WAVE DRIVE® is a microsystem gear unit made by injection molding of thermoplastics — as opposed to the more commonly used silicon - and at the same time presents a novel gear principle which makes it possible to achieve extremely high reduction ratios with very few components in a very compact unit. Utilizing WAVE DRIVE®, a fluid duct regulating flap has been developed that completely contains all its drive elements within the shaft of the flap, thus eliminating the need for an external actuator. A sensor determines the angular position of the flap and completes closed-loop control. In order to enable testing of the small gears for performance characteristics and durability, a special test rig needed to be developed. Special emphasis was put on testing of torque while the gear system is in operation. Most other test systems for small torques can only determine them while the system is at standstill.