of 750 V, 1 kV, 40 kV, 80 kV, 120 kV, 160 kV and 200 kV.The TRMS consisted of a capacitive divider with fixed input and grounding leads, a coaxial cable, a HP 3458A digital multimeter and a computer with a printer. The TRMS had two ranges, 20 kV and 200 kV, depending on the low voltage arm connected to the high voltage capacitor. The TRMS included the low voltage digital multimeter, in such a way that the measuring error of high voltage TRMS should be measured to determine the scale factor of the high voltage divider. Intercomparison results are expressed as the scale factor of the travelling high voltage capacitive divider, the scale factor is dimensionless.Complementary low voltage measurements were also performed to check how the peak voltage is evaluated when harmonics or distortion are superimposed to sinusoidal waveforms. To evaluate this performance an arbitrary waveform generator was included among the travelling devices in such a way that it was possible to compare the peak voltage measured by the TRMS using the provided digital multimeter and the specific intercomparison software and the peak voltage measured by each participant.The coordinating laboratory was LCOE (Spain) and the participating institutes were LNE (France), VTT MIKES (Finland), RISE (Sweden), TÜBITAK UME (Türkiye), PTB (Germany), BIM (Bulgaria), INRiM (Italy), VSL (Netherlands), VNIMS (Russia) and LCOE (Spain).Results of the comparison proved the calibration and measurement capabilities, CMCs, of the participants in the field of high voltage AC measurement, especially when performing peak hv measurements up to 200 kV with expanded uncertainties in the range of 40 mV/V to 80 mV/V.The discrepancy between the results of the two labs claiming the lowest uncertainties, PTB and VTT, was on some measurements significantly larger than the respective uncertainties. One of these labs redesigned its measuring system and a subsequent bilateral comparison arranged between PTB and VTT solved the discrepancy.Undertaking the work collaboratively through EURAMET proved to be an excellent tool to compare calibration and measurement capabilities of NMI and DI, as well as an opportunity for several institutes to improve their CMCs.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 https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Report on APMP key comparison: calibration of line scale (APMP.L-K7)

Main textA regional key comparison on calibration of a line scale, APMP.L-K7 was conducted. KRISS acted as the pilot laboratory, and a total of 15 National Metrology Institutes, (10 from APMP, 3 from EURAMET, 1 from SIM, and 1 from AFRIMETS) have participated in this comparison, where a 500 mm line scale made of low thermal expansion material was circulated during the period from April 2015 to December 2016. This document presents the approved report of the results of this comparison.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 https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCL, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

International comparison CCQM-K165: dimethyl sulfide in nitrogen at 5 nmol mol-1

Main textDimethyl sulfide (DMS) is produced mainly by the metabolic activities of oceanic phytoplankton and the most abundant natural sulfur compound in the atmosphere. DMS plays an important role for climate change since it is oxidized and forms sulfate aerosols in the atmosphere, affecting the Earth's radiation budget directly and indirectly. DMS is designated as one of the target reactive gases and monitored in the World Meteorological Organization (WMO) Global Atmospheric Watch (GAW) programme. It is important to accurately monitor its global background levels with SI traceability for better understanding of the role of DMS in climate change. This comparison is organized by Korea Research Institute of Standards and Science (KRISS). Gas mixtures gravimetrically prepared by KRISS are used for demonstrating measurement equivalence at the highest metrological level. This comparison (Track C) is designed to underpin participants' measurement capabilities of trace level DMS in nitrogen at the nominal amount fraction of 5 nmol mol-1.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 https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Report on the comparison of the realisations of the ITS-90 over the range 234.315 6 K to 933.473 K between Centro Español de Metrología (CEM) and Instituto Nacional de Metrología (SIM.T-K9.2)

Main textThe comparison of the realization of the International Temperature Scale of 1990 (ITS- 90) over the range 234,315 6 K (triple point of mercury) to 993,473 K (freezing point of aluminium) in the National Metrology Institutes of Spain (Centro Español de Metrología - CEM) and Colombia (Instituto Nacional de Metrología - INM) has been organized with the aim to provide support to the Calibration Measurement Capabilities claimed by INM in this range. Due to the participation of CEM in the regional comparison EUROMET.T-K9, the linkage with the corresponding key comparison, CCT-K9, is possible.The measurements of this comparison were performed during September 2018 and June 2020.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 https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCT, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Results of the EURAMET.RI(II)-K2.Ho-166 key comparison for the activity of the radionuclide 166Ho per unit mass of aqueous solution

Main textThis is the final report for the EURAMET.RI(II)-K2.Ho-166 key comparison of the activity of the radionuclide 166Ho per unit mass of aqueous solution which was organized in 2017 by Czech Metrology Institute (CMI) within the joint research project "Metrology for clinical implementation of dosimetry in molecular radiotherapy" (MRTDosimetry; 15HLT06) of the European Metrology Programme for Innovation and Research (EMPIR). The key comparison reference value of (2623.6 ± 3.6) kBq·g-1 was determined from the results of three participants at the reference time of 1 December 2017 00:00 UTC. The details of the comparison are presented and analysed in this paper.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 https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

The CCL-K11 ongoing key comparison. Final report for 2021

Main textFour lasers from three national metrological institutes (NMIs) were compared in the year 2021 as part of the CCL-K11 ongoing key comparison, initiated by the 13th meeting of the Comité Consultative des Longuers (CCL) in 2007. The absolute frequency of R(127) 11-5 (≈633 nm) and of R(56) 32-0 (≈532 nm) transitions of molecular iodine was measured for these lasers following the technical protocol for CCL-K11. The results of these measurements are compiled in the present report. The comparison reports, as communicated by each participant, are included in the main document.For the very first time in this key-comparison a standard working on a different operating principle is reported. CMI participated with a frequency doubled Nd:YAG laser stabilized to an iodine transition (Designation: CMI-YAG1). The technical protocol was deliberately designed to accommodate artefacts of different wavelengths in a common framework. Moreover, CMI participated with a second laser standard also. The institute has different CMC entries for the two laser types. Both entries refer to the same service category of highest metrological level, but are technically well separated. Due to the layout of CCL-K11 the KCRV is immune to a multiple participation of a single NMI. It was thus considered to include both measurements in this report.This document constitutes the 11th final report for the ongoing key comparison CCL-K11.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 https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCL, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

GULFMET.EM.S1 Comparison of Resistance Standards at 100 Ω

Main textComparison of Resistance Standards at 100 Ω between TUBITAK (Turkey), EMI (UAE), NMCC SASO (Saudi Arabia), SCL (Hong Kong), IMBIH Bosnia and HerzegovinaTo 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 https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Final report on GULFMET supplementary comparison of high current transformer measuring systems (GULFMET.EM-S7)

Main textA comparison of high current transformer measuring systems between SE "Ukrmetrteststandard" (Ukraine), TÜBİTAK (Turkey) and NMCC SASO (Saudi Arabia), conducted between December 2020 and December 2021. Current transformer СА535/2 is used as the traveling standard and SE "Ukrmetrteststandard" acted as the pilot laboratory. Measurements were performed at a current from 5 A to 4000 A at frequencies 50 Hz and 60 Hz.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 https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).