Design Of Resonant Oil Detection System

Under the protection of lubricating oil, equipments like engine, gearbox, hydraulic system and so on can operate normally. Oil monitoring technology assists us to timely grasp the message about oil deterioration and machine wear, so as to remind us to take some responding measures as early as possible. Traditional oil detecting method has many disadvantages, for example, its real time performance is not very well, its detecting equipment is huge and expensive. However, detecting method based on oil sensors, which not only possesses good real time performance, but also is very easy to maintain, has become a hot spot in the field of oil detection.According to the domestic and overseas actuality and development trend of oil sensors, a resonant oil viscosity and density sensing device whose sensitive element is QTF(Quartz Tuning Fork) is designed to realize the monitoring of oil quality. Firstly, based on the characteristic of piezoelectric and impedance of quartz crystal, oil viscosity and density measurement principle of QTF sensor is introduced, and the overall scheme of the monitoring system is designed. Secondly, the vibration mode of QTF and its realization are analyzed in theory, modal analysis and static analysis are made with the help of ANSYS, and the preparation of sensor probe is accomplished, Thirdly, a monitoring system hardware circuit which is composed of microcontroller STM32F103ZET6, impedance converter AD5933 and relays FTR-B3GA003Z is designed, on the basis of the circuit, the corresponding software programming is completed, and the system can do impedance measurement automatically. At the same time, in order to display the value of viscosity or density more directly, a upper computer which is matched with the circuit is designed by using Labview. Finally, this system is applied on an experiment, the results shows, in the range of (0-16)cP, the relative error range of viscosity measurement is 6.06%-6.58%. In the range of (820-950)kg/m3, the relative error range of density measurement is 6.20%-6.49%.