The colorimeter principle states that the absorbance of a substance directly relates to its concentration. Therefore, the higher the concentration of a substance, the higher the absorbance reading.
A colorimeter has a number of different parts, including a low-voltage lamp, a set of colored filters, an adjustable aperture and a meter that displays the output. Besides showing up on a meter, the output of the colorimeter test can also be sent to a data logger, computer or chart recorder for analysis. In many cases, scientists are looking for an output range of between 0 and 2, but they prefer the readings to remain below a 1.