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至1085°C的温度范围内实现定点所需的技术。 3. 1.2 本指南未涉及定点电池的设计和施工要求。中给出了典型示例 无花果。1和 2. . 注1: 该示例显示了一个绝缘炉体和两种可选类型的炉芯。左边的核心是三区屏蔽型。 右侧的核心采用热管来减少温度梯度。 1.3 本指南旨在描述良好实践，并建立实现固定点的统一程序。 1.4 本指南强调原则。对原则的强调旨在帮助用户评估单元、改进单元使用技术以及建立特定应用程序的程序。 1.5 就本指南而言，用于准确校准温度计的定点电池仅限于浸入式- 类型温度计，当插入电池的凹口时( 1. )仅表示油井等温区域的温度，以及( 2. )不要通过传热显著改变油井等温区域的温度。 1.6 本指南并不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 以国际单位制表示的数值应视为标准值。 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第节 7. ，在本指南中。 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的用户有责任在使用前制定适当的安全和健康实践，并确定监管限制的适用性。 ====意义和用途====== 5.1 纯材料具有明确的相变行为，相变平台（材料的一个特征）可以作为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被指定为ITS-90上的定义固定点。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（参见 表1和 2. ). 本指南介绍了有关建立参考温度的相变过程的信息。 （A） 定义ITS-90的固定点。 （B） 实现为熔点。 （A） 精心设计、结构和材料纯度良好的电池的数值。质量较差的电池可能无法达到这些值。 （B） 实现为熔点。 5.2 定点电池为用户提供了实现熔点和冰点的方法。如果电池的设计和构造适当，如果其含有足够纯度的材料，并且使用得当，则可以建立不确定度为几毫开尔文或更少的参考温度。 本指南介绍了一些设计和使用注意事项。 5.3 与毫开尔文不确定度要求相比，固定点电池的构造和操作更为严格，但仍能为各种工业校准和热处理目的提供可靠、耐用、易于使用的固定点。例如，任何冰点电池都可以作为熔点电池进行操作，这通常是有利的。这种使用可能导致精度降低，但在特殊情况下，精度可能与冰点相当（见 6.3.10 ). 5.4 本指南中所述的测试程序产生鉴定测试数据，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。它们提供了结果评估，确保了方法的持续可靠性，并深入了解了测试结果差异的原因。该测试程序适用于用于精确温度计校准的固定点电池的最苛刻用途；这可能不合适或成本过高- 适用于所有应用。预计本指南的用户将根据具体需要调整程序。

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 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 and health practices and determine the applicability of regulatory limitations prior to use. ====== 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. (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.