基于图像识别和GPS技术的全自动补偿式微压计的设计

传统的补偿式微压计测量采用手动测量、人眼读数的方式实现数据的获取,人眼读数误差所引入的不确定度在装置整体不确定度中占有很大比重。本文研制了一种全自动补偿式微压计,利用高清摄像头代替人眼读数,利用软件对所采集的图片进行逻辑分析,同时增加传统补偿式微压计不具备的实时液相温度测量、实地重力加速度测量及大气压测量功能,有效减小各影响量对测量结果的干扰。采用滑台电机控制位移,进一步提高测量准确度。经实验证明,本文研制的全自动补偿式微压计具有很好的准确性与可靠性。     

Variability and uncertainty of biokinetic model parameters: the discrete empirical Bayes approximation

In the Bayesian approach to internal dosimetry, uncertainty and variability of biokinetic model parameters need to be taken into account. The discrete empirical Bayes approximation replaces integration over biokinetic model parameters by discrete summation in the evaluation of Bayesian posterior averages using Bayes theorem. The discrete choices of parameters are taken as best-fit point determinations of model parameters for a study subpopulation with extensive data. A simple heuristic model is constructed to numerically and theoretically study this approximation. The heuristic example is the measurement of heights of a group of people, say from a photograph where measurement uncertainty is significant. A comparison is made of posterior mean and standard deviation of height after a measurement, (i) using the exact prior describing the distribution of true height in the population and (ii) using the approximate discrete empirical Bayes prior obtained from measurements of some study subpopulation.     

Measurement Accuracy of Secondary Standards of Sound Pressure in Comparison to Primary Standards

The paper presents the measurement uncertainty achieved in realizing the primary standard of sound pressure at NPL, India and comparison of the uncertainties of secondary calibrations with that of primary standard. The uncertainty associated with calibration of acoustic calibrators, working standard microphones and sound pressure level measurements is discussed. A comparison of the actuator response with that taken from reciprocity setup for working standard microphones is also presented. The major focus of the present work is to highlight the traceability chain established in measurement of sound pressure level and propagation of measurement uncertainties directly from the national primary standard to field measurements, which are very rigorously conducted in transportation noise monitoring, machinery noise diagnostics, noise labeling of electrical appliances and environmental impact assessment studies w.r.t noise abatement and control.     

10 kPa气体活塞式压力计计量性能测试研究

用FPG8601型活塞式压力计作为标准器,对一台测量范围为1.2～10 kPa的气体活塞式压力计的活塞有效面积和鉴别阈进行了测试研究.介绍了标准器的特点和溯源方法,对被测器需要进行全量程测试的必要性和测试程序进行了阐述.测试覆盖了包括被测器测量下限在内的5个不同压力点,计算得到其活塞有效面积的平均值为9.773 71 ...     

双误差回归在离子色谱法测定硫酸根不确定度评定中的应用

采用不确定度连续传递模式,建立了离子色谱法测定岩溶地下水中硫酸根分析结果不确定度的评定模型。评定结果表明,测定结果的不确定度主要来源于标准溶液引入的不确定度、曲线拟合产生的不确定度和测定过程引入的不确定度3部分。采用x,y的相对差,对校准曲线进行双误差回归,对评定过程中各个不确定度分量进行量化,最后通过计算合成得到硫酸根测定结果的不确定度评定模型。     

天然气工作级标准装置的能力提升

介绍了国家石油天然气大流量计量站武汉分站工作级标准装置的组成、测量原理、量值溯源方式以及装置校准能力提升的关键措施,并对其不确定度进行评定。重点分析了“绝压+差压测量”的不确定度,实验法评定压缩因子比值的不确定度,以及标准涡轮流量计修正不确定度。利用传递比较法对评定的不确定度进行了验证,结果表明,该标准装置的不确定度为0.13%~0.16%(k=2),可满足开展0.5级及以下天然气流量计的检定要求。     

0.005级压力式水深测量仪器检定装置的测量不确定度评定

通过GUM法和自适应蒙特卡洛法分别对0.005级压力式水深测量仪器检定装置进行测量不确定度评定,并对GUM法进行了验证。结果表明,压力测量模型比较复杂,2种方法均适合用来评定其测量不确定度,并且在标准不确定度有效位数取1位时,GUM法在各个检测点均通过了验证。同时,合理的数值容差取值非常重要,实际测试中,测量结果位数的选取应考虑仪器的测量精度和使用要求,还要考虑标准仪器的标准不确定度的有效位数。     

脉冲管制冷机内部交变流动过程实验研究第一部分实验装置与数据处理系统

鉴于脉冲管制冷机内部流动过程是复杂的动态交变流动,运行参数、结构参数和调相机构等对内部流动规律的影响还不是十分清楚,建立了脉冲管制冷机内部动态参数测试装置,介绍了实验系统的组成,测试设备和数据采集与处理方法.该实验台能准确测量蓄冷器入口和脉冲管热端的压力波和速度波,通过对它们的幅值与相位的分析,能够系统的得到各种因素对脉冲管制冷机内部流动状态的影响规律.     

Accurate Software-Related Average Current Drain Measurements in Embedded Systems

Performing accurate average current drain measurements of digital programmable components (e.g., microcontrollers, digital signal processors, System-on-Chip, or wireless modules) is a critical and error-prone measurement problem for embedded system manufacturers due to the impulsive time-varying behavior of the current waveforms drawn from a battery in real operating conditions. In this paper, the uncertainty contributions affecting the average current measurements when using a simple and inexpensive digital multimeter are analyzed in depth. Also, a criterion to keep the standard measurement uncertainty below a given threshold is provided. The theoretical analysis is validated by means of meaningful experimental results     

基于流速面积法的明渠流量测量不确定度评定

针对ISO 748进行明渠流量测量不确定度评定,需在测量断面上设置充足的垂线数和测点,且没有考虑底层、表层和两边壁盲区流速插补引入的不确定度问题,提出了一种新型明渠流量测量不确定度评定方法。通过Fluent数值模拟,得出明渠断面垂线流速分布模型和横向平均流速分布模型。在实验测量中,根据两者流速模型分别计算出断面垂线测点不足和垂线数不足引入的不确定度,对明渠流量测量的不确定度进行了评定。结果表明,该方法提高了明渠流量测量不确定度评定的准确性。     

第四代光谱辐射度和色温度国家基准装置的研制

基于高温黑体辐射源BB3500M研究并建立了第四代光谱辐射度和色温度国家基准装置。采用稳流和稳温相结合的反馈工作模式,开启后3 h即达到温度稳定。3 016 K时,1 h内的温度变化小于0.59 K。温度测量直接溯源至Pt-C和Re-C高温共晶点黑体,2 980 K时的测量不确定度为0.64 K(k=1)。光谱辐射亮度和光谱辐射照度的波长范围向短波分别扩展至220 nm、230 nm,长波扩展至2 550 nm,达到全波段光谱辐射亮度CCPR-S1比对的能力。新基准增加了分布温度参数的测量能力,2 353 K和2 856 K的测量不确定度(k=1)分别改善为1.6 K和2.1 K。对基准装置入射光学系统的辐照不均匀性以及短波紫外大气传输过程所带来的散射和吸收进行了数值计算,提出理论修正方法,将辐照不均匀性测量误差减小0.3%,大气传输误差减小0.29%。     

Uncertainty considerations in AC loss measurement of multifilamentary superconducting wires performed via a pickup coil method

The uncertainty of AC loss measurements for multifilamentary superconducting wires by a pickup coil method is evaluated on the basis of the law of propagation of uncertainty. In this evaluation, the effects of measurement conditions, signal processing, and the division of the AC loss into its components (hysteresis loss and coupling loss) are taken into account as elements of uncertainty. The effect of the measurement conditions is evaluated using theoretical expressions of the two main components. Additionally, the effect of signal processing is considered in accordance with the actual processes of the AC loss measurement using experimental outputs. The main factors that contribute to the uncertainty in the propagation process are discussed. The estimated resultant uncertainties are compared to experimental ones for round robin tests of AC loss measurement of Nb-Ti multifilamentary wires exposed to an alternating transverse magnetic field.     

Effect of Power Line Interference on Microphone Calibration Measurements Made at or Near Harmonics of the Power Line Frequency

The electrical measurements required during the primary calibrations of laboratory standard microphones by the reciprocity method can be influenced by power line interference. Because of this influence, the protocols of international inter-laboratory key comparisons of microphone calibrations usually have not included measurements at power line frequencies. Such interference has been observed in microphone output voltage measurements made with a microphone pressure reciprocity calibration system under development at NIST. This system was configured for a particular type of standard microphone in such a way that measurements of relatively small signal levels, which are more susceptible to the effect of power line interference, were required. This effect was investigated by acquiring microphone output voltage measurement data with the power line frequency adjusted to move the frequency of the interference relative to the center frequency of the measurement system passband. These data showed that the effect of power line interference for this system configuration can be more than one percent at test frequencies harmonically related to the power line frequency. These data also showed that adjusting the power line frequency to separate the interference and test frequencies by as little as 1.0 Hz can reduce the effect of the interference by at least an order of magnitude. Adjustment of the power line frequency could enable accurate measurements at test frequencies that otherwise might be avoided.     

Method for modifying axial fan’s guard grill and its impact on operating characteristics

This paper presents the impact of guard grill on aerodynamic integral characteristic, the spectrum of sound pressure level and total sound power level at four characteristic operating points of axial fans with standard guard grill, with optimized guard grill and without guard grill. The study of guard grill’s impact was conducted with measurements at integral level and local outflow velocity field of the axial fan without guard grill. The measurement results of the local outflow velocity field of the axial fan without guard grill at optimal operating point were used to model the optimized guard grill contour. The guard grill of axial fan has a significant impact on aerodynamic integral characteristic at free flow and mostly used operating region. The influence of guard grill is also characteristically reflected in the spectrum of sound pressure level via vortex shedding frequency and consequently at total sound power level of compared axial fans.     

Improving the Traceability of Meteorological Measurements at Automatic Weather Stations in Thailand

A joint project between the National Institute of Metrology Thailand (NIMT) and the Thai Meteorology Department (TMD) was established for improving the traceability of meteorology measurements at automatic weather stations (AWSs) in Thailand. The project aimed to improve traceability of air temperature, relative humidity and atmospheric pressure by implementing on-site calibration facilities and developing of new calibration procedures. First, new portable calibration facilities for air temperature, humidity and pressure were set up as working standard of the TMD. A portable humidity calibrator was applied as a uniform and stable source for calibration of thermo-hygrometers. A dew-point hygrometer was employed as reference hygrometer and a platinum resistance thermometer (PRT) traceable to NIMT was used as reference thermometer. The uniformity and stability in both temperature and relative humidity were characterized at NIMT. A transportable pressure calibrator was used for calibration of air pressure sensor. The estimate overall uncertainty of the calibration setup is 0.2 K for air temperature, 1.0 % for relative humidity and 0.2 hPa for atmospheric pressure, respectively. Second, on-site calibration procedures were developed and four AWSs in the central part and the northern of Thailand were chosen as pilot stations for on-site calibration using the new calibration setups and developed calibration procedures. At each station, the calibration was done at the minimum temperature, average temperature and maximum temperature of the year, for air temperature, 20 %, 55 % and 90 % for relative humidity at the average air temperature of that station and at a one-year statistics pressure range for atmospheric pressure at ambient temperature. Additional in-field uncertainty contributions such as the temperature dependence on relative humidity measurement were evaluated and included in the overall uncertainty budget. Preliminary calibration results showed that using a separate PRT probe at these AWSs would be recommended for improving the accuracy of air temperature measurement. In case of relative humidity measurement, the data logger software is needed to be upgraded for achieving higher accuracy of less than 3 %. For atmospheric pressure measurement, a higher accuracy barometer traceable to NIMT could be used to reduce the calibration uncertainty to below 0.2 hPa.     

High Power CW Wattmeter Calibration at NIST

The National Institute of Standards and Technology has established a measurement capability to support high power systems and devices. The automated wattmeter calibration system operates at power levels of 1 to 1000 W for frequencies from 1 to 30 MHz and 1 to 500 W from 30 to 400 MHz. A cascaded coupler technique is used to extend power measurements to high levels which are traccable to a 10 mW standard thermistor mount. This technique uses an arrangement of nominal 10, 20, 30, 40, and 50 dB couplers with sidearm power meters. The initial step transfers the calibration of the 10 mW standard to the 10 dB coupler/power meter. The standard is then replaced with a wattmeter to be calibrated. RF power is increased 10 dB and the calibration is transferred to the adjacent 20 dB eoupler/power meter. This sequence is repeated with the remaining coupler/power meters until the wattmeter is calibrated at the desired power levels and frequencies. Power ratios calculated from simultaneous power measurements made at each transfer are used to calculate the incident power at the wattmeter. Due to nonideal components, corrections are made for nonlinearities, mismatch, and other errors. Two types of wattmeters have been evaluated at selected frequencies and power levels. Total uncertainties are based on the random and systematic components.     

Measurement Automation to Implement Evaluation Procedure of Four-Terminal-Pair Capacitance Standards Using S-Parameters

The evaluation procedure of four-terminal-pair capacitance standards using S-parameters is very complex as it involves the measurement of different parameters by multiple instruments. It also involves complex computation of effective capacitance as a function of frequency and its associated uncertainty in measurement. The reported paper presents the development of measurement automation program to implement evaluation procedure of four-terminal-pair capacitance standards of values varying between 1 and 1000 pF up to 30 MHz. The measurement automation increases the functionality with a comprehensive and flexible tool set for data acquisition, analysis, reporting and representation of results. The sequence of operations performed by the developed measurement automation program is described in detail. The program configures and measures S-parameters, converts S-parameters into corresponding impedance and admittance parameters, determines series and parallel resonance frequencies. Thereafter, it determines residual capacitive and residual inductive parameters and finally computes the effective value of each capacitance standard as a function of frequency along with the associated uncertainty in measurement. Measurement automation has provided precise and efficient way for the implementation of evaluation procedure of capacitance standards.     

自适应蒙特卡洛法评定肥料中苯并［a］芘含量的测量不确定度

通过Python编写计算程序,完成自适应蒙特卡洛法评定测量不确定度的代码实现,进而评定气相色谱质谱法测定肥料中苯并［a］芘含量的测量不确定度。结果表明,气相色谱质谱仪测定肥料中苯并［a］芘含量的标准不确定度为0.0179mg/kg。探索了自适应MC法在肥料成分含量测定的测量不确定度评定中的应用,结果表明,这种方法具有适用性广、计算过程直观、计算结果可靠的优点。     

Pressure Measurement and Traceability at NIS- Egypt

Pressure sensors, transmitters and transducers are widely used for measuring and controlling the pressure. Tracing of measurement of such pressure sensing instrumentation is very important in many industrial applications. Calibrations of pressure instruments with acceptable uncertainty tracing to the SI units are required. This study aims to study the propagation of uncertainty from SI units through primary standard piston cylinder assembly (PCA) up to 500 MPa. The hierarchy of pressure measurements at NIS is based on using large effective area PCA in defining the pressure of 1 MPa. Primary standard PCA characterization and evaluation are presented then transferring the obtained results to other pressure traceability level is described. Calculation and propagation of uncertainty starting from primary standard to digital pressure gauges, digital pressure calibrators, pressure sensors and pressure transducers were investigated.