1.1 本指南描述了定点电池和辅助设备的基本特征，以及在29°C至1085°C温度范围内实现定点所需的技术。 3 1.2 本指南不涉及定点电池的设计和施工要求。典型例子见 图1和 2 . 附注1: 该示例显示了隔热炉体和两种替代类型的炉芯。左边的铁芯是三区屏蔽型。右边的核心采用热管来降低温度梯度。 1.3 本指南旨在描述良好做法，并为实现定点建立统一程序。 1.4 本指南强调原则。对原理的强调旨在帮助用户评估细胞、改进使用细胞的技术以及建立特定应用的程序。1.5 为了本指南的目的，使用定点池精确校准温度计仅限于浸入式温度计，当插入池的凹槽中时，（ 1 ）仅指示孔的等温区域的温度，以及（ 2 )不会通过热传递显著改变孔等温区的温度。 1.6 本指南没有涉及温度计校准的所有细节。 1.7 本指南旨在补充定点设备制造商提供的特殊操作说明。 1.8 以SI单位表示的值将被视为标准值。本标准不包括其他计量单位。 1.9 以下危险警告仅适用于试验方法部分，章节 7 ，本指南的。 本标准并不旨在解决与其使用相关的所有安全性问题（如果有）。本标准的使用者有责任在使用前建立适当的安全、健康和环境实践并确定法规限制的适用性。 1.10 本国际标准是根据世界贸易组织技术性贸易壁垒委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认的标准化原则制定的。 ======意义和用途====== 5.1 纯材料具有明确定义的相变行为，并且相变平台是材料的特征，可以用作温度计校准的可再现参考温度。一些高纯度金属的熔点或冰点已被指定为ITS-90上的固定点。其他材料的固定点已经足够仔细地确定，可以作为次要参考点（见 表1和 2 ).本指南介绍了与建立参考温度相关的相变过程的信息。 (a) 定义ITS-90的固定点。 (B) 实现为熔点。 (C) 根据国际计量局（BIPM）温度计咨询委员会第二工作组（CCT-WG2）的建议；出版为:Bedford，R.E.，Bonnier，G.，Maas，H.和Pavese，F.，“1990年国际温标上选定的二级参考点的温度推荐值”， 计量学 ，第33卷，1996年，第133页。DOI:10.1088/0026-1394/33/2/3。 (a) 采用谨慎技术使用的设计、结构和材料纯度良好的电池值。质量较低的细胞可能无法接近这些值。 (B) 实现为熔点。 5.2 定点电池为用户提供了一种实现融化和冰点的手段。如果电池被适当地设计和构造，如果它们包含足够纯度的材料，并且如果它们被适当地使用，它们可以建立具有几毫开尔文或更小不确定性的参考温度。本指南描述了一些设计和使用注意事项。 5.3 定点电池的构造和操作可以比毫开尔文不确定性所需的更宽松，但仍然为各种工业校准和热处理目的提供可靠、耐用、易于使用的定点。例如，任何冰点池都可以作为熔点池操作，通常是有利的。这种使用可能会导致准确度降低，但在特殊条件下，准确度可能与冰点的准确度相当（见 6.3.10 ). 5.4 本指南中描述的测试程序产生确认测试数据，作为该程序的重要组成部分。这些数据为定点程序的质量控制提供了基础。它们提供对结果的评估，确保方法的持续可靠性，并深入了解测试结果差异的原因。测试程序适用于精确温度计校准的定点电池的最苛刻用途；它可能并不适合所有应用或具有成本效益。预计本指南的用户将根据具体需求调整该程序。

1.1 This guide describes the essential features of fixed-point cells and auxiliary apparatus, and the techniques required to realize fixed points in the temperature range from 29 °C to 1085 °C. 3 1.2 Design and construction requirements of fixed-point cells are not addressed in this guide. Typical examples are given in Figs. 1 and 2 . Note 1: This example shows an insulated furnace body and two alternative types of furnace cores. The core on the left is a three-zone shielded type. The core on the right employs a heat pipe to reduce temperature gradients. 1.3 This guide is intended to describe good practice and establish uniform procedures for the realization of fixed points. 1.4 This guide emphasizes principles. The emphasis on principles is intended to aid the user in evaluating cells, in improving technique for using cells, and in establishing procedures for specific applications. 1.5 For the purposes of this guide, the use of fixed-point cells for the accurate calibration of thermometers is restricted to immersion-type thermometers that, when inserted into the reentrant well of the cell, ( 1 ) indicate the temperature only of the isothermal region of the well, and ( 2 ) do not significantly alter the temperature of the isothermal region of the well by heat transfer. 1.6 This guide does not address all of the details of thermometer calibration. 1.7 This guide is intended to complement special operating instructions supplied by manufacturers of fixed-point apparatus. 1.8 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.9 The following hazard caveat pertains only to the test method portion, Section 7 , of this guide. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.10 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 5.1 A pure material has a well defined phase transition behavior, and the phase transition plateau, a characteristic of the material, can serve as a reproducible reference temperature for the calibration of thermometers. The melting or freezing points of some highly purified metals have been designated as defining fixed points on ITS-90. The fixed points of other materials have been determined carefully enough that they can serve as secondary reference points (see Tables 1 and 2 ). This guide presents information on the phase transition process as it relates to establishing a reference temperature. (A) Defining fixed point for ITS-90. (B) Realized as melting point. (C) Based on recommendation of International Bureau of Weights and Measures (BIPM) Working Group 2 of the Comité Consultatif de Thermométrie (CCT-WG2); published as: Bedford, R. E., Bonnier, G., Maas, H., and Pavese, F., "Recommended Values of Temperature on the International Temperature Scale of 1990 for a Selected Set of Secondary Reference Points", Metrologia , Vol 33, 1996, pp. 133. DOI: 10.1088/0026-1394/33/2/3. (A) Values for cells of good design, construction, and material purity used with careful technique. Cells of lesser quality may not approach these values. (B) Realized as melting point. 5.2 Fixed-point cells provide users with a means of realizing melting and freezing points. If the cells are appropriately designed and constructed, if they contain material of adequate purity, and if they are properly used, they can establish reference temperatures with uncertainties of a few millikelvins or less. This guide describes some of the design and use considerations. 5.3 Fixed-point cells can be constructed and operated less stringently than required for millikelvin uncertainty, yet still provide reliable, durable, easy-to-use fixed points for a variety of industrial calibration and heat treatment purposes. For example, any freezing-point cell can be operated, often advantageously, as a melting-point cell. Such use may result in reduced accuracy, but under special conditions, the accuracy may be commensurate with that of freezing points (see 6.3.10 ). 5.4 The test procedure described in this guide produces qualification test data as an essential part of the procedure. These data furnish the basis for quality control of the fixed-point procedure. They provide for evaluation of results, assure continuing reliability of the method, and yield insight into the cause of test result discrepancies. The test procedure is applicable to the most demanding uses of fixed-point cells for precise thermometer calibration; it may not be appropriate or cost-effective for all applications. It is expected that the user of this guide will adapt the procedure to specific needs.