目前,测量明渠水流的平均速度是广泛采用流速仪和小型流速仪。利用流速仪,可以在1个点、2个点、3个点或5个点上测定水流横断面上的水流平均速度。用流速仪测量垂直面上的平均速度时,1个点上的误差不低于±5％,2个点或3个点为±(2～4)％,5个点为±2％〔参考文献4〕。在所使用的方法当中,后者最为精确,但为时也最长。苏联水利部中央水利资源综合利用科学研究所已研制出一种改进5点法测量的仪器〔参考文献1〕,使之在测量过程中可以缩短时间的消耗。此种仪器是由测量变换器、杆件和脉冲计数组件构成。主要测量变换器(图1)为一用塑料制成的双叶螺旋(1),内有一根带限制器(3)的轴 At present, the average velocity of open channel water is widely used to measure the velocity and the small velocity meter. Using the current meter, you can measure the average velocity of the water flow in the cross section of the water flow at 1 point, 2 points, 3 points or 5 points. When using the current meter to measure the average velocity on a vertical plane, the error at one point is not less than ± 5%, ± 2% for 2 or 3 points and ± 2% for 5 points. Document 4]. Among the methods used, the latter is the most accurate, but it is also the longest. The Institute of Comprehensive Utilization of Central Water Resources of the Soviet Ministry of Water Resources has developed an instrument that improves the 5-point method [Reference 1] so that it can reduce the time consumed in the measurement process. This instrument is composed of measuring transducer, rod and pulse counting components. The main transducer (Figure 1) is a double-bladed spiral (1) made of plastic with a shaft with a limiter (3)