Can you turn the target wheel motor on and then physically restrain it from turning (e.g with your finger) without damaging the motor? If so, start the motor, hold the target at a known position, start data logging, then release the target. This should give you a profile of the target. It won't be exact, due to the initial acceleration of the motor, but you should see a cyclical pattern that you could then match up to the data you take.
Dave.
