The Experts below are selected from a list of 23742 Experts worldwide ranked by ideXlab platform
Jon R. Pratt - One of the best experts on this subject based on the ideXlab platform.
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evaluation of the accuracy consistency and stability of measurements of the Planck Constant used in the redefinition of the international system of units
Metrologia, 2018Co-Authors: Antonio Possolo, Jon R. Pratt, Stephan Schlamminger, Sara Stoudt, Carl J. WilliamsAbstract:The Consultative Committee for Mass and related quantities (ccm), of the International Committee for weights and measures (cipm), has recently declared the readiness of the community to support the redefinition of the international system of units (SI) at the next meeting of the General Conference on Weights and Measures (cgpm) scheduled for November, 2018. Such redefinition will replace the international prototype of the Kilogram (ipk), as the definition and sole primary realization of the unit of mass, with a definition involving the Planck Constant, h. This redefinition in terms of a fundamental Constant of nature will enable widespread primary realizations not only of the kilogram but also of its multiples and sub-multiples, best to address the full range of practical needs in the measurement of mass. We review and discuss the statistical models and statistical data reductions, uncertainty evaluations, and substantive arguments that support the verification of several technical preconditions for the redefinition that the ccm has established, and whose verification the ccm has affirmed. These conditions relate to the accuracy and mutual consistency of qualifying measurement results. We review also an issue that has surfaced only recently, concerning the convergence toward a stable value, of the historical values that the task group on fundamental Constants of the committee on Data for Science and Technology codata-tgfc has recommended for h over the years, even though the ccm has not deemed this issue to be relevant. We conclude that no statistically significant trend can be substantiated for these recommended values, but note that cumulative consensus values that may be derived from the historical measurement results for h seem to have converged while continuing to exhibit fluctuations that are typical of a process in statistical control. Finally, we argue that the most recent consensus value derived from the best measurements available for h, obtained using either a Kibble balance or the xrcd method, is reliable and has uncertainty no larger than the uncertainties surrounding the current primary and secondary realizations of the unit of mass, hence that no credible technical impediments stand in the way of the redefinition of the unit of mass in terms of a fixed value of h.
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measurement of the Planck Constant at the national institute of standards and technology from 2015 to 2017
Metrologia, 2017Co-Authors: D. Haddad, L. S. Chao, David B. Newell, Jon R. Pratt, Carl J. Williams, F Seifert, Antonio Possolo, Stephan SchlammingerAbstract:Researchers at the National Institute of Standards and Technology (NIST) have measured the value of the Planck Constant to be J s (relative standard uncertainty ). The result is based on over 10 000 weighings of masses with nominal values ranging from 0.5 kg to 2 kg with the Kibble balance NIST-4. The uncertainty has been reduced by more than twofold relative to a previous determination because of three factors: (1) a much larger data set than previously available, allowing a more realistic, and smaller, Type A evaluation; (2) a more comprehensive measurement of the back action of the weighing current on the magnet by weighing masses up to 2 kg, decreasing the uncertainty associated with magnet non-linearity; (3) a rigorous investigation of the dependence of the geometric factor on the coil velocity reducing the uncertainty assigned to time-dependent leakage of current in the coil.
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Invited Article: A precise instrument to determine the Planck Constant, and the future kilogram
Review of Scientific Instruments, 2016Co-Authors: D. Haddad, Frank Seifert, L. S. Chao, David B. Newell, Jon R. Pratt, Carl J. Williams, Stephan SchlammingerAbstract:A precise instrument, called a watt balance, compares mechanical power measured in terms of the meter, the second, and the kilogram to electrical power measured in terms of the volt and the ohm. A direct link between mechanical action and the Planck Constant is established by the practical realization of the electrical units derived from the Josephson and the quantum Hall effects. We describe in this paper the fourth-generation watt balance at the National Institute of Standards and Technology (NIST), and report our initial determination of the Planck Constant obtained from data taken in late 2015 and the beginning of 2016. A comprehensive analysis of the data and the associated uncertainties led to the SI value of the Planck Constant, h = 6.626 069 83(22) × 10(-34) J s. The relative standard uncertainty associated with this result is 34 × 10(-9).
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a summary of the Planck Constant measurements using a watt balance with a superconducting solenoid at nist
Metrologia, 2015Co-Authors: Stephan Schlamminger, D. Haddad, L. S. Chao, David B. Newell, R Liu, Edwin R Williams, R L Steiner, F Seifert, Jon R. PrattAbstract:Researchers at the National Institute of Standards and Technology have been using a watt balance, NIST-3, to measure the Planck Constant h for over ten years. Two recently published values disagree by more than one standard uncertainty. The motivation for the present short communication is twofold. First, we correct the latest published number to take into account a recently discovered systematic error in mass dissemination at the Bureau International des Poids et Mesures. Second, we provide guidance on how to combine the two numbers into one final result. In order to adequately reflect the discrepancy, we added an additional systematic uncertainty to the published uncertainty budgets. The final value of h measured with NIST-3 is h = 6.626 069 36(37) × 10−34 J s. This result is 77(57) × 10−9 fractionally higher than h90. Each number in parentheses gives the value of the standard uncertainty in the last two digits of the respective value and h90 is the conventional value of the Planck Constant given by , where KJ-90 and RK-90 denote the conventional values of the Josephson and von Klitzing Constants, respectively.
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determination of the Planck Constant using a watt balance with a superconducting magnet system at the national institute of standards and technology
Metrologia, 2014Co-Authors: S Schlamminger, D. Haddad, L. S. Chao, David B. Newell, R Liu, R L Steiner, F Seifert, Jon R. PrattAbstract:For the past two years, measurements have been performed with a watt balance at the National Institute of Standards and Technology (NIST) to determine the Planck Constant. A detailed analysis of these measurements and their uncertainties has led to the value h = 6.626 069 79(30) × 10−34 J s. The relative standard uncertainty is 45 × 10−9. This result is 141 × 10−9 fractionally higher than h90. Here h90 is the conventional value of the Planck Constant given by , where KJ-90 and RK-90 denote the conventional values of the Josephson and von Klitzing Constants, respectively.
David B. Newell - One of the best experts on this subject based on the ideXlab platform.
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measurement of the Planck Constant at the national institute of standards and technology from 2015 to 2017
Metrologia, 2017Co-Authors: D. Haddad, L. S. Chao, David B. Newell, Jon R. Pratt, Carl J. Williams, F Seifert, Antonio Possolo, Stephan SchlammingerAbstract:Researchers at the National Institute of Standards and Technology (NIST) have measured the value of the Planck Constant to be J s (relative standard uncertainty ). The result is based on over 10 000 weighings of masses with nominal values ranging from 0.5 kg to 2 kg with the Kibble balance NIST-4. The uncertainty has been reduced by more than twofold relative to a previous determination because of three factors: (1) a much larger data set than previously available, allowing a more realistic, and smaller, Type A evaluation; (2) a more comprehensive measurement of the back action of the weighing current on the magnet by weighing masses up to 2 kg, decreasing the uncertainty associated with magnet non-linearity; (3) a rigorous investigation of the dependence of the geometric factor on the coil velocity reducing the uncertainty assigned to time-dependent leakage of current in the coil.
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Invited Article: A precise instrument to determine the Planck Constant, and the future kilogram
Review of Scientific Instruments, 2016Co-Authors: D. Haddad, Frank Seifert, L. S. Chao, David B. Newell, Jon R. Pratt, Carl J. Williams, Stephan SchlammingerAbstract:A precise instrument, called a watt balance, compares mechanical power measured in terms of the meter, the second, and the kilogram to electrical power measured in terms of the volt and the ohm. A direct link between mechanical action and the Planck Constant is established by the practical realization of the electrical units derived from the Josephson and the quantum Hall effects. We describe in this paper the fourth-generation watt balance at the National Institute of Standards and Technology (NIST), and report our initial determination of the Planck Constant obtained from data taken in late 2015 and the beginning of 2016. A comprehensive analysis of the data and the associated uncertainties led to the SI value of the Planck Constant, h = 6.626 069 83(22) × 10(-34) J s. The relative standard uncertainty associated with this result is 34 × 10(-9).
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a summary of the Planck Constant measurements using a watt balance with a superconducting solenoid at nist
Metrologia, 2015Co-Authors: Stephan Schlamminger, D. Haddad, L. S. Chao, David B. Newell, R Liu, Edwin R Williams, R L Steiner, F Seifert, Jon R. PrattAbstract:Researchers at the National Institute of Standards and Technology have been using a watt balance, NIST-3, to measure the Planck Constant h for over ten years. Two recently published values disagree by more than one standard uncertainty. The motivation for the present short communication is twofold. First, we correct the latest published number to take into account a recently discovered systematic error in mass dissemination at the Bureau International des Poids et Mesures. Second, we provide guidance on how to combine the two numbers into one final result. In order to adequately reflect the discrepancy, we added an additional systematic uncertainty to the published uncertainty budgets. The final value of h measured with NIST-3 is h = 6.626 069 36(37) × 10−34 J s. This result is 77(57) × 10−9 fractionally higher than h90. Each number in parentheses gives the value of the standard uncertainty in the last two digits of the respective value and h90 is the conventional value of the Planck Constant given by , where KJ-90 and RK-90 denote the conventional values of the Josephson and von Klitzing Constants, respectively.
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determination of the Planck Constant using a watt balance with a superconducting magnet system at the national institute of standards and technology
Metrologia, 2014Co-Authors: S Schlamminger, D. Haddad, L. S. Chao, David B. Newell, R Liu, R L Steiner, F Seifert, Jon R. PrattAbstract:For the past two years, measurements have been performed with a watt balance at the National Institute of Standards and Technology (NIST) to determine the Planck Constant. A detailed analysis of these measurements and their uncertainties has led to the value h = 6.626 069 79(30) × 10−34 J s. The relative standard uncertainty is 45 × 10−9. This result is 141 × 10−9 fractionally higher than h90. Here h90 is the conventional value of the Planck Constant given by , where KJ-90 and RK-90 denote the conventional values of the Josephson and von Klitzing Constants, respectively.
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towards a fixed value of the Planck Constant reproducibility and an updated nist 3 watt balance
Conference on Precision Electromagnetic Measurements, 2012Co-Authors: D. Haddad, David B. Newell, Stephan Schlamminger, R Liu, Edwin R Williams, Jon R. PrattAbstract:The scientific community is presently engaged in a historic attempt to fix the value of the Planck Constant h so that it might ultimately serve as a base Constant in a revised system of units. To assist this effort, NIST is examining its existing watt balance experiment, NIST-3, and will measure h once again, aiming at a final rigorous test of reproducibility. The main objectives are to modify and update the existing apparatus so that it can be used both to measure the Planck Constant and to support other experiments related to the mise en pratique for mass, to attempt a determination of the Planck Constant that is largely independent of previous NIST results, and to probe the discrepancy between the value of h measured in 2007 and other latest published results through a careful re-examination of the NIST-3 measurement procedures and uncertainty budget.
Stephan Schlamminger - One of the best experts on this subject based on the ideXlab platform.
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evaluation of the accuracy consistency and stability of measurements of the Planck Constant used in the redefinition of the international system of units
Metrologia, 2018Co-Authors: Antonio Possolo, Jon R. Pratt, Stephan Schlamminger, Sara Stoudt, Carl J. WilliamsAbstract:The Consultative Committee for Mass and related quantities (ccm), of the International Committee for weights and measures (cipm), has recently declared the readiness of the community to support the redefinition of the international system of units (SI) at the next meeting of the General Conference on Weights and Measures (cgpm) scheduled for November, 2018. Such redefinition will replace the international prototype of the Kilogram (ipk), as the definition and sole primary realization of the unit of mass, with a definition involving the Planck Constant, h. This redefinition in terms of a fundamental Constant of nature will enable widespread primary realizations not only of the kilogram but also of its multiples and sub-multiples, best to address the full range of practical needs in the measurement of mass. We review and discuss the statistical models and statistical data reductions, uncertainty evaluations, and substantive arguments that support the verification of several technical preconditions for the redefinition that the ccm has established, and whose verification the ccm has affirmed. These conditions relate to the accuracy and mutual consistency of qualifying measurement results. We review also an issue that has surfaced only recently, concerning the convergence toward a stable value, of the historical values that the task group on fundamental Constants of the committee on Data for Science and Technology codata-tgfc has recommended for h over the years, even though the ccm has not deemed this issue to be relevant. We conclude that no statistically significant trend can be substantiated for these recommended values, but note that cumulative consensus values that may be derived from the historical measurement results for h seem to have converged while continuing to exhibit fluctuations that are typical of a process in statistical control. Finally, we argue that the most recent consensus value derived from the best measurements available for h, obtained using either a Kibble balance or the xrcd method, is reliable and has uncertainty no larger than the uncertainties surrounding the current primary and secondary realizations of the unit of mass, hence that no credible technical impediments stand in the way of the redefinition of the unit of mass in terms of a fixed value of h.
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measurement of the Planck Constant at the national institute of standards and technology from 2015 to 2017
Metrologia, 2017Co-Authors: D. Haddad, L. S. Chao, David B. Newell, Jon R. Pratt, Carl J. Williams, F Seifert, Antonio Possolo, Stephan SchlammingerAbstract:Researchers at the National Institute of Standards and Technology (NIST) have measured the value of the Planck Constant to be J s (relative standard uncertainty ). The result is based on over 10 000 weighings of masses with nominal values ranging from 0.5 kg to 2 kg with the Kibble balance NIST-4. The uncertainty has been reduced by more than twofold relative to a previous determination because of three factors: (1) a much larger data set than previously available, allowing a more realistic, and smaller, Type A evaluation; (2) a more comprehensive measurement of the back action of the weighing current on the magnet by weighing masses up to 2 kg, decreasing the uncertainty associated with magnet non-linearity; (3) a rigorous investigation of the dependence of the geometric factor on the coil velocity reducing the uncertainty assigned to time-dependent leakage of current in the coil.
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Invited Article: A precise instrument to determine the Planck Constant, and the future kilogram
Review of Scientific Instruments, 2016Co-Authors: D. Haddad, Frank Seifert, L. S. Chao, David B. Newell, Jon R. Pratt, Carl J. Williams, Stephan SchlammingerAbstract:A precise instrument, called a watt balance, compares mechanical power measured in terms of the meter, the second, and the kilogram to electrical power measured in terms of the volt and the ohm. A direct link between mechanical action and the Planck Constant is established by the practical realization of the electrical units derived from the Josephson and the quantum Hall effects. We describe in this paper the fourth-generation watt balance at the National Institute of Standards and Technology (NIST), and report our initial determination of the Planck Constant obtained from data taken in late 2015 and the beginning of 2016. A comprehensive analysis of the data and the associated uncertainties led to the SI value of the Planck Constant, h = 6.626 069 83(22) × 10(-34) J s. The relative standard uncertainty associated with this result is 34 × 10(-9).
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a summary of the Planck Constant measurements using a watt balance with a superconducting solenoid at nist
Metrologia, 2015Co-Authors: Stephan Schlamminger, D. Haddad, L. S. Chao, David B. Newell, R Liu, Edwin R Williams, R L Steiner, F Seifert, Jon R. PrattAbstract:Researchers at the National Institute of Standards and Technology have been using a watt balance, NIST-3, to measure the Planck Constant h for over ten years. Two recently published values disagree by more than one standard uncertainty. The motivation for the present short communication is twofold. First, we correct the latest published number to take into account a recently discovered systematic error in mass dissemination at the Bureau International des Poids et Mesures. Second, we provide guidance on how to combine the two numbers into one final result. In order to adequately reflect the discrepancy, we added an additional systematic uncertainty to the published uncertainty budgets. The final value of h measured with NIST-3 is h = 6.626 069 36(37) × 10−34 J s. This result is 77(57) × 10−9 fractionally higher than h90. Each number in parentheses gives the value of the standard uncertainty in the last two digits of the respective value and h90 is the conventional value of the Planck Constant given by , where KJ-90 and RK-90 denote the conventional values of the Josephson and von Klitzing Constants, respectively.
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towards a fixed value of the Planck Constant reproducibility and an updated nist 3 watt balance
Conference on Precision Electromagnetic Measurements, 2012Co-Authors: D. Haddad, David B. Newell, Stephan Schlamminger, R Liu, Edwin R Williams, Jon R. PrattAbstract:The scientific community is presently engaged in a historic attempt to fix the value of the Planck Constant h so that it might ultimately serve as a base Constant in a revised system of units. To assist this effort, NIST is examining its existing watt balance experiment, NIST-3, and will measure h once again, aiming at a final rigorous test of reproducibility. The main objectives are to modify and update the existing apparatus so that it can be used both to measure the Planck Constant and to support other experiments related to the mise en pratique for mass, to attempt a determination of the Planck Constant that is largely independent of previous NIST results, and to probe the discrepancy between the value of h measured in 2007 and other latest published results through a careful re-examination of the NIST-3 measurement procedures and uncertainty budget.
R L Steiner - One of the best experts on this subject based on the ideXlab platform.
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a summary of the Planck Constant measurements using a watt balance with a superconducting solenoid at nist
Metrologia, 2015Co-Authors: Stephan Schlamminger, D. Haddad, L. S. Chao, David B. Newell, R Liu, Edwin R Williams, R L Steiner, F Seifert, Jon R. PrattAbstract:Researchers at the National Institute of Standards and Technology have been using a watt balance, NIST-3, to measure the Planck Constant h for over ten years. Two recently published values disagree by more than one standard uncertainty. The motivation for the present short communication is twofold. First, we correct the latest published number to take into account a recently discovered systematic error in mass dissemination at the Bureau International des Poids et Mesures. Second, we provide guidance on how to combine the two numbers into one final result. In order to adequately reflect the discrepancy, we added an additional systematic uncertainty to the published uncertainty budgets. The final value of h measured with NIST-3 is h = 6.626 069 36(37) × 10−34 J s. This result is 77(57) × 10−9 fractionally higher than h90. Each number in parentheses gives the value of the standard uncertainty in the last two digits of the respective value and h90 is the conventional value of the Planck Constant given by , where KJ-90 and RK-90 denote the conventional values of the Josephson and von Klitzing Constants, respectively.
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determination of the Planck Constant using a watt balance with a superconducting magnet system at the national institute of standards and technology
Metrologia, 2014Co-Authors: S Schlamminger, D. Haddad, L. S. Chao, David B. Newell, R Liu, R L Steiner, F Seifert, Jon R. PrattAbstract:For the past two years, measurements have been performed with a watt balance at the National Institute of Standards and Technology (NIST) to determine the Planck Constant. A detailed analysis of these measurements and their uncertainties has led to the value h = 6.626 069 79(30) × 10−34 J s. The relative standard uncertainty is 45 × 10−9. This result is 141 × 10−9 fractionally higher than h90. Here h90 is the conventional value of the Planck Constant given by , where KJ-90 and RK-90 denote the conventional values of the Josephson and von Klitzing Constants, respectively.
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history and progress on accurate measurements of the Planck Constant
Reports on Progress in Physics, 2013Co-Authors: R L SteinerAbstract:The measurement of the Planck Constant, h, is entering a new phase. The CODATA 2010 recommended value is 6.626 069 57 × 10(-34) J s, but it has been a long road, and the trip is not over yet. Since its discovery as a fundamental physical Constant to explain various effects in quantum theory, h has become especially important in defining standards for electrical measurements and soon, for mass determination. Measuring h in the International System of Units (SI) started as experimental attempts merely to prove its existence. Many decades passed while newer experiments measured physical effects that were the influence of h combined with other physical Constants: elementary charge, e, and the Avogadro Constant, N(A). As experimental techniques improved, the precision of the value of h expanded. When the Josephson and quantum Hall theories led to new electronic devices, and a hundred year old experiment, the absolute ampere, was altered into a watt balance, h not only became vital in definitions for the volt and ohm units, but suddenly it could be measured directly and even more accurately. Finally, as measurement uncertainties now approach a few parts in 10(8) from the watt balance experiments and Avogadro determinations, its importance has been linked to a proposed redefinition of a kilogram unit of mass. The path to higher accuracy in measuring the value of h was not always an example of continuous progress. Since new measurements periodically led to changes in its accepted value and the corresponding SI units, it is helpful to see why there were bumps in the road and where the different branch lines of research joined in the effort. Recalling the bumps along this road will hopefully avoid their repetition in the upcoming SI redefinition debates. This paper begins with a brief history of the methods to measure a combination of fundamental Constants, thus indirectly obtaining the Planck Constant. The historical path is followed in the section describing how the improved techniques and discoveries in quantum mechanics steadily reduced the uncertainty of h. The central part of this review describes the technical details of the watt balance technique, which is a combination of the mechanical and electronic measurements that now determine h as a direct result, i.e. not requiring measured values of additional fundamental Constants. The first technical section describes the basics and some of the common details of many watt balance designs. Next is a review of the ongoing advances at the (currently) seven national metrology institutions where these experiments are pursued. A final summary of the recent h determinations of the last two decades shows how history keeps repeating itself; there is again a question of whether there is a shift in the newest results, albeit at uncertainties that are many orders of magnitude less than the original experiments. The conclusion is that there is room for further development to resolve these differences and find new ideas for a watt balance system with a more universal application. Since the next generation of watt balance experiments are expected to become kilogram realization standards, the historical record suggests that there is yet a need for proof that Planck Constant results are finally reproducible at an acceptable uncertainty.
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towards an electronic kilogram an improved measurement of the Planck Constant and electron mass
Metrologia, 2005Co-Authors: R L Steiner, Edwin R Williams, David B. NewellAbstract:The electronic kilogram project of NIST has improved the watt balance method to obtain a new determination of the Planck Constant h by measuring the ratio of the SI unit of power W to the electrical realization unit W90, based on the conventional values for the Josephson Constant KJ−90 and von Klitzing Constant RK−90. The value h = 6.626 069 01(34) × 10−34 J s verifies the NIST result from 1998 with a lower combined relative standard uncertainty of 52 nW/W. A value for the electron mass me = 9.109 382 14(47) × 10−31 kg can also be obtained from this result. With uncertainties approaching the limit of those commercially applicable to mass calibrations at the level of 1 kg, an electronically-derived standard for the mass unit kilogram is closer to fruition.
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details of the 1998 watt balance experiment determining the Planck Constant
Journal of Research of the National Institute of Standards and Technology, 2005Co-Authors: R L Steiner, David B. Newell, Edwin R WilliamsAbstract:The National Institute of Standards and Technology (NIST) watt balance experiment completed a determination of Planck Constant in 1998 with a relative standard uncertainty of 87 × 10(-9) (k = 1), concurrently with an upper limit on the drift rate of the SI kilogram mass standard. A number of other fundamental physical Constants with uncertainties dominated by this result are also calculated. This paper focuses on the details of the balance apparatus, the measurement and control procedures, and the reference calibrations. The alignment procedures are also described, as is a novel mutual inductance measurement procedure. The analysis summary discusses the data noise sources and estimates for the Type B uncertainty contributions to the uncertainty budget. Much of this detail, some historical progression, and a few recent findings have not been included in previous papers reporting the results of this experiment.
D. Haddad - One of the best experts on this subject based on the ideXlab platform.
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measurement of the Planck Constant at the national institute of standards and technology from 2015 to 2017
Metrologia, 2017Co-Authors: D. Haddad, L. S. Chao, David B. Newell, Jon R. Pratt, Carl J. Williams, F Seifert, Antonio Possolo, Stephan SchlammingerAbstract:Researchers at the National Institute of Standards and Technology (NIST) have measured the value of the Planck Constant to be J s (relative standard uncertainty ). The result is based on over 10 000 weighings of masses with nominal values ranging from 0.5 kg to 2 kg with the Kibble balance NIST-4. The uncertainty has been reduced by more than twofold relative to a previous determination because of three factors: (1) a much larger data set than previously available, allowing a more realistic, and smaller, Type A evaluation; (2) a more comprehensive measurement of the back action of the weighing current on the magnet by weighing masses up to 2 kg, decreasing the uncertainty associated with magnet non-linearity; (3) a rigorous investigation of the dependence of the geometric factor on the coil velocity reducing the uncertainty assigned to time-dependent leakage of current in the coil.
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Invited Article: A precise instrument to determine the Planck Constant, and the future kilogram
Review of Scientific Instruments, 2016Co-Authors: D. Haddad, Frank Seifert, L. S. Chao, David B. Newell, Jon R. Pratt, Carl J. Williams, Stephan SchlammingerAbstract:A precise instrument, called a watt balance, compares mechanical power measured in terms of the meter, the second, and the kilogram to electrical power measured in terms of the volt and the ohm. A direct link between mechanical action and the Planck Constant is established by the practical realization of the electrical units derived from the Josephson and the quantum Hall effects. We describe in this paper the fourth-generation watt balance at the National Institute of Standards and Technology (NIST), and report our initial determination of the Planck Constant obtained from data taken in late 2015 and the beginning of 2016. A comprehensive analysis of the data and the associated uncertainties led to the SI value of the Planck Constant, h = 6.626 069 83(22) × 10(-34) J s. The relative standard uncertainty associated with this result is 34 × 10(-9).
-
a summary of the Planck Constant measurements using a watt balance with a superconducting solenoid at nist
Metrologia, 2015Co-Authors: Stephan Schlamminger, D. Haddad, L. S. Chao, David B. Newell, R Liu, Edwin R Williams, R L Steiner, F Seifert, Jon R. PrattAbstract:Researchers at the National Institute of Standards and Technology have been using a watt balance, NIST-3, to measure the Planck Constant h for over ten years. Two recently published values disagree by more than one standard uncertainty. The motivation for the present short communication is twofold. First, we correct the latest published number to take into account a recently discovered systematic error in mass dissemination at the Bureau International des Poids et Mesures. Second, we provide guidance on how to combine the two numbers into one final result. In order to adequately reflect the discrepancy, we added an additional systematic uncertainty to the published uncertainty budgets. The final value of h measured with NIST-3 is h = 6.626 069 36(37) × 10−34 J s. This result is 77(57) × 10−9 fractionally higher than h90. Each number in parentheses gives the value of the standard uncertainty in the last two digits of the respective value and h90 is the conventional value of the Planck Constant given by , where KJ-90 and RK-90 denote the conventional values of the Josephson and von Klitzing Constants, respectively.
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determination of the Planck Constant using a watt balance with a superconducting magnet system at the national institute of standards and technology
Metrologia, 2014Co-Authors: S Schlamminger, D. Haddad, L. S. Chao, David B. Newell, R Liu, R L Steiner, F Seifert, Jon R. PrattAbstract:For the past two years, measurements have been performed with a watt balance at the National Institute of Standards and Technology (NIST) to determine the Planck Constant. A detailed analysis of these measurements and their uncertainties has led to the value h = 6.626 069 79(30) × 10−34 J s. The relative standard uncertainty is 45 × 10−9. This result is 141 × 10−9 fractionally higher than h90. Here h90 is the conventional value of the Planck Constant given by , where KJ-90 and RK-90 denote the conventional values of the Josephson and von Klitzing Constants, respectively.
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towards a fixed value of the Planck Constant reproducibility and an updated nist 3 watt balance
Conference on Precision Electromagnetic Measurements, 2012Co-Authors: D. Haddad, David B. Newell, Stephan Schlamminger, R Liu, Edwin R Williams, Jon R. PrattAbstract:The scientific community is presently engaged in a historic attempt to fix the value of the Planck Constant h so that it might ultimately serve as a base Constant in a revised system of units. To assist this effort, NIST is examining its existing watt balance experiment, NIST-3, and will measure h once again, aiming at a final rigorous test of reproducibility. The main objectives are to modify and update the existing apparatus so that it can be used both to measure the Planck Constant and to support other experiments related to the mise en pratique for mass, to attempt a determination of the Planck Constant that is largely independent of previous NIST results, and to probe the discrepancy between the value of h measured in 2007 and other latest published results through a careful re-examination of the NIST-3 measurement procedures and uncertainty budget.
