Oil Debris Detection Using Static and Dynamic Capacitance Measurements

This paper describes a capacitance sensing method to detect oil debris contents. Experimental investigations are conducted for both static and dynamic measurements. Static measurements are performed by inserting small metal wires into the oil sample between the two plate electrodes of a capacitor. With a gap of 7mm between the electrodes, it was found that the capacitance measurement can detect metal wires as small as 4 mils (101 μm) in diameter. While measurements of ferrous and the non-ferrous wires show certain measurable differences, a systematic difference between the two sets of measurements cannot be established. The dynamic measurements were conducted by measuring the changes in capacitance between two plate electrodes when a small particle was dropped into the oil between the two electrodes. The passage of a metal particle can be dynamically detected. It is expected that smaller metal debris particles can be detected by reducing the spacing between the two electrode plates in microchannels.