SL42 0 9三臂井径仪用于测量裸眼井的井眼直径。根据联动式三臂井径仪工作原理 ,针对其机械设计方面的局限性 ,提出了分动式三臂井径仪的设计方案 ,即将三支探测臂的关系由联动式改为分动式 ,使每支探测臂都可充分伸展接触到井臂 ,从而提高测量精度。文章着重介绍了仪器的工作原理、设计思想及结构特点 SL42 0 9 Three-arm caliper is used to measure the borehole diameter of open-hole wells. According to the working principle of the linkage type three-arm caliper, according to the limitation of its mechanical design, the design scheme of the split three-arm caliper is put forward. That is to say, the relationship of three detection arms is changed from linkage type to split type, So that each probe arm can be fully extended contact with the well arm, thereby improving the measurement accuracy. The article focuses on the working principle of the instrument, design ideas and structural features