A Study On Rotating Type Pulp Consistency Transmitter

The pulp is two-phase fluid composed water with suspending fiber. Because of the complex characteristics of multi phase fluid system, such as pulp, its consistency measurement is more difficult than some commonly consistency measurement. On the current, consistency measurements for it are almost un-line and online but precision is not high. The online consistency measurement of pulp has a great significance in the industry producing such as measuring, reliability of control & operation and metering, and so on. At present, dynamics method is widely used in engineering. Dynamics method is divided into outer-rotating,inner-rotating,fixed-blade method and moving-blade method and so on, among which the ratio of performance and price of moving blade method is the best. But it belongs to products of middle-end, and don't suit the situation of asking for high measurement precision. Comparing moving blade method, inner-rotating method is a kind of closed-loop meter, and it has high measurement precision, sensitivity and stability. In the thesis, inner-rotating method is adopted and researched to measuring the pulp consistency. In this thesis, firstly, the measuring principle is introduced. Secondly, dynamics model of system is built according to the mechanical structure. Thirdly, the evaluation and analysis on the stability, and then the result of stability is obtained. Fourthly, hardware design and software program for the inner-rotating consistency measurement meter are explained in detail. At last, sensitivity, stability and response speed are analyzed in qualitatively. The performance of the instrument represents not only on the mechanical structure, but also on the choice of control algorithm. To the balance-structure, on the one hand, the right sense organ is important to the system performance, for it directly getting the measurement signal. The exact measurement signal is the key of this system. On the other hand, feedback element is also very important that is the character of close loop system. In the secondary meter, control algorithm affects sensitivity and response speed of system directly. Modified digital PID algorithm is adopt to improving the system's sensitivity and response speed. Result shows the algorithm can not only eliminate dead zone but also accelerate response speed. As result, author believes it is a kind of suitable control algorithm for the system. For the sake of convenient modification of the parameters on the locale, code-download and software upgrade of the system at any moment are required intensively. In this thesis, the idea of online_ programming is brought out for the requirement. According to all kinds of online_ programming methods and the real situation of system, the method of microchip & FLASH is chosen and it has a good effect. Experiment proves that Rotating Type Pulp Consistency Transmitter has achieved prospective aim that is high of measurement precision, sensitivity, stability and reliability.