This website uses cookies to store information on your computer. Some of these cookies are used for visitor analysis, others are essential to making our site function properly and improve the user experience. By using this site, you consent to the placement of these cookies. Click Accept to consent and dismiss this message or Deny to leave this website. Read our Privacy Statement for more.
A Review and Survey of Metrology Outreach Efforts in Post-Secondary Education
Maria Isabel Peña, Georgia Harris
NCSLI Measure | Vol. 11 No. 1 (2016) | 10.1080/19315775.2016.1149011
Publisher NCSL International | Published 6/6/2016 | Pages 37-51
Abstract: 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); and (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.
High-Voltage Divider Calibration with the Reference Step Method
Harold Parks
NCSLI Measure | Vol. 11 No. 1 (2016) | 10.1080/19315775.2016.1149008
Publisher NCSL International | Published 6/6/2016 | Pages 34-36
Abstract: 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.
Pressure Balance Cross-Calibration Method Using a Pressure Transducer as Transfer Standard
Julia Scherschligt , Gregory Driver, Yuanchao Yang, Douglas A. Olson
NCSLI Measure | Vol. 11 No. 1 (2016) | 10.1080/19315775.2016.1149003
Publisher NCSL International | Published 6/6/2016 | Pages 28-33
Abstract: 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.
Calculating Measurement Uncertainty of the “Conventional Value of the Result of Weighing in Air”
Celia J. Flicker, Hy D. Tran
NCSLI Measure | Vol. 11 No. 2 (2016) | 10.1080/19315775.2016.1211458
Publisher NCSL International | Published 10/27/2016 | Pages 27-37
Abstract: 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.
NCSLI Measure | Vol. 11 No. 2 (2016) | 10.1080/19315775.2016.1221681
Publisher NCSL International | Published 10/27/2016 | Pages 38-59
Abstract: 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 in-tolerance 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.
Phasor Measurement Units: Traceable Type Acceptance Testing in Compliance with IEEE C37.118.1a
Jason Watson, Jeffrey Guigue
NCSLI Measure | Vol. 11 No. 2 (2016) | 10.1080/19315775.2016.1204206
Publisher NCSL International | Published 10/27/2016 | Pages 22-26
Abstract: 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.
An FEM Analysis of the Magnetic Fields in the Magnetic Suspension Mass Comparator at NIST
Corey Stambaugh, Edward Mulhern
NCSLI Measure | Vol. 11 No. 3-4 (2017) | 10.1080/19315775.2017.1325029
Publisher NCSL International | Published 10/19/2017 | Pages 63-68
Abstract: 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.
Characterization of the NIST Magnetic Suspension Mass Comparator Facility
Corey Stambaugh, Edward Mulhern
NCSLI Measure | Vol. 11 No. 3-4 (2017) | 10.1080/19315775.2017.1335584
Publisher NCSL International | Published 10/19/2017 | Pages 58-62
Abstract: 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.
Evaluating the Frequency and Time Uncertainty of GPS Disciplined Oscillators and Clocks
Michael Lombardi
NCSLI Measure | Vol. 11 No. 3-4 (2017) | 10.1080/19315775.2017.1316696
Publisher NCSL International | Published 10/19/2017 | Pages 30-44
Abstract: 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.
Issues and Strategies for Improving Measurement Uncertainties for Solid-State Lighting
Joanne C. Zwinkels
NCSLI Measure | Vol. 11 No. 3-4 (2017) | 10.1080/19315775.2017.1356695
Publisher NCSL International | Published 10/19/2017 | Pages 22-29
Abstract: 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.
The NIST Mise en Pratique for the Realization and Dissemination of the Kilogram as Part of the “New SI”
Patrick Abbott, Eric C. Benck, Edward Mulhern, Corey Stambaugh, Zeina J. Kubarych
NCSLI Measure | Vol. 11 No. 3-4 (2017) | 10.1080/19315775.2017.1333368
Publisher NCSL International | Published 10/19/2017 | Pages 45-50
Abstract: 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.
Transport of Masses Under Vacuum for the Redefinition of the Kilogram at NIST
Eric C. Benck, Corey Stambaugh, Edward Mulhern
NCSLI Measure | Vol. 11 No. 3-4 (2017) | 10.1080/19315775.2017.1323565
Publisher NCSL International | Published 10/19/2017 | Pages 51-57
Abstract: 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.
