A mass airflow sensor (MAF) is a device for determining the amount of air entering the engine. The airflow meter transmits information about the airflow rate to the ECU, making it possible to achieve a stoichiometric ratio of the components of the fuel-air mixture. The air mass meter is located in the intake system of the internal combustion engine. The installation site is from the air filter to the throttle valve.
It can measure air consumption:
- mechanical flow meter by volume;
- thermal mass flow meter;
The volume flow sensor is a mechanical volumetric airflow meter that measures air volume by evaluating the movement of the damper in proportion to the amount of airflow. It is not installed on modern cars.
Mass airflow measurement is performed by a mass airflow sensor (other names: hot-wire flow meter, mass airflow sensor). Such devices are based on thermistors. A thermistor is a sensitive element that is subject to heat. For this reason, the device is also called a thermal airflow meter.
Thermal flow meter structurally can be a device:
- wire type with platinum heating filament;
- film type with a silicon crystal coated with platinum layers;
The principle of operation of various types of mass airflow sensors is based on maintaining a constant temperature of the thermistor as a result of heating by electric current. The main differences lie in the design of the most sensitive element.
The passage of air through the thermistor causes the cooling of the heated element. Mass airflow is measured by the voltage converter converting the heating current into an output voltage. This voltage and mass airflow have a non-linear relationship. The received data from the sensor is sent to the ECU by the engine in the form of an analogue or digital signal, which depends on the sensor design. Film type devices are most widely used today.
In gasoline power units, the DMRV is mainly used to determine the moment of fuel injection and the amount of fuel supplied, the moment of spark formation by the ignition system. In diesel engines, the DMRV determines the fuel injection time and regulates the working processes of the EGR system.
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