Research And Realization Of Viscositycoefficient Measuring Instrument

Accurate measurement of viscosity coefficient plays an important role in scientific research and industrial production.There are many methods for measuring viscosity coefficient,but there are few researches on measuring liquid viscosity coefficient by forced vibration method,and the measurement accuracy of similar instruments is not high enough.This paper designs a liquid viscosity coefficient measuring instrument based on forced vibration method,and the main research contents are as follows:(1)Based on the basic concept of viscosity,the influence of temperature and pressure on the viscosity coefficient of liquid is analyzed.The dynamic equation of viscosity coefficient measurement under forced vibration is established and the motion law of vibration system during measurement is calculated by MATLAB.Accurate measurement of phase difference of two-way signals is the key to measuring liquid viscosity coefficient by forced vibration method.In this paper,the phase difference is measured by full-phase FFT method with higher accuracy and smaller calculation amount which improves the measurement accuracy and response speed of the instrument.(2)According to the principle and process of viscosity coefficient measurement by forced vibration method,the mechanical structure and control circuit of viscosity coefficient measurement instrument are designed.In the mechanical structure,the coincidence of the lower sample cup with the central axis of the sensor head is the key to viscosity sensing.In order to improve the reliability of the instrument,an image calibration system for the central axis of the sensor head of the sample cup is designed.In the control circuit,the internal friction measurement circuit of the vibration system and the automatic zero adjustment circuit of the silicon photocell stepping motor are mainly designed.(3)Based on LABVIEW platform,a software control system of viscosity coefficient measuring instrument is built,which realizes the functions of driving signal transmission,silicon photocell signal reception,signal waveform display,data analysis and processing,storage,etc.In the aspect of signal processing,wavelet denoising,phase angle measurement and image analysis and calculation of two-way signals are realized by combining MATLAB.The control system has many functions.According to different functional requirements,this paper designs three subsystems: forced vibration,automatic zero adjustment and image calibration according to the experimental measurement process.After the measuring system is debugged by software and hardware,liquid at different temperatures is measured according to the steps of automatic zero adjustment,image calibration and forced vibration.In this paper,the analysis of experimental data shows that the viscosity coefficient measuring instrument designed has certain effectiveness and practicability.