Patent ID: 7330262

Claim:
A method for determining the content materials of a liquid medium using a light source and an optical detector arranged to define an optical beam path extending through a measuring chamber; wherein the light source directs at least one measuring beam along the optical beam path through the medium, and at least one reference beam along the optical beam path outside of the medium; wherein the medium is sucked into, and evacuated from, the measuring chamber by the displacement of a piston device within the measuring chamber; wherein the piston device cleans at least a portion of an internal surface of the measuring chamber disposed in the optical beam path as the piston is displaced within the measuring chamber; and wherein the spectrometric measurement is carried out when a lower edge of the piston device is congruent with upper edges of respective optical lenses disposed in the optical beam path, and the results of the reference beam and of the measuring beam are calculated for each wavelength or for individual areas of the spectrum in accordance with the mathematical relations: E 1 =L 1 * E spez +C E 2 =L 2 * E spez +C wherein E1=measured extinction in measuring beam E2=measured extinction in reference beam L1=length of measurement path L2=length of reference path E spez =specific total extinction module of the medium C=extinction of the cylinder due to discoloration, opacity and contamination.