Patent ID: 7339178

Claim:
A device for photometric measurement of the concentration of a chemical substance in a solution, comprising: a lamp, which emits electromagnetic radiation in a predetermined wavelength range and at a given intensity value; a first receiving unit in a measuring branch (MB), which receives the radiation transmitted through the solution at a first wavelength; a second receiving unit in a reference branch (RB), which receives the radiation transmitted through the solution at a second wavelength; and a control/evaluation unit connected to said first receiving unit and said second receiving unit, which uses the intensity values determined either by the measurement branch (MB) or by the reference branch (RB), in order to control the intensity of the radiation emitted by said lamp, such that the measured values made available are highly plausible, wherein: in the case of a high concentration of the substance in the solution, said control/evaluation unit uses the intensity value obtained in the reference branch (RB) to control the intensity of said lamp; and in the case of a low concentration of the substance in the solution, said control/evaluation unit uses the intensity value obtained in the measuring branch (MB) to control the intensity of said lamp.