Best encoder/potentiometer for swinging arm position tracking

Our team is looking to use a pivoting arm on our robot that will rotate about 180 degrees. We plan on useing a 1:64 planatary gearbox with a CIM Motor, and a 15tooth sprocket. The 15 tooth sprocket will then turn a 30 tooth sprocket attached to hex shaft that is directly attached to the arm. I am wondering what the best setup would be to track arm position. I have heard of useing an encoder on the motor, or a potentiometer on the arm it’s self. What option would likely work better. Additionally if you could recomend which encoder/potentiometer/… you would use that would be great, do to our team haveing limited experience with encoders outside of the drive Train.

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Use a CTRE encoder and a talon SRX to control it. Using the talon will make it much easier to put the arm under closed loop control.

The trickiest part of most sensor usage is getting the things mounted in a robust way with little or no backlash (such as reading a different angle when going one direction than the other). Figure out how to mount the sensor, whether encoder or potentiometer, and you’ll have some constraints. If all things are equal, yes, encoder.

As to ‘motor or arm’, what do you care most about, the position of the motor, or the position of the arm? You sense what you want to conrol.