本文件规定了用于测定单根碳纤维长丝直径和横截面积的五种试验方法。 不同供应商的长丝横截面形状可能会有很大差异。本文件中使用的术语“直径”适用于所有情况，从横截面为圆形的“真实”直径到非圆形的“视在”直径。 提出的方法不一定直接适用于所有类型的灯丝。产品规格决定了要使用的方法。 如果没有规范，选择合适的方法是一个判断问题。这里给出的细节被认为是足够精确的，可以做出这个选择。

This document specifies five test methods used for the determination of the diameter and cross-sectional area of single carbon fibre filaments. The shape of the cross-section of the filaments from different suppliers can vary significantly. The term "diameter" used in this document applies to all cases, from a "true" diameter, where the filament is exactly circular in cross-section, to an "apparent" diameter where the filament is not circular. The methods proposed are not necessarily directly applicable to all types of filament. The product specification determines the method to be used. If there is no specification, the selection of the appropriate method is a matter of judgement. The details given here are considered to be sufficiently precise to enable this choice to be made.