A colorimeter is a light-sensitive instrument that measures how much color is absorbed by an object or substance. It determines color based on the red, blue, and green components of light absorbed by the object or sample, much as the human eye does. When light passes through a medium, part of the light is absorbed, and as a result, there is a decrease in how much of the light reflected by the medium. A colorimeter measures that change so users can analyze the concentration of a particular substance in that medium. The device works on the basis of Beer-Lambert's law, which states that the absorption of light transmitted through a medium is directly proportional to the concentration of the medium.

Spectrophotometers, also called spectrometers (spectrometer), are scientific instruments that decompose the light with complex components into spectral lines The measurement range generally includes the visible light region with the wavelength range of 380-780 nm and the ultraviolet light region with the wavelength range of 200-380 nm. Different light sources have their own emission spectra, so different luminaries can be used as instrument light sources. Emission spectrum of tungsten lamps: the spectral light of 380nm ~ 780nm from the tungsten light source is refract through the prism, and the continuous chromatogram composed of red, orange, yellow, green, blue, indigo and violet can be obtained. The chromatography can be used as a light source for visible light spectrophotometers.

The instrument mainly consists of light source, monochromator, sample room, detector, signal processor and display and storage system. It is easy to find that most colorimeter would use the membrane control panel for the need of water-proof effect in water environment. The gap between the rubber button and the panel will cause water to enter the circuit board and cause the instrument to be destroyed so that a membrane panel made of waterproof material that can be very useful.