venturi tube for water is a conical body which is pending in the center of pipeline,it can improve the flow field.the high pressure P1 from tube wall which is the flow body has not yet throttling accelerated before vertebral devices;Low pressure P2 are taken from the after centrum rear,and it can draw forth transmitter branch pipe in front of inner vertebral,its square root of differential pressure(P1-P2) is proportional to the rate of flow,then work out a fluid flow,the products are widely used in flow measurement for the liquid,gas or steam of the steel industry,electric power,chemical etc industry.