通过对DC03冷轧钢板的断后伸长率进行测试，分析了断后标距测量位置对断后伸长率测试结果的影响，以及手工测量与引伸计自动测量两种方式的差异，最后对手工测量的断后伸长率A_{50 mm}和A_{80 mm}测试结果的不确定度进行了评定。结果表明：试样的原始标距越长则测得的断后伸长率越小，原始标距越短则测得的断后伸长率越大；采用引伸计自动测量断后伸长率得到的测试结果小于手工测量的测试结果；当包含因子k=2时，该DC03冷轧钢板手工测量得到的断后伸长率测试结果为A_{50 mm}=49.0%±2.0%，A_{80 mm}=40.5%±2.0%。

Through the measurement of percentage elongation after fracture of DC03 cold rolled steel plates, the influence of measuring positions of gauge length after fracture on the measuring results of percentage elongation after fracture was analyzed. The difference between two methods of manual measurement and automatic extensometer measurement was also analyzed. Finally the measurement uncertainty of percentage elongation after fracture A_{50 mm} and A_{80 mm} obtained by manual measurement was evaluated. The results show that:the larger the original gauge length was, the smaller the measured percentage elongation after fracture was; the smaller the original gauge length range was, the larger the measured percentage elongation after fracture was; the measuring results of the percentage elongation after fracture obtained by automatic extensometer were less than those obtained by manual measurement; when the coverage factor k was 2, the percentage elongation after fracture of DC03 cold rolled steel plates obtained by manual measurement was A_{50 mm}=49.0%±2.0%, A_{80 mm}=40.5%±2.0%.