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Measure Articles 2016 (12)

 
Picture of the productA Review and Survey of Metrology Outreach Efforts
Georgia L. Harris, National Institute of Standards and Technology, and Maria Isabel Peña, Doxa Internacional
This article presents a brief history and background of metrology outreach efforts to post-secondary educational programs. It also summarizes a 2015 educational survey carried out by the NCSL International (formerly National Conference of Standards Laboratories, NCSLI) Education Liaison and Outreach Committee working with staff of the U.S. National Institute of Standards and Technology (NIST) and used in part to gather input from post-secondary educational programs that:
    (1) have measurement science courses
    (2) metrology degree programs (at the associate, baccalaureate, and advanced levels)
    (3) have integrated or are considering integrating metrology concepts into engineering or engineering technology programs
Prior recommendations for continued education outreach and integration of metrology into the scientific curricula are reinforced; evidence from the education survey supports the need and value of ongoing, sustained involvement by metrology champions (metrology ambassadors) in education outreach efforts to the college and university community.


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MS16_01_HARRIS
Picture of the productAn FEM Analysis of the Magnetic Fields in the Magnetic Sus.
An FEM Analysis of the Magnetic Fields in the Magnetic Suspension Mass Comparator at NIST
Corey Stambaugh and Edward Mulhern, National Institute of Standards and Technology, Gaithersburg, Maryland, USA

The magnetic suspension mass comparator is a specialized mass comparison system used for vacuum-to-air mass dissemination. Magnetic suspension is used to couple a mass located in a sealed chamber at atmospheric pressure to a mass comparator located in a chamber held under vacuum. The magnetic field distribution determines both the magnitude of the force needed for suspension and the extent to which the magnetic field adversely interacts with external components, an interaction that can lead to systematic errors. A finite element analysis of the magnetic field distribution is carried out and the analysis is compared to direct measurements of the magnetic field distribution. Validation of the finite element model is critical for further improvements to magnetic shielding and for determining the necessary magnetic field strength for suspension.


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MS16_3_4_STAMBA
Picture of the productCalculating Measurement Uncertainty
Calculating Measurement Uncertainty of the “Conventional Value of the Result of Weighing in Air”
Celia J. Flicker and Hy D. Tran, Sandia National Laboratories
The conventional value of the result of weighing in air is frequently used in commercial calibrations of balances. The guidance in OIML D-028 for reporting uncertainty of the conventional value is too terse. When calibrating mass standards at low measurement uncertainties, it is necessary to perform a buoyancy correction before reporting the result. When calculating the conventional result after calibrating true mass, the uncertainty due to calculating the conventional result is correlated with the buoyancy correction. We show through Monte Carlo simulations that the measurement uncertainty of the conventional result is less than the measurement uncertainty when reporting true mass.


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MS16_02_FLICKER
Picture of the productCharacterization of the NIST Magnetic Suspension Mass Comp.
Characterization of the NIST Magnetic Suspension Mass Comparator Facility
Edward Mulhern and Corey Stambaugh, National Institute of Standards and Technology, Gaithersburg, Maryland, USA

The kilogram will be redefined in 2018 and National Metrology Institutes are working to identify and reduce uncertainties related to its realization and dissemination. At the National Institute of Standards and Technology (NIST), a unique system for disseminating the vacuum-based kilogram realization to air is under development. A magnetic suspension mass comparator (MSMC) is utilized to directly compare a mass in vacuum to a mass in air with sources of uncertainty stemming from the measurement environment, the suspension apparatus, and the measurement facility itself. To accurately characterize this process, gravitational gradients were measured, ambient vibrations of the lab characterized, and the ambient environmental stability examined.


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MS16_3_4_MULHER
Picture of the productEvaluating the Frequency and Time Uncertainty of GPS Dis.
Evaluating the Frequency and Time Uncertainty of GPS Disciplined Oscillators and Clocks
Michael A. Lombardi, Time and Frequency Division, National Institute of Standards and Technology, Boulder, Colorado, USA

Global Positioning System (GPS) disciplined oscillators and clocks serve as standards of frequency and time in numerous calibration and metrology laboratories. They also serve as frequency and time references in many industries, perhaps most notably in the telecommunication, electric power, transportation, and financial sectors. These devices are inherently accurate sources of both frequency and time because they are adjusted via the GPS satellites to agree with the Coordinated Universal Time (UTC) time scale maintained by the United States Naval Observatory (USNO). Despite their excellent performance, it can be difficult to evaluate their uncertainty, and even more difficult for metrologists to prove their claims of uncertainty and traceability to skeptical laboratory assessors. This article is written for metrologists and laboratory assessors who work with GPS disciplined oscillators (GPSDOs) or GPS disciplined clocks (GPSDCs) and need to assess their uncertainty. It describes the relationship between GPS time and Coordinated Universal Time (UTC), explains why GPS time is traceable to the International System (SI), and provides methods for evaluating the frequency and time uncertainty of signals produced by a GPSDO or GPSDC.


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MS16_3_4_LOMBAR
Picture of the productHigh-Voltage Divider Calibration
Harold Parks, National Research Council Canada
High-voltage DC measurements, from 10 kV up to several hundred kV, are usually traceable through resistive dividers which have a divider ratio on the order of 10,000 - 100,000. The reference step method [3] provides a highly accurate ratiometric method of calibrating 1,000 V calibrators across a wide range of voltages. We adapt this method for measuring the ratio of high-voltage dividers at low (≤1,000 V) voltages as a first step to establishing traceability at high voltages.


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MS16_01_PARKS
Picture of the productInstrument Adjustment Policies
Paul Reese PSE Operations, Baxter Healthcare Corporation
Instrument adjustment policies play a key role in the reliability of calibrated instruments to maintain their accuracy over a specified time interval. Periodic review and adjustment of assigned calibration intervals is required by national standard ANSI/NCSL Z540.3 and is employed to manage the End of Period Reliability (EOPR) to acceptable levels. Instrument adjustment policies may also be implemented with various guardband strategies to manage false accept risk. However, policies and guidance addressing the routine adjustment of in-tolerance instruments are not so well established. National and international calibration standards ANSI/NCSL Z540.3 and ISO/IEC-17025 do not mandate any particular adjustment policy with regard to intolerance equipment. Evidence has been previously presented where routine adjustment of in-tolerance items may even degrade performance. Yet, this important part of the overall calibration process is often left to the discretion of the calibrating technician based on heuristic assessment. Astute adjustment decisions require knowledge of the random vs. systematic nature of instrument error. Instruments dominated by systematic effects, such as drift, benefit from adjustment, while those displaying more random behavior may not. Monte Carlo methods are used here to investigate the effect of various adjustment thresholds on in-tolerance instruments.


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MS16_02_REESE
Picture of the productIssues and Strategies for Improving Measurement Uncert.
Issues and Strategies for Improving Measurement Uncertainties for Solid-State Lighting
Joanne C. Zwinkels, Measurement Science and Standards, National Research Council of Canada, Ottawa, Ontario, Canada

The use of solid-state lighting (SSL), such as light-emitting-diode (LED) products for general lighting and display applications, has increased dramatically over the past decade. However, there are significant photometric and radiometric metrological challenges with this new lighting technology. The photometric procedures and standards that have been developed for traditional lighting products, such as incandescent and compact fluorescent (CFL) lamps, do not work well for LEDs because they exhibit significantly different characteristics. This paper will discuss these differences in the spectral, geometric, and operating properties of LEDs and how they impact precise photometric measurements and associated performance metrics, such as color rendering index (CRI). The current state-of-the-art uncertainties for photometric measurements of LED lighting products is about a factor of 5 poorer than for traditional lamps, based upon the results of recent interlaboratory comparisons involving both national metrology institutes (NMIs) and accredited laboratories. Reducing the uncertainty of these measurements will have a significant impact on society—both on reducing costs due to energy savings, but also on improving overall lighting quality and performance. For these reasons, there are a number of activities being carried out both at the national and international level to address these LED measurement issues. This article will highlight the current strategies and standardization activities within both the Consultative Committee of Photometry and Radiometry (CCPR) and the International Commission of Illumination (CIE) to develop improved measurement techniques, transfer standards and metrics for the measurement and use of LED lighting in photometry, and to meet consumer needs.


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MS16_3_4_ZWINKE
Picture of the productPhasor Measurement Units
Phasor Measurement Units: Traceable Type Acceptance Testing in Compliance with IEEE C37.118.1a
Jeffrey Guigue and Jason Watson Laboratory Services, Consumers Energy
This article provides a basic overview of Phasor Measurement Unit functionality and describes the process used to develop and implement a traceable Type Acceptance process for commercial Phasor Measurement Units designed to comply with the IEEE standard C37.118.1a. With a growing diversification of electricity generation employing various methods, the need for real-time, high-resolution, traceable measurements of voltage, current, phase, and frequency is critical in maintaining and improving a robust electrical grid.


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MS16_02_GUIGUE
Picture of the productPressure Balance Cross-Calibration Method
Julia Scherschligt, Douglas A. Olson, R. Gregory Driver, National Institute of Standards and Technology, and Yuanchao Yang, National Institute of Metrology, Beijing, China
Piston gauges or pressure balances are widely used to realize the SI unit of pressure, the pascal, and to calibrate pressure sensing devices. However, their calibration is time consuming and requires a lot of technical expertise. In this article, we propose an alternate method of performing a piston gauge cross calibration that incorporates a pressure transducer as an immediate in-situ transfer standard. For a sufficiently linear transducer, the requirement to exactly balance the weights on the two pressure gauges under consideration is greatly relaxed. Our results indicate that this method can be employed without a significant increase in measurement uncertainty. Indeed, in the test case explored here, our results agreed with the traditional method within standard uncertainty, which was less than 6 parts per million.


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MS16_01_SCHER
Picture of the productThe NIST Mise en Pratique for the Realization
The NIST Mise en Pratique for the Realization and Dissemination of the Kilogram as Part of the “New SI”
Patrick J. Abbott, Eric C. Benck, Edward Mulhern, Corey Stambaugh, and Zeina J. Kubarych, National Institute of Standards and Technology, Gaithersburg, Maryland, USA

The International System of Units (SI) will be redefined in 2018 so that the present seven SI base units are realized by a set of defining constants having exact values. For the unit of mass, the kilogram, this means a change in realization from a physical artifact, the International Prototype Kilogram (IPK) to an experiment that uses the Planck constant to measure mass with an uncertainty. Although traditional artifact-based mass metrology will not change, National Measurement Institutes (NMIs) will change the way that they realize the unit of mass and disseminate it to working standards. Much of this change is due to the necessary vacuum environment of the experiments (Kibble balance and x-ray crystal density (XRCD)) that will use the Planck constant to measure mass. At the National Institute of Standards and Technology (NIST), mass measurements, artifact transfers, and storage of standard artifacts will be done in both vacuum and atmospheric pressure environments to produce and maintain SI-traceable mass standards. This process of realization and dissemination is known as a mise en Pratique and consists of four main components, each of which is described.


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MS16_3_4_ABBOTT
Picture of the productTransport of Masses Under Vacuum for the Redefinition Kg
Transport of Masses Under Vacuum for the Redefinition of the Kilogram at NIST
Eric C. Benck, Edward Mulhern, and Corey Stambaugh, Mass and Force Group, National Institute of Standards and Technology, Gaithersburg, Maryland, USA

With the expected redefinition of the kilogram, the National Institute of Standards and Technology (NIST) will utilize multiple vacuum systems as part of the mise en pratique for the realization and dissemination of the unit of mass. The realization of the “redefined kilogram” in a high vacuum environment necessitates the transfer of mass artifacts under vacuum between stations of the NIST mise en pratique. To do this, vertical lifts and ramps, custom load locks, mass manipulation systems, and a mass transfer vehicle have been designed, built, and integrated into each component vacuum system of the mise en pratique at NIST. Here, we describe the design and operation of these systems, as well as their vacuum requirements. Furthermore, we discuss tests carried out on the mass transport vehicle to understand the possible effects moving it between labs may have on the masses.


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MS16_3_4_BENCK