Best Sensor Options for Measuring Ball Position on Ball and Beam (Four Bar Linkage)

I am designing a controller for my university project involving a ball and beam (four bar linkage). I need a way to measure the position of the ball which slides along the beam and convert that position to an electrical signal. My first inclination is to choose a transducer (pressure sensor) but I am open to suggestions.

Thoughts??

Mike

If the ball isn't just a loose ball, you could attach a linear encoder like the ones in this link:
"Posital linear encoders(Linear Encoders)":https://www.posital.com/en/products/linear-sensors/LINARIX-Draw-Wire.php

If it is just a loose ball, you might get an ultrasonic sensor to work.
"Allen-Bradley ultrasonic sensors(Ultrasonic Sensors)":http://ab.rockwellautomation.com/Sensors-Switches/Ultrasonic-Sensors

Or possibly a laser distance sensor.
"Allen-Bradley laser distance sensor(Laser Distance Sensor)":http://ab.rockwellautomation.com/Sensors-Switches/Laser-Sensors/Measurement-Laser-Sensors

No matter what you choose, you'll either get a digital position or a 4-20mA signal that you'll have to convert to a position.

Good luck!