Research And Development Of On-Line Measuring System Of Liquid Viscosity Based On Soft-Sensing Technology

Viscosity is one of the most important physical properties of liquid, and also is an important standard character in the industry of foodstuff, oil paint, polymerization coating, petroleum and other industry. It is very significative to measure liquid viscosity in industrial production and basic study. The domestic on-line viscometer is not satisfying all in function, precision and stability, while the viscometer overseas has good capability, but also is very expensive. Therefore, research on on-line measuring of liquid viscosity is quit important.We combined PLC, Configure software and industrial control computer to develop an on-line measuring system of liquid viscosity, main tasks of which are enhancing measuring precision, reducing measuring cost and realizing measuring on-line.In this paper, we detailedly discuss the fundament and whole scheme of on-line measuring of liquid viscosity from basic theory, hardware composing and software designing. Applying soft-sensing technology to measure viscosity is advanced, and it has three main merits. Firstly, the problem of traditional viscosity measuring instruments perform badly when they are used to measure on-line is solved, secondly, measuring cost is reduced consumedly, finally, maintenance is convenient for the parameters of model are easy to be modified. In order to ensure the accuracy of the model, we apply the statistic discriminance and method of filter to do data pretreatment, and modify the model in time when the model output error beyond limits.To the request of real-time measuring, the communication between PLC and PC is established, and we design data acquisition programmatic which the analog data filter and A/D conversion is realized. Convenient for monitoring liquid viscosity, we design monitoring interface with MCGS and divide it into four function modules, which makes the whole system visual and systematize.Communication between MCGS and MATLAB was realized through DDE technology, and the unsubstantial function of data processing of MCGS is solved availably. Meanwhile, we storage large numbers of collecting data in Access database with SQL technology convenient for reading and management.