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      06-30-2015, 05:50 PM   #16
Daftasabrush
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Drives: F31 340i
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Quote:
Originally Posted by teaston View Post
Exactly, they are ultrasonic sensors, which fire out microwaves to detect movement much like a radar. They don't sense air pressure.
Ultrasonic and microwave sensors are completely different. One cannot do the other.

Ultrasonic is on the left, microwave is on the right. As you can see, they are completely different. The sensors in the F30/F31 are ultrasonic, not microwave. They are also clearly not very sensitive.

Microwaves are perfect for convertibles because you can have them alarmed with the roof down, but I'm not aware of any car manufacturers who use microwave sensors in OEM alarms. All OEM alarms I've come across have had ultrasonics (they are more reliable and more accurate when configured properly).
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