介绍了一种利用超声波在顺程和逆程传播的时间差原理来测量气体流速的流量仪表｡该仪表采用分体式设计,分为测量和显示两大模块｡超声波换能器利用压电陶瓷的压电特性设计而成｡测量模块计算的流速通过D/A转换成标准4~20 mA的电流输出｡仪器的显示模块负责流速､温度､压力的采样和结果的计算､显示,各种参数通过键盘功能修改｡该仪表通过RS-485串行通信接口与计算机连接进行数据传输,计算机可以实时地读取测量数据｡ Design for Ultrasonic Gas-flowmeter of Time Difference ZHOU Li-hua,XIU Ji-ping (Huazhong University of Science and Technology,Wuhan 430074,China) Abstract:Introduced a instrument which can measure the velocity of flowing gas.The instrument was based upon the principle that the time ultrasonic costs at flowing along and against the gas is different.The instrument is designed as two parts:measure module and display module.The design of ultrasonic transducer is based on piezoelectricity of the piezoelectric ceramic.Transferred to 4~20 mA current by DAC,the result of flow velocity is transmitted to display module.It is the duty for display module to sample flow velocity,temperature and pressure,and then calculate and display the result.System parameters are set by the keyboard.Data can be transmitted to computer real time by a isolated RS-485 interface. Key words:ultrasonic; gasflowmeter; singlechip; velocity of flow