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转子式流速仪由于存在内摩阻,n(V)曲线不通过坐标原点,低速段也非直线,临界連V_K以上直线方程与纵坐标有一截距,即 V=Kn+C 式中:V_K—流速,K—水力螺距,n—转子转速,C—摩阻系数。C量值很小,且影响因素多而复杂,研究困难,因此往往被忽视。然而,系数C对低、中速测量精度影响颇大。我国江河水文测验在此速度区所占的面广,持续时间长,特别是北方河流冬季冰下测流。因此,研究检定系数C对于保证水文测验精度具有现实意义。我国各种型号流速仪产品标准对C值的检定范围均有规定,如LS25—1型为0.007±0.003m/S。它对保证仪器测验精度起到一定的作用已被多年来的实践所证明。然而,对于检定系数C值的限幅看法不尽一致。国外一些检定资料也表明了这点,如苏联-3型C=0.013m/s,日本SW15型C=-0.020m/s,西德C—31型C=0.001m/s等,这些均不符合我国标准要求。本文通过大量资料分析指出,C值检定的准确性,不仅是它本身的精度,而且在一定程度上还反映K值的精确度。因此,为了提高仪器精度,C值应缩小,甚至用标准值。本文讨论内容包括:仪器内摩阻对C值的影响,C值稳定性,K、C值之间的检定关系;如何提高系数C的性能;最后提出标准C值建议。本文只是利用其它试验资料以及生产检定中的成果统计加以总结,因此,仅供参考。不当之处,请指正。
Rotor-type velocity meter due to internal friction, n (V) curve does not pass through the origin of coordinates, low-speed section is not straight, the critical line above V_K linear equation with the ordinate there is a intercept, that V = Kn + C Where: V_K- Flow rate, K-hydraulic pitch, n-rotor speed, C-friction coefficient. C small value, and the impact of many and complex, difficult to study, it is often overlooked. However, the coefficient C has a great influence on the measurement accuracy of low and medium speed. China’s river hydrological test in this area covered a wide area, long duration, especially in the northern rivers in winter under the ice flow. Therefore, it is of practical significance to study the verification coefficient C to ensure the accuracy of hydrological tests. China’s various types of current meter product standards for the C value of the test range is provided, such as LS25-1 type 0.007 ± 0.003m / S. It has been instrumental in ensuring the accuracy of instrumental testing that has been demonstrated by many years of practice. However, there is a different view of the clipping limit for the C coefficient. Some foreign test data also show this point, such as the Soviet -3 type C = 0.013m / s, Japan SW15 type C = -0.020m / s, West C-31 type C = 0.001m / s, etc., which are not Meet our standard requirements. This paper through a large number of data analysis pointed out that the accuracy of C value verification, not only its own accuracy, but also to some extent also reflects the accuracy of K value. Therefore, in order to improve the accuracy of the instrument, C value should be reduced, even with the standard value. The content of this article includes: the influence of internal friction on C value, the stability of C value and the relationship between K and C values; how to improve the performance of C; finally, the standard C value is proposed. This article is only to use other test data and production test results to summarize, therefore, for reference purposes only. Improper, please correct me.