水三相点容器的浸没特性及套管对浸没特性的影响

采用步进电机控制器和Labview编程控制,建立了水三相点容器浸没特性的自动测量装置。该装置通过步进电机精确控制温度计在水三相点容器温度计阱内的升降高度,用准确度为0.02×10-6的交流比较仪电桥测量标准铂电阻温度计在计阱内不同高度的电阻值;通过线性拟合,获得水三相点容器的静压修正系数;此外,研究了套管对浸没特性的影响。实验结果表明:温度计阱内径分别为16 mm和18 mm的水三相点容器的静压修正系数实验值与理论值非常接近,差值小于0.4 μK/cm;套管对静压修正系数的影响小于0.5 μK/cm。     

不同计阱的水三相点容器浸没特性的研究

采用步进电机控制器和Labview编程控制,建立了水三相点容器浸没特性的自动测量装置。该装置通过步进电机精确控制温度计在水三相点容器温度计阱内的升降高度,并利用准确度为0．02×10^-6的交流比较仪电桥测量铂电阻温度计在计阱内不同高度的电阻值。通过线性拟合,获得水三相点容器的静压修正系数。实验结果表明：温度计阱内径为16ram和18mm的水三相点容器的静压修正系数理论值与实际值非常接近。     

环境对水三相点温度的影响

本文通过实验研究了环境对水三相点温度的影响。实验结果表明 ,当环境温度为 2 0 5℃ ,环境热辐射引起所测量的水三相点值偏高约 0 1 4～ 0 1 7mK ;热辐射对水三相点温度的影响随着热辐射强度的增强而增大 ;在高精度复现、准确测量水三相点时 ,用黑布罩住温度计及水三相点容器口 ,可以消除环境热辐射的影响。     

冰桥对水三相点的影响

本文通过实验研究了冰桥对水三相点的影响。实验结果表明 ,冰桥引起所测量的水三相点值偏低约 0 0 4mK。因此 ,为了消除冰桥的影响 ,必须将其融化 ,保证冰套可以绕温度计阱自由转动 ,这是高精度复现、测量水三相点的关键     

测量套管铂电阻温度计的水三相点电阻值时应充热导油

测量套管铂电阻温度计的水三相点电阻值时应充热导油李耀南，武荷莲（中国计量科学研究院热工处，北京１０００１３）本文介绍在测量套管铂电阻温度计水三相点电阻值时内管充水和充热导油的实验结果，实验结果表明为避免因固温度计引线之间的绝缘漏电而引入测量误差应采用...     

冰桥对水三相点的影响

本文通过实验研究了冰桥对水三相点的影响。实验结果表明，冰桥引起所测量的水三相点值偏低约0．04mK：因此，为了消除冰桥的影响，必须将其融化，保证冰套可以绕温度计阱自由转动，这是高精度复现、测量水三相点的关键。     

高准确度水三相点容器

水三相点的高精度复现及准确测量是保证国际温标ITS-90实施的关键。水三相点容器内高纯水的同位素组成会影响复现的水三相点温度值。为了提高水三相点复现水平,减小氢氧同位素的影响,研制了带有氢氧同位素分析的石英及硼硅玻璃高准确度水三相点容器。为了评价容器的性能,开展了硼硅玻璃和石英水三相点容器的比对。实验结果表明:同位素修正前,石英玻璃和硼硅玻璃水三相点容器复现的水三相点在0.058mK范围内一致;同位素修正之后,容器之间的差异在0.017mK范围内一致。采用高准确度水三相点容器复现水三相点的扩展不确定度为0.066mK(k=2)。     

液氮冻制冰套法对水三相点温度的影响

介绍了液氮作为冷却剂在水三相点容器内冻制冰套的方法。利用该方法同时在两个不同真空度的水三相点容器内分别冻制冰套。通过实验，研究了此方法对所复现的水三相点温度的影响。实验结果表明：冻制过程中产生的应力以及开始生成的小冰晶引起水三相点温度偏低；并且，其对水三相点温度的影响随着水三相点容器内真空度的降低而增大。随着应力慢慢消除，小冰晶逐渐长大为大冰晶，所复现的水三相点值逐渐回升并趋于稳定。因此，为了高精度复现和准确测量水三相点，采用该冻制方法时，必须将冰套老化至少5天以后，才可以消除其对水三相点温度的影响。     

水三相点处铂电阻温度计稳定时间的研究

众所周知,水三相点是准确复现ITS-90国际温标、准确分度标准铂电阻温度计的关键,在采用标准铂电阻温度计测量水三相点时,需要正确地判断温度计与三相点瓶间是否达到热平衡。我国的标准铂电阻温度计检定规程参照ITS-90国际温标补充文件的建议,规定了一个比较笼统的达到热平衡时间的范围。鉴于水三相点是标准铂电阻分度,检定时最基本也是最频繁使用的固定点,本文作者采用高精密的电桥和水三相点容器,实际测量了常用的三种不同结构的标准铂电阻温度计在预冷和不预冷两种情况下,与水三相点达到热平衡所需要的时间。实验结果表明:在预冷和不预冷两种情况下三种不同结构的温度计达到稳定的时间均不超过五分钟,预冷能有效缩短温计度达到热平衡所需要的时间。     

铂丝位错特性对标准铂电阻温度计稳定性影响的研究

铂丝的位错是影响标准铂电阻温度计性能稳定性的重要因素之一。从微观角度出发,借助X射线衍射(XRD)分析方法,开展了退火时间对铂丝位错密度影响的研究,并利用标准铂电阻温度计退火实验数据进行了验证。结果表明:实际用于标准铂电阻温度计直径为0.07mm的新制铂丝(纯度99.999%)平均位错密度随着退火时间呈指数减小,经过100h退火后位错密度从1012cm^-2下降到1011cm^-2,300h后其位错密度基本保持稳定;新制标准铂电阻温度计在退火前300h其水三相点电阻值明显减小,退火300h后水三相点值变化量小于3mK并趋于平稳,此结果从热处理时间上与铂丝位错实验结果基本吻合。研究结果为标准铂电阻温度计制作工艺的提升及计量检定规程的修订提供技术支撑     

Method for Compensating Heat Flux Errors in Mini-TPW Cell Measurements

Small triple-point-of-water cells (mini-TPW) are used in laboratories to monitor the stability of PRTs. Compared with a standard TPW cell, heat flow in the thermometer well usually disturbs the apparent equilibrium temperature to a larger extent in a mini-TPW cell due to its smaller dimensions. In this paper, the heat flow effect is studied on the basis of experimental data. Special attention is paid to the thermal conduction along a thin thermometer probe and to the self-heating of the probe. A new method for compensating the error due to the heat flow is presented. It is shown that the compensated results are in good agreement with results obtained with standard TPW cells. The determined differences were well within the estimated expanded uncertainty of 2 mK (k = 2). The heat flow effect was studied experimentally by controlling the temperature of the upper part of a PRT inserted in a mini-TPW cell. Also, the effect of different fillings of the measurement well of the cell was studied. Without the compensation, thin metal-sheathed PRTs (1.6 and 2.2 mm) indicated 3 to 9 mK differences between mini-TPW and standard TPW cells.     

Realization of the Triple Point of Water in Metallic Sealed Cells at the LNE-INM/CNAM: A Progress Report

A miniature metallic cell for the water triple point (TPW, temperature 273.16 K) was developed for capsule-type thermometer calibrations for realizations with adiabatic calorimetry techniques. The LNE-INM/Cnam previously developed a copper cell for the water triple point and the techniques for cleaning, filling, and sealing. On the basis of previous work, a new copper cell prototype for the TPW was developed and filled at the LNE-INM/Cnam. Measurements were performed using an appropriate calorimeter and a comparison block containing several thermometers. Preliminary results show a scatter of the temperatures measured at the phase transition of the order of 0.2 mK when measurements are repeated over a short-term period (1 month). A positive drift in the phase transition temperature of about 30μK·month⁻¹ was observed over several months. Studies are in progress to improve the cell, to reduce the reproducibility uncertainty to less than 0.1 mK and to have a phase transition with better temporal stability.     

Correlation Between Immersion Profile and Measured Value of Fixed-Point Temperature

Assessment of thermal immersion effects in the melting and freezing points defined by the International Temperature Scale of 1990 is one of the vital issues of modern thermometry. In documents of the Consultative Committee for Thermometry, the deviation of the experimental immersion profile from the theoretical value of the hydrostatic effect at a height of about 3 cm to 5 cm from the thermometer well bottom is used for the estimation of the uncertainty due to unwanted thermal effects. This estimation assumes the occurrence of solely the hydrostatic effect all along the height of the well inner wall. Real distortions of the temperature gradient at the bottom and at the top part of the well caused by the change of heat-exchange conditions are not taken into account. To define more precisely the temperature gradient along the height of the well, a miniature PRT with a 30 mm sensitive element and a sheath length and diameter of about 60 mm and 6 mm, respectively, were used. Also, the measurements of fixed-points temperature at noticeably different slopes of immersion profiles due to variations of the thermometer heat exchange and phase transition realization conditions were produced by means of a standard platinum resistance thermometer (SPRT). The measurements were carried out at the tin and zinc freezing points. The immersion curves measured with a miniature thermometer demonstrated an increase of the temperature during its lifting in the first 1 cm to 3 cm above the bottom of the well. The measurement results at the zinc freezing point by means of the SPRT have not confirmed the correlation between the immersion curves, the received value of the Zn freezing temperature, and the estimation of its uncertainty.     

Design and Capabilities of the Temperature Control System for the Italian Experiment Based on Precision Laser Spectroscopy for a New Determination of the Boltzmann Constant

This article reports on the construction details of an isothermal cell, referenced to the triple point of water (TPW), together with characterization of its temperature uniformity and stability. The traceability of the temperature measurements is also defined and reported. The cell has an inner chamber of 15 mm diameter, and it is 150 mm long. Its temperature is actively controlled and maintained stable within 0.1 mK, for an unlimited time. The temperature gradient is limited to less than one millikelvin over the length of the cell which is kept in a horizontal position. This accurate temperature control is achieved by means of a series of three vacuum chambers, one inside the other. A special heater, reflectors, standard platinum resistance thermometers, several feedthroughs, an auxiliary thermostat, specific electronics, and dedicated software are used for the active control. The device represents a mixture of cryogenic and contact thermometry techniques, and it has been designed, assembled, and characterized at the Istituto Nazionale di Ricerca Metrologica. This temperature-stabilized cell is a part of a more complex experimental setup, based on near-infrared precision laser spectroscopy, devoted to the experimental determination of the Boltzmann constant.     

Automated Realization of the Triple Point of Water Using the Mush Method

In order to investigate mechanisms of phase transitions of supercooled water in a triple-point-of-water (TPW) cell when a mush method was used to create an ice mantle, an automated apparatus using small TPW cells was developed to obtain the TPW. In this article, the design principle, the apparatus, and the procedure for an automated formation of ice mantles in small TPW cells are described. Supercooled water in small TPW cells spontaneously transformed into uniform metastable dendritic crystals throughout the cells at supercoolings ranging from 5.85 °C to 8.77 °C and then changed into stable hexagonal closed-packed cellular crystals, forming an outer ice mantle from the outside inward. Some pertinent explanations based on thermodynamic solidification theory were used to describe the phase transition process in the mush method. In addition, the experimental results indicated that the realized temperatures of water in the small TPW cells were in good agreement within 0.1 mK approximately 6 h after the initial spontaneous crystallization had occurred. Finally, the small TPW cells (s/n 008 and s/n 001) were directly compared with a conventional TPW cell (s/n NIM-1-211); the temperature differences between the small TPW cells and the regular TPW cell were less than 0.21 mK.     

较低温度条件下SSE影响红外温度计校准的实验研究

讨论了光源尺寸效应（SSE）现象,并应用SSE系数对红外温度计的SSE特性进行估计。介绍了用于较低温度条件下测量SSE的实验装置,应用该装置对几种红外温度计进行了测试。测试结果表明,当黑体辐射源的光阑孔径大于40 mm时,可以不考虑SSE的影响。该结论适用于大多数工业用温度计的校准。     

金属外壳水三相点容器

水三相点是ITS-90国际温标中最重要的定义固定点,其复现不确定度是传递到整个温标的.目前,通常采用不同的冻制方法在硼硅玻璃或石英水三相点容器内冻制均匀的冰套来复现水三相点.冻制过程中,由于在水三相点容器内生成冰桥,会造成容器的破裂.为了解决此难题,研制了金属外壳水三相点容器,利用高纯水自发相变原理,在液体槽内自动冻制...     

Development of Chinese Standard Type of Rhodium-Iron Resistance Thermometer

New rhodium alloy wires with 0.52 % atomic of iron have been drawn, and several batches of RhFe thermometer with strain-free construction and helium-filled platinum capsule have been made using these new alloy wires and old alloy wires which were made in the 1980s in China. In one of the constructions, the coil of wire is inserted into twisted glass tubes, and in the other, it is laid in grooves on a fused-silica crossed frame. The resistance versus temperature relationship and interpolating characteristic of Chinese RhFe thermometer are similar to those of Tinsley 5187U thermometer from 1.5 K to 27 K. The resistance changes of most thermometers are less than that of equivalent to 0.2 mK at 4.5 K after they are exposed to fifty thermal cycles from room temperature to liquid helium temperature. This standard type of rhodium-iron resistance thermometer is now commercially available. Instead of the regular annealing temperature, which is \(750\,^{\circ }\)C, two batches of RhFe thermometers are made with the annealing temperature of \(850\,^{\circ }\)C and \(950\,^{\circ }\)C. The interpolating characteristics of RhFe thermometers will be studied to find new calibration method.     

A self-calibrating rhodium-iron resistive SQUID thermometer for the range below 0.5 K

We report on experiments with a prototype resistive SQUID device which show that it can serve both as a primary noise thermometer and as a secondary resistance thermometer in the range 0.01–0.52 K. The resistor in the circuit was made from an alloy of Rh with 0.5% Fe whose resistivity has an appreciable temperature dependence in this range. The high sensitivity of the SQUID allowed the resistance to be measured very accurately with negligible dissipation of heat. Since values of absolute temperature could be obtained by noise thermometry, the device was in effect a self-calibrating resistance thermometer. This combination of features is a rarity in thermometry in general, and may be unique in this temperature range. A version of this new thermometer has been fabricated and tested in the range 0.01–0.52 K. The results of experiments with this prototype are described, its limitations are examined, and ways of improving it are outlined.Division of Quantum Metrology, National Physical Laboratory, Teddington, Middlesex, U.K.NRC-NBS Postdoctoral Associate.