Colorimeters are utilized in colorimetry. Colorimeter measures how absorbent a wavelength of light is, via a particular solution. Applying the Beer-Lambert law, a colorimeter helps to figure out a solution’s concentration. According to the Beer-Lambert law, a solute’s concentration is always in proportion to its absorbancy.

A colorimeter has several very important parts. They include a light source, a meter that allows the user to read the detector’s output, an aperture (which is adjustable), colored filters, a cuvette which holds the solution, a photo-resistor (or some other type of detector) which measures the light being transmitted. It may also include a voltage regulator which helps to protect against fluctuations in the main’s voltage. An additional detector, cuvette and light path may be required as well.

Colorimeters often use optic filters which are interchangeable, in order to choose the light wavelength in which the solute most absorbs. This helps to improve accuracy. The range of the wavelength will often fall within the following range, 400 to 700 nanometers. For individuals that would like to work in the ultraviolet range, which falls under 400 nanometers, it is necessary to make some changes to the colorimeter. Today, the filament filters and lamps can be replaced with light emitting diodes of varying hues.

Cuvettes are another important part of the colorimeter. Cuvettes can be taken out and inserted by hand, when a manual cuvette is being used.  Automated cuvettes are another option. These contain a flow-cell, which allows for the continuous flowing of the solution.

Colorimeters also include outputs. Outputs can be displayed via either a digital or analogue meter. Several scales may be used, including an absorbance or transmittance scale. The former is a linear scale which reads between 0 and 100%. The latter is a logarithmic scale which reads from 0 to infinity. Outputs can be sent several places. They include a computer, data logger or chart recorder.