Development of Interdigitated Electrode Sensors for Monitoring the Dielectric Properties of Lubricant Oils

Abstract

Proper lubrication is a necessary step in protecting the engine of any vehicle. Regular changing of the lubricating oil becomes an important part of keeping the vehicle running for an extended life. Currently, lubricant oil is changed based on a scheduled time frame or set mileage. It would be advantageous, however, to be able to detect the properties of oil and tell when lubricant change is necessary to reduce waste and excess cost. The goal of this research is to develop and optimize an IDT sensor to measure the change in the capacitance value of lubricant oil. To optimize the sensor, four design parameters were chosen and varied between several series of IDT electrodes. The electrodes were fabricated and tested to observe how each of the parameters, electrode width, finger thickness, finger spacing and number of fingers, would affect the sensitivity of the capacitance measurements. Several trends of how they affect the sensitivity were observed and the relative importance of each factor was determined. In general, a maximization of the sensing area by increasing electrode width and finger thickness was the most influential. The spacing of the electrode fingers is also a very important factor though the biggest changes are only seen at very small spacing’s. The effect of substrate material was also studied and was found to have some effect.