中文摘要：

理论推导了使用参比法的超声检测二元混合气体的微量气体浓度的计算公式。基于超声传播在不同浓度的混合气体中具有微小时差的特性，设计了微量气体浓度检测系统。利用该系统对空气中六氟化硫（SF6）气体浓度进行了实验验证，验证结果与理论计算吻合，对空气中的六氟化硫来讲，检测的分辨率优于30×10^-6（V／V）。

英文摘要：

The calculation formula of testing the micro-concentration of binary gas mixture by the ultrasonic technique using the comparing method was deduced. Based on the characteristic of tiny time delay of ultrasonic transmission in the different concentration gas mixtures, a system for micro-concentration gas detection was de- signed. The system completed the detection of sulfur hexafluoride （SF6） concentration in air, and the detection results fitted the theory very well by the detection resolution outgoing 30 ×10^-（V/V）.