This website uses cookies to store information on your computer. Some of these cookies are used for visitor analysis, others are essential to making our site function properly and improve the user experience. By using this site, you consent to the placement of these cookies. Click Accept to consent and dismiss this message or Deny to leave this website. Read our Privacy Statement for more.
Coating Thickness Gages: Calibration and Measurement Uncertainty
James Ingram, Jr.
NCSLI Measure | Vol. 1 No. 1 (2006) | 10.1080/19315775.2006.11721308
Publisher NCSL International | Published 3/1/2006 | Pages 46-49
Abstract: There are many manufacturing processes that require the measurement of coatings. In the past the coating thickness gages were checked in the field with some sort of thin film placed on the bare metal or with a plated square of steel from the National Institute of Standards and Technology. Times have changed along with advances in technology. Coating thickness gages now come in many varieties. Instead of just plating on steel they now also measure many types of coatings
on various substrates. These newer gages can measure thickness with an uncertainty of ± 1 % or better. These uncertainty requirements, along with more and more quality system demands, mean the gages are showing up at the metrology lab for calibration.
This paper covers coating thickness gages based on both magnetic and eddy current measurement techniques. The basic design and calibration requirements are discussed along with a report of repeatability studies and the main contributions to measurement uncertainty. The old reference materials used for calibration had a best uncertainty of ±3 % and worse. A review of the standards available, to meet the ± 1 % calibration requirement of the gages, is also presented.
Experimental Design of NCSLI 2005 Josephson Voltage Standard Interlaboratory Comparison
Yi-Hua Tang, Clark Hamilton, Harold Parks, David Deaver, Barry Wood
NCSLI Measure | Vol. 1 No. 1 (2006) | 10.1080/19315775.2006.11721306
Publisher NCSL International | Published 3/1/2006 | Pages 36-40
Abstract: The National Conference of Standards Laboratories International (NCSLI) 2005 Josephson voltage standard (JVS) Interlaboratory Comparison (ILC) provides participating laboratories with a means of comparing dc voltage measurements
in order to meet accreditation or contractual requirements, and to establish reliability, confidence, and improved system operation. Several changes in procedures are implemented in the 2005 JVS ILC.
Improving Worldwide Traceability of Measurements: How BIPM and ILAC are Collaborating
Andrew Wallard
NCSLI Measure | Vol. 1 No. 1 (2006) | 10.1080/19315775.2006.11721307
Publisher NCSL International | Published 3/1/2006 | Pages 42-45
Abstract: National Metrology Institutes and National Accreditation bodies share an interest in the effectiveness of national measurement systems. This paper considers some recent steps to help ensure the close collaboration needed to
achieve this aim.
Measurement of Impulse Spectrum Amplitude for Use in EMI Susceptibility Tests
D.R. Larson, N.G. Paulter
NCSLI Measure | Vol. 1 No. 1 (2006) | 10.1080/19315775.2006.11721309
Publisher NCSL International | Published 3/1/2006 | Pages
Abstract: A system for measuring the impulse spectrum amplitude of the output of impulse generators and the response of receivers is described. The calibration procedures used in this measurement system were recently modified, which resulted
in a reduction in the time for measurement and in the magnitude of the published uncertainties. The uncertainties for the bandwidth of 10 MHz to 4 GHz have been reduced from 0.5 dB to less than 0.02 dB for the parameter of impulse spectrum amplitude.
Mary Abbott, John Stoup, Bryon Faust, Ted Dorian, Eric Stanfield
NCSLI Measure | Vol. 1 No. 1 (2006) | 10.1080/19315775.2006.11721310
Publisher NCSL International | Published 3/1/2006 | Pages 56-65
Abstract: A number of new or revised services in dimensional metrology are presented. Included are: a lower cost, high accuracy calibration for sphere diameter; reduced uncertainty in roundness calibration; a new instrument for measurement
of the thermal expansion coefficient of gauges and other material, extended capabilities of ring gauge calibration on the M48 CMM, and a system for in-situ calibration of deformation of gauge blocks in mechanical comparison.
NCSLI Measure | Vol. 1 No. 1 (2006) | 10.1080/19315775.2006.11721311
Publisher NCSL International | Published 3/1/2006 | Pages 66-69
Abstract: Now that the International Laboratory Accreditation Cooperation (ILAC) multi-lateral mutual recognition arrangement (MRA or simply the ILAC Arrangement) has been in force for almost four years with 53 signatories from 43 economies as of 1 January 2006, have we achieved our goal of “one test, one calibration, one accreditation accepted everywhere.” The answer is only marginal at best. Part of the reason for such modest success is that purchasers, regulators and the general consuming public who look for accreditation as assurance of technical competence are neither familiar with internationally recognized accreditation body marks (or symbols) nor do they understand the intent of MRAs. Moreover, a signatory cannot simply tell specifiers of accreditation to accept reports or certificates with the accreditation symbol of MRA partners because a signatory's scope of recognition may be less than the full set of services offered by the accreditation body. After more than two years of debate and design, ILAC agreed to have its own world accreditation mark. Implementation of the ILAC MRA mark began in late 2004. The mark can be used by accredited laboratories on their test reports and calibration certificates for declaring to their clients that the results provided are recognized under the ILAC MRA.
Uncertainty Budgets for Comparison Calibrations of Thermocouples
K.M. Garrity, D.C. Ripple
NCSLI Measure | Vol. 1 No. 1 (2006) | 10.1080/19315775.2006.11721305
Publisher NCSL International | Published 3/1/2006 | Pages 28-34
Abstract: By means of concrete examples, we discuss the determination of an uncertainty budget for calibration of thermocouples by comparison techniques. In the first example, the calibration of a type T thermocouple (copper versus copper-nickel alloy) in a stirred liquid bath with a platinum resistance thermometer as a reference is considered. The second example is the calibration of a type K (a nickel-chromium versus nickel-aluminum alloy) thermocouple at temperatures up to 1200 °C in a tube furnace, using a platinum-rhodium alloy thermocouple as a reference. Methods for determining the magnitudes of these uncertainties are given for each uncertainty component.
100 mV AC-DC Transfer Standard Measurements Using An AC Josephson Voltage Standard
Paul D. Dresselhaus , Samuel P. Benz, Charles J. Burroughs
NCSLI Measure | Vol. 1 No. 2 (2006) | 10.1080/19315775.2006.11721322
Publisher NCSL International | Published 6/1/2006 | Pages 50-55
Abstract: NIST is implementing the Josephson arbitrary waveform synthesizer as an ac Josephson Voltage Standard (ACJVS). Over the past few years we have demonstrated precise measurements of synthesized sine waves at rms voltage amplitudes
up to 170 mV. The system can generate a variety of precision voltage outputs including dc voltages and ac sinewaves, so it can be used as a quantum-based voltage source for ac metrology. In this paper, we explore the capability of the ACJVS as an
audio frequency calibration source for the lower voltage ranges of an ac-dc transfer standard such as the 220 mV range where the transfer standard uses a high-impedance input buffer amplifier. In particular, we investigate the ACJVS measurement accuracy
over the frequency range from 1 kHz to 10 kHz at 50 mV and 100 mV. This work demonstrates the feasibility of a practical ac Josephson voltage standard based upon a quantum voltage source that produces precisely calculable ac and dc voltages.
Implementation of Programmable Josephson Voltage Standard to NIST Voltage Dissemination System
Yi-Hua Tang, June Sims
NCSLI Measure | Vol. 1 No. 2 (2006) | 10.1080/19315775.2006.11721321
Publisher NCSL International | Published 6/1/2006 | Pages 42-48
Abstract: For about seventy years, from the establishment in 1901 of the predecessor of NIST, the National Bureau of Standards (NBS), until about 1972, the U.S. legal volt was maintained by groups of electrochemical cells. In 1972, NBS
began to exploit the fundamental quantum nature of the Josephson Effect to monitor and correct for the mean drift of these electrochemical cells. Since that time, though the Josephson Effect has formed the basis for the U.S. legal volt, the primary
standard cell groups have continued to play a critical role in disseminating the volt through the NIST volt calibration service. This is because the classic Josephson array standards present significant barriers to routine use in a calibration system,
and standard cells offer significant advantages, both in their long-term predictability and their lower noise, compared to other types of voltage standards, such as Zener standards. Standard cells, however, are affected by power outage, environmental
temperature fluctuation, internal degassing, vibration, etc., sometimes exhibiting permanent voltage shift after such disturbances. The programmable Josephson voltage standard (PJVS) is based on an improved junction technology and provides a stable
output voltage without problems shown by traditional Josephson voltage standards. Their unique properties make it attractive to use the PJVS as a possible replacement for the primary standards cell groups that are still in use in the NIST volt dissemination
chain. The implementation of the PJVS will improve both the reliability and the efficiency of the dissemination system. This paper describes the working principle of the PJVS and the present implementation status of the PJVS in the NIST voltage dissemination
system.
NIST Calibration Uncertainties of Thermistor Thermometers over the Range from −50 °C to 90 °C
J. Gartenhaus, C.D. Vaughn, Gregory Strouse
NCSLI Measure | Vol. 1 No. 2 (2006) | 10.1080/19315775.2006.11721320
Publisher NCSL International | Published 6/1/2006 | Pages 36-41
Abstract: The National Institute of Standards and Technology (NIST) Industrial Thermometer Calibration Laboratory (ITCL) is responsible for calibrating several different types of industrial thermometers including thermistors. In order
to develop and validate a new uncertainty estimate for the calibration of thermistors from −50 °C to 90 °C, seven negative temperature coefficient thermistors were repeatedly calibrated by comparison, and at the ice melting point (MP). The thermistor
calibration uncertainties (k = 2) are approximately 2.4 mK at the ice MP, 1.8 mK in the range −50 °C to 0 °C and 2.0 mK to 7.0 mK in the range 0 °C to 90 °C.
Simplifications from Simulations: Monte Carlo Methods for Uncertainties
A.G. Steele, R.J. Douglas
NCSLI Measure | Vol. 1 No. 2 (2006) | 10.1080/19315775.2006.11721323
Publisher NCSL International | Published 6/1/2006 | Pages 56-68
Abstract: Monte Carlo simulation is a tool of choice for exploring the probabilistic interpretation of ISO Guide-compliant uncertainty budgets. It is particularly appealing to those uncomfortable with the classical development of statistics
by theorems and lemmas. The technique is useful when creating and defending calibration uncertainty statements and when interpreting the results of inter-laboratory comparisons for critical purposes such as ISO 17025 accreditation. We explain the
Monte Carlo technique, and demonstrate how to use the Excel spreadsheet environment to build simple yet powerful programs that can provide insight and understanding to metrologists and clients alike. This subject should appeal to potential users of
the ISO Guide and its (Draft) Supplement One who are seeking rigor and simplicity.
Stabilization of Standard Platinum Resistance Thermometers for Calibration on the International Temperature Scale of 1990
Dennis Minor, Gregory Strause
NCSLI Measure | Vol. 1 No. 2 (2006) | 10.1080/19315775.2006.11721319
Publisher NCSL International | Published 6/1/2006 | Pages 30-35
Abstract: At the National Institute of Standards and Technology (NIST), the calibration of standard platinum resistance thermometers (SPRTs) on the International Temperature Scale of 1990 (ITS-90) is performed in the Platinum Resistance
Thermometer Calibration Laboratory over the temperature range from −189 °C to 962 °C. As part of the internal measurement assurance program, the stability of an SPRT prior to calibration is used to determine if the thermometer is suitable for calibration
within the NIST-assigned ITS-90 realization uncertainties. To qualify for calibration, the resistance of the SPRT at the triple point of water, R(TPW), must repeat to within the equivalent of 0.2 mK after exposure to no more than five thermal annealing
cycles. The annealing cycle used depends on the temperature range of the calibration and the amount of change between the ‘as received’ R(TPW) value and the values recorded during previous NIST calibrations. The stabilization techniques used and the
impact on the overall stability of the SPRT during a calibration are given.
Voltage Envelope vs. Power Envelope in RF/Microwave Signals
Woo Chi
NCSLI Measure | Vol. 1 No. 2 (2006) | 10.1080/19315775.2006.11721324
Publisher NCSL International | Published 6/1/2006 | Pages 70-71
Abstract: This paper will examine the differences between voltage envelope and power envelope, then show an actual case that occurred during a Naval Air Systems Command (NAVAIR) standard procurement. The confusion over the specifications
led to one manufacturer making the test equipment using the voltage definition, and another manufacturer using the power definition. Finally, recommendations will be made on steps to prevent this in the future.
An Accurate Pulse Measurement System for Real-Time Oscilloscope Calibration
David Bergman
NCSLI Measure | Vol. 1 No. 3 (2006) | 10.1080/19315775.2006.11721330
Publisher NCSL International | Published 9/1/2006 | Pages 22-29
Abstract: An accurate sampling system for calibrating the pulse response of real-time digitizing oscilloscopes up to 100 V is described. The measurement system is the result of ongoing efforts at the National Institute of Standards and
Technology (NIST) to establish and maintain capability in waveform sampling metrology. A low-noise sampling probe in conjunction with a frequency-compensated resistive attenuator measures repetitive pulses with attainable amplitude uncertainty less
than 0.2 % of the pulse amplitude at 1 μs following the pulse transition. The probe and attenuator are calibrated against a wideband sampling probe and 50 Ω attenuator combination that serves as a reference standard requiring only a dc calibration.
The method used to calibrate the low-noise probe and attenuator is described along with a tally of error sources. The biggest contributor to Type B uncertainty is the tuning of the attenuator's frequency compensation, achieved through a digital filter.
Fiber Deflection Probe Uncertainty Analysis for Micro Holes
Bala Muralikrishnan, Jack Stone
NCSLI Measure | Vol. 1 No. 3 (2006) | 10.1080/19315775.2006.11721332
Publisher NCSL International | Published 9/1/2006 | Pages 38-44
Abstract: We have recently reported on a new probe, the Fiber Deflection Probe (FDP), for diameter and form measurement of large aspect ratio micro-holes (100 qm nominal diameter, 5 mm deep). In this paper, we briefly review the measurement
principle of the FDP. Then, we discuss different error sources and present an uncertainty budget for diameter measurements. Some error sources are specific to our fiber probe such as imaging uncertainty, uncertainty in determining calibration factor,
and misalignment of the two optical-axes. There are other sources of error that are common to traditional coordinate metrology such as master ball diameter error, tilt in hole's axis, temperature effects etc. Our analysis indicates an expanded uncertainty
of only 0.07 qm on diameter.
Legal and Technical Measurement Requirements for Time and Frequency
Michael Lombardi
NCSLI Measure | Vol. 1 No. 3 (2006) | 10.1080/19315775.2006.11721335
Publisher NCSL International | Published 9/1/2006 | Pages 60-69
Abstract: This paper discusses various technologies and applications that rely on precise time and frequency, and explores their legal and technical requirements for measurement uncertainty. The technologies and applications discussed
include financial markets, the wired and wireless telephone networks, radio and television broadcast stations, the electrical power grid, and radionavigation systems. Also discussed are the legal and technical requirements for “everyday” metrology
situations, including wristwatches, commercial timing devices, and radar devices used by law enforcement officers.
NCSLI Measure | Vol. 1 No. 3 (2006) | 10.1080/19315775.2006.11721331
Publisher NCSL International | Published 9/1/2006 | Pages 30-36
Abstract: The National Metrology Institutes (NMIs) push the boundaries of metrological capability to ever-greater heights, spurred on by advances in science and technology, the demands of industry and the needs of society. Many new products
and processes, new science and technology, indeed new markets and the legislation that governs them, depend on good metrology. It would therefore seem logical that metrology and measurement are intrinsic elements in planning the processes on which
they impact, yet often they are not routinely addressed, or at least not in a timely way. The NMI mission includes delivering benefits to the national economy or quality of life for our citizens by working to overcome this inertia. However, in a global
economy we increasingly need to rethink our definitions of national impact, as nowadays many drivers and their consequent effects are no longer confined within national boundaries. This paper will reflect on the mechanisms by which metrology impacts
our past, present and future, the interplay between national and global perspectives, and suggests new approaches for embedding metrology “upstream” into our economies and lives.
Reduction of Thermal Gradients by Modifications of a Temperature Controlled CMM Lab
Hy D. Tran , Orlando Espinosa, James Kwak
NCSLI Measure | Vol. 1 No. 3 (2006) | 10.1080/19315775.2006.11721333
Publisher NCSL International | Published 9/1/2006 | Pages 46-50
Abstract: The Sandia Primary Standards Lab Coordinate Measuring Machine Lab (CMM Lab) was built in 1994. Its temperature controls were designed to be state of the art at 20.00 ± 0.01 C and relative humidity 36 ± 4 %. Further evaluation
demonstrated that while the control achieved the desired average air temperature stability of 10 mK at a single point, the CMM Lab equipment had vertical temperature gradients on the order of 500 mK. We have made inexpensive minor modifications to
the lab in an effort to reduce thermal gradients. These modifications include partitioning temperature sensitive equipment from operators and other heat sources; increasing local and internal air circulation at sensitive equipment with fans; and concentrating
the flow of this circulated air into the HVAC control sensor. We report on the performance improvements of these modifications on machine temperature gradients during normal operation, and on the robustness of the improved system.
NCSLI Measure | Vol. 1 No. 3 (2006) | 10.1080/19315775.2006.11721334
Publisher NCSL International | Published 9/1/2006 | Pages 52-59
Abstract: What does the weights and measures system in the United States look like, and what impact does it have on commerce? Every state in the United States has its own weights and measures program, and many states have county and city
run programs within their own jurisdiction. More importantly, each of these programs has sovereignty within its jurisdiction. There are over 650 independent regulatory jurisdictions in the United States. How then, can laws and regulations be applied
uniformly? How can U.S. commerce be assured of accurate measurement and consistent application?
A Direct Comparison System for Measuring Radio Frequency Power (100 kHz to 18 GHz)
Ronald Ginley
NCSLI Measure | Vol. 1 No. 4 (2006) | 10.1080/19315775.2006.11721347
Publisher NCSL International | Published 12/1/2006 | Pages 46-49
Abstract: A direct comparison power measurement system has been developed to measure power sensor effective efficiency in the 100 kHz to 18 GHz frequency range. This system is capable of measuring thermistor and thermoelectric based power
sensors. Several problems needed to be addressed in the development of the system, including RF leakage from the power sensors and its effect on system electronics, the sensitivity of the power meter and digital volt meter to extraneous signals, and
the effect of compensation beads, if there were any, in the sensors. This article covers these problems, provides a discussion of the system design, presents the uncertainty analysis for the system, and finally compares measurement results to measurements
made using the NIST 0.05 GHz to 50 GHz system and the voltage/impedance technique.
A Theory for RF and Microwave Scalar Reflectometer Errors
Robert Moyer
NCSLI Measure | Vol. 1 No. 4 (2006) | 10.1080/19315775.2006.11721346
Publisher NCSL International | Published 12/1/2006 | Pages 38-44
Abstract: Scalar reflectometers afford a relatively inexpensive means to measure reflection coefficient magnitudes at RF and microwave frequencies. Unfortunately, the measurements include errors that arise from vectorial imperfections
within the reflectometer hardware. While a vector network analyzer can help correct for the imperfections, a scalar analyzer has only limited capability to do so, and there is often confusion about the extent of the corrections that can be made. This
paper provides a careful analysis of rf and microwave scalar reflectometers and discusses two common ways to initialize them. The results (1) show the advantages, and remaining weaknesses, of the open/short method for initializing a 4-port reflectometer,
(2) demonstrate the irrelevance of detector reflection coefficients, (3) reveal the advantages of 4-port over 3-port reflectometers, and (4) present expressions showing how the worst-case errors in scalar reflectometer measurements vary, depending
on the properties of both the reflectometer and the device under test.
ANSI/NCSL Z540.3:2006: Requirements for the Calibration of Measuring and Test Equipment
Del Caldwell
NCSLI Measure | Vol. 1 No. 4 (2006) | 10.1080/19315775.2006.11721344
Publisher NCSL International | Published 12/1/2006 | Pages 26-30
Abstract: This paper provides an introduction to the new ANSI/NCSL Z540.3 standard and its approach to prescribing requirements for a calibration system that controls the accuracy of the measuring and test equipment used to ensure that
products and services comply with prescribed requirements. The new ANSI/NCSLI Z540.3 standard replaces Part II of the current standard, ANSI/NCSL Z540-1 (R2002). Z540.3 consists of six clauses, each of which is described: Scope; References; Terms
and Definitions; General Requirements; Calibration System Implementation; and Calibration System Assessment and Improvement. This paper also discusses the three requirements that received the most interest and discussion during the development process:
(1) Measurement decision risk criteria; (2) Test uncertainty ratios; and (3) Use of calibration laboratories accredited to ANS/ISO/IEC 17025.
Gravimetric Calibration of Volumetric Standards with Capacities Exceeding Five Gallon
L.F. Eason
NCSLI Measure | Vol. 1 No. 4 (2006) | 10.1080/19315775.2006.11721349
Publisher NCSL International | Published 12/1/2006 | Pages 60-72
Abstract: Recently, the demand for volumetric measurements with greater accuracy and smaller measurement uncertainties has increased dramatically. In response, the metrology laboratories of the Arizona, Maine, Michigan, and North Carolina
weights and measures programs have established gravimetric calibration capabilities for volume standards (provers) with capacities up to 100 gallons (500 liters). This collaborative effort with the National Institute of Standards and Technology (NIST),
Weights and Measures Division (WMD), has improved volumetric prover calibration accuracy and uncertainty significantly. Accuracy is a measure of how close a measurement is to the actual value. Uncertainty is a measure of how well the value is known.
Smaller uncertainties in laboratory standards have lead to similar improvements in field prover calibrations up to 2000 gallons. Prover calibration improvements facilitate better meter calibrations. Consequently, petrochemical terminals can have more
confidence in inventory records, reducing inexplicable product losses. Apparent losses that once were ignored because they were less than the existing measurement uncertainty can now be investigated. Meters can be adjusted before loss totals increase.
Gravimetric volume calibration makes use of existing mass comparator balance technology and mass standards commonly available in the State metrology laboratories. Any volume up to the limit of available mass standards and balance capacity can be calibrated
without the expense of the multiple volume standard provers typically required for calibration of non-standard volumes. Thus, metrology laboratories benefit from significant cost savings in addition to improving their calibration process. Since gravimetric
calibrations are traceable to mass, fewer laboratory volume standards must be calibrated by NIST, providing another cost savings to laboratories. Prior to large volume gravimetric calibration, volume transfer calibration uncertainties (k = 2) from
NIST were reported at 130 ppm (3.1 cubic inches for a 100 gallon prover). Using this uncertainty as a starting point, laboratories then had to add their own process uncertainty factors and reported significantly higher uncertainties for field provers.
Using gravimetric calibration, a technician proficient in mass metrology can expect to attain expanded uncertainties (k = 2) of 70 ppm (1.6 cubic inches for a 100 gallon prover). These advances in gravimetric calibration improve volume measurements
at all levels, from the laboratory, to the terminal, and to the retail market.
Remote Time Calibrations via the NIST Time Measurement and Analysis Service
Michael Lombardi , Andrew Novick
NCSLI Measure | Vol. 1 No. 4 (2006) | 10.1080/19315775.2006.11721348
Publisher NCSL International | Published 12/1/2006 | Pages
Abstract: The National Institute of Standards and Technology (NIST) now offers a new remote calibration service designed to assist laboratories that maintain an accurate local time standard. The service monitors the local time standard
by continuously comparing it to the national time standard and reports the comparison results to the customer in near real-time. This new service, called the NIST Time Measurement and Analysis Service, or TMAS, works by making simultaneous common-view
measurements at NIST and at the customer's laboratory with up to eight Global Positioning System (GPS) satellites. Each customer receives a time measurement system that performs the measurements and sends the results to NIST via the Internet for instant
processing. Customers can then view their standard's performance with respect to NIST in near real-time, using an ordinary web browser. Time is measured with a combined standard uncertainty of less than 15 nanoseconds, and frequency is measured with
an uncertainty of less than 1 × 10−13 after 1 day of averaging. This paper describes the multi-channel GPS common-view technique used by the service and the measurement system sent to each customer. It also explains how NIST calibrates each measurement
system prior to shipment, how measurement results are reported to the customer, and how the measurement uncertainties are estimated.
NCSLI Measure | Vol. 1 No. 4 (2006) | 10.1080/19315775.2006.11721343
Publisher NCSL International | Published 12/1/2006 | Pages 22-25
Abstract: Following international discussion of the traceability issues arising in the measurement of materials properties, the Comité International des Poids et Mesures (CIPM) in October 2005 accepted the proposal to set up an ad hoc
Working Group on Metrology of Materials (WGMM). The WGMM is assessing a wide range of materials properties, looking particularly at the need for improved traceability routes, data comparability, and the availability of appropriate reference materials.
The Working Group on Materials Metrology will report to CIPM in October 2007, with the intention of raising the profile of materials metrology internationally and engaging the leading National Measurement Institutes in recognising and addressing known
difficulties in demonstrating traceability of many material properties to the Système International of units (SI). Terms of Reference have been agreed, and the first meeting took place at the United Kingdom's National Physical Laboratory in May 2006.
This paper describes the range of properties being investigated and highlights the studies being undertaken by the WGMM members.
Uncertainties Related to Thermal Expansion in Dimensional Metrology
Ted Dorian
NCSLI Measure | Vol. 1 No. 4 (2006) | 10.1080/19315775.2006.11721345
Publisher NCSL International | Published 12/1/2006 | Pages 32-37
Abstract: Thermal expansion effects are very important in dimensional metrology. In this paper a measurement model, and associated equations, are developed for the case of a one-dimensional measurement of a steel test gage using a measuring
machine and master gage. After presenting the uncertainty components for this measurement, several example measurement situations with different levels of temperature control are calculated and discussed. For each situation, the magnitude of the different
sources of uncertainty are compared in order to rationally allocate resources to improve the overall measurement uncertainty.
