Hi. I want to know the location(coordinate x y) of a tiny metal ball (around 3 mm in diameter) lying still on a flat wooden table surface. Near the ball (2- 4 cm in distance) there are also human hands, plastic balls and a sheet of paper. Can I use multiple hall sensors or capacitive sensors or any sensor to know the coordinate (x y) of the ball only? *Note that when I say coordinate it may mean relative to certain fixed spot.

Thank you in advance for any reviews or comments

If the ball was Magnetic, you could use Halls sensors routed in the underside of the table.
You could use beams(Led type) so they would be placed all around the perimiter, and wherever the 2 beams were broke is where the ball is.

So if the ball is magnetic I could use hall sensors. I am guessing the hall sensor can detect the distance between itself and the magnetic ball? So two hall sensors will give the location at the intersection of two distances? Can the hall sensor itself be lying on the table instead of underside it?

Sorry but I think LED beams will misinterpret other objects other than the magnetic ball that blocks it.

Again, thanks.

If you place Hall sensors on the board, it will limit the movement of the ball.
I would think you would want the ball to be located anywhere on the board, sensors on the board, I feel, will be in the way.
What all is going to be on this board?

Not really. Yes, the ball may likely be relocated from original location, but only within 10 cm from original location at most. If that is what you mean then maybe the sensor won't be in the way?

Objects are human hand, plastic balls and a sheet of paper, all located close to the ball (a few centimeters) (all roughly non magnetic)