Uncertainty Assessment of Measurement in Variation Coefficient of Drip Irrigation Emitters Flow Rate

A comparison analysis on the uncertainty of the emitter coefficient of flow rate variation method for two emitter test devices is presented. The effect and adaptability of two Type A uncertainty methods, traditional and maximum entropy, are discussed for the manual and automatic emitter test devices. Several conclusions from the analysis and test date are: the automatic device has a higher accuracy than manual device and it is suggested that the automatic device be used; Type B standard uncertainty, which is not based on a series of test data, has less proportion in combined standard uncertainty than Type A standard uncertainty; the expanded uncertainty of the maximum entropy method in manual and automatic devices are 13% and 16% higher than that of conventional method in manual and automatic devices, respectively; the distribution density functions and the skewness coefficient of maximum entropy method are more accurate fitting than the conventional method, and the minimum number of tests for the maximum entropy method is two times the required number for the conventional method.