Sensing the thermal conductivity of deteriorated mineral oils using a hot-film microsensor

In recent years, the monitoring of oil-based liquids has gained increasing importance in various branches of the industry. In this contribution, we discuss the application of a miniaturized thermal conductivity sensor for the monitoring of water contamination and deterioration processes in mineral oil. The sensor, which works on the hot-film principle, features a molybdenum resistive structure simultaneously serving as heater and sensing element. The experimental results show that both water contamination and deterioration processes in mineral oil lead to an increased thermal conductivity indicating the potential of thermal conductivity sensors in the field of oil condition monitoring. Finally, we analyzed the sensor's performance numerically in order to further evaluate its applicability and possible design modifications.