Broadband method for precise microwave spectroscopy of superconducting thin films near the critical temperature

We present a high-resolution microwave spectrometer to measure the frequency- dependent complex conductivity of a superconducting thin film near the critical temperature. The instrument is based on a broadband measurement of the complex reflection coefficient, S 11, of a coaxial transmission line, which is terminated to a thin film sample with the electrodes in a Corbino disk shape. In the vicinity of the critical temperature, the standard calibration technique using three known standards fails to extract the strong frequency dependence of the complex conductivity induced by the superconducting fluctuations. This is because a small unexpected difference between the phase parts of S 11 for a short and load standards gives rise to a large error in the detailed frequency dependence of the complex conductivity near the superconducting transition. We demonstrate that a new calibration procedure using the normal-state conductivity of a sample as a load standard resolves this difficulty. The high quality performance of this spectrometer, which covers the frequency range between 0.1 and 10 GHz, the temperature range down to 10 K, and the magnetic field range up to 1 T, is illustrated by the experimental results on several thin films of both conventional and high temperature superconductors.     

Online conductivity calibration methods for EIT gas/oil in water flow measurement

Electrical Impedance Tomography (EIT) is a fast imaging technique displaying the electrical conductivity contrast of multiphase flow. It is increasingly utilised for industrial process measurement and control. In principle, EIT has to obtain the prior information of homogenous continuous phase in terms of conductivity as a reference benchmark. This reference significantly influences the quality of subsequent multiphase flow measurement. During dynamic industrial process, the conductivity of continuous phase varies due to the effects from the changes of ambient and fluid temperature, ionic concentration, and internal energy conversion in fluid. It is not practical to stop industrial process frequently and measure the conductivity of continuous phase for taking the EIT reference. If without monitoring conductivity of continuous phase, EIT cannot present accurate and useful measurement results. To online calibrate the electrical conductivity of continuous phase and eliminate drift error of EIT measurement, two methods are discussed in this paper. Based on the linear approximation between fluid temperature and conductivity, the first method monitors fluid temperature and indirectly calibrates conductivity. In the second method, a novel conductivity cell is designed. It consists of a gravitational separation chamber with refreshing bypass and grounded shielding plate. The conductivity of continuous phase is directly sensed by the conductivity cell and fed to EIT system for online calibration. Both static and dynamic experiments were conducted to demonstrate the function and accuracy the conductivity cell.     

红外热像仪外场测温的大气透过率二次标定

为了实现测温红外热像仪的外场精确测温,研究了大气透过率的二次标定。建立了红外热像仪的外场远距离测温标定模型,采用一个标准面源黑体和红外热像仪对大气透过率进行了二次标定。首先,用标准面源黑体的设置温度标定大气透过率的二次修正系数;然后,在已知目标感兴趣区域发射率的情况下,用二次修正系数对未知辐射源测量值进行修正,实现未知辐射源目标辐射温度的准确测量。实验显示,随黑体设置温度从50℃不断升高(二次大气透过率近似为1),大气二次透过率修正系数在50～100℃内迅速下降,在100～200℃内下降趋势减缓,逐渐接近于约为0.7的常数。实验结果为测温红外热像仪外场精确测温提供了保证。     

GENERAL PROCEDURE FOR UNCERTAINTY EVALUATION OF A TEMPERATURE CALIBRATION BATH

ABSTRACT

The objective of this paper is to develop a general procedure for evaluation of various temperature calibration baths or furnaces. Since the uncertainties of transfer measurement and temperature standards, such as standard platinum resistant thermometers in particular, are decreasing, metrological characteristics of calibration baths and furnaces are becoming a limiting factor in temperature calibration by comparison. Due to the fact that a time invariance of metrological characteristics of calibration baths (gradients, stability, repeatability, etc.) represents a major contribution to the total calibration uncertainty, the exact knowledge about a calibration bath is of an utmost importance.

A general procedure for baths with different types of a media is proposed, which enables continuous monitoring of bath parameters in order to evaluate uncertainty contributions to a measured (calibrated) thermometer. There is no ideal calibration system, i.e., without inhomogeneity or gradient. Basic gradients that could be observed in calibration baths are vertical and horizontal gradients. They may also be recognized as axial and radial gradients in a case where cylindrical equalizing blocks are used inside a calibration bath. For the proper use of such a system in a process of calibration and measurement, gradients should be precisely determined.

Gradients appear as a change of a temperature reading of a thermometer due to a change of its position inside a calibration bath. By this method, a realistic uncertainty contribution could be defined as opposed to under-or overestimated values of uncertainties, thus enabling an optimal use of a particular calibration bath. Examples of real data are taken from cryostat measurements. Otherwise, seven other temperature calibration baths and furnaces in the laboratory have been evaluated in the same way.     

Nondestructive measurement and high-precision evaluation of the electrical conductivity of doped GaAs wafers using microwaves

A nondestructive method for measuring the electrical conductivity of doped GaAs wafers using a compact microwave instrument is presented. Based on the characteristics of the microwave detector and the fact that the microwave measurement is independent of the thickness of the wafer, the analytical and explicit expressions to evaluate the electrical conductivity of the wafer are derived. Using this method, only the voltages of the reflected signals for two wafer samples whose conductivities are known are required to calibrate the two undetermined constants in the equation. Then, the conductivity of any other wafer can be evaluated by substituting the measured voltage of the reflected signal into the explicit expressions. Seven different doped GaAs wafers with thickness larger than 350 μm and conductivities in the range of 1.3 × 10(4) S/m to 7.6 × 10(4) S/m are measured in the experiment, two of which are used for calibration. The evaluated results agree well with those obtained by the conventional Hall effect measurement method, with an evaluation error less than ±4.5%. The proposed method is potentially useful for the contactless and nondestructive evaluation of the electrical conductivity of any kind of semiconductor wafer.     

Determination of optimum measurement points via A-optimality criterion for the calibration of measurement apparatus

A procedure for optimal selection of the measurement points to get the best calibration characteristics (for the chosen optimality criterion) of measuring apparatus is proposed. The coefficients of the calibration characteristics are evaluated by the classical least squares method. For this work, the A-optimality criterion has been used as an optimality criteria. As an example, the problem of optimal selection of the standard pressure setters (the piston gauges) during calibration of the differential pressure gage is solved. Obtained values of the optimum measurement points for the calibration of the differential pressure gage are checked via actual experiments.     

Dynamic junction temperature measurement for high power light emitting diodes

Junction temperature of high power light emitting diodes (LEDs), which is crucial for the thermal management of solid-state lighting, needs to be measured accurately. In this paper, a dynamic junction temperature measurement system for LEDs was proposed and the calibration including instrument calibration and factor K calibration were presented. The influence of the fast switch time in dynamic junction temperature test was analyzed and measurement errors caused by sampling delay were quantified. To prove the accuracy of the present system, comparison experiment was conducted. It shows a good agreement between the experimental data and reference value. Experiments also show that the measurement accuracy of the instrument can be up to 0.1?°C, and the standard error of temperature measurement can be controlled within 1%.     

油田水中新型水驱示踪剂氟苯甲酸的气相色谱-质谱分析

建立了油田水中新型水驱示踪剂 2 -( 2 -FBA)的痕量分析方法。该方法将过滤、固相萃取、衍生等样品前处理技术有效地结合在一起 ,应用气相色谱 -质谱 ( GC/ MS)技术对其进行定性和定量测定。结果表明 :方法具有较高的灵敏度和可靠的不确定度 ,油田水取样量为 2 5 0 m L时 ,2 -FBA最低检测限达 4ng/ L。 40 0 ng/ L2 -FBA的单次测量结果扩展不确定度为 5 0 ng/ L,即相对扩展不确定度优于 1 4%。本方法采用 4-甲基 -氟苯甲酸 ( 4 -TMFBA)作为内标物质校正衍生及测量过程。2 -FBA的浓度为 5～ 2 0 0 0 ng/ L,标准曲线的相关系数>0 .9998。此方法适用于油田、环境、生物、药物等样品中痕量 2 -FBA的快速、准确分析。同时也为其它氟代苯甲酸作为油田示踪剂提供了分析方法     

工业电导信号测量仪的研制

提出了一种基于新的激励模式的电导信号测量仪.该装置采用双极性脉冲电压源作为激励源,与交流激励的电导测试系统相比,削弱了介质电极化现象,简化了电路设计,并提高了数据的采集速度和精度.同时还专门设计了具有防腐、避免电化学反应及带有温度补偿的专用电导测量探头.经测试,该系统测量准确、抗干扰能力强,满足了工业流程中溶液电导特性的实时测量要求.     

奶牛乳腺炎智能检测仪的设计与研究

为了及时、准确地检测出奶牛的乳腺炎，本文根据奶牛感染乳腺炎引起乳汁电导率和pH值变化的原理，设计出了一种基于单片机控制的智能型奶牛乳腺炎自动检测仪。该仪器能够根据乳汁电导率和pH实测值的大小判断出奶牛是否感染乳腺炎，并由专家系统给出相应的治疗措施，同时可由仪器的时钟系统和温度测量系统分别将测量时间和测量时乳汁的温度记录下来，并保存在单片机系统的存储器中（或通过RS485通讯接口传输到PC机保存）。通过对一段时间内的测量值进行分析可以制定出相应的营养方案和管理方案。该仪器既能独立使用又能安装在自动挤奶系统来实现在挤奶的同时对乳腺炎的在线检测。实验表明：本仪器具有快速、准确、检测成本低、使用简单方便的特点，该检测仪对临床乳腺炎检测的正确率为94％，对隐性乳腺炎检测的正确率为67％。     

一种高功率LED热阻的测试方法

叙述了利用动态电学测试方法测量高功率LED热阻和结温的原理、试验装置、测量步骤和影响测试结果的因素。研究结果表明,该方法具有测试结构简单、稳定性高等特点,可作为高功率LED热阻和结温的标准测试方法。     

Compact and accurate digital thermometer based on Anderson’s loop and Pt-100 sensor

A simple and practical digital thermometer with an accuracy better than 0.1°C over a near-room-temperature (from −10°C to 50°C) measurement range has been developed. The instrument is compact and battery operated and provides for both digital and analog outputs. A four-lead platinum thermal sensor, driven by a constant current loop, allows for accurate temperature readings with high immunity to the contact resistances and to their variations. A low-noise electronics allows for temperature measurements with a 1 mK resolution. By experimentally characterizing the non-linearity of the adopted Pt-100 sensor, a suitable readout correction table has been calculated in order to compensate for the sensor non-linear behavior. This compensating procedure allows for a wider (from −50°C to +200°C) and higher accuracy (0.05°C) measurement range. The ultimate accuracy was essentially limited by the accuracy of the temperature standard used for calibration.     

阳极溶出镉在线分析仪的同步校正方法

针对基于阳极溶出伏安法水质镉在线分析仪溶出峰的电流值受环境温度影响问题,提出了一种同步校正的改进方法。该方法利用样品和校正液溶出峰电流信号随温度同步变化特性,在一个样品测量周期内同时进行校正液的测定,并将两者的溶出峰电流线性比较而计算出样品浓度。实验结果表明,镉溶出峰电流值随温度的升高而增大,当温度从5℃上升至43℃时,溶出峰电流值增大了近2.3倍,且影响机制为镉离子在工作电极表面扩散层的迁移速率主要受温度控制。采用改进的同步校正方法,镉在线仪器在5~43℃测量值的误差均小于10%,有效解决了仪器测量值对环境温度敏感问题。     

邻二氮杂菲分光光度法测定镁合金中铁含量测量结果的不确定度评定

对邻二氮杂菲分光光度法测定镁合金中铁含量的不确定度来源进行了辨别,并在此基础上对测定过程中的不确定度分量进行了合理评定。测量不确定度主要来源于试样称量、标准溶液配制、校准曲线拟合、各种玻璃量器的使用及测量重复性。依据不确定度评定的步骤,分析和计算得到了各分量标准不确定度及合成标准不确定度,最后合成标准不确定度乘以95%置信概率下的扩展因子2获得测量结果的扩展不确定度。     

Calibration of a white light interferometer for the measurement of micro-scale dimensions

Calibration is central to most measurement procedures. This is especially true in those cases where a large number of difficult-to-identify and difficult-to-control factors hinder the experimenters in their efforts to obtain reliable measurement results. Dimensional measurements of features on the micro- and nano-scales is one such case. A white-light interferometer (WLI) microscope can perform measurements of a variety of measurands over a broad dimensional range: from surface texture characterisations on the nano-scale to measurements of step heights of several millimetres. Calibration methods based on the hypothesis of a linear calibration curve can be inadequate to express the relationship between measurement results and traceable reference materials (RMs). A calibration procedure built into a commercially available WLI microscope is critically compared with methods presented in an international standard. This comparison is enabled by a cost-effective procedure for establishing traceable RMs in the micro-range. Advantages of calibration procedures based on more than one RM are then demonstrated within the ranges from 180.5 to 219.5 μm and from 1.5 to 501.5 μm. Calibration methods involving regression modelling of transformed measurement results are considered for these two intervals to overcome the highlighted weaknesses of the calibration procedure built in the examined WLI.     

Substrate properties affect the mass loss rate in collodion at liquid helium temperature

A previous measurement showed that mass loss from collodion supported by thin carbon films was linear with electron exposure at liquid helium temperature. No other organic solid had shown a linear loss of mass at any temperature. When measurements of collodion were done using titanium supports, the loss of mass proceeded exponentially with exposure at liquid helium temperature. This result suggested that the differing electrical conductivities of these substrates might be the cause of the different mass loss effects. Carbon films, which are typically used at ambient temperatures, have much lower electrical conductivity at very low temperature than titanium films. This suggested that specimen preparation materials and techniques used routinely for room temperature studies may need to be modified when microscopy is done using superconducting objective lenses. For both substrates, the rate of mass loss is slowest at liquid helium temperature.     

基于多光谱显微成像的颗粒表面温度分布测量

分别采用彩色相机和多光谱相机构建辐射测温系统,利用黑体炉进行温度模型标定实验,并基于BP神经网络对标定数据进行训练得到测温模型。通过蜡烛火焰的温度测量实验,验证了测温模型的可靠性,且结果显示多光谱成像测温系统的测温精度高于彩色相机测温系统。针对常规辐射成像测温系统空间分辨率不足的问题,采用多光谱相机结合显微镜搭建了显微测温平台,对高温热台内的单石油焦颗粒燃烧过程进行记录,得到了石油焦颗粒表面的温度分布以及随时间的温度变化过程。     

Robust computational framework for wire-mesh sensor potential field calculations

With the development of the next generation of nuclear reactor safety system codes fast underway, increased importance has been placed on enhancing physical closure correlations and amassing representative benchmark-quality experimental data for validation purposes. Wire-mesh sensors, a reputable experimental measurement technique with sufficient spatial and temporal resolution to serve such goals, and related data reconstruction algorithms have been the subject of renewed interest as researchers attempt to characterize their measurement uncertainty. To assist in such investigations, the present work establishes a comprehensive numerical framework with which to quantify the electric potential field around wire-mesh sensors. Using the finite-volume foundations of OpenFOAM, a numerical solution algorithm is developed to predict the transmitted electric current between transmitter and receiver electrodes for both homogeneous and heterogeneous electrical conductivity fields. A detailed verification against seminal numerical calculations and robust validation procedure is included to ensure the accuracy of the proposed methodology. Parametric studies of spherical bubble diameter, lateral crossing position, and spheroidal shape influence are conducted to provide preliminary insights into wire-mesh sensor operation and the suitability of various calibration approaches. Observed trends in the transmitted currents reveal overshoots relative to calibration conditions, which are fundamentally linked to the maldistributed electric potential field in heterogeneous bubbly flows. The present investigation offers a vital first step towards a comprehensive multi-physics model of multiphase flow around a wire-mesh sensor.     

Development of remote calibration system for pressure standard

A remote calibration technology for disseminating pressure standard has been developed. In the remote calibration, a transfer standard is transported from a calibration laboratory to a client’s site where a calibration item is used. Using the transfer standard and the internet, the calibration item is calibrated on site. For the remote calibration, integrated transfer standards were newly developed in different pressure ranges. Each transfer standard includes a pressure controller, two or three precise pressure transducers, environmental measurement devices and an inclinometer in one box. Also the calibration protocol was examined to perform the remote calibration efficiently using the transfer standard. In order to prove the effectiveness of the remote calibration, the demonstration experiments were performed domestically and internationally. Here, the calibration protocol for the remote calibration and the functional overview of the newly developed transfer standards are described. The experimental results are also shown.     

Screening method for early detection of mastitis in cows

Mastitis in cows is an inflammation of the mammary gland usually caused by bacterial infection of udder tissues. This disease causes considerable damages to the cattlemen when reducing the quantity and the quality of the produced milk. An early detection and corrective action can lead to early cure. Although the universal method to measure mastitis levels is by determining the somatic cell counts per milliliter of milk, the electrical conductivity of milk could be a rapid test for checking the acceptability of milk to monitor the effects of udder infection. In this paper a low-cost circuit for estimating the quality of raw milk based on AC electrical conductivity measurements is proposed. It consists in the use of a modified Wheatstone bridge to minimize the parasitic effects. A conductivity cell consisting of two electrodes and a coaxial cable was also designed. The temperature of the milk is also measured and compensated its effect. This system can help the farmer to detect quickly and economically the state of health of their cows from a simple measurement of electrical conductivity performed on the dairy farm itself.