Air Flow Meter
An air flow meter is a device that measures air flow that is how much air is flowing through a tube. However, it does not measure the volume of the air passing through the tube; instead it measures the mass of air flowing through the device per unit time. In simple words, it is an application of mass flow meters for a special medium.
It is used in some automobiles in order to measure the quantity of air going into the internal combustion engine. The vane or flap type air flow meters such as Bosch L-Jetronic and early Motronic EFI systems or Hitachi actually measure air volume, whereas afterwards the "hot wire" and "hot film" air mass meters measure speed of air flow. Sometimes in the flap type meter which includes a spring, which returns the internal flap to the initial position is tensioned too tightly, it can restrict the incoming air and it would cause the intake air speed to increase when not opened fully.
Air flow meters monitor air in many manufacturing processes. In many industries, “Combustion air”, is added to boiler fuel just before fuel ignition to ensure the proper ratio of fuel to air for an efficient flame. Pharmaceutical factories and coal Pulverizers use forced air as to force the particle movement and to ensure a dry atmosphere. It is also monitored in mining and nuclear environments to ensure the safety of people