低温流量测量

低温流体的许多性质比较特殊 ,其流量测量不同于一般流体。文中对文丘里流量计、涡轮流量计和相关流量计等几种常用低温流量计的原理、基本技术参数和应用范围进行了介绍 ,并且对这几种流量计的性能进行了比较。     

Realization of a multipath ultrasonic gas flowmeter based on transit-time technique

A microcomputer-based ultrasonic gas flowmeter with transit-time method is presented. Modules of the flowmeter are designed systematically, including the acoustic path arrangement, ultrasound emission and reception module, transit-time measurement module, the software and so on. Four 200 kHz transducers forming two acoustic paths are used to send and receive ultrasound simultaneously. The synchronization of the transducers can eliminate the influence caused by the inherent switch time in simple chord flowmeter. The distribution of the acoustic paths on the mechanical apparatus follows the Tailored integration, which could reduce the inherent error by 2–3% compared with the Gaussian integration commonly used in the ultrasonic flowmeter now. This work also develops timing modules to determine the flight time of the acoustic signal. The timing mechanism is different from the traditional method. The timing circuit here adopts high capability chip TDC-GP2, with the typical resolution of 50 ps. The software of Labview is used to receive data from the circuit and calculate the gas flow value. Finally, the two paths flowmeter has been calibrated and validated on the test facilities for air flow in Shaanxi Institute of Measurement & Testing.