GF07.07-P-6000SM Component description for a hot film MAF sensor 22.3.04

ENGINE  113.986
ENGINE  113.987
ENGINE  113.988
ENGINE  113.989


B2/5 Hot film mass air flow sensor (HFM-SFI)

Task
The hot film MAF sensor detects the suctioned in air mass and the integral temperature sensor for the intake air temperature.
 
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Design

9/3 Flow rectifier
9/4 Housing
9/5 Electrical connection:
Pin 1: Reference mass
Pin 2 : Circuit 87
Pin 3: HFM sequential multiport fuel injection/ignition system signal (air mass)
Pin 4: Power ground for HFM sequential multiport fuel injection/ignition system
Pin 5: Not assigned
9/6 Adhesive molding
9/8 Hybrid printed circuit board
9/9 Cover

B2/5 Hot film mass air flow sensor
 
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Schematic representation

R1, R2 Fixed resistor
RH Heating resistor
RL Temperature resistor
rs Sensor resistor
 
    P07.07-2009-05

Function
The elecronics in the hot film mass air flow sensor controls 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).
 
If a temperature change occurs as a result of increased or reduced air flow, the electronic control corrects the voltage at the heating resistor until the temperature difference (160°C) is reached again. This control voltage is used by the ME control unit (N3/10) as a measure for the metered air mass.

The intake air temperature is detected by the integral NTC resistor and transmitted to the ME control unit as a voltage signal.