A Capacitive Sensor System for Water-in-Oil Emulsions

Abstract

For a stable performance of mechanical equipment, the detection of water content in oils is of crucial importance. Typical examples are automotive oils, e.g. engine, brake and transmission oils, where water content in the order of a few percent needs to be detected. In this paper, we analyzed the suitability of capacitive sensor using permittivity change for water-in-oil emulsions. Using the principle of the cross capacitor, the related sensor response according to the change of water content in oils could be obtained. The electrodes of the cross capacitor were formed around PVC(Polyvinyl Choloride) tube by attaching a copper film. The sensor output was obtained by the 555 timer which is the capacitance-to-frequency converter. The frequency change was also recorded and displayed by PC using LabVIEW monitoring program. Thus, the system can be used for continued monitoring of the base oil’s quality even in case of an apparent water contamination.