Karman Vortex Air Flow Meter Operation

Intake air flow reacting against the vortex generator creates a swirling effect to the air downstream, very similar to the wake created in the water after a boat passes. This wake or flutter is referred to as a "Karman Vortex." The frequencies of the vortices vary in proportion to the intake air velocity (engine load).

Karman Vortex Air Flow Sensor

The vortices are metered into a pressure directing hole from which they act upon the metal foil mirror. The air flow against the mirror causes it to oscillate in proportion to the vortex frequency. This causes the illumination from the photo coupler's LED to be alternately applied to and diverted away from a photo transistor. As a result, the photo transistor alternately grounds or opens the 5-volt KS signal to the ECM.

Karman Vortex Signal

This creates a 5 volt square wave signal that increases frequency in proportion to the increase in intake air flow. Because of the rapid, high frequency nature of this signal, accurate signal inspection at various engine operating ranges requires using a high quality digital multimeter (with frequency capabilities) or oscilloscope.

ASSIGNMENT NAME:

1. Explain the purpose of a Mass Air Flow sensor?

2. List the different types of Mass Air Flow Sensors?

3. Explain in detail the constructions and how a MAF (hot wire type) works?

4. What type of voltage signal is produced by a MAF and what would you expect to change as RPM is increased?

5. Explain in detail the testing procedure of a MAF sensor.

6. Explain in detail the constructions and how a VAF (Vane Air Flow Meter) works?

7. What type of voltage signal is produced by a VAF and what would you expect to change as RPM is increased?

8. Explain in detail the constructions and how a Karmen Vortex works?

9. What type of voltage signal is produced by a Karmen Vortex and what would you expect to change as RPM is increased?

Karman Vortices
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