极坐标法测量齿形的精度分析

从方法论的角度分析了极坐标法齿轮测量系统的标准量、瞄准、测微和定位误差对渐开线齿形测量精度的影响。通过分析得出极坐标法比展成法更易达到较高测量精度的结论。     

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.     

A dynamic gravimetric standard for trace water

A system for generating traceable reference standards of water vapor at trace levels between 5 and 2000 nmol/mol has been developed. It can provide different amount fractions of trace water vapor by using continuous accurate measurements of mass loss from a permeation device coupled with a dilution system based on an array of critical flow orifices. An estimated relative expanded uncertainty of ±2% has been achieved for most amount fractions generated. The system has been used in an international comparison and demonstrates excellent comparability with National Metrology Institutes maintaining standards of water vapor in this range using other methods.     

塔式起重机检测技术准确性的分析

塔式起重机作为特种设备之一,其检测的准确性是预防安全事故最重要的举措。为提高检测的准确性,依据相关国家标准,结合实际检验工作对检测项目进行优化,并阐述了提高机械及电气方面检测准确性的检测方法,为实际检测工作提供参考。     

Evaluation of discrete displacement transducer by spectral analysis of surface roughness

A discrete displacement transducer using an optical technique and attached to a commonly used stylus instrument is described. The proposed transducer plays an important role in generating a digital output of surface profile from the viewpoint of sampling error. The working accuracy is discussed with reference to the spectral analysis of surface roughness.     

量子计量基准的现状

与传统的计量基准相比较,量子计量基准具有准确度高、可在多个地点复现等一系列显著优点,在近40年来得到了很快的发展。目前,长度、时间、电学等方面的量子基准已逐步建立,测量准确度提高了几个数量级。本文对长度、时间、电学等方面的量子基准的发展现状作了介绍;对国际计量界在用量子基准代替质量单位这一经典计量学中的顽固堡垒方面所提出的几种解决方案及其进展情况作了阐述。在新世纪中,量子计量基准将得到进一步的发展和完善。     

A new method for determining geometric accuracy in the axis of movement of machine tools

Measurements of geometric accuracy in machine tools, especially of errors in moving machine parts against their theoretical axes, are taken by means of displacement pick-ups moving along a reference standard^1,2, such as a cylindrical test specimen. This procedure is impeded by physical form errors in the standards, especially for heavy machines, as well as by adjustment errors in the standards against the machine part to be measured. These disadvantages can be avoided by using a non-material standard like a laser beam with a four quadrant photodiode as sensor and a special analysis of the measurement data.     

计算机控制高精度磨齿机设计研究

为克服基圆展开法锥面砂轮磨齿机换向带来的传动误差及磨削速度变化大的问题,在工件轴上设置一个附加旋转运动和工作台直线运动的伺服驱动环节,把一个变化控制的机械运动分解为常量与变量的合成,常量部分通过刚性传动链实现无误差运动匹配,变化量部分由伺服系统调节,使产生的传动误差比例份额变小,提高了系统的整体传动链精度.磨削时的展成过程运动均匀,机床调整方便,机械传动系统中无高难技术,结构简单,易保证高的机床制造精度,成本低.     

电感耦合等离子体质谱法直接测定土壤中有效硼的研究

以沸水提取土壤中的有效硼,结合电感耦合等离子体质谱,建立一种测定土壤中有效硼含量的方法。与常规检测土壤有效硼含量的方法相比,该方法简便、快速、检出限低,具有良好的准确度和精密度。通过对国家土壤有效态一级标准物质测试,测定结果与参考值吻合。方法的检出限为2.5ng/g,相对标准偏差为2.53%,平均回收率为98.2%。     

Inter-laboratories comparison at 100 GΩ and 1 TΩ level to evaluate the traceability transfer from INRIM in the field of high dc resistance

A National inter-laboratories comparison of dc resistance at 100 GΩ and 1 TΩ among the National Institute of Metrological Research (INRIM) and eight Secondary Electrical Calibration Laboratories was carried out in 2010. All the involved Laboratories made their measurements with a method based on a Multifunction Calibrator (MFC) and on a digital multimeter (DMM), both used in their dc voltage function.These and other Secondary Electrical Laboratories are traceable to National Standards by means of the calibration at INRIM of a complete set of primary standards or, alternatively, by means of the calibration of a high accuracy DMM or of a Multifunction Transfer Standard (MTS) or of few primary standards. All the relative differences between each Laboratory’s value and its reference value obtained in the comparison were within their relative expanded uncertainties. This result showed that the traceability transfer methods from INRIM to Electrical Secondary Laboratories lead to satisfactory results in the field of high dc resistance.     

Porosity measurements by X-ray computed tomography: Accuracy evaluation using a calibrated object

Accurate identification and measurement of internal voids and porosity is an important step towards improvement of production processes to obtain high quality materials and products. Recently, the importance of knowing the exact size, shape, volume and location of defects has become even higher as tighter requirements and new standards have been introduced in industry. There are several well-established methods for defects evaluation based on various principles (both destructive and non-destructive). However, all conventional methods have various deficiencies and the information about internal voids/porosity that can be extracted is limited. Most of these drawbacks can be overcome by using X-ray computed tomography (CT). Unlike other methods, CT provides full three-dimensional information about shape, size and distribution of internal voids and porosity; however, the accuracy of measurements is still under investigation. Hence, further evaluations on CT porosity measurements must be performed in order to consider X-ray computed tomography a reliable instrument for the assessment and detection of internal defects.A reference object with artificial defects was used in this research work in order to evaluate the accuracy of porosity measurements by CT. The reference object was manufactured by ultra-precision micro-milling. The object contains dismountable components with embedded internal hemispherical features that simulate internal porosity. The artificial porosity was micro-milled on top surfaces of dismountable cylindrical inserts. The hemispherical calottes were thereafter calibrated by traceable coordinate measuring systems and calibrated values were compared to actual values measured by a CT system. The accuracy of CT porosity measurements was then evaluated based on results obtained on various measurands, using different software tools and measuring procedures, comparing real scans to numerical simulations and investigating the influence of CT system parameters settings on measurement results.     

CAD/CAM软件在集流管加工中的灵活应用

介绍具有复杂曲面且精度和表面粗糙度要求较高的集流管的加工方案设计.为了既经济又达到必须的精度,综合利用国内外两种CAD/CAM软件优势的方案,克服了模拟型数控系统的缺点,达到了加工目的.     

A tester for artificial respirators

All equipment used for resuscitation must be validated before use. This is possible only if means are available for simulating the human airways and lungs, reproducing the conditions in which the respirators will be employed. It is also important that such simulators be capable of determining all variables (flow rate, respiratory rate, pressure, etc.) that can be regulated with an artificial ventilator in full agreement with international standards. This paper illustrates the development of a lightweight, portable prototype lung model with a compliant bellows whereby various lung conditions can be simulated. The prototype was validated using a fixed-capacity reference model which ensures good measurement accuracy, though its weight and bulk are by no means inconsiderable. The investigation was carried out by sizing each component in accordance with international and American standards.     

关于混凝土配料秤（称重系统）准确度的探讨

混凝土配料秤是定量自动衡器的一个分支,对其准确度的要求越来越高,笔者以在实际工作中的对配料秤准确度方面的一点体会,就影响混凝土配料秤计量准确性的相关方面进行探讨,供同行参考。     

Accuracy modeling,analysis and radical error distribution of 3-RPR planar parallel mechanism

Output accuracy performance is directly determined by geometric errors and working poses of a mechanism. Accuracy sensitivity as geometric error transmission coefficient, closely relates to pose configuration and geometric parameters. This research focuses on accuracy of a 3-RPR planar parallel mechanism: firstly, established 3 models in an analytic form, to describe relationship between output errors and geometric ones, then they are mutually verified statistically. Secondly, the anisotropy and periodic fluctuation of position errors, independently contributed by each category of geometric errors, are illustrated; and mirror symmetric trajectories and poses generating output errors with mirror symmetry, are also revealed by numerical simulation. Finally, the radical accuracy model in an analytic form, was established through variance and covariance analysis on output errors. We concluded that the radical error of the movable platform in central symmetric poses, follows Rayleigh distribution pattern. Through statistical comparison with Monte Carlo simulation, the radical error model was demonstrated, that provided a reference for accuracy design for other planar parallel mechanism.

     

A review of the existing performance verification infrastructure for micro-CMMs

The performance verification of micro-CMMs is now of intense interest because of their capability to perform length measurements in three dimensions to high accuracy with low uncertainties. Currently, verification of micro-CMMs is completed in the spirit of existing specification standards, because strict adherence to these standards is often difficult. This review aims to present and discuss verification techniques available for micro-CMMs: specification standards, existing calibrated test lengths and traceability routes that can be associated with micro-CMMs. Three specification standards used in the testing of CMMs will be considered. In addition, a wide range of calibrated test lengths are reported, and any advantages and disadvantages associated with their use are discussed. It is concluded that micro-CMMs cannot yet be verified in accordance with existing specification standards. Suggestions are made for future standardisation work required to rectify these issues.     

一种光纤光栅渗压计的研制

为解决传统电类渗压传感器在野外使用时易受雷击,在复杂电磁干扰下受干扰严重难以正常工作,且测量信号不易远距离传输,不带温度补偿功能等问题,该文设计了一种带温度补偿的光纤式渗压传感器,重点阐述了光纤光栅渗压传感器工作原理和结构设计,参照相关标准对传感器性能进行了验证,其重复性误差0.5%FS,迟滞误差0.5%FS,综合误差1%FS。实验结果表明,该传感器测量精度高,测量稳定性好,特别适合于在水利水电工程、交通工程、市政建筑等领域渗透压力、扬压力的测量。     

新型智能量块检定仪的研究

本文介绍了一种按新的量块检定标准研制的以８０３１单片机为核心的智能检定仪，它具有自动超差报警、自动定等定位、自动量程转换及精度高等特点，文中详细阐述了硬软件原理及其设计，并介绍了主要技术指标及数据处理方法。     

Comprehensive assessment algorithm for calculating CEP of positioning accuracy

This study aims to evaluate the inertial navigation systems’ performance. To this end, we comprehensively investigate 12 methods for calculating the circular error probability (CEP). Using data processing techniques, we classify these methods into three categories: parameterization of one-dimensional variables, computation of bi-normal random variables, and numerical integration. From these methods, we develop algorithms and programs, which are subsequently applied in evaluating the positioning accuracy of navigation systems. Using the algorithms and programs, we perform simulations to evaluate applicability and evaluation accuracy under the same initial conditions. Practical test data are employed to validate the results. Using the comparison of the methods as bases, we put forward a comprehensive practical method regarding sample number and evaluation accuracy. Our results serve as a theoretical reference for the development of different approaches to assessing inertial positioning accuracy in accordance with applicable standards.