An IR-absorption sensor system for the determination of engine oil deterioration [automotive applications]

Fourier-transform infrared (FT-IR) spectroscopy has become a major method in used oil laboratory analysis. The degradation of several oil components can be detected in the IR absorption spectrum. One of the most significant parameters is the oxidation, which is related to the change in absorption at a characteristic wavelength λ=5.85 μm. However, for online oil condition monitoring, laboratory FT-IR analysis equipment is too bulky and much too expensive. Thus, we developed a sensor prototype setup, which determines the absorption at 5.85 μm and a reference wavelength, where the absorption is scarcely affected by oxidation. The underlying concept is suited for implementation in an online condition monitoring system. The setup involves a broadband source, a fluid cell for IR transmission through an oil sample, narrow band IR filters to select the two bands, and a broadband IR-sensor. We present illustrative sample results and comparisons to results obtained with FT-IR spectroscopy.