Vogl J.,BAM |
Kipphardt H.,BAM |
Del Rocio Arvizu Torres M.,CENAM |
Manzano J.V.L.,CENAM |
And 15 more authors.
Metrologia | Year: 2014
The measurement of the purity of zinc based on the determination of six analytes is reported. Each participant was asked to report one result for the sum of the six requested impurities and the individual results for the six impurities. The results had to be reported in mass fractions, accompanied by a full uncertainty statement including a combined standard uncertainty and an expanded uncertainty with a coverage factor applied. Each participant was free to use any suitable method(s) for the measurement of the individual impurities. In case several methods were used for one specific impurity, only one (composite) result had to be reported. For Cd and Ni a spread unusually high for IDMS was observed in parallel measurements. This spread is reflected in the relative uncertainties for Cd and Ni, which are untypically large for double IDMS analysis. For the purpose of impurity analysis in zinc, comparability of measurement results for aluminium as an analyte is possible within the target uncertainty of 30 %.
News Article | November 29, 2016
NIST’s Patrick Abbott with one of the two smaller balances, used for the vacuum-to-air studies. Credit: National Institute of Standards and Technology When the kilogram, the world's basic unit of mass, gets a new definition in 2018, it will be based not on a physical artifact but a constant of nature. However, researchers will still need to "realize" the new definition, or translate it into a physical object, to make it possible to distribute the new standard to the laboratories and industries that need it. Of the two methods that are major contenders for this realization process – watt balances and silicon spheres – both require delicate measurements in vacuum. But most day-to-day mass measurements take place in regular air. This means that in order to disseminate the new kilogram, researchers must find reliable ways to compare a mass measured in vacuum to one measured in air. The world's national metrology institutes (NMIs) are each developing protocols to use in their own countries. But someone needs to check to make sure that their various methods are working well and getting comparable results. So the International Bureau of Weights and Measures (BIPM), an intergovernmental organization that has custody over the current official kilogram standard, asked a few NMIs to perform a dry run of their proposed methods of dissemination, as part of a pilot study to ensure that the plans for distributing the new definition are feasible. NIST just completed its dry run this month. "For this pilot study, each NMI has done a primary realization of a kilogram using either a watt balance or silicon sphere," says Patrick Abbott of the Mass and Force Group in NIST's Physical Measurement Laboratory. "The idea was: How well can we take that primary realization and pass it on?" Presently, the U.S. standard for mass is a plum-sized cylinder of platinum-iridium called K20, which is regularly calibrated against the world's current definition for the kilogram – the International Prototype Kilogram (IPK), housed at BIPM headquarters in Paris. After redefinition, K20 will be replaced by a new U.S. standard: the NIST-4 watt balance. NIST staff began the pilot study by calibrating a sample mass, made of platinum-iridium, in their watt balance. But the next step – transferring the calibration to masses in air – was a bit tricky. Air contains water and other impurities that are adsorbed by the surfaces of the masses used in the calibration process. So a mass measured in air will be slightly heavier than that same mass measured in vacuum. The nagging question for metrologists is, by how much? NIST researchers have prepared a couple of ways to overcome this problem. The first involves a room-sized double-decker instrument that uses magnetic levitation to float a mass in the air, to balance it against a mass in vacuum, and do a direct comparison of the two. Eventually, this instrument – called the Magnetic Suspension Mass Comparator – will be the preferred method of disseminating the kilogram. But it is still being constructed and tested, so it was not used in the dry run. The second method involves using a set of smaller instruments at NIST. These balances are able to compare the masses of two objects at a time in either regular air or in vacuum. Prior to the dry run, NIST staff used one of these apparatus to conduct a study gauging exactly how much mass is added to an object when it goes from vacuum to air, based on its material and the smoothness of its surface. With this information, the NIST researchers took the mass that had been calibrated using the watt balance, removed it from vacuum, and compared it – in air – to a pair of stainless steel working standards, of the type that might be used to calibrate customers' weights. The team applied the corrections that it gathered from its adsorption studies to make the jump from vacuum to air. To connect these findings to the current definition for mass, the team also measured all of these test masses against one of the official U.S. mass standards, whose definition is tied to the IPK. Abbott says he expects the BIPM will be ready to share results from the pilot study by early next year. Other participating NMIs include the National Research Council of Canada (NRC Canada) and France's Laboratoire National de Métrologie et d'Essais (LNE), each of which has its own watt balance, as well as the National Metrology Institute of Germany (PTB) and the National Metrology Institute of Japan (NMIJ), which use silicon spheres. Explore further: Vacuums provide solid ground for new definition of kilogram
Bailat C.J.,IRA |
Keightley J.,NPL |
Nedjadi Y.,IRA |
Mo L.,Australian Nuclear Science and Technology Organization |
And 21 more authors.
Metrologia | Year: 2014
Detailed uncertainty reporting is imperative for proficiency tests and comparison exercises since uncertainties need to be comparable and trusted by all the participants. Even though participants do their best to follow the Guide to the Expression of Uncertainty in Measurement1, ambiguities and divergences about uncertainty evaluation remain. Consequently, to analyze the situation, the CCRI (II) Uncertainties Working Group proposed a comparison exercise (CCRI(II)-S7) about the uncertainty evaluation of a relatively simple primary activity measurement: The standardization of a 60Co source by coincidence counting. To be able to understand how various NMIs calculate coincidence counting uncertainties, our study focused on two of the dominant uncertainty components commonly quoted for 4 αβ-γ coincidence counting in the International Reference System (SIR) submissions and Key Comparison exercises: Efficiency-extrapolation and weighing. Participants from twelve different laboratories were sent the same set of measurement data from the analysis of a 60Co solution standardized at the National Physical Laboratory (NPL). Our study demonstrated the extent of the different interpretations of the uncertainty components. Some factors causing large discrepancies were isolated and are discussed. Further studies of other techniques using a similar approach would be beneficial for the metrology community.
Yu K.M.,Korea Research Institute of Standards and Science |
Kim W.S.,Korea Research Institute of Standards and Science |
Han K.S.,Korea Research Institute of Standards and Science |
Hsu J.C.-M.,CMS |
And 11 more authors.
CPEM Digest (Conference on Precision Electromagnetic Measurements) | Year: 2014
A key comparison for the 10 Mo and 1 Go resistance, APMP.EM-K2, has been carried out by the Asia-Pacific Metrology Program(APMP) Regional Metrology Organization(RMO). The purpose is to establish the degree of equivalence of resistance among the national metrology institutes(NMIs) within APMP, in support of CIPM Mutual Recognition Agreement(MRA). The key comparison artifacts are three 10 Mo and three 1 Go resistance standards which was loaned from NIST and the 13 NMIs were participated in the comparison. The results will be presented at the conference. © 2014 IEEE.
Vogl J.,BAM |
Yim Y.-H.,KRISS |
Lee K.-S.,KRISS |
Goenaga-Infante H.,LCG Group |
And 12 more authors.
Metrologia | Year: 2014
Pb, present in trace amounts in a metal matrix sample, provides a real world test of the whole chemical and instrumental procedure. By comparing the Pb isotope ratio results obtained for the bronze sample with the Pb isotope ratio results from the Pb solution, potential biases arising from the processing of the bronze sample could be effectively identified and separated from the instrumental effects arising from the measurement and data processing protocol. Each participant was free to use any method they deemed suitable for measuring the individual isotope ratios. When several methods could be used by a participant, only one composite result was to be reported. The materials were selected so that the Pb isotopic compositions of the samples were within the natural range of the Pb isotopic compositions as tabulated by IUPAC. The results showed that single collector instruments can provide accurate Pb isotope ratio results in real samples; however matrix separation must be carried out. MC-ICPMS and MC-TIMS data are consistent with each other and agree to within 0.05 %. The corresponding uncertainties can be considered as realistic uncertainties and mainly range from 0.02 % to 0.08 %.
Kniel K.,PTB |
Osawa S.,NMIJ |
Chanthawong N.,NIMT |
Frazer R.,NGML |
And 2 more authors.
Metrologia | Year: 2014
The EURAMET TC-Length decided to run an intercomparison of involute gear standards as a regional comparison with non-European involvement. From the beginning 4 NMIs and 2 competent measurement institutes with worldwide reputation for gear metrology participated at this international comparison. One of the measurement institutes (NGLM) was registered as DI during the comparison. The circulation of the standards was scheduled for 11 months starting on August 2008 with the participation of 6 NMIs. The comparison of the presented results shows that discrepancies of the values of the compared measurands of some participating NMIs in some cases were too big and below the expectations, which leaves room for further improvement. The mishandling of the standards demonstrated the needs to improve the metrological skill in some cases or to take better precautions to avoid the improper handling of the transfer standards.
Horibe M.,NMIJ |
78th ARFTG Microwave Measurement Conference: High Power RF Measurement Techniques, ARFTG 2011 | Year: 2011
Coaxial air lines are air-dielectric transmission lines with highly accurate dimensions and are used as reference impedance standards in measurement and by the calibration laboratories. An LRL calibration kit (Anritsu 3657-1) is composed of five air lines to allow calibrations from a few hundred MHz to 70 GHz. The conventional traceability for the impedance is via the dimensional measurements of the air lines. The traceable standards are gages calibrated by the NIST. There is no standard method for establishing metrological traceability of electrical line impedance measurements. Horibe and Ridler provide a good basis for comparing the dimensional and scattering parameter measurements of the coaxial air lines. This paper reports the results of the bilateral comparison on the 3657-1 kit between the NMIJ (National Metrology Institute of Japan) and Anritsu. The dimensional difference between the two laboratories was compared using normalized error. The results of the electrical measurements of 1.85 mm coaxial air lines were also used for demonstration of metrological traceability. © 2011 IEEE.