Application Of The NIST Testing Strategies To A Multirange Instrument
Author(s): A. D. Koffman, T. m. Souders
Abstract/Introduction:
A new modeling and test point reduction technique for analog and mixedsignal devices has been developed at the National Institute of Standards and Technology (NIST). This technique has been applied as a case study to a manufacturers thermal transfer standard for potential use in testing and calibration. An empirical model is formulated using complete test data from many devices collected from several production runs. The model is then algebraically reduced using singular value decomposition and QR decomposition. Once the fmal reduced model is obtained, it is used to test devices which are measured only at a reduced set of test points. The model allows accurate prediction of device behavior at all other test points. Techniques for optimal model size selection are discussed. Device modeling results are presented and compared to complete test data.
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Document ID:
9482E2CE
Pitch Diameter Measurements Of 60 Degree Screw Thread Plug Gages
Author(s): W. G. Hatzman, Jr.
Abstract/Introduction:
Threaded fasteners are a common choice in a wide range of fastening applications because of their interchangeability, low cost, and impressive ability to withstand stress. The users of threaded fasteners commonly rely on inspection gages which are used to check fasteners for thread form and size conformance.
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Document ID:
417F26E1
Position Measurement Of Internal Screw Threads
Author(s): Bruce Armstrong
Abstract/Introduction:
The most accurate method for measuring the position of internally threaded holes of an assembly has been debated recently. One method uses the Pitch Diameter of the internal threads as a datum for determining hole position. A seemingly more elegant method, which was previously advocated, uses the Minor Diameter of the internal threads as a datum for determining thread position. Using the Minor Diameter as a datum is initially easier to accommodate, and appears to be more straightforward. Unfortunately, using the Minor Diameter as a datum leads to false conclusions about threaded hole position. The manner by which threads are designed and dimensioned leaves the Minor Diameter with much larger size and positional tolerances than the Pitch Diameter. In addition, the Minor Diameter is a non-functioning surface that does not reflect the position of the mating male threads when assembled. It is acknowledged that to locate on the Minor Diameter as a cylindrical surface Regardless-of-Feature-Size (RFS) is easier than locating on the thread Pitch Diameter RFS. However, it shall be shown that locating on the Minor Diameter RFS is inherently less accurate for determining hole position than using Pitch Diameter as a datum with the seemingly less accurate Maximum-Material-Condition (MMC) criteria. This paper shall show that, considering the total process, locating on the Pitch Diameter with MMC criteria is more accurate and overall easier than using Minor Diameter as a datum RFS.
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Document ID:
11BF0D1B
Variations In Size Measurements By Indicating Gaging Systems
Author(s): Ralph Veale, Arthur Strang, Chou Hsiao-Yu
Abstract/Introduction:
The National Institute of Standards and Technology has investigated the efficacy of indicating gaging systems used to measure pitch diameter and functional size of threaded fasteners. Three external systems and four internal systems, representing four manufacturers, were used in the test. Twenty-seven external threads and eleven internal threads were measured. Some of the samples were purposely produced with form errors near and beyond product tolerances. The study shows that when the form errors are outside the product tolerances, indicating gages from different manufacturers give different results and do not always match the values obtained by alternate methods. Results of the tests are presented in tabular form.
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Document ID:
2E4571A5
Spatial And Measurement Bias And Variability In Environmental Measurements
Author(s): J. Jeffrey Van Be Evan J. Enghmd
Abstract/Introduction:
Analytical methods in the laboratory have typically been the focus of attention for QA/QC programs that are developed to minimize and assess errors in environmentaJ measurements. Unforhmately, significant bias and variability occurs before data are reported from the laboratory, and traditional QA&C programs are often inadequam to identify and control these errors. A common problem in developing those QA/QC programs is the lack of clearly stated objectives that would allow everyone involved in the environmentaJ sampling to properly allocate their limited resources consequently, significant sources of error that could affect basic decisionmaking process are often neglected. The decision maker often is unaware of the significant sources of error in the coJlection and analysis of environmental samples and often spends too much money on potential problem areas that have little impact on the decision-making process. Tbis paper provides a framework for prospective de&ion makers and people involved in environmental measurements to develop an integrated, coordinated approach to minimizing, assessing, and controlling spatial and measurement errors.
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Document ID:
0873E818
Environmental Measurements At The Epa Region 9 Laboratory
Author(s): Brenda Bettencourt
Abstract/Introduction:
The United States Environmental Protection Agencys (EPA) Region 9 Laboratory is responsible for conducting analyses in support of EPAs programs and regulations. Region 9 includes Arizona, Nevada, California, Hawaii, the Navajo Nation, and several Pacific Islands. The data produced by the Region 9 Laboratory may be used for monitoring, enforcement, or criminal investigation purposes.
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Document ID:
009F9DE2
Equipnent IlAN/LGEIlENT (POOL/CRIB) Iflpleflentation Growing Pain
Author(s): James P. Tavernier
Abstract/Introduction:
THE START-UP OF AN INSTRUMENT POOL BRINGS WITH IT MANY PROBLEflS AND ISSUES THAT NUST BE RESOLVED. ALTHOUGH IT MAY BE THOUGHT OF AS A STRAIGHT FORWARD APPROACH, THERE IS MUCH PLANNING THAT MUST BE ACCOflPLISHED PRIOR TO THE INITIALIZATION. THE FOLLOWING ARE THE ISSUES THAT MUST BE ADDRESSED . 1. mANAGEMENT CONmITMENT AND SUPPORT REQUIREtlENTS 2. EDUCATION AND ACCEPTANCE OF USING DEPARTMENTS 3. DETERMINATION OF POOL AND NON-POOL EQUIPMENT 4. FlANPOWER REQUIREMENTS 5. FINANCIAL ASPECTS 6. LEASE AND RENTAL AGREEMENTS 7. INTERFACE WITH OTHER GROUPS (PROPERTY, ACCOUNTING, ETC.) 8. ACCESSORIES ACCOUNTABILITY 9. DATABASE REQUIREmENTS
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Document ID:
80C11D5C
Biomedical & Pharmaceutical Metrology
Author(s): John Michk
Abstract/Introduction:
A general discussion of the Food and Drug Administrations regulation of the manufacture of pharmaceuticals, medical instruments, and devices. Particular attention is given to the practice of quality metrology in compliance with the FDAs GLPs, CGMPs, and GMPs.
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Document ID:
A409C627
Length Metrology Of Complimentary Small Plastic Rulers
Author(s): Daniel T. Doiron
Abstract/Introduction:
The national measurement system concerns the relationships between individual measurements and the specific units of measure. In some cases, gage blocks for example, there are standards, a large body of scientific research, and considerable effort taken to trace the accuracy of blocks used in manufacturing back to the unit of length. The international trend to laboratory accreditation (NVLAP, NAMAS, etc.) is a formalization of the idea of assuring measurement accuracy by assessment of laboratory practice and evaluation of a measurement systems relation to the unit of length.
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Document ID:
51F0B087
A Summary Look At Uncertaintids In Dimensional Measurements Made At Nonstandard Temperatures
Author(s): Dennis A. Swyt
Abstract/Introduction:
A recent IS0 proposal to change the international standard reference temperature for dimensional measurements from 20 C to 23 C, while unadopted, is of technical import l. Since referring measurements to a standard temperature serves to reduce actual variations in dimensions of parts due to thermal-expansion effects as well as uncertainty in measurements, a shift in reference temperature can increase each, that is, both variations and uncertainties. This is an extract of an extended NIST paper which looks at possible errors and likely uncertainties in dimensional measurements due to thermal-expansion effects where those measurements are made away from the reference temperature 2, either the specific interval of 3 C due to a change to the proposed 23 C or an arbitrary interval due, for example, to the settling of a temperature control system at other than the standard reference temperature.
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Document ID:
A76411A2
Laser Rotary Encoders In Smallest Computer Disk Drive And Largest Telescope
Author(s): Charles P. Wang
Abstract/Introduction:
Based on the Laser Doppler DisplacementMeter( LDDM)Technologyand using two laser beams to measure two displacements separated by a fixed distance, the rotational angle which is equal to the difference in displacements divided by the laser beam separation, can be measured. This technique is insensitive to translation, runout or other non-rotational motions. The resolution is 0.01 arcsec and the accuracy is 0.1 arcsec. The application of this encoder in servo track writing of computer disk drives and in pointing and tracking of the Very Large Telescope will be described.
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Document ID:
1FB6D73B
Low Voltage Considerations In Josephson Array Voltage Measurements
Author(s): Thomas J. Mego, Adam Daire,
Abstract/Introduction:
This paper presents considerations for making low level DC measurements of voltage. The considerations are illustrated using the practical example in metrology of voltage reference comparison against a Josephson Array. Procedures for identifying, minimizing, and correcting sources of uncertainty will be discussed. In this example, Keithleys new 2002 8 12 digits DMM with plug-in nanovolt preamp combines the high-resolution and high-sensitivity needed to make voltage reference measurements approaching O.OOlppm total uncertainty. But only if we also control uncertainty due to Thermal EMF, leakage currents, magnetic interference, and other error sources to the 1 OnV level.
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Document ID:
2E199749
Instrument Calibration Using The Pneumatic Deadweight Tester
Author(s): Charles J. Reed
Abstract/Introduction:
one of the most difficult problems facing the instrument engineer is the accurate calibration of pressure of differential pressure measuring instruments. The deadweight tester or gauge is the economic answer to many of these problems.
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Document ID:
FAECFB14
A Revised Uncertainty Analysis For The NIST 30-MHZ Attenuation Calibration System
Author(s): Jeffrey A. Jargon
Abstract/Introduction:
Although the 30.MHz Attenuation Calibration System has been in operation for many years at the National Institute of Standards and Technology, several modifications have been made to the system since the last published uncertainty analysis. The linear displacement of the standard attenuators receiving coil is now measured with a laser interferometer instead of a steel ruled scale and optical projector, and a new comparison receiver has been installed in the system. The expanded uncertainty is on the order of & 0.003 dB per 10 dB step. Type A uncertainties depend upon the repeatability and resettability of the system and the device under test. Type B uncertainties are due to the standard waveguide below-cutoff (WBCO) attenuator, the resolution of the comparison receiver, the change in level of the precision phase shift standard, the level set attenuator, rf leakage, and mismatch uncertainty
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Document ID:
C8899C32
Polynomial Modeling Of Analog-To-Digital Converters1
Author(s): Otis m. Solomon, Jr.
Abstract/Introduction:
Analog-to-digital converters are frequently modeled as a linear polynomial plus a random process. The parameters of the linear polynomial are the familiar gain and offset of the analog-to-digital converter. The output of the random process is uniformly distributed on plus or minus the least significant bit of the analog-todigital converter. In this paper, the transfer function of an analog-to-digital converter is modeled as a nonlinear polynomial plus a random process. This model can explain the generation of harmonics by the analog-to-digital converter, but the simpler linear model cannot. The parameters of the nonlinear polynomial are estimated from the response to the analog-to-digital converter to a sine wave. The model parameters are used to estimate the nonlinear part of the transfer function of the analog-to-digital converter.
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Document ID:
2E4EEB59
An Integrated Approach To 3% - 4% Digit Multimeter Calibration
Author(s): Richard A. Roddis
Abstract/Introduction:
Todays calibration manager is facing an increasing focus on Quality and Company-wide Quality Management, typified by the increasingly widespread adoption of ISO9000. Which is making the calibration managers task more complex and time consuming. At the same time, an increasingly competitive business environment means that the calibration manager is expected to conform with these changing requirements while at the same time reducing budgets. In short, todays calibration manager is expected to perform more with less.
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Document ID:
B1ACDAF7
Sampling Methods For Measuring Circles And Cylinders In Coordinate Measuring Machines.
Author(s): U. Babu, J. Raja, R.J. Hooken
Abstract/Introduction:
In recent years, computer controlled coordinate measuring machines (CMM) have become the preferred method for dimensional measurement in industry. CMMs can provide detailed dimensional data for individual features such as circles and cylinders. In addition they are also capable of evaluating the relationships between various part features. In a CMM, discrete points on the part surfaces are measured first, and then a substitute geometry is fitted to the measured set of points. The results from a CMM inspection are affected by the errors that occur during data acquisition and substitute geometry computation, see figure 1. The accuracy of the machine and the probing system, systematic and random deviations of the measured surface from the ideal, number and distribution of points measured (sampling methods) are some of the factors that contribute to the uncertainty of measurement. The choice of algorithms used in the substitute geometry computation, their sensitivity, and bias to the input data contribute to errors on the software side and also lead to the methods divergence problem. Several factors that contribute to methods divergence problem have been identified, and efforts are underway to solve these problems. These include, mathematization of the basic Geometric Dimensioning and Tolerancing principles 2, development of standards for CMM software and standards for performance testing of CMMs
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Document ID:
AA74E0A7
A Novel Cmm Interim Testing Artifact
Author(s): S.D. Phillips, B. Borchardt, G. Caskey, D. Ward, B. Faust, D. Sawyer
Abstract/Introduction:
NIST is currently developing equipment and techniques to rapidly assess the performance of Coordinate Measuring Machines (CMMs). This will allow the frequent testing of CMMs to insure that they measure parts accurately. A novel interim testing artifact, which can be described as a pseudo three dimensional calibrated ball plate, has been developed. Unlike an actual 3D ball plate, this artifact is lightweight, relatively inexpensive, easy to calibrate, and adaptable to different sizes and styles of CMMs. The artifact is composed of ball bars which are calibrated for ball roundness, ball diameter, and sphere center-to-center length. These ball bars are kinematically mounted on supporting arms and can rotate (in 45 degree increments) to sweep out most of the CMM work zone. The horizontal and inclined arms are interchangeable and are available in lengths from 300 mm to 1.5 m. Specific technical innovations include a design which separates the functions of dimensional calibration accuracy from structural rigidity, the ability to carry out the interim test entirely under computer control, and a complete CMM system evaluation. The project is a joint effort between NIST, DOD, DOE, and private industry. The program is expected to be completed by 1994, and the testing equipment will be available as a commercial product through domestic industry.
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Document ID:
7EA289A6
Mass Measurement Process Error Determination And Control
Author(s): Jerry Everhart
Abstract/Introduction:
In todays competitive marketplace, it is imperative that systems of production and services be improved. This continuous improvement process requires the use of quality tools to understand and control systems of production and services. Furthermore, the application of quality tools requires that all processes be measured. Traditionally, product data analysis has been the primary area of focus with little emphasis placed on the quality of the data obtained. It is important to realize that knowledge of product quality can only result from quality data and quality data results from quality measurements (Figure 1). Product data contains the actual product value, its variation and measurement error. Measurement error includes, to some degree, instrument uncertainties, uncertainties to the measurement process, uncertainties due to entiomnental effects and operator uncertainties. Understanding, determining, and controlling measurement uncertainties is essential to improve systems of production and services. The required determination and control of product measurement uncertainties require the use of standards.
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Document ID:
8F4A7A3F
Examination Ofparameters Thatcancauseerrorin Mass Determinations
Author(s): Randall m. Schoonover
Abstract/Introduction:
We present the following quotation of Condon and Odishaw l as a succinct definition of mass: The property of a body by which it requires force to change its state of motion is called inertia, and ma is the numerical measure of this property
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Document ID:
9C4CDA8D
Measurement! Instrument Surveillance And Traceability For Weighing Machines I!sed In Production And Quality Control
Author(s): Arend Helms
Abstract/Introduction:
All essential instruments which are used in the production or in the quality control field of a manufacturer must necessarily conform with the quality requirements of the final product. As most of the manufactured products comprise a number of supply parts on the one hand and as they must cope more or less internationally with other devices and systems on the other hand it is advisory that all control instruments meet the international standards and fulfil the internationally harmonised traceability conditions. How this can be achieved, is shown for weighing machines ( balances and scales ) which are either integrated in production lines or utilised for quality control purposes.
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Document ID:
1C9422B9
The Emergence Of Multimedia Computing In Support Of Knowledge Work
Author(s): Jerry A. Van Os
Abstract/Introduction:
Multimedia refers to the delivery of information in intuitive, multisensory ways through the integration of previously independent and distinctive media-sound, still images, live-action video, animation, and text-in a single presentation under the control of a computer platform. Multimedia has the potential to provide designers with more freedom of communication and users with an effective form of information delivery.
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Document ID:
90CFBF19
A Fast Autobalancing, Direct-Reading Tvc For Ac Calibration
Author(s): L. Julie
Abstract/Introduction:
The continuing military requirements for calibration of precision AC voltage sources and other AC devices has resulted in the design of a high accuracy and highproductivity automated AC/DC transfer standard for U.S. Army calibration laboratoriesl. The new instrument adds miniaturization and automation to the best design features of earlier AC/DC TVC transfer standards originated at NIST and elsewhere.
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Document ID:
AFF63844
Methods For Accounting For Dependencies Between Components Of Measurement Uncertainty
Author(s): Semyon G . Rabinovich
Abstract/Introduction:
The basic mathematical formulas that determine the correlation coefficient between random quantities are discussed and transformed into formulas for practical calculations related to estimation of measurement uncertainty. As an example, an indirect measurement of the electrical resistance of a resister is considered in detail. Also, an alternative method of estimation of uncertainty of an indirect measurement based on transformation of the data of the indirect measurement into the data of a set of direct measurements is proposed. It is shown that in cases where the existing method based on correlation coefficientcan be used, the new method simplifies all calculations. In addition, our method can be used in cases where the correlation coefficient method is not applicable.
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Document ID:
5BB1820B
A State-Of-The-Art Mass Metrology Laboratory
Author(s): Walter E. Kupper
Abstract/Introduction:
In the physical set-up of a mass calibration facility the key elements are: a) electronic mass comparator balances, b) efficient use of computers, c) an appropriate laboratory environment. New electronic mass comparators are significantly faster and more productive than their mechanical predecessors. Productivity is further enhanced by interfacing the balance directly to a computer. The proper building environment is still essential, although electronic mass comparators are more forgiving of less than perfect conditions. The paper gives an overview of the relevant factors in setting up a mass calibration laboratory, supplemented by a slide presentation of the mass calibration laboratory at the Maryland Weights and Measures.
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Document ID:
71492CC3
Mass Standards Beravior And Traceability Assurance
Author(s): Emil Hazarian
Abstract/Introduction:
The paper describes the comportment of the Los Angeles County Metrology Laboratory Primary mass standards at 1 kg and 100 g levels. These are the starting restraints of the Mass Measurement Assurance Program state-of-the-art mass calibration. These weights are generating the corrections and uncertainties in the upper range -- up to 2,268 kg (5,000 lb) and in the lower range down to 1 mg (2.23-06 lb). Therefore the analysis of the variation of these standards is performed for a twenty year period of time, and possible cause for this variation is pointed out
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Document ID:
0FBBF786
Advanced Optical Technology: Advanced Boresight Equipment - An Electra-Optical Angular Measurement System
Author(s): James J. Jaklitsch
Abstract/Introduction:
The Advanced Boresight Equipment (ABE) program was established to evaluate current boresight requirements for the Army, Navy, and Air Force and develop a common boresight unit for all fixed wing and rotary wing aircraft. Current boresight equipment for all three services is heavy, bulky, cumbersome, and requires excessive time to use. In addition, each airframe has unique boresight equipment with unique logistics, training, and support requirements. The ABE design provides a solution to current equipment shortcomings.
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Document ID:
0981F06F
Sampling Inspection Methods For Radiological Surveys
Author(s): R. J. Tuttle, G. Subbaraman
Abstract/Introduction:
Following cleanup of a radioactively contaminated facility or site, surveys must be performed to demonstrate compliance with regulatory release limits and guidelines. Surveys produce measured estimates of residual radioactivity at selected locations. Rarely can these locations provide complete 100% coverage of an entire affected area, and the effectiveness of the survey as a basis for judging the acceptability of an area can be improved , over the comparison of results with limits, by the use of statistical interpretation. Two methods of survey interpretation are presented end compared. One method is based on an extension of sampling inspection by variables, as currently presented in ANSI/ASQC 21.9-1980, and has been used in several decommissioning projects under both NRC and DOE jurisdiction. The other method is that presented in NURBG/CR- 5849, which draws on EPA approaches to confirming the acceptability of an area. These methods are explored in terms of measurement techniques, effort required, statistical basis, and interpretation. Specific examples are provided.
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Document ID:
40F0AF29
Progress Report On The Implementation Of The IS0 Guide To The Expression Of Uncertainty In Measuremew
Author(s): Barry N. Taylor, Chris E. Kuyatt
Abstract/Introduction:
The lOO-page Guide to the Expression of Uncertaintyi n Measurement, which is the culmination of a 16 year effort to reach an international consensus on expressing measurement uncertainty, was published in October 1993 by the International Organization for Standardization (ISO) in the name of the seven organizations that supported its development: the International Bureau of Weights and Measures (BIPM), the International Electrotechnical Commission (IEC), the International Federation of Clinical Chemistry (IFCC), ISO, the International Union of Pure and Applied Chemistry (IUPAC), the International Union of Pure and Applied Physics (IUPAP), and the International Organization of Legal Metrology (OIML). The Guide represents the current international view of how to express measurement uncertainty based on the approach recommended by the International Committee for Weights and Measures (CIPM) in 1981. The CIPM approach has already been adopted by many organizations, including the Western European Calibration Cooperation (WECC), EUROMET (an organization which coordinates the work of European national standards laboratories), the National Conference of Standards Laboratories (NCSL), and several large U.S. companies, and the publication of the Guide is expected to give further impetus to the worldwide adoption of that approach. The Guide was prepared by a joint working group consisting of experts nominated by the BIPM, IEC, ISO, and OIML, and the authors played an active role in its preparation.
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Document ID:
94BB1D04
Progress And Problems With The Implementation Of The IS0 Guide On Uncertainty
Author(s): Keith Ekrhardt
Abstract/Introduction:
Standard statistical methods -- including confidence intervals, standard errors, and hypothesis tests built into statistical software -- are based on a relative-frequency interpretation of probability. Unfortunately, the theory behind this methodology can not directly address most problems of uncertainty analysis in metrology, because these often include systematic errors and/or Type B components of uncertainty. The ISO/CIPM approach to uncertainty analysis is an attempt to extend statistical methods by proposing a formula that is justified on the basis of analogy and examples, but which does not rest on a complete and self-consistent theory. At least that is its current status, in my opinion.
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Document ID:
012C17DB
Progress And Problems With The Implementation Of The IS0 Guide On Uncertainty
Author(s): Carroll Croarkin
Abstract/Introduction:
The National Institute of Standards and Technology has recently adopted a guideline for uncertainty analysis which follows the spirit of the recently published IS0 Guide. This has the advantage of standardizing on a method of presentation which is easily transportable from one calibration hierarchy to another. The statistical ramifications of this approach have been addressed by the previous speaker, Keith Eberhardt. In this talk, we cover some of the practical problems that NIST scientists, technicians, and statisticians have encountered in implementing the new policy and strategies for dealing with these problems.
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Document ID:
0EAC9F9E
The Constant Current Loop: A New Paradigm For Resistance Signal Conditioning
Author(s): Karl F. Anderson
Abstract/Introduction:
A practical single constant current loop circuit for the signal conditioning of variable-resistance transducers has been synthesized, analyzed, and demonstrated. The strain gage and the resistance temperature device are examples of variable-resistance sensors. Lead wires connect variable-resistance sensors to remotely located signal-conditioning hardware. The presence of lead wires in the conventional Wheatstone bridge signal-conditioning circuit introduces undesired effects that reduce the quality of the data from the remote sensors. A practical approach is presented for suppressing essentially all lead wire resistance effects while indicating only the change in resistance value. Theoretical predictions supported by laboratory testing confirm the following features of the approach: (1) the dc response (2) the electrical output is unaffected by extremely large variations in the resistance of any or all lead wires (3) the electrical output remains zero for no change in gage resistance (4) the electrical output is inherently linear with respect to gage resistance change (5) the sensitivity is double that of a Wheatstone bridge circuit and (6) the same excitation and sense wires can serve multiple independent gages. An adaptation of the current loop circuit is presented that simultaneously provides an output signal voltage directly proportional to transducer resistance change and provides temperature information that is unaffected by transducer and lead wire resistance variations. These innovations are the subject of NASA patent applications.
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Document ID:
25C9FFCE