An analytical biochemistry system featuring a substrate with reactants immobilized thereon at fixed, known locations, a holder supporting the substrate and a manipulator for transporting the holder to a fixed sample and to an inspection station. The first and second luminescent devices are driven by a rectified AC voltage for providing light of a first color. The average grain size should be from 8-30 m, preferably from 12-20 m. A controller is included for detecting capacitive changes in the capacitive sensors, wherein when the controller detects a capacitive change in a capacitive sensor, the controller alters an illumination state of a light source associated therewith.