Novel sensor cell design and algorithm to online realize stable and cost effective optical concentration measurements at fluctuating light source situations

The spectroscopic optical absorption technique is widely used for estimation of substance concentration. It is based on the wavelength specific determination of light extinction in an absorption cell that is caused by the interaction of light with the molecules of the claimed substance. The absorption measurement is an indirect method because a light attenuation (often only at a few spectral measurement points) is used. This measurement is not only influenced by the substance absorption but also unwanted by disturbances and changes of light emission, guiding and receiving. New optical methods for realizing an online reference for a robust absorption measurement has been designed and investigated. Compared to commonly used methods the designed technique is not complex but effective and also well suited for small sensor application. The utilized concept is based on the variation of the effective absorption path length within a sensor cell in a simple way. Stable absorption measurements at the presence of strong spectral changes of the light source intensity are shown here to demonstrate the potential of the developed technique.