Abstract: Disclosed is an integrated, multi-module luminescence measuring system. The system can selectively conduct lifetime decay or steady-state measurements of light emitted by a sample which receives exitation light. The system includes: a sample chamber which directs monochromatized, focused excitation light from a selected source at a selected sample and directs any resultant emitted light through a monochromator to either a first gated photodetector or a second regular photodetector. Also present is a reference module with a regular photodetector which may selectively receive a portion of the excitation light. A lifetime decay detector module pulses a selected light source and the gated photodetector so that a converter produces digital signals related to output signals from the photodetector, the digital signals representing the integral of the intensity of the emitted light over a selected time.