Design and Development of Capacitive Type Quasi-digital Sensor and Instrument to In-situ monitoring of the viscosity of Lubricant Oil

Lubricant oil is used as protective layer between the metallic surfaces of gears and bearing of large rotating machinery for smooth operation of power plants and other heavy industries. Viscosity of lube oil plays an important role in reducing friction between rotating parts. Over the period of time, due to oil aging, its viscosity decreases along with deterioration in its various physical and chemical properties. Timely replacing of lube oil at critical viscosity level set by industry standards with fresh one can avoid the potential damage to the rotating machinery and unplanned shutdowns. This article presents development of a capacitive type quasi-digital sensor for real time measurement of lubricant oil viscosity. In addition to sensor an instrument is also developed to read the output from the sensors, to communicate the data to computer, and display on LCD. An experiment is conducted to check the capability of the sensor and instrument for measurement of lubricant oil viscosity. The sensitivity of the sensor is 232Hz/m. Pa.s, and the accuracy is ±10 m.Pa.s. A python based Graphical User Interface (GUI) is also developed to plot real time viscosity and temperature graphs by collecting the sensor data from COM port of the PC.