The paddle wheel flow meter is a simple and low-cost velocity-type flow meter that uses fluid kinetic energy to drive the paddle wheel to rotate. The flow velocity and flow rate are calculated by the rotation speed. It is widely used for measuring the flow of clean liquids such as water and chemical liquids. The pipe is equipped with a freely rotating paddle wheel (impeller). The fluid flow impacts the paddle blades, so that the paddle wheel speed is proportional to the fluid flow velocity.