A multi-functional photometer includes a scanning mechanism having a housing (10) that bears a movable linkage (12). The linkage is coupled to an optical scanning head (18) and incorporates optical fibers for transmitting radiant energy to and from the scanning head. The arm comprises a C-shaped "elbow" member (14), pivotally attached to a "shoulder" member (16). In turn, the "shoulder" member of the arm is pivotally connected to the housing. Dynamic couplings join the optical fibers such that the shapes thereof remain fixed regardless of the orientation of the arm. The housing further incorporates a Cartesian-coordinate table (20) for positioning the scanning head with respect to a microplate (22) that contains a plurality of analyte samples.