ZW09 The venture tube is a differential pressure producing flow device that is used to measure flow rate through a pipe. Pressure difference between the pressure measured at high pressure connection and low pressure connection is proportional to square of the flow rate through the flow device. The Venturi tube is related to the Venturi effect. For a conical tube with a changing cross-section (large → small → large), the smallest part is called the throat neck. When the gas flows through, due to the reduction of the cross section of the tube, the flow velocity increases and the pressure decreases. The minimum flow velocity of the cross-section and the maximum pressure are the smallest. The volume of fluid flowing through each cross-sectional area at the same time is equal. The fluid flowing through the venturi changes its speed due to the change of the cross-sectional area, and a pressure difference is generated.