hi, i have a new project which require me to analyze the dependence of tangential velocity to angular velocity between two different sizes of wheels. can anyone help me how can i measure and show the speed of the wheel? other than using sensors? or if using sensor is a good idea, brief me a simple one? and by the way, i will be using motors and some potentiometer to control the speed. i havent build this thing so i'd appreciate some ideas. thanks