Abstract: A device for conducting a transmission measurement includes a system for generating a light wave consisting of a first and a second wavelength fraction, in addition to an optical channel guiding the light wave to a sample tube with a sample, wherein the light wave permeates the sample tube with a sample. The device also has a motion unit for producing a relative movement of the light wave along the sample tube. A receiver for receiving and separating the first and second wavelength fragments after the light wave has permeated the sample tube with a sample is also provided. A converter converts the first wavelength fraction into a first digital measuring value describing the degree of transmission in the first wavelength and converts the second wavelength fraction into a second digital measuring value describing the degree of transmission in the second wavelength.