Abstract: The invention provides a d.c. motor and motor control circuit to conduct characterization tests on materials by applying constant loads to or affecting constant displacements of physical samples of various materials for transient tests purposes. The actuator, a voice coil motor, and a wave shaping input circuit in associated motor control circuitry provide stable, precise control of load during creep tests without backlash and stick slip and stable precise control of displacement during a relaxation test without dither thus providing rapid response whereby results may be obtained in milliseconds and further permitting the same equipment to be employed for dynamic tests. The motor is controlled by an underdamped servo loop which in turn receives a command signal from a filter circuit having a rise time optimized with respect to the mechanical constants of the system.