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of the earliest detectable changes in a system and the most
detrimental to lubricant health. Water contamination not only
reduces oil's lubricating ability, but also increases oxidation and
can lead to the formation of rust, a common corrosive wear
element. It has been shown that 1% water in a lubricating system
can cause a 90% reduction in life of a journal bearing, while the
life expectancy of rolling bearings can be reduced by 70% in the
presence of just 0.1% water. Traditional Condition-based
Maintenance (CBM) methods that use sampling and offline oil
analysis are expensive, non-repeatable, and do not provide a real-
time assessment of oil condition. Available online methods for oil
health estimation have not exhibited the sensitivity or the maturity
required for a standalone, in-situ application.
In order to monitor water contamination in lubricant, the
authors have developed the Smart Oil Sensor (SOS), a multi-
sensor device that measures several properties of oil, including oil
quality, water content, and temperature. The SOS addresses the
shortcomings of existing offline methods for detecting water
contamination. SOS's on-line fluid analysis process can determine
oil health in real-time, thus greatly reducing cost and waste, as
well as providing a faster, on-demand assessment of oil condition.
The SOS employs a patent-pending, low-powered, broadband
impedance spectroscopy measurement coupled with model-based
analysis and multi-sensor data fusion techniques to predict fluid
quality and degradation. The SOS uses advanced classification and
prediction algorithms in conjunction with historical data fusion to
generate a robust output for water content level and includes an
'Early Warning Module' to detect sudden, drastic changes in health
state.
By combining several sensing methods and reasoning
techniques, the SOS is capable of detecting minute levels of water
and salt water contamination in lubricant (as low as 50 ppm) and
tracking the contamination beyond saturation levels. It is known
the relationship between bearing life and water contamination

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