Measurement Library

Measurement Science Conference Publications (2004)

NIST Calibration On Liquid Flow Measurement: Piston Prover Facility
Author(s): T. T. Yeh, P. I. Espina, G. E. Mattingly, N. R. Briggs
Abstract/Introduction:
This paper presents the uncertainty characterization of NISTs new hyd flow calibrator (HLFC). This facility uses a passive piston prover technique driven by pumps while the measuring piston is passively stroked through interval. The facility is typically operated using MIL-C-7024C fluid,u but us other fluids offers a wider range of fluid properties. The level. NIST i hydrocarbon liquids calibration service will reach 760 lpm (200 gpm).
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Document ID: E98AF9F1

Test For Gas Species Dependence In The Motion Of A Small Bell Prover
Author(s): Thomas O. Maginnis
Abstract/Introduction:
It has been suggested that there may exist a weak gas species dependence in the K-factor of volumetric flow standards such as bell provers and piston provers. Such a dependence would arise, for example, from imperfect bell counterbalancing due to gas buoyancy effects when flowing a gas that has a density at test conditions substantially different from air, assuming the counterbalance to be exact for air. It has previously been shown that any significant departure from constant velocity motion of a volumetric prover during the timed measurement can cause a systematic error in such instruments. A test was made using three gases of significantly different density in a small bell prover, at multiple flow rates. The time for the bell to travel to ten different displacements was measured and recorded for each flow rate and gas. The data provide a sensitive test for any gasdependent acceleration present in the system.
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Document ID: 30C1E64D

Laser Measurement Of Trident D5 Launch Tubes
Author(s): Henry Meinders
Abstract/Introduction:
In January of 2000, Naval Surface Warfare Center (NSWC) Corona Division conducted laser measurements of six D5 launch tubes on board the USS Tennessee. There were two purposes in conducting these measurements: 1) To quantify any out of tolerance conditions on the launch tubes due to their service life, and 2) To prove the capability of a new measurement system for more accurate and timely data gathering. This paper presents some of the technical challenges overcome in developing the laser measurement system and performing the measurements at the Strategic Weapons Facility Atlantic (SWFLANT) dry dock facility. In developing the measurement system we faced several problems including correctly positioning the laser, maintaining line of sight from the laser, and restrictions from permanently modifying the platform used to gain access to the tube. During actual measurement we encountered environmental challenges, vibration influences, scheduling conflicts, varying tube surface conditions, and data reduction difficulties. The measurements were successfully performed, and the condition of the tubes was successfully evaluated. The ability of the laser tracker measurement system to accurately and efficiently gather dimensional data on the loading tubes was proven.
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Document ID: FB8EB283

Laser Interferometer Measurements Of Glass Scales
Author(s): Shawn Mason, Michael Czech
Abstract/Introduction:
This paper will present the in-house development and implementation of a calibration process for Glass Scales using a laser interferometer, precision stage, video camera and optics.
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Document ID: B3450486

Teaching The Science Of Measurement
Author(s): Mladen Borsic, Pasquale Daponte
Abstract/Introduction:
Metrology - the science of measurement - has been rapidly developing in the past decades. The requirement of international trade, accepted all over, is to verify the declared quality of the goods by the results of the measurements of the relevant parameters, extend the numerousness of the measurements, and improve the reliability of measurement results. Computer controlled instruments equipped with analogue-to-digital converters generate new measuring methods. International standards regulate many of the measuring procedures. Regional and international organizations organise laboratory intercomparisons focusing on measurement results, including accuracies and traceability. How do you teach modern metrology in such a continuously changing situation? The authors discuss the possible curriculum of metrology for universities and high schools.
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Document ID: 4152E08B

The More Things Change
Author(s): Herbert Oneil, Tiia Oneil
Abstract/Introduction:
This paper is a combined view of one familys look at metrologys education over two generations the first view is from an instructor with over thirty five years exposure to metrology from entry level Pmel Tech. to supervisor of Depot Level Metrology, as well as, guest lecturer at Boeing. The second view is from a recent graduate who has interned in the fieldshe will list some reasons why she chose this field of study as well as reactions to itthe paper addresses the lack of upcoming metrology techs who will fill in for the current crop of retiring metrology folks
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Document ID: A0EE4F3D

Comparisons Of Bayesian Approaches To Combining Results From Multiple Methods
Author(s): Hung-Kung Liu, Charles Hagwood, Nien Fan Zhang
Abstract/Introduction:
The problem of determining a consensus mean and its uncertainty from the results of multiple measurement methods or laboratories is an important NIST problem. Many solutions, both Bayesian and non- Bayesian, to this problem have been proposed over the years. In this paper, we propose an unied approach to some of the Bayes solutions by specifying the consensus mean as a measurable function of the method means and some ancillary variable. This Measurement Equation Approach conforms to the rules set in the ISO Guide to the Expression of Uncertainty in Measurement (ISO GUM). When the measurement equation is linear in the ancillary variable, the uncertainty of our Bayes estimator has a decomposition that is ISO GUM compliant. We will also examine desirable criteria for an objective performance comparisons of the solutions to this problem, and use them to compare the existing solutions.
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Document ID: 4764CCF8

Evaluating Coordinate Measurement Machine Software Geometry Uncertainties Using National And International Standards
Author(s): Craig m. Shakarji, John Raffaldi
Abstract/Introduction:
The contribution of software to the uncertainty of measurements is an important but often overlooked aspect of uncertainty evaluations in many aspects of metrology. In coordinate metrology, software is often relied upon for complicated fitting of data, filtering, calibrations, and statistical calculations. Metrology equipment using software can range from hand-held digital calipers to coordinate measurement machines spanning several meters and can occur in almost any industry. Historically, it has been shown that software has often been responsible for measurement errors. While some of these errors have been reported, others are still surfacing. This paper highlights some of the causes, errors, and recommends using National and International Standards laboratories to evaluate the uncertainty component due to software.
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Document ID: BFD852B5

Technical Protocol For The Cipm Key Comparison For Water Flow, CCM.FF.K1
Author(s): J. S.Paik, K. B. Lee, B. R. Yoon
Abstract/Introduction:
The National Metrology Institutes (NMIs) of the World are interested in determining the degree of equivalency of their water flow calibration facilities. To that aim, and under the auspices of the Comite International Des Poids Et Measures (CIPM), a Key Comparison (KC) is to be conducted. This paper provides the following elements for the planned KC: Outline Description of the transfer standard and its transportation Assembling of the transfer standard Installation Measurement procedure Reporting of the measurement results Data analysis The CCM approved version of the test protocol for this KC follows.
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Document ID: D7B9A288

The Current Plans For A Cipm Key Comparison In Hydrocarbon Liquids
Author(s): Richard Paton, Dr. Michael Reader-Harris
Abstract/Introduction:
The plans for the CIPM key comparison in hydrocarbon liquids are described. The reasons for the choice of fluid and the package design (a turbine meter and a screw-type positive displacement meter) are given briefly.The data are presented in terms of Strouhal number v Reynolds number. The test results and conclusions are presented. In particular with the NEL package in one configuration three tests were undertaken at 20 C, one test at 15 C, and one at 25 C. At a Reynolds number of 130000 all the Strouhal numbers for each meter were within 0.016% of the mean value. When a Youden plot was used, the data were scattered close to the positive 45 line with the maximum deviation from that line being 0.007%.
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Document ID: B0BF3882

High Precision Dimensional Calibrations: Use Of Self-Calibration Techniques To Bring State-Of-The-Art Levels Of Measurement Uncertainty Into Everyday Industrial Practice
Author(s): James G. Salsbury, Christopher Lee, Bunji Aoyama, Don Reder
Abstract/Introduction:
The continued tightening of dimensional tolerances combined with the demand for accreditation of calibration services is pushing the limits of many organizations capabilities. This is particularly relevant when the cost of lowering calibration uncertainty is high. This paper explores the journey taken by a dimensional metrology manufacturer to develop cost effective, on-site, calibration procedures with measurement uncertainty that approaches, or sometimes is even lower than, the levels offered by the state-of-the-art procedures at the best national metrology institutes worldwide. The focus of this uncertainty improvement journey is the calibration of one particular type of dimensional form measuring instrument, the roundness measuring machine. For a common, industrial, off-the-shelf, measuring instrument, the roundness machine has some of the tightest specifications. On-site calibration of these instruments needs to be done with an uncertainty that is often lower than what is offered for the calibration of the appropriate reference standards at most national metrology institutes. The challenge faced by the manufacturer is to demonstrate traceability and achieve the required uncertainty given the demanding requirements. This paper will explore these challenges and present some novel solutions that allow state-of-the-art measurements to be economicallyreduced to everyday practice.
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Document ID: EB8835B6

Solutions For The Data Rich And Analysis Poor
Author(s): D. Bruce Galloway, Jesus Urquijo
Abstract/Introduction:
No one wants to be data rich and analysis poor. This paper starts from the very basics of statistical theory and walks the reader through a process by which anyone can perform advanced analyses on test data. Armed with the theoretical background in descriptive statistics and characteristics of the normal curve, the paper takes a practitioner turn and shows how to apply these theoretical tools to answer questions about the sources of test data. Topics covered include testing for normality, prediction of defective product, agreement between different testers, relationships between variables, Statistical Process Control, Leiberman Statistical Control Limits, repeatability, and a brief application of hypothesis testing. Theres a concluding section that outlines an approach to getting your raw data into a format thats conducive to analysis.
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Document ID: 67925D7E

Missile Test Confidence Via Test Systems Certification And Associated Data Analysis
Author(s): David Maupin
Abstract/Introduction:
This paper discusses missile data analysis from production and fleet return test runs. This data can be used to detect a wide array of potential problems. I will look at how this data can be used by the manufacturers and depots that collect it. I will also examine data analysis visual display chart types and how to effectively group the results. Future trends in the use of the analysis programs will also be briefly explored.
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Document ID: 9DA2587F

Vector Network Analyzer Calibrations In An ISO/IEC 17025 Accredited Laboratory
Author(s): Dr. Li Pi Su, Van Q. Black, George K. Walden, Larry Tarr
Abstract/Introduction:
The Electromagnetic Standards Laboratory (ESL), US Army Primary Standards Laboratory (APSL), is committed to providing services to its customers which are accurate, traceable to the National Institute of Standards and Technology (NIST), delivered on-time, and continually improving.
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Document ID: 55D33025

Modelling Of Temperature And Pressure Sensor Calibrations For Evaluating The Uncertainty
Author(s): Klaus-Dieter Sommer, Manfred Kochsiek, Albert Weckenmann
Abstract/Introduction:
The modelling of the measurement is the key element of the evaluation of the measurement uncertainty in accordance with the basic concept of the Guide to the Expression of Uncertainty in Measurement (GUM). The model equation expresses the relationship between the measurand and all relevant input quantities which may contribute to the measurement result and its associated uncertainty. It serves a basis for Gaussian uncertainty propagation or, in case of non-linear systems, for the propagation of the probability density distributions. A practical an highly versatile modelling concept has been developed. It gets on with only a few generic structures, and it has led to a modelling procedure which is structured into five elementary steps. This modelling concept will be presented with examples of temperature an of pressure sensor calibration.
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Document ID: 0D5BD2B9

CCM.FF-K4 Draft Technical Protocol For Volume Intercomparison At 20 L And 100 Ml - Piloted By Centro Nacional De Metrologia Cenam()
Author(s): R. Arias, m. Maldonado
Abstract/Introduction:
[Abstract Not Available]
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Document ID: B26F7FE5

The High-Pressure Gas Facilities Of The World And The Current Plans For A Cipm Key Comparison, CCM.FF.K5
Author(s): D. Dopheide, B. Mickan, R. Kramer, m. Van Der Beek
Abstract/Introduction:
The National Metrology Institutes (NMIs) of the World are interested in determining the degree of equivalency of their high-pressure gas flow calibration facilities. To that aim, and under the auspices of the Comite International Des Poids Et Measures (CIPM), a Key Comparison (KC) is to be conducted. This paper describes the calibration and measurement capabilities (CMCs) of the high-pressure natural gas facilities for natural gases and compressed air. From them, one can conclude some logical things to do in this situation regarding the selection of transfer standards, the way to perform a CIPM Key Comparison, the definition of the reference value, and the presentation of lab-tolab differences. The following main topics for the planned KC are discussed: Mutual interest of, and benefit for the participants. Prerequisites for participation in CIPM KC. Different ways and views to perform a comparison. Selection and characterization of appropriate transfer standards for high-pressure gases. Data reduction method. The most current version of the test protocol for this KC follows.
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Document ID: C706D993

Process Capability Determination Of An Industrial Manufacturing Process Using Computer Software And Hardware Tools
Author(s): Akram Hossain
Abstract/Introduction:
Quality means suitability for use and it is inversely proportional to variability of product, service, people, process, and environment. However, it is the dynamic state that is associated with each of the above and that meets or exceeds expectations of a customer. Quality improvement is therefore the progressive reduction of variability. The gradual reduction of process and product variability can be done by successive determination and removal of the causes responsible for the variability. Determination of Process Capability is not hard, but it is frequently overlooked. It should be done first in any quality improvement program. It must be repeated on a periodic basis to ensure that the process stay fit to produce product of desired specification. If the process is incapable, then it is managements responsibility to either improve the process or accept poor quality product.
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Document ID: AFA2F378

Do It Yourself Statistics
Author(s): Dennis W. Dubro
Abstract/Introduction:
Most metrologists have a mixed background in statistics. It is often learned on the fly and we constantly refer to textbooks for formulae and tables. This is usually adequate but not very satisfying, especially when a formula needs to be extended to cover a situation different from the example. Statistics has the strange characteristic that the common knowledge is easily referenced and memorized, but it is significantly harder to find out just a little bit more or why. We hear that the answer is in advanced textbooks which are all very ominous to look at and require a thorough reading from page one to understand anything that appears in a later chapter.
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Document ID: 66D15B1A

Developing A Proficiency Testing Plan For Your Laboratory
Author(s): Jeff C. Gust
Abstract/Introduction:
Whether responding to new requirements from accreditation bodies, or ensuring that your laboratory quality system meets the requirements of ISO 17025, developing a documented plan for Proficiency Testing benefits the laboratory. Formal development of a Proficiency Testing Plan provides a long term roadmap for laboratories to ensure validation of all calibration services that they provide, and conveniently summarizes corrective and preventive actions that result from participation in proficiency testing. When developing a Proficiency Test Plan, it is important to optimize the costs to the laboratory by ensuring that the minimum requirements are met and the entire technical scope of the laboratory is covered in the required timeframe. This presentation will discuss the proficiency testing requirements from the International Laboratory Accreditation Cooperation, through the regional accreditation organizations, to the accreditation bodies, and the laboratory itself. Information will be shared on the development of the NIST Weights and Measures Division Proficiency Test Policy and Plan that was jointly developed by NIST and Quametec Proficiency Testing Services. Examples of Proficiency Testing Plans for laboratories will be provided.
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Document ID: C6FEF6F4

Adding Value With Proficiency Testing
Author(s): Henrik S. Nielsen
Abstract/Introduction:
Accreditation bodies are increasingly using proficiency testing as a tool to ensure the credibility of their accreditation programs by requiring the laboratories they accredit to demonstrate that they can live up to their uncertainty claims in interlaboratory comparisons. Accredited laboratories mostly see proficiency testing as an added expense they are forced to incur which adds little or no value. However, when used appropriately, proficiency testing can reduce a laboratorys risk of producing incorrect measuring results. While focusing on the En (normalized error) approach, the paper explores the underlying assumptions and associated limitations in various reporting methods traditionally used in proficiency testing. It discusses the important steps that are necessary to ensure that correct conclusions are drawn from a proficiency test and the exposure and potential unnecessary cost participating laboratories are subject to, if these steps are not taken. Additionally, the paper covers some personal experiences, where the author has gained valuable knowledge of measuring processes and their limitations as a participant in interlaboratory comparisons.
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Document ID: F515FE85

Special Topics In SPC Of Measurement
Author(s): Phil Stein
Abstract/Introduction:
The SPC (Shewhart) control chart has wide and powerful applications in measurements and calibration. Most metrology practitioners know this in principle, but dont use charts because they dont know which ones to use, or exactly how to make or interpret them. This talk will answer all these questions and more from a technical perspective, and will also discuss why SPC is so important in measurements.
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Document ID: C662600B

The Spreadsheet As A Statistical Analysis Tool In Metrology
Author(s): Dilip A. Shah
Abstract/Introduction:
The Excel spreadsheet is available to most metrology professionals. The spreadsheet software allows the professional to combine text, formulas, data and graphics, making it a popular tool among scientists and engineers. This paper discusses some practical applications in metrology using the built-in and other user-developed Excel spreadsheet functions. Applications including Regression, ANOVA and Hypothesis Testing are among the several topics covered.
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Document ID: 205BFE10

The Calibration Interval Analysis Process Using Binomial Data And The Intercept Exponential Model
Author(s): Dennis Jackson
Abstract/Introduction:
The use of the intercept exponential measurement reliability model provides a very powerful and general approach to estimating calibration intervals. The analysis process indicates data that should not be used in the estimation process. The data that should be excluded includes: Unusually low measurement reliabilities for early resubmission times Late resubmission times that do not represent actual usage Results from historical data that no longer have the same reliability behavior as the current population.
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Document ID: 4056FB16

Development Of A Bench-Top Time Proportional Humidity Generator With Chilled Mirror Hygrometer Reference Standard
Author(s): Jeff Hawkins, Ken Soleyn
Abstract/Introduction:
Divided-flow volumetric mix ratio techniques for the creation of controlled humidity environments have been in use for many years. These techniques typically operate under flow rate control whereby a continuous stream of saturated air (wet) is mixed in selected proportion with a continuous stream of dry air. The resultant mixed air stream embodies a partial water vapor pressure somewhere between zero and the saturation vapor pressure, dependent upon the selected volumetric mixing ratio. The design approach for this bench-top humidity calibration chamber utilizes volumetric mixing of dry air and saturated air via time proportioning of a three-way solenoid activated valve. An integrated NIST traceable chilled mirror hygrometer provides humidity measurement for feedback control of the test environment via microprocessor controlled time proportioning of the wet and dry air streams. System design considerations and validation data chronicling the chambers accuracy, stability, and response time are presented.
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Document ID: 568FA1CB

Realization Of The Freezing Point Of Indium Using Stainless Steel-Cased Cells
Author(s): Xumo Li, Mingjian Zhao, Deming Chen
Abstract/Introduction:
A new stainless steel-cased indium cell has been developed and tested. The new cell design is described in detail. A new cell was compared against a traditional fused silica-cased indium cell, and the difference between them was within 0.2 mK. Multiple cells of the new design were compared with each other, with the differences well within 0.2 mK. The longterm stability of the new cell was checked after about ten months of use and no obvious drift has been detected. The expanded uncertainty (k2) was estimated to be 0.7 mK, which is good enough for the calibration of standard platinum resistance thermometers. The new cell can be used in a portable furnace to obtain almost the same uncertainty. The stainless steel is less fragile than fused silica as a cell case material, so the new cell provides many advantages compared with a fused silica-cased cell: the new cell can be shipped instead of being hand-carried, it is much more robust and durable, and it is easier to use.
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Document ID: CECD2C84

New Standards And Techniques For Testing Cmm Software, Asme B89.4.10 And ISO 10360-6
Author(s): Dr. Paul D. Thomas
Abstract/Introduction:
When a Coordinate Measuring Machine (CMM) measures a feature on a part, the CMM software performs a best-fit calculation to construct a substitute feature from the raw data. The geometric dimensions and tolerances from the blueprint are then calculated from these substitute features. The best-fit algorithms can be eliminated as a source of error by testing the CMM software off-line, avoiding influences from the operator, the workpiece, the environment, and the CMM hardware. The ASME B89.4.10 1 and ISO 10360-6 2 standards describe a testing procedure to evaluate the performance of CMM software by using reference data sets that have a known, exact solution. These standards describe the minimum number of data sets required and the size, aspect ratio, and location ranges that should be included to completely test the performance of the CMM software. While these standards are intended for evaluating least squares best-fits, the testing method can easily be extended to minimum zone, maximum inscribed, and minimum circumscribed best-fits, which are required by the ASME Y14.5-M 3 and ISO 1101 4 standards on dimensioning and tolerancing.
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Document ID: EDEBA128

Understanding And Dealing With High Frequency Error Sources In Oscilloscope Calibration
Author(s): Paul Roberts
Abstract/Introduction:
Oscilloscope calibration has traditionally been considered part of the DC & LFAC workload. Nowadays the average scope found on a development engineers or test technicians bench is a 1GHz bandwidth device, and bandwidths of several GHz are common. The processes and equipment used to calibrate these higher bandwidth scopes have also increased in frequency, taking oscilloscope calibration into the realm of RF & Microwave. Metrologists and calibration technicians increasingly have to deal with a variety of high frequency considerations such as VSWR and matching errors. Understanding how these effects influence the results and how oscilloscope calibration methods address them can simplify the task of scope calibration, reduce errors and ease the burden of uncertainty analysis.
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Document ID: 5182C708

Sources Of Uncertainty In Molecular Dynamics Simulations
Author(s): Raymond D. Mountain
Abstract/Introduction:
In addition to the ubiquitous concern about the adequacy of the force field used in molecular dynamics simulations of liquids, there are two interrelated sampling issues that must be addressed. Both issues involve the generation of adequate samples of properties of interest. These issues are illustrated using a simulation of the pressure of water at ambient conditions.
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Document ID: 8950A8EE

Uncertainty Associated With Virtual Measurements From Computational Quantum Chemistry Models
Author(s): Karl K. Irikura, Russell D. Johnson III, Raghu N. Kacker
Abstract/Introduction:
The output of a computer model for the value of a measurand is frequently referred to as a virtual measurement to distinguish it from a physical measurement determined from laboratory experiments. Any measurement, physical or virtual, is incomplete without a statement of its associated uncertainty. The science and technology of making high quality physical measurements and quantifying their uncertainties has matured over many decades. The science and technology of making virtual measurements is evolving. In this paper we propose an approach for quantifying the uncertainty associated with the predictions of the properties of molecules from computational quantum chemistry models. The proposed approach is based on the Guide to the Expression of Uncertainty in Measurement published by the International Standards Organization (ISO) and makes use of the Computational Chemistry Comparison and Benchmark Database (CCCBDB) maintained by the National Institute of Standards and Technology (NIST).
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Document ID: 35B2CD36

The Harmonized High-Pressure Natural Gas Cubic Meter In Europe And Its Benefit For The User And Metrology.
Author(s): D. Dopheide, B. Mickan, R. Kramer, m. P. Van Der Beek
Abstract/Introduction:
The paper describes the method of the harmonization process for the natural gas cubic meter and the backgrounds of the harmonized reference values for the cubic meter of Natural Gas which are in use in Germany and The Netherlands since November 1st 1999, see 1. The prerequisites of the harmonization process, underlying procedures, results obtained so far and the mutual benefits will be pointed out as well as the economic consequences for the European market. This harmonization process can be considered as the first step towards the realization of a European unit of volume for Natural Gas at operating conditions.
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Document ID: 389D8C32

Uncertainty Issues Associated With A Volumetric Primary Flow Standard
Author(s): Thomas Kegel
Abstract/Introduction:
A project has been initiated to upgrade a volumetric primary flow standard that has been operating since 1970. Planned improvements include new instrumentation, improved startup flow capacity, analysis of the diverter valve system and additional tank volume data. A new uncertainty analysis is being developed in conjunction with these efforts. This paper concerns that analysis, it is divided into two major sections. The first provides a review of uncertainty components described in previous publications. The second section is a discussion of the uncertainty in temperature measurement.
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Document ID: 0A841D66

Uncertainty And Traceability For The CEESI Iowa Natural Gas Facility
Author(s): Aaron Johnson, Tom Kegel
Abstract/Introduction:
This paper presents an uncertainty analysis for the CEESI Iowa natural gas calibration facility. The facility calibrates flow meters up to flows of 10.7 actual m3/s, at nominal pressures of 7174 kPa. Flow meters are calibrated by a set of nine turbine meter standards that are ultimately traceable to NIST. The analysis shows that the facility can achieve an uncertainty of 0.30% at a 95% confidence level.
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Document ID: 11C9AA3C

Un-Certainty For Un-Conventional Masses
Author(s): Emil Hazarian
Abstract/Introduction:
The paper will present the concerns and specifics of the uncertainty assessment for non-denominated masses, parts of force machines used for the calibration of load cells.
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Document ID: 958470F7

Youden Plots Applied To Interlaboratory Comparison Mass Measurements
Author(s): Frank E. Jones
Abstract/Introduction:
Data from an interlaboratory comparison study involving 10 laboratories, each of which made mass measurements on 4 1-kilogram artifacts, were analyzed using techniques of Youden. Using these techniques, precision and systematic error or bias, were easily separated. The artifacts (weights) were all fabricated from stainless steel of approximate denstity 8,000 kg/m3. The NIST and other laboratory kilograms were in the form of cylinders with height approximately equal to the diameter of the base. In addition, one of the weights was in the form of a hollow sealed cylinder (with height approximately equal to the diameter of the base) with an approximate density of 3,000 kg3 used in conjunctionwith a tube-shaped weight of approximate density 8,000 kg/m3, configured as a tube with surface area approximately that of its mate. Also, in addition, one weight was configured of solid concentric rings that exaggerated the surface area of a normal weight and another weight with an exaggerated height-to-base ratio to accentuate sensitivity to temperature effects.
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Document ID: 0A609530

Reproducibility: A Major Source Of Uncertainty In Weighing
Author(s): John P. Clark, A. Harper Shull
Abstract/Introduction:
Balance confirmation tests usually include eccentricity, linearity, and repeatability. The latter is a measure of the random variability of the instrument. Further, repeatability is usually based on 10 consecutive measurements of a mass standard in a short period of time. The test results are used to verify the balance performs within manufacturers specifications. These test results are often used in calculating an estimate of the uncertainty in measurements made with the balance.
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Document ID: B02F42E9

How To Achieve ISO 17025 Certification In 10 Easy Steps
Author(s): Benny R. Smith
Abstract/Introduction:
The increasing popularity of ISO 17025 as a means of insuring product quality has spawned a flurry of demand for compliance. This paper presents an approach for achieving compliance through internal auditing and careful selection and application of process controls.
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Document ID: 01390D6D

Avoiding Pitfalls In Measurement Uncertainty Analysis
Author(s): Benny R. Smith
Abstract/Introduction:
Pitfalls, both subtle and obvious, await the new or casual practitioner of measurement uncertainty analysis. This paper describes the more common mistakes that are made and gives a prescription for staying out of trouble. A worked example illustrates the preferred technique.
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Document ID: F5084CD8

Inergration Of ISO 10012 Into Us Measurement Processes
Author(s): Bill Mccullough
Abstract/Introduction:
This paper presents an overview of ISO 10012 and that standards approach to measurement systems. While rooted in time proven metrological principles, 10012 extends those principles to wherever quantitative measurement are made. Some new words, or usages, are explored and shown to simply be new ways to express old processes. Customers requirements that product conform to determined requirements provides opportunities for improvement in the measurement process. ISO 10012 provides guidance and tools to help those whose product is measurement.
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Document ID: 6493A655

The Implementation Of Toroidal Throat Venturi Nozzles To Maximize Precision In Gas Flow Transfer Standard Applications
Author(s): P. Delajoud, m. Girard, m. Bair
Abstract/Introduction:
The use of toroidal throat critical flow Venturi nozzles for the measurement of the mass flow of gasses is well known and described in ISO and ANSI/ASME standards. A new flow module uses nozzles as the basis of a high precision transfer standard system to cover the range of flow from 0.02 to 40 gs-1 (1 to 2 000 Nlmin-1) and beyond. In the new module, a gas conditioning system defining an isothermal, unidirectional flow stream is combined with a toroidal throat Venturi nozzle. The calculations used to derive flow include secondary corrections not usually considered and are applied at Reynolds numbers well below the limit defined by the ISO standard. The back pressure ratios necessary to assure critical flow in these conditions have been determined experimentally over the full flow range as a function of Reynolds number and at absolute upstream pressures from 20 to 500 kPa for a variety of nozzle sizes. Experiments to evaluate the influence of operating conditions on the measurement precision of the modules have been conducted. The results confirm the suitably of the new design as an intercomparison artifact and as a tool for the dissemination of reference mass flow values.
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Document ID: 5176453D

The Premature Unchoking Phenomena Of Critical Flow Venturis
Author(s): Richard W. Caron, Charles L. Britton, Thomas m. Kegel
Abstract/Introduction:
The choking pressure ratio (CPR) for a Critical Flow Venturi (CFV) is defined as the ratio of the maximum permissible exit pressure to the inlet pressure that can exist across the venturi and still maintain sonic velocity at the throat. One dimensional isentropic flow theory states that when sonic velocity exists in the throat of a CFV, the throat static pressure is at a given percentage of the inlet stagnation pressure. The exact value is dependent upon the specific heat ratio of the gas. For air, the throat static pressure should be 0.528 of the inlet stagnation pressure. A conical diffuser is attached downstream of the throat of a CFV to assist in the pressure recovery of the device. Actual test data has shown that the static pressure downstream of the CFV can be substantially higher than the 0.528 pressure ratio between the inlet and throat. The seemingly obvious conclusion that can be drawn is that the minimum CPR for any CFV will be equal to 0.528 or higher.
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Document ID: 4CE28FCE

Inter-Laboratory Comparisons And Application Uncertainties Of Dry Piston Provers
Author(s): Harvey Padden
Abstract/Introduction:
Uncertainty analyses are essential to proper metrology. However, error sources can be accidentally omitted or miscalculated, so empirical verification of the uncertainty analysis is necessary. We have previously presented analyses asserting combined expanded uncertainties of 0.095% to 0.110% for our dry piston flow provers. To allow for miscalculation, we can be conservative and claim only 0.15%, but it is still necessary to verify the uncertainty by empirical means. At this level of accuracy, the only means of verification is through peer-to-peer interlaboratory comparisons. In the last year, we have performed informal comparisons of a single pair of provers with a number of national and private laboratories on three continents. We necessarily developed comparison methodology taking into account the particular characteristics of the instruments being compared. In order to do so, we also performed studies of the effects of certain error sources, such as inventory volume.
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Document ID: F467E852

Initial Measurement Results For 40 NIST Rm 8240 Standard Bullets
Author(s): J. Song, E. Whitenton, L. Ma, T. Vorburger, A. Zheng
Abstract/Introduction:
The RM (Reference Material) 8240 standard bullets are developed at the National Institute of Standards and Technology (NIST) to support the National Integrated Ballistics Information Network (NIBIN), recently established by the Bureau of Alcohol, Tobacco and Firearms (ATF) and the Federal Bureau of Investigation (FBI). The RM bullets are designed as both a virtual and a physical bullet signature standard. The virtual standard is a set of six digitized bullet signatures originally profiled from six master bullets fired at ATF and FBI using six different guns. By using the virtual signature standard to control the tool path on a numerically controlled diamond turning machine at NIST, 40 RM bullets were produced. A bullet signature measurement system based on a stylus instrument was developed at NIST. A comparison parameter and an algorithm using auto- and cross-correlation functions were proposed for qualifying the bullet signature differences between the RM bullets and the virtual bullet signature standard.
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Document ID: 0A0305A3

Enhancing Secondary Force Transfer Standard Performance
Author(s): Michael Tovey
Abstract/Introduction:
Primary standard force calibrations are performed by dead weights in the earths gravity field. Because of the expense of dead weight test facilities, particularly for high capacity requirements, many force calibrations are performed using secondary standards such as strain gage based force transducers (load cells) and proving rings, which are in turn calibrated by primary standards. The performance of strain gage based force transducers as secondary transfer standards has continued to improve. A summary measurement uncertainty analysis for a secondary standard force calibration is presented in order to identify the more significant factors contributing to measurement uncertainties. These factors are discussed with a view of achieving lower uncertainties in the future.
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Document ID: DA7869D0

Having Confidence In Specifications
Author(s): David Deaver
Abstract/Introduction:
This paper presents some of the challenges in creating instrument specifications from a manufacturers perspective and some of the difficulties using specifications as an estimate of uncertainty from a users perspective. Despite the difficulties, specifications are the most common means of determining the Type B uncertainty for the standard when making a GUM (Guide to Uncertainty of Measurement) compliant uncertainty analysis. An explanation is presented for the practice of providing 95% and 99% confidence specifications, warranting only the 99% specifications, and verifying the 99% specifications to 95% confidence.
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Document ID: 58764D1E

Covariance And Correlation Demystified
Author(s): Ricardo A. Nicholas
Abstract/Introduction:
Covariance and correlation can be somewhat of a mystery to evaluators of measurement uncertainty. Covariance, in particular, appears to be the most enigmatic, and therefore the least likely to be used. That need not be the case for those willing to learn or recall a few simple statistical theorems and study a small number of examples. A minimal mastery of them is a prerequisite to achieving a well-rounded competency in measurement uncertainty evaluation. Enabling the uncertainty evaluator to understand, calculate and correctly use these quantities in their work is the thrust of this paper.
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Document ID: 8B709FA6

Development Of A Cd-Rom Metrology Course At NIST
Author(s): Georgia L. Harris
Abstract/Introduction:
The NIST Weights and Measures Division (WMD), formerly the Office of Weights and Measures (OWM), conducts training in mass metrology at Basic, Intermediate, and Advanced levels. Over the years, the demand for these courses greatly exceeded the availability. In addition, requests are regularly received to provide refresher training and to provide training onsite. Available resources are not adequate to meet the number of requests. In view of the needs, WMD decided to develop a CD-ROM training course and to transfer the contents of a one-week hands-on course to an interactive, multimedia CD-ROM metrology course that would include interactive activities, knowledge checks, examples, video demonstrations, and numerous specialty graphics and photos.This paper presents 1) background information about the project, 2) an overview of the NIST Weights and Measures Division Basic Mass Metrology Seminar, 3) the process used for content development and review (from the original request for proposal and project description to final product review and delivery), and 4) numerous lessons learned during the development of the course. The course material is being translated into Spanish for even wider distribution and metrology support.
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Document ID: 8517417E


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