How do on-vehicle mobile wheel balancers work?

[mohammad]

I discovered that you can buy a balancer that works while the wheel is still mounted to the car. How does this work? I do not see a sensor that allows the machine to identify wheel position. I also do not understand what the buttons on the machine do or why it needs a connection to the tripod.

- http://nitromac.com/en/urunler/otomo...lans-makinesi/
- https://www.zetamak.com/detay_en_18_...-balancer.html

I imaging the light at the top is for some sort of reflector that you would stick to the tire but I do not see any sensor on the machine for this.


I would appreciate any photos/video/documentation people have