Semi-liquid seal drip water meter national standard technical indicators and parameters GB778-1996: Metering for classification as Class A, B grade, C grade, D grade four measurement levels. Four measurement level characteristic traffic, overload traffic flow and conventional four levels are the same, the difference is the difference between the boundary flow and minimum flow rate; especially low traffic area test points is the difference between one and two times. From the measurement point of view, with the measurement level increases, the lower the lower zone test point, especially with 15-caliber starting flow as an example: A grade wet to 14L / h, dry to 16L / h; B grade wet for 10L / h, dry to 12L / h; C grade wet or dry are 4L / h; D grade wet or dry are the 2L / h. Now market a dripping turn starting flow meter can be achieved 0.5--1L / h, from the point of starting flow meter can reach more than D grade, but flow measurement can only reach the Class B rating level. In fact, the impact of this class is to accelerate the rotation of the impeller meter hole as power source, easy to plug the hole, and the filter area than ordinary water meter and valve malfunction scaling easy, drip metering lose, the consequences are not as Class B ordinary water meter. Currently being revised national standards, international standards, our country will ISO4064-1: 2005 by comparing the current national standard adds test methods for the measurement accuracy is improved. 15 caliber, for example: Q3 = 2.5m3 / h, Q3 / Q1 = A grade 40m3 / h, Class B 80m3 / h, C-level 160m3 / h, D grade 200m3 / h; Q2 / Q1 = A grade 2.5m3. / h, Class B 4m3 / h, C grade 1.6m3 / h, D grade 1.6m3 / h. Q3 is worse than usual flow Q1 minimum flow greater range than on the large, Q2 Q1 transitional flow worse than the minimum flow rate of the smaller high level of accuracy. China's production enterprises with international standards there is a gap, after the transition period of five years, the revised national standards, national standards after five years is equivalent to international standards.