The Karman vortex air flow meter is used only on limited applications (7M-GTE and Lexus 1UZ-FE & 2JZ-GE engines). The meter is smaller and lighter than the vane type meter and offers less resistance to incoming air flow.
The sensor operates on the principle of measuring the vortices created as air flows past a pillar shaped vortex generator. The frequency with which these vortices are created increases in direct proportion to the amount of air flowing across the vortex generator. Vortex frequency is detected by a photocoupler and converted into a variable frequency digital signal by the sensor. An intake air temperature sensor is also incorporated into the Karman vortex air flow meter. For more information about operation of this air flow meter and its signals , refer to section 5, "Electronic Engine Controls."
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