Design And Implementation Of Water Meter Based On Condensation Gravimetric Method

The health problem caused by air pollution has been paid great attention by the governments and people of all countries. The problem of controlling air pollution is mainly focused on the management and control of flue gas in thermal power plant and industrial boiler. Humidity of flue gas, one of the important parameters of flue gas conditions, has great influence on desulfurization and dust-removal system of flue gas. Therefore, the research on the measurement technology of flue gas humidity is of great significance. According to the principle of gravimetric method, aimed at the defects of the existing gravimetric method measuring device, this paper designs a measuring device of flue gas humidity based on condensation gravimetric method. The main work is as follows:1. In view of the deficiency of the existing gravimetric method, the following improvements are proposed. Air tightness of the device was checked before measuring. A condenser between the sampler and the drying tube was connected to improve the accuracy of measurement by drying after condensing. In order to improve the degree of automation, the weighing platforms for the condenser tube and the drying tube were installed respectively to measure the moisture content of condensing and drying constantly. A dew-point-meter was connected after the drying tube to measure the dew point of residual moisture of flue gas after condensing and drying, which was used to judge the effect of moisture absorption of desiccant, and then the moisture content of flue gas was calculated after condensing and drying.2. Aimed at the above improvement, the STM32 processor was selected for hardware platform, and the work principle of each module was introduced in detail. The design scheme of hardware circuit was also elaborated, mainly including water weighed circuit, level detected circuit, air tightness detected circuit, mass flow controller circuit for flow controlled and sampled, temperature monitored circuit for the condenser, EEPROM storage circuit, sampling pump controlled circuit, display and key circuit and some peripheral circuits.3. In software selection, firstly, the design process and design ideas of software were described in detail. Inspired by the thought of modular programming, the software was divided into small pieces to progressively realize. Then, focuses on the description of the initialization of system timer, system clock, interrupt vector and serial port. On the basis of above, we write application to realize LCD initialized and data written, IIC bus data transmission, system parameter collection, data storage and other tasks. In order to effectively suppress the random pulse interference, the data of the obliquity and weight was processed by using the algorithm of removing extreme value and moving average, Temperature compensation was given based on BP neural network, and the effect was significant.4. In order to verify the filtering algorithm which can suppress the random pulse jamming in weighting results, the results of A/D conversion were displayed on the computer by using the serial port. By the comprehensive analysis of the laboratory data of humidity measurement and the live data which measured from machine which used resistance, capacitance moisture and laser, the results show that the relative deviation is large in low humidity, but can properly be solved by extending the sampling time to increase the moisture content of condensation and absorption. In the case of high humidity, the relative deviation is small. It is with better correlation compared with resistance-and-capacitance method, laser method, and wet-and-dry-bulb method which meets the requirements of reliability and stability.