涵盖拉伸和压缩试验中使用的五个伸长计等级，根据标距长度的重复性以及指示伸长的可读性、重复性和准确性进行分级。描述了在室温下用于分级的标准校准方法，并说明了校准装置的要求。校准报告的发布说明，以及引伸计的某些结构特征和校准设备的使用建议。还包括标称标距长度为25、50、100和200 mm的引伸计的各种应变和延伸值的综合分级要求表。

Covers five grades of extensometers used in tension and compression testing, grading being in terms of repeatability of gauge length, and readability, repeatability and accuracy of indicated extension. The standard methods of calibration used at room temperature for grading purposes are described, and the requirements for calibrating devices are stated. Instructions for the issue of reports of calibration are included together with recommendations on certain constructional features of extensometers and the use of calibrating equipment. Also included are comprehensive tables of grading requirements for a wide range of values of strain and extension for extensometers of nominal gauge lengths 25, 50, 100 and 200 mm.