The control system for controlling the speed of a turbine or other rotating member typically includes means for providing a setpoint or reference signal that represents the desired rotational speed. A servo circuit compares the setpoint signal with a feedback signal representing the actual speed to produce an error signal that is used to minimize the difference between the setpoint and actual speeds. Although for some applications a setpoint controller could simply comprise a potentiometer, there are many applications for which a more precise and versatile method of controlling the setpoint is required. For example, during testing of a propeller turbine drive, it may be required to rotate the propeller at a known rate for a prescribed time period, then accelerate the propeller to a second known rate at a prescribed ramping (i.e., acceleration) rate, etc. In carrying out such a program, the convenience and versatility of the setpoint controller can be a significant factor in minimizing testing time, an important consideration during wind tunnel testing in which the on-line testing time is limited and expensive. An even more demanding application for a setpoint controller is one in which the speed of two related elements must be controlled. An example of such an application is wind tunnel testing of a twin turbine counter-rotating propeller system for a jet aircraft engine. To test such a system, it is necessary to rapidly cycle between different speed levels for the different propellers, and to provide means for precisely establishing the relative speeds and relative acceleration or decelerations of the individual propellers. No prior setpoint controller or controller systems have been found adequate to efficiently test such a system.