Air Flow Meter/Sensor: Description and Operation

Karman Vortex - Operation:

PURPOSE
The volume air flow meter accurately measures the amount of air entering the engine.

LOCATION
Mounted to the air cleaner on the right side of the engine compartment.

CONSTRUCTION
The Karman-Vortex style volume air flow meter is built quite differently than conventional air flow meters. Inside the sensor housing is a LED, a photo transistor and a spring mounted mirror.

OPERATION
Light from the LED shines onto the mirror portion of the sensor. As light is reflected off of the mirror, it is output by the photo transistor as a voltage. As air flow increases through the sensor, vortices in the air flow exert pressure on the mirror. Because the vortex created in the sensor is not constant, the force on the mirror occurs as vibrations. When the mirror vibrates, light from the LED striking the photo transistor reflects the vibrations. The vibrations are converted to a voltage signal and fed to the ECU.