In addition to a single beam spectrophotometer, which has only one beam of light, a double beam spectrophotometer may also be used. A double beam spectrophotometer has two beams of light, one passing through a reference liquid and one passing through the sample. To use a double beam spectrophotometer, follow the instructions outlined for the single beam spectrophotometer for the cell compartment labelled "sample", but leave a cuvette with the reference liquid in the compartment labelled "reference" for the duration of the experiment.

The Perkin Elmer Lambda 3™
Double Beam UV/Vis Spectrophotometer

Diode array spectrophotometers are also widely used. A diode array spectrophotometer is manipulated in a similar fashion to a single beam UV/Vis spectrophotometer; however, while a single beam spectrophotometer passes individual wavelengths of light through a sample and records the absorbances at each wavelength, a diode array spectrophotometer passes all specified wavelengths through the sample at once and records all absorbances at the same time.