用弓高弦长法测量大直径和不完整圆直径时测量不确定度分析

弓高弦长测量法是大直径工件或不完整工件直径测量的常用方法。本文推导出可测弓高与待测直径之比和灵敏系数的关系，并通过测量不确定度的分析，提出了判定弓高弦长测量法使用范围的准则，同时提出了该方法用于弓高大于弦长的测量场合时优于直径的直接测量法的推论。

Uncertainty Analysis for Arc Height Chord Length Method Used to Measure Big diameter and Incomplete Circle Diameter

Arc height chord length measuring method is the classical method to measure the diameter of big-diameter workpiece or incomplete-circle workpiece. The relation between the ratio of measurable arc height and diameter to be measured and sensitivity coefficient has been derived in this paper. By the analysis of measuring uncertainty, the determination criterion of application scope for the arc height chord length is put forward, as well as the derivation that arc height chord length method has a superiority over the diameter direct measuring method when the arc height is greater than chord length is put forward.