Study Of Multifunctional Liquid Viscosity Detection Device Based On Rotation Method

The liquid viscosity measurement device has important application value in petroleum, chemical and food industry. There are some shortages of the existing liquid viscosity measurement methods and measuring devices.In this thesis, the existing methods and devices of liquid viscosity measurement are introduced and summarized at home and abroad. And the rotation method, one of the traditional measuring methods, is studied in depth. Finally, a new method based on rotation method is proposed. This method changes the measurement of viscous torque into the measurement of deceleration time by proper simplifications to fluid viscosity definition. Based on the method, a multi-function liquid viscosity measurement device which can measure liquid viscosity, liquid temperature and pH value, is developed. The thesis gives detailed description of the system design, including viscosity detection structure, temperature sensor and pH sensor with the signal processing circuit, and the measurement and control system based on DSP, which is used as calculation and control core. The system contains the control of the motor speed and the measurement of deceleration time, and the detection and transformation of the input signals is also included. The general timer of DSP is used to measure the deceleration time, whose precision can absolutely meet the system requirements. Therefore, the torque sensor need not be used in the actual measurement, thus simplifying the structure of the viscosity measurement unit. In which the methods improving stability and accuracy are used, a self-tuning fuzzy PI control algorithm is used for motor control, M/T algorithm is used for the measurement of the speed, and a calibration method is used for the improvement of the precision of the conversion.In this thesis, the simulation model of the system is built by using Matlab/Simulink platform. A device of the system is developed and the viscosity measurement experiments are done by using sucrose solutions with different percentage. The viscosity measurement method has good stability by comparison and analysis. The feasibility of the method is verified. To improve the measurement precision further, the measured values are properly corrected. At last the relative error is less than five percents.