Ehrlich Charles D, Rasberry Stanley D
National Institute of Standards and Technology, Gaithersburg, MD 20899-0001.
J Res Natl Inst Stand Technol. 1998 Jan-Feb;103(1):93-105. doi: 10.6028/jres.103.005. Epub 1998 Feb 1.
There is a growing requirement for an internationally accepted system of recognition of measurement capabilities and relationships within and among countries, to facilitate seamless global commerce and trade. As a result, metrologists worldwide have recently developed increased interest in the concept and definition of traceability. Classically, traceability provides a way of relating the results of a measurement (or value of a standard) to higher level standards. Such standards are usually national or international standards, and the comparisons used to provide the traceability must have well-understood uncertainties. An additional complexity arises because all instruments and standards are subject to change, however slight, over time. This paper develops approaches for dealing with the effects of such time-dependent changes as a part of traceability statements. The use of metrological time-lines provides a means of effectively visualizing these relationships in a statement of traceability. When the rate of change in the measurement process is sufficiently small, the approach proposed here is less important. However, documented measurement assurance procedures are required at all levels so that appropriate uncertainties may be estimated with confidence. When laboratory or national boundaries are crossed in the traceability process, other factors come into play, and the original concept of traceability can become obscure. It is becoming common to hear the term "equivalence" used to describe these more complex measurement relationships.
对于一个国际认可的、用于识别各国国内及国家间测量能力和关系的系统的需求日益增长，以促进全球无缝的商业和贸易。因此，全球的计量学家最近对可追溯性的概念和定义产生了越来越浓厚的兴趣。传统上，可追溯性提供了一种将测量结果（或标准值）与更高层次标准相关联的方法。此类标准通常是国家标准或国际标准，且用于提供可追溯性的比较必须具有明确的不确定性。另一个复杂因素是，随着时间的推移，所有仪器和标准都会发生变化，无论多么微小。本文提出了一些方法，作为可追溯性声明的一部分来处理此类随时间变化的影响。使用计量时间线提供了一种在可追溯性声明中有效可视化这些关系的方法。当测量过程中的变化率足够小时，这里提出的方法就不那么重要了。然而，各级都需要有记录的测量保证程序，以便能够自信地估计适当的不确定性。当在可追溯性过程中跨越实验室或国界时，其他因素就会起作用，可追溯性的原始概念可能会变得模糊。现在经常听到用“等效性”这个术语来描述这些更复杂的测量关系。
