| Just as its name implies,the melting point meter is an instrument for measuring organic crystal's melting point. The organic crystal's melting point is its extremely important inherent physical and chemical parameter. Also it is the characteristic temperature of the organic crystallization's phase changing process. In the modern organic chemistry, measuring the crystal melting point is an essential method in analyzing the crystal's purity. With the improvement of the producing process, the purity of the crystal material plays a very important role in the products'quality. But there still exist some difficulties in measuring the purity of the crystal material directly. So by measuring the crystal material's melting point, the purity of the organic crystal can be determined, so as to confirm whether it does meet the product quality's requirements.At present, the precision of the domestic melting point meter is generally lower than the overseas, yet its price stays high. Therefore, developing a kind of high-accuracy and low-cost melting point meter is urgently needed. Based on studying the development of the domestic and foreign melting point meter, we design out a kind of low-cost, high-accuracy, and good linearity melting point meter in this article. This melting point instrument has the advantages of simple hardware-structure and complete-functions. In this topic, we choose MSC1210Y5 monolithic integrated circuit which promoted by Texas Instruments (TI) Corporation of America as the core chip. It owns 24 high accuracy∑-△A/D switches, programmable amplifier, 3 times of 8051 essences speeds, large capacity Flash memories storage, and it supports SPI or I 2C buses and many auxiliary equipments. With high analog-digital integration rate, it is a kind of high-performance composite signal chip. The main subject of this article is to study the algorithm in melting point temperature control, so we established a kind of system algorithm which suits to the melting point based on the improvement and innovation of the existing control algorithm PID. We use LabView software assistance to complete the adjusting of the PID controller parameter. It not only improves the PID coefficient installation effect, but also gives the experimental results in the form of charts. As a result the tester can easily analyses the experimental results and shortens the whole research and development cycle. In summary, through the research of the algorithm in melting point temperature control, I have mainly completed the following tasks in this article:1. Through consulting the correlation domestic and international data, I select monolithic integrated circuit MSC1210 to complete the hardware circuit design, which not only simplifies the hardware of the circuit, but also saves the hardware cost.2. By sending the measured signal from the serial port communication to upper monitor for processing, I complete the parameter adjusting, optimize and debug PID algorithm coefficient, reduce the debugging cycle and also improve the accuracy of the coefficient installation under the assistance of the upper monitor.3. Through the comparative study of various algorithms, I select the suitable digital incremental PID algorithm for this article. Finally I complete the adjustment of the melting point control system's non-linear error, and make some innovative research on sequence rise of temperature. |
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