共查询到19条相似文献,搜索用时 203 毫秒
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金属(碳)-碳(M-C和M(C)-C)高温共晶固定点(以下简称高温固定点)的出现给温标复现方法带来了一次变革,并有可能成为下届温标新的定义固定点.文中介绍了目前常见的高温固定点坩埚的典型结构,描述了高温固定点的灌注工艺及灌注方法.为对固定点的不同灌注方法及其效果进行研究,使用石墨衬套和碳纤维石墨材料作内衬,灌注了Co-C和Pt-C高温固定点.对灌注的高温固定点初步的复现实验结果显示,Co-C、Pt-C的短期复现重复性均优于50 mK,进一步证明了高温固定点作为新温标定义固定点的可行性. 相似文献
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本文叙述了复现13.8—273.16K ITS—90温标和建立1.2—273.16K范围国家温度基准的途径和方法;列出了作为内插仪器的铂电阻温度计的性能数据;ITS—90温标低温范围各定义固定点的复现和比对结果。最后对所建立的ITS—90国家温度基准所保持的温度值进行了不确定度综合分析。各定义固定点的复现性为±0.1mK,13.8—273.16K范围ITS—90国家温度基准的总不确定度为2mk,1.2—24K范围ITS—90国家温度基准的总不确定度为2.8mk。 相似文献
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根据国际温度咨询委员会辐射测温工作组(CCT-WG5)对世界各国计量机构开展Co-C共晶点研制工作的相关要求,设计并搭建了Co-C共晶点灌注系统,采用直接共晶法成功灌注了满足复现实验要求的Co-C共晶点坩埚。针对直接共晶灌注法效率低、坩埚破裂风险大的缺陷,提出了对灌注方法的改进方案,并依据该方案成功灌注了2个Co-C共晶点坩埚。对灌注的Co-C-2#共晶点进行了复现试验,结果显示:拐点温度的不确定度为5.3 mK,满足小于10 mK的CCT要求;短期重复性为9.6 mK,满足小于20 mK的CCT要求。 相似文献
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At NMIA, radiation thermometers are calibrated by comparison with a number of reference radiation thermometers which are themselves calibrated using fixed-point cells on the ITS-90 temperature scale (In, Sn, Zn, Al, Ag, and Au). The suitability of NMIA fixed-point cells used for standard platinum resistance thermometers (SPRTs) is evaluated by the comparison of ensembles of cells at each fixed point, and by participation in the international BIPM Key-Comparisons K3 and K4. However, the NMIA fixed-point cells used for radiation thermometry are typically much smaller (only 110 mm in length) and the thermowell length immersed in the metal much shorter (85 mm) than those used for SPRTs. Further, the insulation at the front of the crucible needs to accommodate the F/10 viewing cone of the radiation thermometers, so significant temperature gradients exist near the top of the crucible. As a consequence, the conduction errors obtained using SPRTs are too large to be of practical use. A convenient methodology based on the use of a Au/Pt thermocouple, together with a protective tube assembly to reduce conduction errors, has been developed. This allows the convenient measurement of the phase transition temperature traceable, at the 30 mK level, to the fixed-point cells used at NMIA to realize and maintain the ITS-90 scale. As the measurements are made in situ, the temperature environment, and hence the geometry and formation of the liquid?Csolid interface during melting and freezing, are similar to that occurring when used with radiation thermometers. Results are presented for ITS-90 fixed points up to Ag, establishing formal traceability of radiation thermometry fixed-point cells to NMIA??s primary ITS-90 cells. 相似文献
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A fixed point based on Ga-In eutectic alloy with a phase transition temperature of 288.798 K (15.648°C) is proposed and studied.
This temperature makes it possible to accomplish a phase transition without the use of external thermostat devices.
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Translated from Izmeritel’naya Tekhnika, No. 5, pp. 26–30, May, 2008. 相似文献