Research On Method Of Liquid-level Intelligent Detection For The Ubbelohde Viscometer

Viscosity measurement plays an important role in the application of many modern production fields such as crude oil extraction,textile production,and lubricating oil use.In recent years,the demand for viscosity measurement accuracy and adaptive performance has been increasing,and the continuous improvement of viscosity measurement methods has been promoted,enriched and developed.Ubbelohde viscometer is a measuring instrument for measuring viscosit y based on the capillary method.It is widely used in industrial production.The liquid-level detection through the timing point of the capillary chronograph is a key factor in visco sity measurement,so the accuracy and efficiency of the viscosity measurem ent are largely determined by the liquid-level detection,real-time performance of the measurement time and the intelligence of the viscosity measurement instrument.As the liquid-level detection process of current Ubbelohde viscometers is usually affected by lots of noise as well as the fact that the timing point is inaccurate and the adaptive and real-time performance of the measurement is not high,a liquid-level adaptive detection method is proposed in this thesis to fulfill the automatic liquid-level detection and suppress the effect of noise.Based on the method,an intelligent detection system of Ubbelohde Viscometer is designed with the embedded μC/OS-III operating system for task management and scheduling.EmWin graphical software libraries are used to design a human-computer interactive interface for enriching the function of human-computer interaction.Firstly,the background and significance of viscosity measurement and the concept of viscosity are introduced.Then various types of viscosity measurement methods are analyzed.After the introduction of viscometers with traditional and new measuring methods,the research and analyses of the existing liquid-level detection methods and the current development status of Ubbelohde viscometer are carried out.Secondly,by studying the principle of liquid-level detection,and detecting the signal characteristics of liquid levels,an adaptive liquid-level detection algorithm based on K-L divergence is proposed to get timing points accurately from information entropy.The implementation method of the algorithm is described in detail,and the anti-noise performance simulation experiments are conducted.The results verify that the liquid level detection algorithm can effectively suppress the influence of noise and ensure the measurement accuracy.Thirdly,the composition and working principle of Ubbelohde Viscometer are discussed.The intelligent liquid-level detection system of Ubbelohde Viscometer is designed and implemented.The schematic circuit diagram of each hardware module is given and the PCB of the system is designed.Then the μC/OS-III embedded operating system is transplanted to STM32F407.Each user’s task and priority are assigned and the systematic software design is finished.Finally,a level detection and viscosity measurement experiment based on liquid-level detection system is conducted and the results show that the liquid level detection method proposed in this thesis has good self-adaptability.The repeatability is less than 0.35% and the measurement error is less than 0.10%,which is better than the national viscosity test standards.In addition,the instrument has a good real-time performance and human-computer interaction.