AbstractAn online condition monitoring system based on the measurement of viscosity and density of liquids is presented and applied to three different measuring tasks relevant for industrial and automotive applications. One topic is oil characterization in hydraulic systems. It is shown that by measuring over varying temperature and pressure, additional physical properties can be made available for online condition monitoring, which are difficult to measure otherwise. These include, for example, the coefficient of thermal expansion and the bulk modulus, which is also related to the proportion of dissolved air. In the second application we investigate the efficiency of a passive oil defoamer and estimate the percentage of free air. Finally, the suitability of the measurement system for the determination of the diesel fraction in the engine oil as caused by the regeneration cycles of the diesel particulate filter is demonstrated.
Validation of a soft sensor network for condition monitoring in hydraulic systems