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.     

功率天平的研究进展及其在质量基准重新定义中的应用

质量单位千克的重新定义是新世纪计量领域面临的一项挑战,而功率天平是重新定义质量基准的新技术中最有希望的一种。文中介绍了功率天平的工作原理和组成,并简要说明了目前功率天平的研究状况。随着相关技术的发展,有望实现质量自然基准的定义。     

阿伏伽德罗常数测量技术的研究现状

随着现代测量技术的发展,质量实物基准必将被质量自然基准所代替,而阿伏伽德罗常数NA是最有可能实现质量单位＂千克＂重新定义的基本物理量之一。另外,阿伏伽德罗常数的测定对于重新定义物质的量的单位＂摩尔＂也具有重要作用。文中重点介绍了单晶硅粒子法测定阿伏伽德罗常数的最新进展,并分析了其在千克重新定义中的作用。     

能量天平不确定度分析与整体系统改进

将质量单位千克溯源到普朗克常数上是目前计量领域公认的实现质量重新定义的方法。能量天平法则是我国提出的用来测量普朗克常数与复现质量的一种方案。与国外采用的功率天平法相比,能量天平法拥有静态测量的优点。第一代能量天平系统已经完成了整体系统实验,对其不确定度的详细分析,有助于进一步优化设计方案,改进实验过程。最后得到其整体的不确定度为2.5×10~(-6)。针对其中主要的不确定度来源,在第2代能量系统中分别提出了相应的改进办法,为进一步降低实验不确定度提供了保证。     

高精密恒电流库仑滴定法测定苯甲酸纯度

高精密恒电流库仑法是国际上公认的基准测量方法,根据法拉第电解定律,通过质量、电阻、电动势、时间等基本物理量及法拉第常数来进行样品测定,直接溯源到国际单位SI,不需要用标准物质进行比对。采用高精密恒电流库仑法测定苯甲酸纯度,测定结果扩展不确定度:0.014%,实验证实该方法具有高准确性,测量精度<0.02%。     

砝码计量标准建标问题探究

法定的技术检定机构,承担着建立计量标准,进行量值传递的职责,作者认为有些机构以一个项目只建一个最高等级的计量标准,在自己内部进行量传,这种做法是不适宜的,本文从技术和管理两个方面针对这个问题进行了分析和阐述。     

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.     

Stability assessment of density reference liquids supported by GC–MS analysis (density reference liquids stability supported by GC–MS)

Density measurements are frequently associated to specific requirements to evaluate the quality of a process or to determine mass and/or volume of the material. Certified reference liquids can be used to assure metrological traceability of density measurements to the SI with uncertainty lower than 0.005%. This paper presents the new approach of INRIM to set density standards.     

Development of an optical measurement method for “sampled” micro-volumes and nano-flow rates

Radiopharmaceuticals used in nuclear medicine for therapy or diagnosis (molecular imaging, PETscan, scintigraphy) are characterized in terms of volume activity before injection to patients. The current measurement process relies on dose calibrators which have to be calibrated by transfer standards, traceable to primary standards. For very short half-life radionuclides (few minutes), the metrological traceability can only be assured through an on-site calibration with primary standards. However, until now, there is no primary system for the direct measurement of such high activity radioactive solutions. This study presents the sub-system under development for the measurement of a sampled volume of the order of 1 μL with an associated relative target standard uncertainty of 1%. The volume of solution is a key parameter in activity per unit of volume calibration of radiopharmaceuticals solutions. This article focuses on the volume measurement method development and its validation by comparison to the gravimetric method.The paper, in a first part, describes the developed method and the associated hardware and software. The authors have chosen a non-contact optical method implemented by a microscope camera and associated optics in front of a transparent capillary.The second part of the paper describes the measurement process. Several image processing steps are described and the traceability to dimensional units is presented.Finally, the paper presents some validation results by comparison to a gravimetric measurement, including repeatability and accuracy tests. Further development and improvements, necessary for the finalization of the prototype and the measurement of nano-flow rates are discussed.     

Precisely measuring the Planck constant by electromechanical balances

To eliminate the last artefact unit, kilogram, in the seven basic SI units, the possible new definition of kilogram by fixing the Planck constant is being considered. National Metrology Institutes, the BIPM and academic institutions have built several electromechanical balances such as watt balance to measure the Planck constant by an equivalence of mechanical and electrical energies. This paper reviewed the principle, apparatus and recent progress of different electromechanical balances. The tendency for measuring the Planck constant and the future of kilogram have also been predicted.     

高精密库仑滴定法测定三氧化二砷的纯度

高精密库仑滴定法是国际上公认的基准测量方法,该方法根据法拉第电解定律,通过质量、电阻、电动势、时间等基本物理量及法拉第常数来进行三氧化二砷纯度的测定,直接溯源到国际SI单位,不需要用标准物质进行比对。样品以氢氧化钾溶液溶解,通过电解产生碘与亚砷酸盐定量反应,以死停终点法确定终点。该方法具有很高的测量精度和准确性。     

电子皮带秤示值误差测量不确定度分析

随着韶钢铁前计量管理系统的正式运行,担负着铁前各单位工序之间物料输送计量用的电子皮带秤,在各单位成本核算,降低能源消耗,提高经济效益的需要作用日益主要。为此,对承担煤炭、焦炭、烧结矿等物料输送计量的电子皮带秤的计量性能提出了更高的要求,本文在对电子皮带秤进行计量检定,判断是否符合国家计量检定规程的要求之外,试对其计量检定过程中不确定度来源进行分析,从定量的角度分析计量皮带秤的计量性能。     

用计量型AFM对一维纳米基准栅的标定及不确定度估计

利用轻敲模式的计量型AFM对公称栅距为240nm一维基准样板进行了标定,在充分分析AFM的结构和特性、测量过程、数据处理的基础上,得到了基准栅的平均栅距估计值和扩展不确定度。通过全面的不确定度分析,估计值的扩展不确定度达到了亚纳米量级。该不确定度分析表明,对于纳米量级测量,不确定度估计不仅需要全面掌握测量仪器、测量过程中各种测量不确定因素的影响,还需要考虑和估计常规测量过程中可以忽略的二次误差的影响。     

International comparison of volume measurement for a 1 kg silicon sphere between KRISS and NMIJ

1 kg single-crystal silicon spheres are presently used as primary density standards in many countries. The absolute density of the spheres is determined from the measurements of their mass and volume in conformity with the definitions of the SI base units. Since the mass of the spheres is almost 1 kg, a mass comparison with the prototype of the kilogram can be performed with very low uncertainty. Absolute volume measurements for the spheres therefore have a crucial role in realizing a reliable density traceability system. To confirm the reliability of the volume measurement, the volume of a silicon sphere was measured independently using optical interferometers at the Korea Research Institute of Standards and Science (KRISS, Korea) and the National Metrology Institute of Japan (NMIJ, Japan). An optical interferometer with an etalon scanning system was used at KRISS. On the other hand, an optical interferometer with an optical frequency scanning system was used at NMIJ. The volume was measured at 20 °C and 0 Pa, and the results are in agreement with each other within their uncertainties. Details of the two interferometers and the comparison results are described.     

CMM touch trigger probes testing using a reference axis

A new method of testing of touch trigger probes for coordinate measuring machines (CMM) has been proposed. The concept is based on measurements of the distance between reference and triggering points in various directions. The reference points are established by the rotation axis of a precise rotary table. The advantage of this method relies on easy realisation with application of a commercial device for roundness error measurement. The accuracy of the presented method is much higher in comparison with the existing procedures of CMM probes calibration.The mathematical principle of the method has been presented and used for evaluation of its uncertainty. The validity of the method was experimentally confirmed by means of one- and two-stage type probes.     

Interferometric,absolute sensor of angular micro-displacement

A design of a new, absolute sensor for measurement of an angular micro-displacement is presented. In this sensor deflections of incident laser beam generate changes of the constant of the interference fringes that are created by the double arm special interferometer. Fringe constant is determined using a CCD camera and proposed analysis algorithms. Sensor's operating principle and metrological properties are presented. Sensor was tested using reference interferometer. Obtained measurement uncertainty is equal to ±10 μrad in the multi-milliradian range. The concept of a two-sensor system for increasing twice the measuring range is presented.     

Metrological evaluation of skin conductance measurements

Electrodermal activity is a frequently measured physiological response in various applications. It is also being increasingly used in clinical applications. Numerous published papers report results of skin conductance measurements in absolute values, but few are concerned with the quality of results. This paper describes a procedure for metrological evaluation of skin conductance measurement. Three commercial devices for measuring skin conductance were calibrated by comparison with a precision digital ohmmeter used as a reference. Combined measurement uncertainty of skin conductance meters was calculated by means of uncertainty of reference instrument and uncertainties due to measurement repeatability, reproducibility, resolution and environmental condition. Additionally, a procedure for evaluation of the effect of electrode displacement and electrode gel was shown. A model of finger skin conductance profile was build. Measurement uncertainty analysis showed that contributions due to resolution and sensitivity of the measuring device, usually obtained from specifications, are negligible when compared to uncertainty of measuring method. Our results indicate that measurement uncertainty does not meet target uncertainty requirements for certain applications.     

Evaluation of the uncertainty of an optical machine with a vision system for contact-less three-dimensional measurement

Optical machines with a vision system containing a video camera are designed to perform contact-less three-dimensional measurements. They are becoming more widely used in the industrial sector because of the many possibilities for automation they permit and because of the speed and economies in measurement tasks that can consequently be obtained. Within dimensional control these machines introduce significant characteristics of flexibility, savings and reliability. Therefore the purpose is to identify the principal metrological characteristics of such machines and so characterise the metrological traceability of the measurements obtained from them. The aim is to qualify each part of the optical machine as well as on the whole. Previously, no metrological traceability of this equipment has been provided in primary metrology, either at national (SIT—Sistema di Taratura in Italia—Calibration System in Italy) or at international level (EA–European co-operation for Accreditation). For this reason we develop a mathematical model that permits the evaluation of the measurement uncertainties in the use of such a device. The purpose is to obtain the certification of the measurement results furnished by the optical machine in as broad a context as possible. The experimental results of the tests are introduced for validating the proposed method. This paper provides the basis of the expression of the uncertainty of a measurement result obtained using the optical measurement machines and it shows the necessary requirements for the numerical evaluation of such uncertainty.     

镉新原子量测定计量学与 MC-ICP-MS测定水稻中的镉含量(英文)

天然镉是与铜矿共生的高挥发性元素 ,含有 8个稳定同位素。测量其同位素丰度的不确定度只能达到 0 .9%～ 4.8%。因此 ,必须按国际理论和应用化联合会原子量和同位素丰度分会 ( IUPACCAWIA)的要求来测定天然丰度镉的新镉原子量。IUPAC CAWIA要求的条件和步骤是采用高真空蒸馏法纯化浓缩镉和天然镉样品 ,测量和计算这些样品中杂质元素的含量 ,用计量学称重法制备同位素混合样品 ,用多接收电感耦合等离子体质谱 ( MC-ICP-MS)和热电离质谱 ( TIMS)测定镉的同位素比值 ,计算镉原子量并评估相关的不确定度。一些国家实验室用 MC-ICP-MS获得了稻米中镉的含量 ,可用作对照的关键参考值是 1 4 .48± 0 .0 87nmol·g- 1。