Abstract: An apparatus for automatically detecting angular motion of a test object, such as a clutch output, utilizing photoelectric devices in combination with helically apertured light shutters, the electric outputs of the photoelectric devices being interpreted by analog logic. Provision is made for a predetermined number of warm-up rotations of the test object to assure normal working conditions, for a predetermined reference threshold of detected motion, for controlled sequencing of the test object for testing for motion at various predetermined angular positions, and for determining malfunctioning of the test sequencing control.