length measuring instrument

例句：

1. 1. This is a precision rulerfor measuring lengths.
   这是一把用于测量长度的精密直尺。
2. 2. Theengineer used a caliper to measure the pipe's diameter.
   工程师用卡尺来测量管道的直径。
3. 3. The scientist used amicroscope to observe the microscopic structureof the sample.
   科学家使用显微镜观察样本的微观结构。