A capacitive sensor for online oil monitoring based on dielectric constant is introduced.The hardware and software systems is designed to detect small capacitance.On the basis of this

online oil monitoring experimental system is developed.The detection experiment on lubricants with different iron content shows that the sensor can effectively distinguish them.Experimental study on the law of the temperature and oil pressure affect on sensor characteristics shows that it is approximate to linear relationship between temperature

pressure and capacitance

that is to say

temperature and pressure affect on dielectric constant of lubricants is approximately linear.The curves of capacitance change with temperature and pressure is achieved by least-squares fitting

which can provide a reference for oil online monitoring based on dielectric constant.