UV-Vis spectrophotometers offer a compelling advantage with respect to both initial investment and operational expenses. One common issue is stray light, which occurs when unwanted. Because they are simple to operate, there is little chance of a UV-VIS spectrometer being used improperly. With UV-VIS spectrometers, setup is key. You must clear the area of any outside light. A ultraviolet spectrophotometer is an instrument that measures how much light a chemical sample absorbs at specific ultraviolet wavelengths.