A non-contact apparatus for acquiring velocity information off of an internal rotating housing of an Adams-type centrifuge (10). The apparatus includes a bidirectional transmitter of radiant energy, such as a fiber-optical member (52), positioned at the axis of rotation of the exterior rotatable housing of the centrifuge. A ring (58) of reflective, spaced-apart, members is formed on the lower surface of the rotatable housing adjacent the end of the fiber-optic member. Radiant energy from an exterior, fixed, light source (42) is transmitted through the fiber-optic member and is incident upon the rotating ring. Radiant energy reflected off of the reflecting members of the ring passes back through the fiber-optic member and can be sensed in an externally located, stationary optical sensor (66). The optical sensor generates a train of electrical pulses in response to the incident pulses of reflected radiant energy.