spectrophotometer ultraviolet spectrometer A piece of apparatus that consists of: a light source; a holder for the sample; a diffraction grating or monochromator to separate the different wavelengths of light; a detector, and is used to measure spectra in the ultraviolet range (190-400 nm). [CHMO] UV spectrometer ultraviolet spectrometer ultraviolet spectrometry UV spectrophotometer ultra-violet spectrometer