What sensor (encoder) to use for shooter?

Our shooter is built of 2 small wheels connected together with a timing belt, and a CIM motor is mounted directly on the first wheel.
What kind of encoder can I use to get the RPM of the wheels?

A photo of the shooter is attached.





*Consider using a one-per-rev optical or magnetic proximity sensor.

What is the operating RPM range of the wheels?

We normally just use the CIM at max voltage because we use it mainly for autonomous, I want the encoder just to make it more stable and reliable.

I guess the RPM is between 4000 to 4500.
Can u add a link to show me how does the proximity sensor looks like?

We used an allen-bradley photosensor and put a piece of retroreflective tape on the perimeter of our wheel. Although we didn’t have the time to actually use it in our code, we proved that it works to a reasonable accuracy at 5000rpm (there isn’t any empirical data on how accurate that I remember, but for this application you can get a pretty big error without problems). I’d like to hear from a team that actually got to use one of these sensors in their code.