Soda Can Organizer How Is It That Soda Towers ALWAYS Know To Stop When Your Cup Is Full?

How is it that soda towers ALWAYS know to stop when your cup is full? - soda can organizer

I work in a movie theater and I poured soda all the time. I put the cup on the grid in the tower of soda, slips and hits a tab, and the tower of soda, soda ash DISTRIBUTION, until only the top concerns of the cup. NO soda on the spill. The tower just know that he needs to stop. So I thought that perhaps had to do the tilt of the grating, the shape of the glasses or the weight of the drink something with this ability, but I can assure you that none of these factors. I have tried a variety of shapes and weights Cup and have put different amounts of force in the tower of soda form, but that has always made soda come just before the overflow container. Even if I actually tried to fill a container, once spilled soda ... But the tower of ash is still very mysterious, and I would be very happy if someone could please explain how you know, my cup is full. Thank you very much.