孔板流量计测量天然气质量流量不确定度分析

孔板流量计属于标准型节流式差压流量计,依据其测量天然气质量流量计算公式可推知孔板流量计质量流量测量的不确定度来源于六个方面:流出系数的不确定度、可膨胀性系数的不确定度、测量管内径的不确定度、孔板开孔直径的不确定度、差压测量的不确定度、天然气密度测量的不确定度。     

条码打印计价秤比对示值误差的不确定度分析与评定

本文依据JJF1059.1-2012《测量不确定度评定与表示》计量技术规范,结合计量比对实例,介绍了条码打印计价秤示值误差的不确定度的来源和评定方法,并通过实际测量,对最大秤量15kg的条码打印计价秤测量关键点（2.5kg和15kg秤量点）的示值误差的不确定度进行评定。本文的研究为同类计量器具的示值误差不确定度评定提供了实际参考。     

孔板流量计测量天然气质量流量不确定度分析

孔板流量计属于标准型节流式差压流量计,依据其测量天然气质量流量计算公式可推知孔板流量计质量流量测量的不确定度来源于六个方面:流出系数的不确定度、可膨胀性系数的不确定度、测量管内径的不确定度、孔板开孔直径的不确定度、差压测量的不确定度、天然气密度测量的不确定度。     

关于不确定度评估的若干问题

根据ISO测量不确定度评估导则的基本理论,对力值、硬度、扭矩等计量专业的测量不确定度评估方法进行了研究。结合质量、压力、流量、容量、光学和化学等计量专业不确定度评估实践,对校准,计量,检测不确定度评估的基本要点进行了系统分析,其中包括基本概念,基本计算公式,计量传递链,评估过程,评估要点等。     

关于不确定度评估的若干问题

根据ISO测量不确定度评估导则的基本理论,对力值、硬度、扭矩等计量专业的测量不确定度评估方法进行了研究.结合质量、压力、流量、容量、光学和化学等计量专业不确定度评估实践,对校准,计量,检测不确定度评估的基本要点进行了系统分析,其中包括基本概念,基本计算公式,计量传递链,评估过程,评估要点等.     

测量不确定度评定及其在电学计量中的应用

对于计量数字的获取,可以说电学计量中关于不确定度的评定非常重要的一个方式,而且应用广泛。对于测量不确定度的评定方法、重要性和意义以及运用进行了详细的分析,同时和最近几年来的研究资料相结合,对电学计量中测量不确定度的应用进行了分析。     

直流电能计量标准装置测量结果的不确定度评定

高准确度直流电能计量标准装置用于检定或校准下一级的直流标准电能表,构成直流电能量值溯源体系中的重要一环。本文分析了高准确度直流电能计量标准装置的测量结果的不确定度,列出了测量不确定度分量的主要来源：电压测量、电流测量、电能脉冲测量,用A类评定方法和B类评定方法进行了不确定度评定。     

浅谈砝码的测量不确定度评定

不确定度评定是计量检验检定部门考核验收的重要环节，本文通过一些具体的实例，阐述了在测量不确定度评定过程中遇到的一些问题，诠释了什么是不确定度，不确定度的来源。用通俗易懂的语言阐述了产生不确定的一些因素，并用实际试验讲解了我们如何进行计量标准的测量不确定度评定。     

阵列式皮带秤检定测量结果不确定度评定研究

本文重点分析了阵列式皮带秤检定测量过程中的误差来源,结合应用实例基于相关数学模型对检定测量不确定度的主要来源和因素进行了系统分析,给出了实物校验过程中对造成测量不确定度的主要因素,并依此开展了计算合成不确定度和扩展不确定度的研究,进而对阵列式皮带秤检定测量结果开展了测量不确定度评定,获得了其计量精度等级。     

基于GPS的圆柱度测量不确定度分析与评定

本文在GPS不确定度理论的基础上,阐述了PUMA测量不确定度管理程序及其关键环节;在对圆柱度的测量过程研究的基础上,分析了圆度仪测量圆柱度的测量不确定度影响因素及评定模型,利用PuMA管理程序,实现了圆度仪测量圆柱度的测量不确定度的规范评定,证明了PUMA管理程序可用于几何特征量测量或者测量设备计量特征校准的测量程序.     

Uncertainty study of fiscal orifice meter used in a gas Algerian field

Uncertainty variation of a fiscal orifice measurement system used in an Algerian natural gas exportation station is studied using data from a natural gas production field known as Gas Tin Fouye Tabankort (GTFT) located in the south-east of Algeria. The expected results are uncertainty calculus over a range of temperature and pressure variation and to the customs authorities’ allocation.In fact, each quantity of measured fluid flow has certain uncertainty and then the fiscal measurement station is very important for gas exportation, which means the income. Therefore, the pursuit of flow metering device uncertainty and its influence on the measured quantities in the transmission networks is very important.For that, the uncertainty caused by flowmeter in the measurement station causing economical revenue fluctuations is studied. The work was done to justify why there is a production decrease of hydrocarbons without identifying reasons during summer. The difference between the mass flow rate quantity produced and the transmitted value was important that is why our work is done to clarify exactly from where the problem can come.The measurements setting with two operating conditions (gas temperature and pressure) show that the uncertainty is dominated by seasonal temperatures and pressures variations which induce fluctuation in gas and pipe temperatures and influence the metrological performance of the transmitters. Indeed, the metrological measurement chain performance is affected also by these two operating conditions.The present work is done according to the ONML (National Legal Metrological Office) instructions regarding differences between the measured and the seller values represented by the mass flow rate.In natural gas transmission network, the important problem in the management and control of the network is represented by the unaccounted for gas, a quantity of measuring error which is to be considered in the equation of network balancing. One of the unaccounted for gas sources are the environmental conditions and systematic measurement errors.In this work, the calculation of the combined uncertainty of the mass flow rate measured by an Orifice fiscal gas metering plant is done. From the results founded, the authors confirm that the uncertainty in the measurement system causing by the climatic conditions generates unaccounted for gas.     

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%.     

Gas mass-flow meters: Measurement and uncertainties

The application of gas mass-flow meters (GMFM) sensors needs the knowledge of its measurement model and measurement uncertainties. It was already known that the GMFM output model depends on gas mass-flow and gas composition. In this work, different throughput GMFM sensors were used for different gas flow rates and gas composition in order to verify and to improve the GMFM measurement model.A direct calibration procedure and a dynamic volumetric method were applied both to get the measurement model and to evaluate the performance of gas sensors and GMFM sensors against certified reference materials and suitable standards. Additionally, the obtained data were used both to calculate the uncertainties of gas mass-flow measurement and to improve the GMFM gas response factors.The calculated uncertainties of the GMFM direct measurement was approximately 2% of the measured value. The uncertainty of the dynamic volumetric method developed in this work was found as approximately 5% of the measured value and that was mainly influenced by the uncertainties of the standards used.     

天然气单体烃氢同位素组成质谱分析

用色谱 -热转换 -质谱 ( GC/ TC/ MS)对天然气单体烃氢同位素组成进行了测定。实验表明 :热转换温度、进样量和分流比等条件的改变对氢同位素组成的测量结果有影响。以文 3 1井甲烷氢同位素组成 ( -1 5 4‰ )为参考 ,对天然气中甲烷、乙烷和丙烷氢同位素组成的测量不确定度进行了分析。结果表明 :甲烷和乙烷的测量精度都较高 ,但由于参考标准的不确定度较大 ,所以测量结果的不确定度较大     

软X射线辐射测量

在软X射线辐射测量中,和光度学一样,光源标准和探测器标准都同时存在,长春光机所八十年代初,研制了真空紫外光谱区的标准光源;近两年研制了软X射线标准探测器稀有气体电离室和传递标准探测器Al₂O₃光二极管。电离室光谱响应的稳定性和重复性好于±2%;光谱辐射绝对定标的不确定度小于±5%。Al₂O₃光二极管光谱响应稳定性好于±2%,数只二极管的一致性好于±6%。     

Method of measuring the change in volume of a diaphragm bellows used in a volume displacer of a constant-pressure gas flowmeter (with a practical guide)

Construction of constant-pressure gas flowmeters utilizing directly driven bellows and diaphragm bellows as volume displacers were described in recent decades. They have important advantages: accuracy, reliability, easy operation and maintenance.Difficult is to scale sufficiently accurately the changes in volume at compression, to evaluate the uncertainty of this measurement, and to include all the emerging uncertainties into generated throughput uncertainty budget.A compensation method has been proposed for precise measurement of this dependence. This paper presents guides for the implementation of it. The requirements that must be met to achieve a very low uncertainty are described. The method was used for measuring two diaphragm bellows of different sizes as example illustrating achievable values. The attained uncertainty of measurement is analyzed and a procedure is described for determination of the volume of the displaced gas and its uncertainty when using a directly driven diaphragm bellows in a constant-pressure gas flowmeter.     

The uncertainty of torque primary standards: a comprehensive analysis

The development of high-accuracy torque primary standards constitutes the first step towards the harmonisation of the unit of measurement and the realisation of a reliable traceability chain for torque transducers, torque wrenches and screwdrivers. In this paper, a detailed analysis of the uncertainty budget of torque primary standards is proposed. On the basis of the characteristics of the realisations set up by some of the European National Metrological Institutes, as they are available in the literature, the order of magnitude of the uncertainty such systems can achieve is derived. To this extent, attention has been focused on the main questions in the design and in carrying out the measurement of the quantities that determine the main contributions to the uncertainty. Particularly, from the latter point of view, an investigation on the measurement of the friction torque, which is responsible for the degradation of the metrological performances in the lower part of the working range, has been performed.     

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.     

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.     

Critical aspects of the uncertainty budget in the gravimetric PM measurements

The interest in particulate matter (PM) exposure studies leaded the regulatory authorities and the air quality management community in updating new air quality standards. In order to characterize the current exposure experienced by people, measurement should be carried out also taking into account periodic PM concentration fluctuations. For this purpose continuous or semi-continuous measurement techniques were developed even if the reference method used to measure the air quality standards is still based on the gravimetric analysis of particle collected through filtration technique over a period of 24 h.In this work the authors carried out a metrological characterization of the gravimetric method in measuring PM concentrations. The critical aspects of the technical standard in evaluating the uncertainty budget of PM measurement are stressed and the influence of single uncertainty contributions to the combined uncertainty is also shown. Finally, a comparison between European and US standards in PM measurement is made.