A mass air flow sensor is used to find out the mass of air entering a fuel- Injected international combustion engine. The air mass information is necessary for the eingine control unit(ECU) to balance and deliver the correct fuel mass to the engine. Air changes its density as it expands and contracts with temperature and pressure. In automotive applications, Air density varies with the ambient tempreature, Altitude and use of a turbocharger and this is an ideal application for a mass sensor.