US Patent 7426875 Low flow rate measurement and control

A turbine wheel flow measuring transducer located in a fluid receiving chamber is provided for measuring low flow rates of fluids, whether liquids, gases, or mixtures, and in controlling the fluid flow rates. The transducer is in the form of a small diameter turbine wheel having a plurality of semi-circular lateral openings in its outer periphery. The openings are sequentially presented to the incoming fluid into the chamber and the turbine wheel rotates according to the fluid flow rate. Measuring and controlling of fluid flow rates as low as 4-5 milliliters per minute and as high as 100 milliliters per minute is permitted.