Air flow meter
（重定向自Airflow meter）
An air flow meter, is a device that measures air flow, i.e. how much air is flowing through a tube. It does not measure the volume of the air passing through the tube, it measures the mass of air flowing through the device per unit time. Thus air flow meters are simply an application of mass flow meters for a special medium. Typically, mass air flow measurements are expressed in the units of kilograms per second (kg/s).