A method of measuring the video acuity of a physical imaging system is disclosed. Therefore, the relative rotation angle of the motor housing respective to the gear housing can be adjusted so that the tension of the belt can be easily controlled and the generation of vibration and noise of the belt can be prevented. Location information of the device, as well as a time at each location, may also be stored in the database. The system further allows more targeted discounting at a lower cost, and substantially reducing fraud by eliminating post purchase coupon processing and redemption.