超声波流量测量中流速计算方法的对比

Comparison of flow rate calculation method for ultrasonic flow measurement

超声波流量计(UFM,Ultrasonic Flow Meter)通过测量管路中顺流和逆流方向的超声波传播时间变化计算流速,因此超声波传播时间的准确测量对流量计的精度影响至关重要.对超声波流量计的测量方法进行研究,从环境温度的变化、时间测量的准确性、不确定度的计算3个方面,对比超声波传播时间差法和频率差法对流量测量精度的影响.通过超声波流量测量实验,验证了在流量计未校准的情况下,与频率差法相比,时间差法的测量精度更高,且其校准系数曲线的线性度更好,校准后可在全流量范围内获得更高的测量精度.

Ultrasonic flow meter （UFM） calculates the flow rate, by measuring the difference of ultra- sound transit time between the upstream direction and downstream direction. For the purpose of accurate flow measurement, transit time difference method and frequency difference method were compared from three as- pects： change of environment temperature, accuracy of time measurement, and uncertainty calculation. Ultra- sonic flow measurement experiment shows, when the flow meter is not calibrated, compared with frequency difference method, transit time difference method can achieve better accuracy. The calibrated factor for the transit time difference method is more linear, so better accuracy is achieved for full flow range measurement.