For use in a low-temperature region below the triple point of water (TPW), the National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology (NMIJ/AIST) developed a precise comparison system of capsule type standard platinum resistance thermometers (CSPRTs) for dissemination of the International Temperature Scale of 1990 (ITS-90). This study compared eight CSPRTs with a reference CSPRT using the comparison system to study non-uniqueness at the low temperature. We also evaluated characteristics of new type of low-temperature platinum resistance thermometers with about 1000 Ω of resistance at TPW (PT-1000), which was recently developed by Netsushin Co. Ltd. to obtain better temperature sensitivity of resistance at a low temperature. The PT-1000 sensor is made from a high-grade platinum wire, similarly to standard platinum resistance thermometers of the ITS-90. We calibrated four PT-1000s based on the ITS-90 and evaluated their characteristics by comparison with a reference CSPRT. Results indicate that the character of the temperature scale of PT-1000s is very close to that of CSPRTs down to 14 K.

中文翻译：

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用于低温测量的新型 1000 Ω 型 PRT 的 ITS-90 非唯一性和特性评估

为了在水三相点（TPW）以下的低温区域使用，日本国家计量院、国家先进工业科学技术研究所（NMIJ/AIST）开发了胶囊型标准铂电阻温度计的精确比较系统(CSPRT) 用于传播 1990 年国际温标 (ITS-90)。本研究使用比较系统将八种 CSPRT 与参考 CSPRT 进行比较，以研究低温下的非唯一性。我们还评估了新型低温铂电阻温度计的特性，TPW 电阻约为 1000 Ω（PT-1000），这是由 Netsushin Co. Ltd. 最近开发的，以获得更好的低温电阻温度灵敏度。PT-1000 传感器由高级铂丝制成，类似于 ITS-90 的标准铂电阻温度计。我们基于 ITS-90 校准了四台 PT-1000，并通过与参考 CSPRT 进行比较来评估它们的特性。结果表明，PT-1000s 的温标特性与 CSPRT 的温标特性非常接近，低至 14 K。