Research And Development Of Singlechip-based Sulfur Dioxide Detector

Combustion processes of the coal and petroleum are the main artificial pollution sources discharging the sulfur dioxide, so it is important to measure the concentration of sulfur dioxide in fume.The methods about measuring the concentration of sulfur dioxide via detector is presented in this paper. Specifically, based on the electrochemistry sensor of sulfur dioxide, we have developed a kind of low-cost and high-accuracy intellectual detector which can detect the concentration of the sulfur dioxide in fume and also can adapt to more abominable environment. The measuring principle, the overall structure, the hardware design, the realization of the software and the design of the communication interface in the detector development are studied in detail in the paper.In the hardware, the present detector consists of fume route and. According to the characteristic of the sensor, the structure of two sensors in the fume route is adopted. The temperature of the fume is lowered naturally and the water in fume is thus got rid of fast by separator of gas and water. The hardware circuit design of the system includes the circuit of detecting sulfur dioxide concentration, the temperature and humidity, the driver circuit of pump and valve, the communication interface circuit, the setting circuit of baudrate and address. Based on AT89C52 singlechip, the detector converts the faint current signal of the sulfur dioxide sensor to voltage signal through I/V convertor and the pre-amplifier. Then through the multi-range, high-accuracy A/D convertor, the signal of sulfur dioxide concentration is stored in the singlechip in the form of digital. In this system, we design the general standard RS-232/485 serial interface, the V/I converting circuit and the 4～20mA linear current interface.We have probed into application in the embedded system of C language in software design, and also have fully utilized the abundant library functions and strong data processing ability of C language. The software includes 3 parts such as controlling, data processing and communication procedure. In the paper, we give the method of checking form based on module 2 by searching the 16 bits Cyclic Redundancy Check Code (CRC-CCITT). Experiments show that the reliability in system communication is guaranteed and the computational speed is greatly improved.The focuses of this paper are: the circuit design of potentiostatic instrument and signal processing for sulfur dioxide, the communication interface design and the realization of the system software. At present, the circuit and software part of the detector have already been finished.This detector is suitable for concentration measuring in fume desulfurization project and other relatively sulfur dioxide measuring of high concentration. Its successful development has great potential in applications.