基于指数法评估激光量热仪吸收测量不确定度

为了掌握熔石英样品在紫外波段的吸收特性,研究了精确评估激光量热仪测量不确定度的方法。介绍了激光量热仪的吸收测量原理,选用指数法对吸收测量数据进行了拟合;通过分析各吸收率测量结果的影响分量,建立了测量不确定度评估模型;对各输入量的估计值以及估计值的标准不确定度逐一进行计算,并对影响吸收率测量结果的拟合计算参数A、γ进行了修正。考虑背景温度漂移对被测样品温度测量的影响,利用Matlab编程分析了线性、非线性温度漂移对吸收计算结果的影响,获得其相对标准不确定度及相对扩展不确定度分别为2.6%和5.2%。最后,更换熔石英基底并进行多次吸收测量,计算了吸收率10次测量结果平均值的相对标准不确定度为2.3%,相对扩展不确定度为4.6%,与评估结果基本相同。     

Improvements to estimate ADCP uncertainty sources for discharge measurements

The use of moving boat ADCPs (Acoustic Doppler Current Profilers) for discharge measurements requires identification of the sources and magnitude of uncertainty to ensure accurate measurements. Recently, a tool known as QUant was developed to estimate the contribution to the uncertainty estimates for each transect of moving-boat ADCP discharge measurements, by varying different sampling configurations parameters through the use of Monte Carlo simulations. QUant is not only useful for estimating ADCP discharge measurement uncertainty, but also for identifying contributions of the various sources of uncertainty.However, the software requires long computational times, and the method to estimate the uncertainty of multiple-transect measurements does not consider the correlation of the variables between transects. Therefore, improvements in QUant are needed to optimize its application for practical purposes by hydrographers immediately after discharge measurements.This work presents four approaches for optimizing the performance of QUant to estimate the contribution to the uncertainty of different selected variables on ADCP discharge measurements and describes a new method of estimating multi-transect uncertainty with the QUant model that considers the correlation of errors in selected variables between transects. The approaches for optimization and the new multi-transect uncertainty method are evaluated using a dataset of 38 field measurements from a variety of riverine settings.     

Estimation of uncertainty for sulfonated grafted low density polyethylene dosimeter using thermoluminescent dosimeter

In this work, one type of thermoluminescence dosimeter low density polyethylene grafted by acrylic acid acrylamide, acrylic acid actinamide polymer film (LDPE-g-p (AAm/AAc)) was irradiated by ⁶⁰Co therapeutic gamma ray dose. This work deals with the case of sulfonated grafted film which has good properties such as thermal stability, and good dosimetric properties. The various sources of uncertainty for this type of thermoluminescence dosimeter under study were analyzed. The uncertainty budget tables for radiation measurements were declared. For the used procedure, these uncertainties multiply the coverage factor equal 2 to obtain the expanded uncertainty at 95% confidence level. The combined uncertainty does not exceed 6.3%. The results suggested that, the expanded uncertainty at 95% confidence level should be added to the value of measurements to obtain the accurate dose.     

PTB330型气压传感器示值误差测量不确定度评定

文章通过建立模型,分析了PTB330型气压传感器测量结果的不确定度来源、评定测量结果的不确定度分量,得出了示值误差测量的合成标准不确定度及扩展不确定度。文章选取10台气压传感器按照自动气象站气压传感器检定规程要求,对各检定点进行测量结果不确定度评定,为同类型的气压传感器测量的检定结果提供科学的参考依据。     

Calibration procedures and uncertainty analysis for a thermal mass gas flowmeter of a new generation

This paper deals with the differences between traditional and new technology gas meters, and focuses specifically on the calibration procedure and uncertainty evaluation of CTTMFs (Capillary Type Thermal Mass Flow Meter). In particular, measurements performed on a sample set of commercial CTTMFs for natural gas in domestic/residential (G4) applications allowed to evaluate the modifications to calibration procedures required by the new generation, digital, gas flow meters. Indeed, traditionally natural gas is metered by means of volumetric measurement techniques, while the modern, static gas flow meters (thermal and ultrasonic ones) are based on electronic flow sensors. This implies that the gas volume through the meter is measured by sampling the flow rate at selected time points and integrating the flow rate in time. The measurement time becomes therefore an important parameter, thus requiring a thorough rethinking of the calibration procedure. In order to analyse the effects of the various parameters, a series of ad-hoc calibrations were performed. Specifically, one set of calibrations was performed with constant totalized volume, while the other required a constant measurement time. In order to highlight the novelties that will have to be implemented in ordinary calibration procedures to get the best of the new technologies, the two procedures as performed on a sample set CTTMFs will be compared; the theoretical (generic) evaluation of the associated uncertainty will also be presented. Measurements were carried out at the test facility of INRIM, the Italian National Metrology Institute.     

面向对象的大尺寸测量不确定度分析

测量结果必须说明不确定度。常规尺寸的解析法和标准比对法难以适用于评价大尺寸测量不确定度,尤其是特定拟合任务结果的不确定度。针对大尺寸测量的特殊性,研究基于蒙特卡罗的评价方法评价大尺寸特定测量对象的不确定度,并用计算机可视化直观表示离散点云。利用离线仿真评价测量不确定度,用于设计最优采样策略。以激光跟踪仪测量大型圆形截面工件分析为例,给出测点对称、均匀分布和半径约束等优化测量思想。最后应用于激光跟踪仪测量隧道构件的实例当中。仿真和实际实验表明,蒙特卡罗评价和离散点云表示法可准确、直观评价大尺寸测量特定测量对象的不确定度,制定的最优采样策略可提高测量精度。     

一种力平衡气体活塞压力计原理及不确定度验证

文章介绍了一种新型的、用于微小表压和绝压测量的力平衡式气体活塞压力计的工作原理、压力复现的计算公式以及不确定度等,并在表压状态下,通过与标准比对的方式,对该气体活塞压力计的原理及宣称的不确定度进行了实验验证,实验结果证明了厂商给出的不确定度指标的正确性.     

a study on the propagation of measurement uncertainties into the result on a turbine performance test

Uncertainties generated from the individual measured variables have an influence on the uncertainty of the experimental result through a data reduction equation. In this study, a performance test of a single stage axial type turbine is conducted, and total-to-total efficiencies are measured at the various off-design points in the low pressure and cold state. Based on an experimental apparatus, a data reduction equation for turbine efficiency is formulated and six measured variables are selected. Codes are written to calculate the efficiency, the uncertainty of the efficiency, and the sensitivity of the efficiency uncertainty by each of the measured quantities. The influence of each measured variable on the experimental result is figured out. Results show that the largest uncertainty magnification factor (UMF) value is obtained by the inlet total pressure among the six measured variables, and its value is always greater than one. The UMF values of the inlet total temperature, the torque, and the RPM are always one. The uncertainty percentage contribution (UPC) of the RPM shows the lowest influence on the uncertainty of the turbine efficiency, but the UPC of the torque has the largest influence to the result among the measured variables. These results are applied to find the correct direction for meeting an uncertainty requirement of the experimental result in the planning or development phase of experiment, and also to offer ideas for preparing a measurement system in the planning phase.     

Development of the precision planar motor stage using a new magnet array and robust control with the parametric uncertainty model

This paper discusses the development of a new precision motor stage, where a new magnet array is proposed and a new robust controller is implemented. Several planar motor parameters, such as the air gap flux density and flux linkage, are analytically evaluated by the scalar potential, and, thus, about a 5–8% increase is observed for the proposed magnet array. A new robust controller is also proposed using the parametric uncertainty model, which can effectively control the movement during both stable and cogging positions. The performance of the robust controller is evaluated, and it shows much higher robustness and about a 200% higher position accuracy when compared with the conventional PID controller. Therefore, the developed planar motor stage is successfully designed and implemented, and, thus, proposes great potential for most of the positioning applications in the field of semiconductor equipment and machine tools.     

Measurement uncertainty evaluation of conicity error inspected on CMM

The cone is widely used in mechanical design for rotation, centering and fixing. Whether the conicity error can be measured and evaluated accurately will directly influence its assembly accuracy and working performance. According to the new generation geometrical product specification(GPS), the error and its measurement uncertainty should be evaluated together. The mathematical model of the minimum zone conicity error is established and an improved immune evolutionary algorithm(IIEA) is proposed to search for the conicity error. In the IIEA, initial antibodies are firstly generated by using quasi-random sequences and two kinds of affinities are calculated. Then, each antibody clone is generated and they are self-adaptively mutated so as to maintain diversity. Similar antibody is suppressed and new random antibody is generated. Because the mathematical model of conicity error is strongly nonlinear and the input quantities are not independent, it is difficult to use Guide to the expression of uncertainty in the measurement(GUM) method to evaluate measurement uncertainty. Adaptive Monte Carlo method(AMCM) is proposed to estimate measurement uncertainty in which the number of Monte Carlo trials is selected adaptively and the quality of the numerical results is directly controlled. The cone parts was machined on lathe CK6140 and measured on Miracle NC 454 Coordinate Measuring Machine(CMM). The experiment results confirm that the proposed method not only can search for the approximate solution of the minimum zone conicity error(MZCE) rapidly and precisely, but also can evaluate measurement uncertainty and give control variables with an expected numerical tolerance. The conicity errors computed by the proposed method are 20%-40% less than those computed by NC454 CMM software and the evaluation accuracy improves significantly.     

Application and uncertainty analysis of a balance weighing system used in natural gas primary standard up to 60 bar

A new 3-ton balance weighing system was designed and built up for a high level mass-time primary standard of natural gas up to 60 bar in CVB. The system is composed of a 3-ton electromagnetic balance, two tanks with thermal isolation, two platforms, two roller guide rails and two big weights which are used for special test. To achieve a lower uncertainty and the security application in natural gas measurement, several special methods were used in the system. Firstly, the tanks and platforms can be moved together steadily on the roller guide rail to be connected with pipeline system or to be weighted by the balance which also reduces the pipeline length between tanks and pipeline system. Secondly, the substitute weighing method is used for high accurate weighing. Finally, the whole system is located in a thermal isolated room with temperature and humidity controlling. Technical details, performance tests, uncertainty analysis and the future improvement ideas of the balance system are presented in the paper. The uncertainty analysis shows that the mass measurement uncertainty of gas can achieve less than 1.0g and the maximum relative standard uncertainty of natural gas mass measurement would be no more than 0.022%.     

LNG energy transfer uncertainty–sensitivity to composition and temperature changes

Determining and reducing the measurement uncertainty of LNG energy transfer in custody transfer operations is considered extremely important and challenging for industry. The European Metrology Research Programme (EMRP) for Liquefied Natural Gas (LNG) has been focused on reducing the uncertainty in the evaluation of LNG energy transfers by improving existing measurement methods, validating new measurement methods and development of new traceable calibration systems. Part of this project was to produce realistic measurement uncertainty budgets and to determine the sensitivity of the overall LNG energy transfer uncertainty to changes in the composition and temperature of different LNG cargoes.This paper provides details on the development of an uncertainty budget and the results from the sensitivity study. It was found that the uncertainty in the LNG energy transfer ranged from 0.56% to 0.77% when using the uncertainty budget for 461 LNG cargoes. The variation was mainly due to the difference in the LNG composition and its associated uncertainty.     

Comparison of GUM and Monte Carlo methods for evaluating measurement uncertainty of perspiration measurement systems

Measurement uncertainty is an important parameter to express measurement results including means and reliability. The uncertainty analysis of the biomedical measurement system needs to be established. A perspiration measurement system composed of several sensors was developed. We aim to estimate the measurement uncertainty of this system with several uncertainty sources, including airflow rate, air density, and inlet and outlet absolute humidity. Measurement uncertainty was evaluated and compared by the Guide to the expression of the uncertainty in measurement (GUM) method and Monte Carlo simulation. The standard uncertainty for the perspiration measurement system was 6.81 × 10⁻⁶ kg/s and the uncertainty percentage <10%. The major source of the uncertainty was airflow rate, and inlet and outlet absolute humidity. The Monte Carlo simulation could be executed easily with available spreadsheet software programs of the Microsoft Excel. GUM and Monte Carlo simulation did not differ in measurement uncertainty with precision to two decimal places. However, the sensitivity coefficient derived by GUM provided useful information to improve measurement performance, which was not evaluated with the Monte Carlo simulation method.     

Evaluation and uncertainty analysis of vectorial tolerances

Recently, the integration of coordinate measuring machines (CMMs) and computer-aided design (CAD) systems has promoted a new approach to the evaluation of workpiece geometry; namely, vectorial dimensioning and tolerancing. This new approach is promising, because it defines process-related dimensions and tolerances clearly and distinctly. Therefore, it enables proper manufacturing control and process diagnosis. However, current proposal of vectorial tolerancing has several limitations. First, the current orientation vector is inadequate for representing true three-dimensional (3D) orientation. As a result, the orientation of a free-form surface cannot be properly established. Second, there has been little discussion of vectorial tolerance evaluation. This paper proposes a new rotation vector that provides a more general mathematical basis for representing vectorial tolerances. A nonlinear, best-fit algorithm has been developed to evaluate vectorial tolerances for both analytical geometric elements and free-form surfaces. To study the uncertainty of the best-fit result caused by sampling strategy and dimensional errors, sensitivity analysis of the evaluated parameters was investigated. Simulation and experiment showed that the developed model can predict the uncertainty of the evaluated parameters accurately.     

Presentation of a test rig with its experimental procedure and uncertainty analysis of measurements for batch type fluidized bed drying of corn and unshelled pistachio nut

This paper gives the hardware and software of a test rig with its experimental procedure, methodology and uncertainty analyses of measurements for batch type fluidized bed drying of corn and unshelled pistachio nut. The test rig is designed, constructed and operated for the analyses of drying performance of corn and unshelled pistachio nut in a batch type fluidized bed drying. The details of the test rig, the experimental procedure, the uncertainty analyses and the investigation of the effects of drying parameters on drying performance are the major scope of the paper. The accuracy of the experimental study herein is based on velocity, pressure, temperature and moisture measurements. Therefore it is vital and sensitive phenomenon for the determination of the uncertainties of the measurements before the current study as is the case with all other studies. The test rig is designed and constructed in accordance with literature review which is mentioned briefly in this paper. The basic terminology which is used in this study is also introduced herein. The overall uncertainties of velocity, pressure, temperature and moisture measurements are performed and found as 1.7%, 1.3%, 0.3% and 1.6%, respectively. Some pioneering studies related on conventional batch type fluidized bed dryers operated under atmospheric pressure are also tabulated as an original contribution to literature. Moreover, the effects of the particle mass, drying air temperature and drying air velocity on drying performance of the batch type fluidized bed dryer which is assisted with a conventional electrical heater unit are outlined without going into details in thermo- and fluid-dynamics of drying process.     

火花源发射光谱仪测定HRB500钢筋中钒、铌含量的不确定度评定

火花源发射光谱仪测定钢筋中钒、铌含量,测量不确定度主要来源于样品测定重复性、类型标样、工作曲线、高低标校正、环境的温度、仪器稳定性及仪器分辨力。依据JJF1059—1999对测量结果的不确定度进行了评定和表述,对各个不确定度分量进行了计算和合成。     

Analytical estimation of coordinate measurement uncertainty

The paper presents the assumptions and theoretical background of analytical method of estimation the coordinate measurement uncertainty. The uncertainty for each characteristic is estimated separately. Mathematical model for each characteristic uses the minimal number of so-called “characteristic points” of the measured workpiece. Each characteristic is defined by a formula presented in a form where it is a function of coordinates’ differences’ of characteristic points. The uncertainty budget for the coordinates’ differences includes influences of particular geometrical errors of CMM, probing system errors, as well as temperature errors. The applied algorithms of uncertainty estimation use the type B method according to the rules of GUM.     

Improvement and uncertainty evaluation of mercury sealed piston prover using laser interferometer

Many NMIs (National Measurement Institute) and calibration laboratories are using a mercury sealed piston prover as calibration system for gas flow meter. But it has problems in deciding measuring volume, traveling time of piston and generating low flow rate below 10 cc/min. In this study, a new structure of a piston prover is designed and its flow measurement uncertainty is evaluated according to ISO/IEC 17025. A laser interferometer, instead of optical sensors used in a typical piston prover, is employed to measure testing time and moving distance of the piston, accurately. A new material of the piston is used to eliminate contaminated particles from the material of the piston body. Uncertainty is calculated by evaluating various uncertainty factors which have influence on gas flow measurement. The expanded uncertainty of the piston prover is 0.11% at the confidence level of 95%. The uncertainty evaluation procedure of this study would be useful in flow measurement uncertainty determination of other types of gas flow measurement systems.