Measurement Library

Measurement Science Conference Publications (1998)

Traceability In The Mexican Petroleum Industry.- A Key Factor For Custody Transfer Operations
Author(s): Luchsinger H., Arias R., Maldonado m., Loza A., Reza J.
Abstract/Introduction:
The National Metrology Center of Mexico (CENAM) has been involved for the past 18 months in calibration services for the mexican petroleum company (PEMEX). The services include in site calibrations of metering systems for liquid fuels custody transfer in marketing terminal stations, of pipelines metering devices, and road tanks. All calibration certificates issued by CENAM are directly traceable to national standards. A key contribution of CENAM in this project, as a result of intensive data analysis, is the inclusion of temperature effects on master meter calibrations for better measurements in custody transfer transactions, a barely considered effect in similar metering systems. The awareness and evaluation of the temperature effect leads to the elimination of a systematic error in each field measurement.
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Document ID: 79D0EF8A

Determination Of Gear Artifact Measurement Uncertainty On Coordinate Measurement Machines By Measurement Decomposition And Utilization Of Reference Artifacts
Author(s): Bill Rasnick, Bruce Cox, Mike Sherrill
Abstract/Introduction:
The requirement for primary-level calibration of gear profile and gear tooth alignment has led to development of a method for quantifying the measurement uncertainty on the artifact being calibrated that does not rely on a transfer comparison This method, developed jointly by National Institute of Standards and Technology (NIST) and Oak Ridge Metrology Center (ORMC) personnel, consists of breaking down the measurement method into simpler components and quantifying these components using generally accepted refenence artifacts with low uncertainties, (gage blocks, ring gages, spheres, etc.). Once quantified, these components are added in quadrature according to NIST Technical Note 1297, 1994 Edition1. Verification of this method can be accomplished by intercomparisons with other methods and laboratories.
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Document ID: 544D34DD

Verifying The Variation In Threaded Setting Plug Pitch Diameter Transfer To Contact Mated Internal Thread By Measurement And Calculation, Including Functional Size Analysis
Author(s): Arthur G. Strang
Abstract/Introduction:
Transfer of groove diameter from external thread mated to an internal thread exceeds industrial claims. The simple Jeffcott C correction accompanying the thread wire calibration is only reliable for X and W tolerance for lead and flank angle on threads. Present procedures for measuring groove diameter, calculating pitch diameter and functional size need clarification. A method for determining the true pitch diameter of a mated internal thread (assembly size) is introduced and may be a reliable method to asses the accuracy of measured screw thread characteristics.
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Document ID: 556BAC97

Uncertainty For Differential Gaging For 60 External Straight Threads
Author(s): Arthur G. Strang
Abstract/Introduction:
Differential gaging for statistical process control in the manufacturing of threaded fasteners is becoming increasing popular. By routinely measuring threaded fasteners taken directly from screw machines, operator can make corrections to obtain minimum defects. Three groups of 10 external threads for size 0.5-13UNC were carefully measured in the laboratory by three metrologists -1) W tolerance plug gages, 2) plug gages with threaded product form variations, and 3) random off-the-shelf fasteners. The indicating gage values were plotted for deviations from measured true pitch diameter and from the best calculated values for functional size from measurements of the thread characteristics. All indicating gage designs were investigated. Estimates of expanded uncertainty were for both laboratory measurements and the indicating gage measurements.
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Document ID: 446D847D

A Guarding Technique For Regions Containing Potential Gradients
Author(s): Karl F. Anderson
Abstract/Introduction:
Conventional guarding prevents regions containing a single electrical potential from exchanging electrical charge with the rest of the environment through imperfect insulation. A new guarding technique prevents electrical charge exchange from regions containing potential gradients. Conventional guards are shown to be a special case of guards for potential gradients. The gradient guard, charge channel and guard group versions of the technique are discussed. Experimental results demonstrate that a current-carrying conductor, having a significant IR drop and protected within a charge channel can have the same entry and exit current despite poor and varying insulation performance from the conductor to the environment.
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Document ID: B5EEBCF8

Interlaboratory Comparisons
Author(s): Woodward G Eicke
Abstract/Introduction:
In the past ten years, a surge of interest in interlaboratory comparisons (round-robins) in physical metrology has emerged as another tool to ensure traceability to national and international standards. Interlaboratory comparisons are now being conducted by ad hoc groups formed specifically for the task and under the auspices of organizations such as the National Conference of Standards Laboratories (NCSL), NASA and others. This paper will examine interlaboratory comparisons in light of todays growing need to document traceability and verify measurement capability. A brief report on the status of NCSLs development of a recommended practice for interlaboratory comparisons is also included.
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Document ID: 4D76FA4C

Making The Measurement Plan
Author(s): Philip G. Stein
Abstract/Introduction:
The supplier shall determine the measurements to be made and the accuracy required, and select the appropriate inspection, measuring, and test equipment that is capable of the necessary accuracy and precision, and part of 4.11.1 says Inspection, measuring, and test equipment shall be used in a manner which ensures that the measurement uncertainty is known and is consistent with the required measurement capability. During my career as a consultant, I have helped many companies achieve registration to one of the ISO standards by examining their quality systems, most particularly paragraph 4.11. My experience is that neither of the above quoted requirements are done very well, and that most assessors and registrars dont have the experience necessary to properly evaluate applicants efforts in these areas. The solution is Measurement Planning - a defined process by which the measurement uncertainty required of M&TE is determined, and the capability of the measurement system is determined and shown to be adequate in order to satisfy the letter and spirit of the requirement.
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Document ID: 0C3BB921

Accreditation On The Shop Floor
Author(s): Peter B. Crisp
Abstract/Introduction:
Many organizations are now aware of accreditation as a means of providing formal recognition of their measurement capabilities and are contemplating the best approach to becoming accredited. Usually, the first step is to gain accreditation of the best controlled areas i.e. a Standards Laboratory supporting a production or service facility. Standards Laboratories are usually well controlled and have highly trained staff and are therefore an obvious choice for the first stage of accreditation because they will most easily meet the accreditation criteria. However, if the customer demand for accredited calibration certificates is high, then having to route work through the standards laboratory will increase the turn-around time, distract standards staff from their normal duties and increase the chance of potential damage to expensive and perhaps irreplaceable equipment. It is only when the normal point of calibration - the shop floor - is accredited that such potential problems (in terms of the standards laboratory) disappear. This paper relates the experience of extending accreditation to cover Waveteks production and service areas and examines the pros and cons of doing so. It is hoped that our experience will provide useful information to other organizations contemplating accreditation of their normal working areas.
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Document ID: 67078CE0

Ensuring The Traceabilitv Of Oscilloscope Calibration
Author(s): Mark V. Ashcroft
Abstract/Introduction:
Oscilloscope calibration used to be a costly process, calling for substantial investment in time, equipment and operator training. Traceability to National Standards was also expensive and difficult to achieve, with the limited accuracy of analog oscilloscopes in particular making it difficult to justify the time and expense. A new breed of oscilloscope calibrator has emerged that dramatically reduces calibration costs by allowing the process to be automated. However, the traceability problem remains and can only be overcome if traceability is considered an integral part of the calibrator design. Design for traceability in the calibrator not only reduces cost of ownership, it can also reduce calibration uncertainties in line with the requirements of the latest digital-storage oscilloscopes and active scope probes. In this paper the generation of fast edges and leveled sinewaves, which are used for transient response testing, gain flatness and bandwidth testing of oscilloscopes, are used as examples to illustrate how careful calibrator design can ease traceability problems and improve accuracy. The availability of higher order standards via which oscilloscope calibrators can be traceably calibrated to National Standards is also discussed. Relatively few calibration laboratories can support the high frequency parameters required, resulting in significant calibration costs, shipping costs and equipment downtime. A novel calibrator architecture is described that eases these problems by confining high frequency parameter calibration to active heads that can be detached from the calibrator mainframe unit and sent to a calibration laboratory via normal mail services
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Document ID: 01730F15

Validation Of A Calibration Management Software Package
Author(s): Jim Erickson
Abstract/Introduction:
There has never been a greater need for control over manufacturing processes than in todays pharmaceutical manufacturing environment. As this requirement has increased, so has the need for better management of the measurement equipment used to measure and control these processes. Fundamental to managing this measurement equipment is assuring it is properly calibrated and maintained. Most pharmaceutical manufacturers are being faced with an increasing number of instruments requiring calibration, while simultaneously reducing the resources available to maintain them. One popular method for minimizing the resources needed for maintaining instrumentation is the implementation of a commercial off-the-shelf (COTS) software package for managing the measurement equipment. Under cGMPs this software application must be validated, as it is a part of the quality assurance of the manufactured product.
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Document ID: 31E5DAE8

Gas Piston Gage And Ball Gage Calibration, Effective Area, And Cross-Floating: New Approach
Author(s): Frank E. Jones
Abstract/Introduction:
The calibration variables, force F and pressure P, are conventionally used to calculate effective area A for piston gages and ball gages. Essentially, F is divided by P to arrive at A. In many gas piston gages and ball gages, A appears to depend on pressure at pressures at which distortion with pressure is insignificant. It is shown in this paper that curvature of plots of A against P is due to the fact that the ratio of F to P is not intrinsically constant for devices. The relationship between P and F is shown to be represented much better by an equation of the form P a + bF derived from linear least squares analysis of calibration data. Recent results1 have shown that this procedure is very effective in developing very efficient equations for calculating pressure for gas piston gages and ball gages. The cross-floating technique used to determine the effective area of a test gage by floating it at the same pressure against a reference gage of presumed known effective area is examined in the context of this new analysis.
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Document ID: 2D225662

Direct-Scanning Alpha Spectrometer For Americium And Plutonium Contamination
Author(s): W. C. Ward, H.E. Martinez, T.O. Nelson, A.N. Morgan, P. L. Serrano
Abstract/Introduction:
A multichannel instrument has been developed for automated in situ measurements of trace 239Pu and 241Am contamination on a surface whose alpha count is dominated by 235U and 234U decay. The hemispherical scanning assembly incorporates a vacuum chamber with a rotary table, 13 fixed ion-implanted silicon detectors, spectroscopy electronics, and software for preprocessing, automatic calibration, measurement, discrimination, and postprocessing. The system produces an overall contamination estimate as well as a complete log and three-dimensional display of the location of areas of high surface contamination. We present performance data as well as discrimination algorithms, system integration, calibration, and control issues, and dynamic geometric efficiency calculations related to the design and qualification of the instrument.
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Document ID: F51F1A59

Revised Uncertainty Of The NIST 30 Mhz Phase Shifter Measurement Service
Author(s): Jeffrey A. Jargon
Abstract/Introduction:
Although the measurement service for 30 MHz phase shifters has been in operation for many years at the National Institute of Standards and Technology (NIST), modifications have been made to the system and changes in and phase shift is a fundamental requirement policy on statements of uncertainty have occurred since the last published analysis. The linear displacement of the standard phase shifter is now measured with an are ultimately referenced to 30 MHz. electronic counter instead of a mechanical one, and a new comparison receiver has NIST can measure both incremental been installed in the system. Uncertainties of the system are due to the standard phase shifter, resolution of the comparison receiver, mismatch within the system, phase shift of the standard waveguide below-cutoff (WBCO) attenuator, and repeatability. The individual components are stated and combined to comply with the NIST policy on statements of uncertainty. The combined standard uncertainty is on the order of 0.28 per 30 increment.
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Document ID: 5C5CF972

Long Term Stability In A Calibrated Time-Domain Network Analyzer
Author(s): Donald C. Degroot And Jeffrey A. Jargon
Abstract/Introduction:
We report on a fully calibrated digital sampling oscilloscope with time-domain reflection/transmission (TDR/T) capabilities. This system, known as a time-domain network analyzer (TDNA), calibrates Fourier-transformed TDR/T waveforms using a conventional network analyzer error model, and is used to measure the rf and microwave responses of devices and interconnects. While our TDNA measurements closely match data obtained with a commercial frequency-domain network analyzer (FDNA), we observe a difference in the TDNA results that increases with frequency. By comparing identical TDNA calibrations, we determine the upper bounds on the uncertainty due to the repeatability limits and show the overall accuracy of our TDNA system to be limited by the oscilloscopes ability to repeat measurements in the short term. Remarkably, this measurement uncertainty did not increase when making measurements as long as one week after the initial calibration.
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Document ID: B52AB263

An Approach To Automating Mass Metrology Systems
Author(s): David A. Dikken
Abstract/Introduction:
An automated measurement system has been designed and implemented for mass metrology laboratories. The design includes both hardware and software components which provide control charts for the evaluation of balance performance, continuous recording and charting of environmental conditions in balance weighing chambers and the laboratory, implementation of operating procedures for calibration, and report generation. The structure of the system includes digital data collection from balances, environmental instruments, and laser bar-code readers. Data is reduced and analyzed using control charts and statistical techniques including linear regression, students t-test, and F ratio tests. The system is paperless until calibration reports are generated. Wireless technician workstations are developed using laptop PCs and radio frequency networks. Primary considerations in the development included improved measurements, increased efficiency, enhanced uniformity, cost savings, and thorough recording and documentation.
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Document ID: EE35E5AA

Do You Just Want Traceability, Or Are You Serious About Flow Measurements?
Author(s): David A. Todd, Jr.
Abstract/Introduction:
This paper examines the implications of traceability as it pertains to flow measurement and flowmeter calibration. Contrasted with other areas of metrology, the absence of a maintainable unit of flow vis-a-vis the prototype kilogram, triple point cell or Josephson array complicates any attempt to define traceability in the usual manner. Having a flow measuring device calibrated at NIST, for example, or at another facility in possession of certain documentation, does not in itself provide evidence that a particular flow system will produce measurement results having a specified uncertainty. Growing interest in quality system registration and, more significantly, laboratory accreditation, has placed renewed emphasis on assessing the actual output of measurement processes in real terms. These issues are addressed, along with some discussions of approaches which can be used to validate the performance of flowmeter calibration systems on a quantitative basis.
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Document ID: 760D95C6

Measurement Comparison Programs In A Flow Calibration Facility
Author(s): Thomas m. Kegel
Abstract/Introduction:
A measurement comparison program (MCP) is an important component of a calibration laboratory measurement assurance program. It consists of using an artifact to compare the results of one laboratory with those of another. An MCP will maintain traceability and uncover any systematic effects that may be present but undetectable based on an uncertainty analysis. This paper discusses application of MCP techniques to flow measurement. Topics include artifact design, data interpretation, and the current status of some ongoing MCP activities.
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Document ID: 32D77570

Ondestructive Assay Techniques For A Vitrified Waste Form
Author(s): J. R. Hurd. G. W. Veazey, T. H. Prettyman, D. J. Mercer, T. E. Ricketts, R. K. Nakaoka
Abstract/Introduction:
Rocky Flats Environmental Technology Site (RFETS) is currently considering the use of vitrified transuranic (TRU)-waste forms for the final disposition of several waste materials. To date, however, little non-destructive assay (NDA) data have been acquired in the general NDA community to assist in this endeavor. This paper describes the efforts to determine constraints and operating parameters for using NDA instrumentation on vitrified waste. The present study was conducted on a sample composed of a plutonium-contaminated ash, similar to that found in the RFETS inventory, and a borosilicate-based glass. The vitrified waste item was fabricated at Los Alamos National Laboratory (LANL) using methods and equipment similar to those being proposed by RFETS to treat their ash material. The focus of this study centered on the segmented gamma scanner (SGS) with 1/2-inch collimation, a technique that is presently available at RFETS. The accuracy and precision of SGS technology was evaluated, with particular attention to bias issues involving matrix geometry, homogeneity, and attenuation. Tomographic gamma scanning was utilized in the determination of the waste form homogeneity. A thermal neutron technique was also investigated and comparisons made with the gamma results.
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Document ID: C5387FB5

Digital Multimeter Calibration
Author(s): Fred Hubbard
Abstract/Introduction:
Digital multimeters (DMMs) have evolved from the voltage-only digital voltmeters (DVMs), first introduced in the mid-1950s. Todays digital multimeters have more ranges, more functions, and greater accuracy than ever before, presenting a growing challenge to the metrologist.
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Document ID: 52172AE9

Title: Calibration Not Required-Surely You Cant Be Serious!
Author(s): Philip G. Stein
Abstract/Introduction:
Its pretty clear when simple measurement tools should be subject to calibration control or measurement assurance. Its not so obvious for large automated pieces of process equipment measuring internal parameters such as time duration, temperature, pressure, or working current. Must these embedded instruments be controlled, or are they exempt (Calibration Not Required)?
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Document ID: 80B3C165

Interlaboratory Comparisons
Author(s): Woodward G Eicke
Abstract/Introduction:
In the past ten years, a surge of interest in interlaboratory comparisons (round-robins) in physical metrology has emerged as another tool to ensure traceability to national and international standards. Interlaboratory comparisons are now being conducted by ad hoc groups formed specifically for the task and under the auspices of organizations such as the National Conference of Standards Laboratories (NCSL), NASA and others. This paper will examine interlaboratory comparisons in light of todays growing need to document traceability and verify measurement capability. A brief report on the status of NCSLs development of a recommended practice for interlaboratory comparisons is also included.
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Document ID: EF873D0B

New Eal Guidelines For The Calibration Of Dry-Block Calibrators In Europe
Author(s): Tom m. Hansen
Abstract/Introduction:
Ametek Denmark A/S is part of the AMETEK GROUP with headquarters in the USA, and has for the last 12 years been among the worlds leading manufacturers of temperature and pressure calibrators. 95% of the total production is being exported to the most important industrial countries in the world via an extensive net of local distributors. Therefore, also calibration with traceability to national and international standards is a very important part of Ametek Denmarks activities.
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Document ID: 109B3E21

Validation Of Electronic Pressure Calibrators
Author(s): Bogdan m., Maziarz John, G. Gregor
Abstract/Introduction:
Pressure calibration offers many challenges to the calibration industry as it demands high accuracy over wide range of pressures and temperature. Traditionally, deadweight testers have been used to perform high accuracy calibrations. Recent advances in the electronic pressure calibrator technology permit for these devices to serve applications traditionally reserved for deadweight testers (such as calibration of flow computers in custody transfer). These applications prove very hard to penetrate for the calibrators. As a rule, individual instruments are subjected to grueling verification tests and often fail because the conditions of the tests are not carefully controlled. This paper discusses issues, problems and solutions found in application and verification of electronic pressure calibrators. Principle differences between deadweight testers and calibrators are discussed to include accuracy statements. A detailed account of corrections needed to realize rated accuracy of a deadweight tester is given and complemented by series of tips and techniques for proper use of electronic calibrators. Finally, a step by step procedure is given for setting up and carrying out verification tests in environmental chambers. We conclude that such chambers offer very unstable test environment for pressure verifications. The limitations of the system can be overcome by limiting the volume of test system and shortening the data collection process to minimize fluctuations in temperature.
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Document ID: 37DAC5D7

Capturing The Sub Micro-Radian
Author(s): J. R. Ban
Abstract/Introduction:
The pursuit of the sub micro-radian uses tilt and alignment controls, capability studies and uncertainty analysis. Tt begins with the definition of an axis of rotation, continues with a measurement technique that includes alignment to the rotational axis. The process proceeds with measurements and analysis and ends in a result caged with a statement of uncertainty. There are several types of misalignments. The error is dependent on the geometry. Some misalignments cause a tilt, some are interactive with the internal geometry of the artifact or instrument, some are complex and some may not be significant at all. The error functions for the tilt and interactive types are the most difficult to visualize. These complex functions can be very significant in the world of the sub micro-radian. The geometry for these phenomenon is discussed. The metrology used to determine the capability of dividers, autocollimators, theodolites, pentaprism, polygon, parallel mirror and the laser interferometer angular optic is presented.
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Document ID: FA11215F


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