Hot Film Mass Air Flow Sensor, Function

Hot Film Mass Air Flow Sensor, Function




Schematic representation
R1, R2 Fixed resistor
RH Heating resistor
RL Temperature resistor
RS Sensor resistor

The electronics in the hot film mass air flow sensor control the temperature of the heating resistor (RH) by means of a variable voltage so that its temperature is 160°C above the intake air temperature detected by the temperature resistor (RL).
The temperature of the thermistor is measured over the sensor resistance (RS).

Temperature changes which take place as a result of an increased or decreased flow of air regulate the electronics according to the voltage of the thermistor until the temperature difference of 160�C is again reached. This control voltage is used by the engine control unit as a measure for the metered air mass.

The intake air temperature is measured by a further NTC resistance in the hot film mass air flow sensor.