Two-Way Random-Effects Analyses and Gauge R&R Studies

An important prerequisite of any sensible data-based engineering study is the quantification of the precision of gauges or measuring equipment to be used in data collection. It has long been understood that in the event that more than one individual will use a particular gauge, “measurement variation” for that gauge can include not only a kind of “pure error” component but an “operator” or “technician” component as well. Furthermore, it is well known that the two-way random-effects model provides a natural framework for quantifying the different components of measurement variation. Some parts of standard practice in the “gauge R&R studies” aimed at quantifying measurement precision, however, are unfortunately at odds with what makes sense under this model. Thus, the purpose of this primarily expository article is to explain in elementary terms the use of a two-way random-effects model for gauge R&R studies, to critique current practice, and to point out some simple improvements that can follow from more careful attention to the model and well-established practice in the general linear model.     

Evaluation of Measurement Systems with a Small Number of Observers

The standard R&R study for evaluation of measurement systems assumes that participating observers constitute a random sample. Often there are only a few observers, all of them included in the study. An alternative measure for the gauge R&R is proposed for this situation, and it is shown that this may improve the perception of the quality of the measurement system markedly, especially with only a few observers. Finally it is shown that a simple estimator can be used, with a bias limited to just a few percent.     

Gauge capability studies for attribute data

A gauge repeatability and reproducibility (R&R) method is developed to assess the capability of a measurement system. Although gauge capability studies have received substantial attention, few studies have investigated attribute data despite their wide application in industry. The primary aim of this research is to develop a procedure, based on the generalized linear model, to evaluate the R&R of a measurement system for attribute data. To calculate repeatability of a system, the procedure integrates the iterative weighted least squares (IWLS) method and deviance analysis. The proposed procedure is applied to an inclusion measurement system to verify its adequacy to model the process capability. Copyright © 2007 John Wiley & Sons, Ltd.     

Confidence Intervals for Unbalanced Two‐factor Gauge R&R Studies

We consider methods for constructing confidence intervals in a two‐factor gauge repeatability and reproducibility (R&R) study when there are unequal replicates. We consider both random and mixed models and propose a general approach using unweighted sums of squares. Computer simulation is used to determine how well confidence intervals maintain the stated confidence level. The main conclusion is that the method performs well under a variety of conditions typically encountered in gauge R&R studies. The method is simple and the intervals can be computed in a spreadsheet program. Copyright © 2005 John Wiley & Sons, Ltd.     

KJY-II型精密孔径仪的测量不确定度分析

KJY—Ⅱ型精密孔径仪是测量环规内径的专用仪器，已经在环规计量检定规程中(JJG894—95)被推荐为检定二等环规的首选仪器。本文着重分析了仪器的不确定度问题。     

Realization of Negative Gauge Pressure Standard in the National Metrology Institute of Indonesia

Accurate negative gauge pressure measurement is the key factor for many scientific and industrial applications such as clean room technology, medical treatment, and pharmaceutical production. However, there are not much publications regarding to the technical guide when it comes to negative pressure measurement, although several comparison of negative gauge pressure has been performed in Europe. In this study, two methods for negative pressure calibration have been successfully implemented by National Standardization Agency of Indonesia with using pressure balance. The first method is by generating the negative pressure in the bell jar of the pressure balance, and the second method is by using pressure balance in absolute pressure mode and additional barometric pressure measuring instrument. Both methods measurement results show linear relation from the negative to positive pressure and show good agreement by each other with the normalized error (En) less than 0.40 from – 1000 to 1000 hPa with uncertainty up to 0.073 hPa. The expanded uncertainty of the second method is relatively larger due to dominant contribution from the uncertainty of the barometer used. Therefore, it can be concluded that both methods can be used in order to provide traceability for negative gauge pressure measurement instrument in Indonesia.     

A Comparison of Methods for the Evaluation of Binary Measurement Systems

Many quality programs prescribe a measurement system analysis (MSA) to be performed on the key quality characteristics. This guarantees the reliability of the acquired data, which serve as the basis for drawing conclusions with respect to the behavior of the key quality characteristics. When dealing with continuous characteristics, the Gauge R&R is regarded as the statistical technique in MSA. For binary characteristics, no such universally accepted equivalent is available. We discuss methods that could serve as an MSA for binary data. We argue that a latent class model is the most promising candidate.     

Measurement System Analysis in a Production Environment with Multiple Test Parameters

The purpose of measurement system analysis (MSA) is to separate the variation among devices being measured from the error in the measurement system. The total measurement system error can be further decomposed into variance components associated with the measurement equipment and repeatability. An analysis of variance approach based on a variance component model is used to model the variables of interest. Once estimated, the variance components are used to compute various metrics, which quantify the adequacy of the measurement system for the application in which it is used. Confidence intervals computed on the variance components and metrics indicate the amount of precision in the estimates. The MSA is typically conducted on a single measurement variable with a single measurement instance. The aim of this paper is to extend the univariate single-instance case to a common manufacturing test scenario where multiple parameters are tested on each device with a sequence of tests, which may include retest and test and repair steps. The methods presented are illustrated with examples from an industrial application.     

Vertical caliper gauge with digital readout for absolute dimensional measurements

A new gauge configuration for the measurement of outside dimensions up to 70 mm is described. The main advantage of the instrument is that it can be used to perform absolute measurements, i.e., without adjustment operations. The instrument has potential applications in many industries engaged in the manufacture of parts in relatively small lots.Translated from Izmeritel'naya Tekhnika, No. 10, pp. 32–33, October, 1993.     

Evaluation of digital PCR for absolute DNA quantification

The emerging technique of microfluidic digital PCR (dPCR) offers a unique approach to real-time quantitative PCR for measuring nucleic acids that may be particularly suited for low-level detection. In this study, we evaluated the quantitative capabilities of dPCR when measuring small amounts (<200 copies) of DNA and investigated parameters influencing technical performance. We used various DNA templates, matrixes, and assays to evaluate the precision, sensitivity and reproducibility of dPCR, and demonstrate that this technique can be highly reproducible when performed at different times and when different primer sets are targeting the same molecule. dPCR exhibited good analytical sensitivity and was reproducible outside the range recommended by the instrument manufacturer; detecting 16 estimated targets with high precision. The inclusion of carrier had no effect on this estimated quantity, but did improve measurement precision. We report disagreement when using dPCR to measure different template types and when comparing the estimated quantities by dPCR and UV spectrophotometry. Finally, we also demonstrate that preamplification can impose a significant measurement bias. These findings provide an independent assessment of low copy molecular measurement using dPCR and underline important factors for consideration in dPCR experimental design.     

Microcomputer-Controlled Precision Pneumatic Pressure Generator

An increasing variety of avionics require precision pneumatic pressure stimuli during organization and intermediate maintenance. The accuracy and long-term stability requirements approach the best mercurial standards. Pressure stimuli must be coordinated and varied at precise rates that are beyond the frequency response of mercury columns and many electromechanical sensors. Test systems are frequently required to simultaneously monitor and evaluate unit under test (UUT) response and generate pneumatic stimuli. In addition, the environment is frequently hostile, maintainability is paramount, performance must always be known and warmup time must be nil. Comprehensive trade studies, tests, and analyses were performed. This initial work indicated a new pressure generator should be a "smart" instrument and should use a pressure sensor not a density sensor. Current field and production experience indicates performance objectives have been exceeded and this new type of precision pressure generator can be readily incorporated in a variety of test systems or be used "stand-alone". This paper discusses the design implementation, features, and characteristics of this microcomputer controlled precision pneumatic pressure generator-a new "smart" test instrument.     

Transfer of Near-Infrared Multivariate Calibrations without Standards

A novel approach to the transfer of multivariate calibration is proposed. This method is based on the finite impulse response (FIR) filtering of a set of spectra to be transferred, using a spectrum on the target instrument to direct the filtering process. Often, the target spectrum is the mean of a calibration set. The method is compared against direct transfer and piecewise direct transfer on near-infrared reflectance spectra in two representative data sets. Results from these studies suggest that FIR transfer compares favorably with piecewise direct transfer in terms of accuracy and precision of the match of transferred spectra to the predictive calibration models developed on the target instrument. Unlike piecewise direct transfer, FIR transfer requires no measurement of standard samples on both the source and target spectrometers. Details and current limitations of the FIR transfer method are presented.     

Entwicklung eines Ionisationsmanometers mit Feldemitterkathode

Development of an ion gauge with field emissionin cryogenic vacuum environments cathode for pressure measurements The measurement of UHV or even XHV pressures in low‐temperature vacuum systems has always been considered as a metrological problem. In principle, conventional hot‐cathode ion gauges can be used for pressure measurement in cryogenic vacuum environments. However, as a consequence of their high heat generation several disadvantages must be taken into account. With the development of an ion gauge of extractor‐type whose heat‐generating thermionic cathode is replaced by a non‐thermal field emission cathode, a promising approach to realize a reliable pressure gauge for cryogenic vacuum applications can be presented in this paper. The gauge equipped with a CNT cathode was investigated both experimentally and by numerical simulations in terms of their operating characteristics. It has been successfully demonstrated that the modified extractor gauge works reliably under low temperature conditions and provides meaningful pressure readings.     

Process Yield Analysis for Nonlinear Profiles in the Presence of Gauge Measurement Errors

Process yield plays an important role in many manufacturing industries for measuring process performance. However, gauge measurement errors have significant effect on process capability analysis. In this study, we present a method based on the yield index to evaluate the process yield of nonlinear profiles in the presence of gauge measurement errors. The results indicate that the presence of gauge measurement errors in the data leads to different behaviors of the yield index estimator according to the existence of the gauge variability. Our proposed test procedure can be easily used to determine whether or not manufacturing processes meet the quality requirements when gauge measurement errors are considered. A real example from a manufacturing process is used to demonstrate the applications of the proposed method. Copyright © 2015 John Wiley & Sons, Ltd.     

自动标准压力发生器动态控制准确度分析

自动标准压力发生器(以下简称发生器)性能的一个重要指标是准确度。当发生器处于动态控制模式及使用面板显示时需要考虑附加控制准确度。本文通过对PACE6000系列的发生器进行比对实验,以活塞式压力计为标准器,高准确度数字压力计为参考对象,得出了其控制准确度,最后给出了以0.01级数字压力发生器为标准器、0.05级数字压力计示值误差的测量不确定度分析,其内置压力传感器的最大允许误差须为±0.008%。     

Practical interpretation of metrological traceability on gauge block as to VIM 3

In ISO/IEC Guide 99:2007, i.e. the International Vocabulary of Basic and General Terms in Metrology-3rd edition (VIM 3), the term “traceability” is replaced by “metrological traceability”, giving it a new definition as property of a measurement result which can be related to a reference. In essence, “metrological traceability” can offer an evidence of measurands tracing to the primary standards which can realize the SI units, and offer a documented unbroken chain of calibrations, thus considered as one of the most important terms in VIM 3. National Measurement Laboratory (NML, Chinese Taipei) has long operated its main mission of calibration implemented along with peer assessed traceability of its measurement systems, which demonstrate a calibration hierarchy conventionally in schematic approach. In dealing with definition of the new term “metrological traceability” in VIM 3, this paper elaborates in taking additionally a newly mathematical approach rather than schematic approach only to realize the practical interpretation of “metrological traceability” to show how the unbroken calibration chain is functioning seamless and robust on the gauge block measurement system in NML. Through such study activities, we well assure our strong confidence on technology inheritance of gauge block and the other measurement systems with sufficient metrological know-how in NML, which can continually pass to each entry level metrologist.     

BP神经网络在测试系统动态补偿中的应用

测试系统的非线性动态补偿是仪器技术的一个重要方面．采用BP神经网络对测试系统进行动态补偿．BP神经网络的结果决定于网络输入、隐层和输出节点．由于其非线性映射特性,BP神经网络完全能够反映测试系统的动态响应特性．采用了收敛速度较快的递推预报误差算法训练神经网络．试验结果表明,BP神经网络的特性完全能够满足测试系统的动态补偿要求．表明本文的方法是有效的．     

Sample size dependence of flaw distributions for the prediction of brittle solids strength using additive Weibull bimodal distributions

A method to evaluate the mean strength of brittle solids at short gauge length from experiments performed at higher gauge length is proposed for bimodal fracture behavior. The method based on additive Weibull bimodal distributions takes the evolution of the relative proportion of flaws along the gauge length into account via a gauge length dependent mixing parameter. A linear dependence of this parameter vs. the gauge length is proposed. The approach is assessed using experimental results on carbon and E-glass fibers. The new method provides values for the average tensile strength of the fibers at 100 μm up to 27% higher than those calculated using the classical approach. The underestimation of the classical approach can be attributed to the weight of the severe category of flaws at short length that is considered to be the same as that determined at the experimental gauge length, which can be several orders higher. A simplified approach taking into account solely the more severe category of flaw is shown to be applicable for the prediction of the strength at short gauge length independently of the nature of the fiber.     

The extension of the calibration of a mass spectrometer into the ultrahigh vacuum region

This paper describes how a mass spectrometer head and ion current amplifier system which has been calibrated as a partial pressure gauge in the high vacuum region, may have that calibration extended so that it can be used in the ultrahigh vacuum region. The technique is based on the measurement of the isotope ratio of the calibration gas. The paper also reports on the application of this technique to a particular instrument.     

Determining the short-term instability of quartz oscillator frequencies

Summary The measurement results show that phase shift in the instrument depends but very little on the voltages of the frequencies being compared or the sources of supply, thus providing the possibility of using the above instrument for comparing frequencies of crystal oscillators continuously throughout the day and night with great precision.This instrument in conjunction with the phase shifter can also be used as a phase meter for measuring phase shift with great precision. Thus, the error in measuring a phase difference at 60 kc does not exceed 1 · 10^–4 rad.If required it is possible to raise the precision of frequency deviation measurements by either increasing the sensitivity of the discriminators by means of larger input voltages to the discriminator, or by multiplying the frequencies under comparison.