Multivariable Electrical Resonant Sensors for Independent Quantitation of Aging and External Contaminants in Lubricating Oils

Oil lubricants in machinery deteriorate over time due to aging or accidental introduction of external contaminants. Limitations of existing oil sensors include their poor sensitivity for early diagnostics and the inability to quantify several parameters of interest in oil. Here, in this paper, we describe a sensing approach that is free from these limitations of existing oil sensors, and demonstrate its applicability for independent quantitation of oil aging and external water leaks into the oil. To achieve this performance, the technical novelty of our oil sensor was two-fold: (1) we implemented a resonant sensor design to enhance detection sensitivity in oil and (2) we solved the convoluted problem of inability to quantify several parameters of interest in oil by operating the resonant sensor with several independent outputs. This technical novelty of our oil sensor resulted in a 20 – 400-fold improvement in the limit of detection of water versus two types of the state-of-the-art oil sensors, such as a capacitance and tuning fork sensors, and independent quantitation of oil aging and contamination, unavailable from existing oil sensors. We validated the oil health sensors in diverse industrial assets such as a locomotive engine, a helicopter engine, and a wind turbine gearbox. Our technical solution can be attractive for independent quantitation of diverse properties of other industrial fluids.