the first and second pulleys 12 14 and in engagement with the belt 10 depending on its particular application the belt 10 may be applied to drive one or more mechanisms or to carry one or more loads in conveyor fashion for the purpose of discussing the present invention a load driven by the belt 10 is represented by the inertia component 22 in fig2 in accordance with the present invention the system requires means for measuring motion of a driven component after driving power has been cut off thus an encoder 24 and encoder timer 26 are provided to measure rotational movement of the rotational drive shaft driven pulley 12 fixed to the motor 20 the encoder 24 and encoder timer 26 are interfaced with a controller 28 the controller 28 may be interfaced with or may be one and the same with a control system 30 for controlling other functions associated with the system including motor timing control the motor drive system 30 includes a digital to analog d a converter 32 and an amplifier 34 a method according to the present invention for inertia testing a machine such as the system described with respect to fig1 2 is now described in the context of testing for proper belt tension first the tension of the belt 10 is set using a conventional force gage using the controller 28 an operator invokes a diagnostic program the controller 28 issues a driving signal via the motor drive system 30 to the motor 20 causing the motor 20 to accelerate to a predetermined fixed velocity when.