The Algorithm for Processing Key Comparisons to Establish Equivalence between National Standards

To establish equivalence between national standards, it is proposed to consider a priori the key comparisons made as regards the selection of data belonging to a single population. It is also proposed to estimate reference values as arithmetic means or medians. All national standards are recognized as equivalent with these values for the uncertainties established from the comparisons.     

Statistical Interpretation of Key Comparison Reference Value and Degrees of Equivalence

Key comparisons carried out by the Consultative Committees (CCs) of the International Committee of Weights and Measures (CIPM) or the Bureau International des Poids et Mesures (BIPM) are referred to as CIPM key comparisons. The outputs of a statistical analysis of the data from a CIPM key comparison are the key comparison reference value, the degrees of equivalence, and their associated uncertainties. The BIPM publications do not discuss statistical interpretation of these outputs. We discuss their interpretation under the following three statistical models: nonexistent laboratory-effects model, random laboratory-effects model, and systematic laboratory-effects model.     

比对参考值与等效度计算方法探讨

介绍了计算比对参考值的平均法和考虑了比对实验室量值与参考值的相关性的等效度不确定度计算方法,提出采用加权平均法计算参考值时应考虑比对传递或修正环节引入的不确定度对权重的影响,指出在分析计算参考值的不确定度或外部独立量值的最佳估计值的不确定度时应考虑实验室量值间的相关性的影响。     

Identification and Handling of Discrepant Measurements in Key Comparisons

In a key comparison one or several measurement objects are circulated among a number of laboratories, each of which measures the quantities represented by the objects. In order to compare the measurement results obtained by the participating laboratories, the values represented by the circulated objects have to be established. These values, known as the key comparison reference values, and their associated uncertainties can easily be calculated by the method of least squares from the measurement results provided by the participating laboratories. Since this method requires that the measurement results be mutually consistent, a hypothesis that sometimes has to be rejected at a reasonable level of significance, a procedure for identification and handling of discrepant measurements is needed. In this paper such a procedure is suggested. It is demonstrated that although a key comparison reference value is attracted to a discrepant measurement result that has an uncertainty much smaller than the remaining results, the suggested procedure is able to identify this discrepant result. It is also demonstrated that the exclusion of a discrepant measurement result from the calculation of the reference values does not amplify the discrepancy of that result. As the discrepant result is not excluded from the comparison itself, the exclusion of the result in the calculation of the reference values should therefore be uncontroversial.     

Evaluating Data from Regional Key Comparisons

An algorithm is proposed for calculating the degree of equivalence for national standards that participated in regional metrological organization (RMO) comparisons in relation to key comparison reference values (KCRV), including an analysis of possible correlations between measurements. Two types of key comparison are considered, which differ in that the reference value is provided either by a measure or by a measuring instrument.__________Translated from Izmeritel’naya Tekhnika, No. 4, pp. 11–17, April, 2005.     

Linking the Results of CIPM and RMO Key Comparisons With Linear Trends

A statistical approach to link the results of interlaboratory comparisons with linear trends is proposed. This approach can be applied to the case that the comparison artifacts have the same nominal values or the measured quantities have the same magnitudes. The degrees of equivalence between the pairs of National Metrology Institutes that have not participated in the same comparisons, and their corresponding uncertainties are established. The approach is applied to link the CCEM-K2 and SIM.EM-K2 comparisons for resistance at 1 G Ω level.     

Classification of Statistical Models Used in Analyzing Comparisons of Test,Checking, and Calibration Laboratories

Five statistical models are considered for interlaboratory comparisons, which are based on either a priori information (available before the measurements are made) and a posteriori information (obtained after the measurements).__________Translated from Izmeritel’naya Tekhnika, No. 5, pp. 3–8, May, 2005.     

An algorithm for detecting drift in the value of the comparison standard when analyzing the data of key comparisons of national standards

An algorithm for revealing the piecewise-linear drift of the value of the comparison standard when making international comparisons is proposed. The probabilities of errors of the 1st and 2nd kinds are estimated and recommendations are made on choosing the parameters of the algorithm. A comparative analysis of different algorithms for identifying a point of discontinuity of the piecewise-linear drift model is carried out. __________ Translated from Izmeritel’naya Tekhnika, No. 2, pp. 68–72, February, 2008.     

Measuring the Specific Activity of 238Pu in Solution for International Key Comparisons

Two methods are considered for measuring the specific activity of ²³⁸Pu in solution that have been used at the Mendeleev All-Russia Metrology Research Institute in key comparisons of national standards for radionuclide activity units: the 4(PC)-LX coincidence method and the defined solid-angle one. The results for the specific activity from the two methods have agreed within the estimated combined uncertainty of 0.15%.     

CCT-K7水三相点容器国际关键比对

在国际互认框架内,国家计量标准的国际等效性是通过国际计量委员会（CIPM）的咨询委员会组织的一系列国际关键比对来确定的。温度咨询委员会（CCT）委托国际计量局（BIPM）作为主导实验室组织了由20个国家实验室参加的CCT-K7水三相点容器国际关键比对。比对结果表明：这些国家基准水三相点值在0．171mK范围内一致。此外,为了减小国家实验室复现水三相点的系统差,需要进一步研究同位素组成对水三相点温度的影响以及同位素修正。     

Key comparisons CCEM.RF-K-20 in the area of electric field strength measurements

The method of calibration of a portable standard on equipment of the state standard GéT 45-94 for electric field strength is presented. Analysis of the results of key comparisons CCEM.RF-K-20 is provided. __________ Translated from Izmeritel’naya Tekhnika, No. 9. pp. 69–72, September, 2007.     

Analysis of Comparison Data from Acceleration Measurements

The Evaluation Guidelines [1] specify general analysis methods for key comparisons of measurement data where their reasonable application is subject to some preconditions. We discuss a real example of comparison data that can be analyzed in formal accordance with the Guidelines. But we prefer a model-based analysis benefiting from the intrinsic relation of the data. Indeed, this method is founded on the principles of the Guidelines. In our example, the laboratories participating in the key comparison have carried out a series of calibration measurements of a particular accelerometer. The values from this series correspond to the measurements at different excitation frequencies. A physical model describing the frequency dependence is known. The proposed model-based analysis estimates the unknown model parameters taking the values from the series of the laboratories simultaneously into account. If the derived model and the data are consistent, the model function gained represents the reference values. The advantage of the model-based analysis is that we utilize the a priori knowledge we have at our disposal. We obtain better reference values, i.e., the uncertainties associated with the reference values are considerably lower.     

Reference materials and evaluation of thermophysical properties data

This paper presents a general review of the governmental activities in Japan on reference materials and evaluation of thermophysical properties data and then describes recent developments at the National Research Laboratory of Metrology (NRLM) in the field of thermophysical properties and related standards. As for reference materials, the past and present activities organized by the government and a few related associations are reviewed from the point of view of establishing traceability systems, whereas, on the evaluation of thermophysical properties, the framework of collaborative research for establishing data base systems by network sharing is mentioned. Then the recent studies of NRLM on the measurements and standards of thermophysical properties as well as its calibration services are summarized.Presented at the Japan-United States Joint Seminar on Thermophysical Properties, October 24–26, 1983, Tokyo, Japan.     

Reference Values of the Dielectric Constant of Natural Gas Components Determined with a Cross Capacitor

A novel toroidal cross capacitor was used to measure accurately the dielectric polarizability(p) (i.e., the dielectric constant as a function of the pressure) of helium, argon, nitrogen, methane, and carbon dioxide atT=50°C. The data extend up to 7 MPa (5 MPa for CO₂) and may be useful for calibrating on-line, capacitance-based systems that are designed to measure the heating value of natural gas. The uncertainties ofandpare 4×10^–6and (3.0×10^–5 p+84 Pa), respectively. The properties of helium that had been calculatedab initiofrom quantum mechanics were used to verify that the cross capacitor deformed in a predictable manner under hydrostatic (gas) pressure. Thus, a common cause of systematic errors in measuring the dielectric constant of gases was avoided. For helium, the rms deviation of(p) from the calculations was only 2.7×10^–7. This suggests that the estimated uncertainty is very conservative.     

材料疲劳试验数据中可疑观测值的计算及程序处理

介绍了材料疲劳试验数据中可疑观测值的判断原理,并设计了一种用于计算材料试验数据中可疑观测值的软件。该软件使用Visual C#语言编写,可以从试验数据中挑选出可疑观测值,并能计算出平均值和标准差等数据,计算完成后输出显示可疑观测值及其在数据组中的具体位置,最后用实际测试数据对软件的功能和计算准确性进行了验证。结果表明：该软件计算结果准确,使用方便、灵活,提高了材料疲劳试验数据的处理效率;该软件也可用于材料其他试验数据中可疑观测值的计算。     

甲烷中微量气体标准物质分析方法研究及量值的比对

建立了甲烷中微量气体标准物质的分析方法和实验条件;考察了该分析方法的不确定度;得出甲烷中微量气体标准物质浓度在(1 ～50)×10-6(mol/mol)范围内,方法不确定度小于1％的实验结果.实验过程对重量法制备的系列气体标准物质量值进行了分析方法的比对,一致性验证结果在1％内吻合.该项研究成果代表国家最高实验室参与了...     

甲烷中微量气体标准物质分析方法研究及量值的比对（续二）

建立了甲烷中微量气体标准物质的分析方法和实验条件;考察了该分析方法的不确定度;得出甲烷中微量气体标准物质浓度在（1～50）×10-6（mol/mol）范围内,方法不确定度小于1%的实验结果。实验过程对重量法制备的系列气体标准物质量值进行了分析方法的比对,一致性验证结果在1%内吻合。该项研究成果代表国家最高实验室参与了国际计量委员会组织的CCQM-K66的关键比对,得到了满意的实验结果,获得了国际的等效度。     

甲烷中微量气体标准物质分析方法研究及量值的比对(续一)

建立了甲烷中微量气体标准物质的分析方法和实验条件;考察了该分析方法的不确定度;得出甲烷中微量气体标准物质浓度在(1～ 50)×10-6(mol/mol)范围内,方法不确定度小于1％的实验结果.实验过程对重量法制备的系列气体标准物质量值进行了分析方法的比对,一致性验证结果在1％内吻合.该项研究成果代表国家最高实验室参与了...     

An Estimate of the Reliability of Reference Data on the Electromagnetic Properties of Materials at High and Microwave Frequencies

The estimate of the reliability of reference data is based both an analysis and determination of the statistical significance of the error of experimental data, and also on the good agreement of a fairly complete set of data, obtained in different series of measurements, on different equipment, in different laboratories, and also of published data.