基于微型镓基共晶固定点的温度传感器在轨校准方法研究

介绍了微型镓基共晶固定点的灌注工艺和准绝热相变特性测量系统;结合空腔黑体和非近位安装的温度传感器,研究了Ga-Sn和Ga-Zn共晶固定点的相变温坪重复性和Ga固定点的相变温坪长期稳定性;通过特定的热环境下镓及2个镓基共晶固定点三者熔化过程中温度传感器测量到的相变温坪值,对嵌入空腔黑体底部的温度传感器进行校准,其校准结果与实验室常规校准方法得到的结果差异均小于2mK。实验结果表明:在热环境保持不变的条件下,随着相变时间的增加,相变温坪值就越靠近理论上相变物质的熔化温度,即固定点与温度传感器测孔之间的异位温差越小;对于Ga-Sn和Ga-Zn共晶固定点,温度传感器测量到的相变温坪值与加热功率呈线性关系,零功率下的单点校准温度分别为20.352℃和25.187℃。     

准绝热法微型镓固定点相变特性研究

介绍了可用于原位校准的微型镓相变固定点形成过程,准绝热测试系统的结构和工作原理,测量了微型镓相变固定点在准绝热测试系统中的相变特性。实验结果表明微型相变镓固定点的相变温度与加热功率之间存在强线性关系,其线性拟合因子R2为0.995 7,并且随着功率越降低,其相变熔化温度越接近镓固定点的标准值。在相同的准绝热复现条件下,其相变温度的复现性优于2 mK。     

新型镓熔点自动复现装置

介绍了中国计量科学研究院新型镓熔点自动复现装置, 该装置的固定点炉采用半导体三段冻制及加热技术实现了镓熔点复现的自动化, 通过精密控温及合理的结构设计获得优良的温度稳定性与均匀性。该装置镓熔点使用当前最新提纯技术的99.999 99%高纯镓金属及完善的灌注技术。实验结果显示, 该固定点装置温坪持续了70 h以上,前20%～80%温坪变化小于0.15 mK,复现性为0.07 mK, 该装置的扩展不确定度为0.36 mK（k=2）。     

镓熔点温坪复现研究

镓熔点是ITS-90国际温标中重要的定义固定点,在温度计量研究中起着重要作用。由于高纯镓从液态转化为固态时,体积膨胀约3.1%,传统玻璃外壳的镓熔点容器在冻制过程中很容易造成损坏。为了解决这一难题,设计了一种具有金属外壳的镓熔点装置,以该装置为对象,开展了2种不同镓熔点复现方法和2种不同复现装置对镓相变温坪影响方面的研究,并与国外同类型装置的性能进行了比较。实验结果表明:不同镓点容器复现的镓熔点温度在0.02 mK范围内一致,高纯镓中的微量杂质是造成差异的主要原因;外液-固界面复现方法比双液-固界面复现方法得到的温坪值低0.09 mK;不同复现装置对镓熔点温坪的影响较小。     

红外高光谱大气探测仪星载固定点黑体辐射源的研制

介绍了中国计量科学研究院为风云三号05星红外高光谱大气探测仪研制的微型镓固定点星载黑体辐射源。设计了黑体辐射源空腔,其有效发射率优于0.997。针对星载固定点黑体辐射源的结构设计和性能测试展开了研究:星载固定点黑体辐射源17 ℃的温度均匀性仿真结果优于0.01℃;黑体辐射源在真空下均匀性优于0.02 ℃,稳定性优于0.002 ℃(90 min内);在通过满足航天应用的力学冲击等实验后,镓固定点的复现性优于0.03 ℃;微型固定点相变温坪复现实验加热功率与拐点值之间存在较好的线性关系。     

便携式锡凝固点复现技术研究

以中国计量科学研究院最新研制的小型锡凝固点装置为基础,开展不同的凝固速率及诱导技术对锡凝固点温坪复现影响的研究,致力于获得适合本装置最优的复现技术.实验结果显示:两支室温下的石英诱导棒分别诱导60s左右,固定点炉温度设置在比温坪值低0.6K,能够获得较理想的温坪曲线,温坪时长约9h,复现性为0.18mk,扩展不确定度1.40mK(k =2)     

新型便携式镓熔点炉的研制

中国计量科学研究院最新研制的便携式镓熔点炉采用了先进的半导体制冷和控温技术及有效合理的制冷块分布方式,实现对镓熔点容器的冻制与复现自动化.实验结果显示:该固定点炉从底端起140mm范围内的垂直温场小于0.03℃,温坪时间达到80h以上,复现性优于0.06mK.     

基于准绝热的锌固定点复现装置

ITS-90温标固定点温坪受到诸多方面的影响,温场是其中重要影响因素之一。为提升温场性能弥补漏热造成的影响,借鉴低温固定点中广泛采用的绝热原理,设计基于准绝热的锌固定点装置,温场梯度性能由传统固定点的100 mK提升至20 mK,固定点高纯金属使用量由2.0kg降至200 g。实验结果表明该装置的温坪可持续时间较长,复现性0.1 mK,既能大幅度提升温场性能,同时达到了装置小型化、可重复使用经济实用的目的,又为高纯金属中微量杂质对相变温度的影响评估降低温场因素的干扰提供研究基础。     

微型双温度固定点容器研制

基准固定点传递技术应用于现场温度校准已成为提高工业温度测量水平的一种重要途径。采用多孔石墨坩埚半包围结构,内部对称填充了高纯铟(In)和锡(Sn)2种金属,研制了一种应用于现场校准的微型双温度固定点容器。实验结果表明,In点熔化温坪持续时间约为2 h,Sn点熔化温坪持续时间约为3 h,In和Sn的温坪复现的扩展不确定度分别为4.0 mK 和4.4 mK(k=2),可满足工业现场对精密铂电阻温度计的校准需求。     

开口镓熔点装置的复现及气压修正

中国计量科学研究院自行研制的开口镓熔点装置实现了对镓熔点冻制及复现的自动化,建立了开口镓熔点配置标准铂电阻温度计组成的基准装置。实验结果显示:镓熔点熔化温坪长达50h,镓熔点的复现性为0.1mK,闭口结构与开口结构镓熔点量值差异经过气压修正后由0.13mK减小至0.06mK,镓熔点温度-气压线性拟合曲线所得数值与90温标中给出的镓熔点气压修正系数一致。     

Bi-In-Sn合金熔化温坪优化方法探索

为了提高红外遥感高精度测量水平,研发适用于红外遥感测温范围的次级固定点已成为提高在轨温度标定精度的重要手段.针对红外遥感领域涉及的温度范围(190～350 K),研制了Bi-In-Sn三元合金固定点.为提高三元合金温坪复现水平,采用预熔方法对三元合金固定点进行预处理,分析不同热工况对三元合金温坪的影响,获得适用于该三元...     

Ga-In共晶固定点复现及赋值研究

次级固定点进一步分度温度计应用于温度校准已成为减小温度量值传递不确定度的重要方法.围绕Ga-In二元合金,以高复现水平为目标,详细介绍了大尺寸固定点容器研制、固定点灌注过程,开展了固定点复现性、亚配比剩余镓温坪验证实验研究;采用了切线交点法、均值法、三次多项式拟合法3种相变温度取值方法对Ga-In固定点进行了评价和分析...     

真空镓固定点黑体辐射源研制

为满足红外遥感载荷实验室辐射定标需求,实现红外遥感辐射量值溯源到ITS-90国际温标,研制了真空镓固定点黑体辐射源.黑体腔开口直径为25 mm,深度220 mm,内部喷涂高发射率涂层,通过仿真计算黑体腔的发射率优于0.9999.在真空下测试了镓固定点相变坪台的复现性为4.4 mK,坪台稳定性优于2 mK.测量了镓固定点...     

三段控温固定点炉复现铝凝固点研究

固定点炉垂直温场均匀性是影响ITS-90国际温标固定点温坪质量的重要因素.为了提高铝凝固温坪的复现水平,设计了三段控温固定点炉,利用金属外壳铝固定点容器,研究了垂直温场均匀性及其影响因素;在此基础上,采用连续热流密度法高精度复现了铝凝固点.实验结果表明:通过调整上部、中部、下部炉温的设置,可改善固定点炉温场均匀性,铝凝...     

Study on the Impurity Effect in the Realization of Silver Fixed Point

The application of a thermal analysis model to estimate the temperature depression from the ideal fixed-point temperature is important, especially when the chemical analysis of the sample in a cell is insufficient or the cell might have been contaminated during fabrication. This study extends previous work, on thermal analysis with the tin point, to an investigation of the impurity dependence of the silver-point temperature. Close agreement was found between the temperature depression (\(-0.36\) mK) inferred from the thermal analysis of the measured fixed-point plateau and the temperature depression (\(-0.32\) mK) inferred using the sum of individual estimates (SIE) method with an impurity analysis based on glow discharge mass spectrometry. Additionally, the results of the thermal analysis manifest no significant dependence on the rate of solidification, and the scatter of observed gradients was within 0.36 mK among five plateaux with different temperature settings of the furnace. Although the results support the application of both the SIE method and thermal analysis for the silver point, further experiments with cell-to-cell comparisons linked to thermal analysis, a study of the thermometer-furnace systematic effects, the oxygen effect, and the locus of the freezing plateau should be investigated to reach a firm conclusion.     

溴苯熔点研制及复现方法研究

研制了可用于工业铂电阻温度计现场校准的溴苯熔点.对溴苯过冷度、熔点复现性进行了实验研究,并比较了基于曲线拟合法和切线交点法的两种熔点取值方法,最后对溴苯熔化温坪用于现场校准的实用性进行分析,提出了溴苯熔点的使用建议.实验表明:溴苯凝固前的保温温度越接近其凝固点温度,过冷度越小;溴苯熔化时保温温度越高,升温速率越大,熔化...     

A Concerted International Project to Establish High-Temperature Fixed Points for Primary Thermometry

Research into high-temperature fixed points above 1,100°C has made significant progress since they were first reported in 1999. In particular, it has been established that single cells are repeatable at the sub-50 mK level, and intra-cell reproducibility at the 100 mK level has been demonstrated even at temperatures as high as 2,500°C. The fixed points have been used to compare temperature and radiometry scales over a wide temperature range, and are being developed and established as secondary references for thermocouple calibrations. However, before they can be fully accepted as primary temperature references, much work remains to be done, namely: (1) Establishment of long-term stability of the fixed-point temperature; (2) Development of robust procedures for the reliable construction of the fixed-point cells (to ensure routine intra-cell reproducibility of 100 mK); (3) Demonstration of long-term robustness of the fixed-point cells; (4) Assignment of thermodynamic temperatures to a selected set of fixed points; (5) Agreement and acceptance of these temperature values by the CCT; (6) Agreed methods on how to take full utility of these new fixed points into any future International Temperature Scale (ITS)—or the current ITS-90 via an addendum to the mise en pratique for the definition of the kelvin. To ensure that this work progresses to completion in a reasonable time frame, a research project, under the auspices of the CCT-WG5, has been formulated and is currently in progress with the aim of achieving the above mentioned targets by 2012. This article will describe this project and detail partner contributions.     

Modeling of Transient Heat Transfer in Zinc Fixed-Point Cell

The current fixed-point calibration practice relies on furnaces that provide best achievable uniform temperature distribution, limiting the temperature gradients to about 10 mK to 20 mK along the ingot length. This paper outlines a numerical study conducted to further reveal the influences of the temperature gradients on the physical process involved and to bring some estimates for their influence on the plateau behavior. The mathematical model of the physical process is presented, along with the numerical models used through the FLUENT software package: the transient conductive heat transfer model, the discrete ordinates radiative heat transfer model, and the solidification model. The final model is reduced to axial symmetry for the sake of feasibility with the available computational resources. The convective heat transfer is neglected as it was considered to be of minor importance for the process itself. The geometrical model covers the entire fixed-point cell assembly and distinguishes each of its elements. The paper presents six cases, varying the temperature gradients in the boundary conditions and the cold-rodding. Their influence on the physical process is explained through the temperature fields presented. The study shows that a gradient of ±1 K · m^?1 influences the plateau solely in its duration by either prolonging or shortening it by approximately 20 min.