中文摘要：

基于超声技术和复杂可编程逻辑器件（CPLD）实现对两路同频超声传输过程中不仅是半个周期以内的相位差，而且大于半个周期乃至多个半周期的相位差的检测，仿真实现了微量气体浓度宽量程范围的检测，为基于超声技术的微量气体浓度检测的量程拓展提供了’技术借鉴。

英文摘要：

Based on ultrasonic technology and complex programmable logic device （CPLD）, the phase difference detection of less than or more than half a cycle, and even spanning more semi-cycles, is carried out in the transmission process of two channels of ultrasonic. Also the wide-range micro-concentration gas test is achieved by simulation. This research provides a technical reference for the measuring range expansion of micro-concentration gas detection based on ultrasonic technology.