MSP430单片机氯气联机检测系统设计外文文献及翻译 第3页
Chlorine gas sensor adopts Membrapor’s Cl2/C-20 constant potential electrolytic chlorine gas sensor, which has the advantages of high sensitivity, good linearity, stable operation and moderate cost [7]. Fig 12 shows the Amplification circuit. A1 is a voltage follower, provides constant voltage for the sensor. The output current from sensor is amplified by A2, then send to the ADC of MSP43F2013. Result from circuit simulation shows that this circuit can change 20uA signal into 2.4V with good linearity.
Fig. 12. Amplification circuit
Data from experiment shows that the output signal of chlorine gas sensor is easily affected by temperature.
Fig 13 shows that the signal of 0℃ is only 90% of that of 20 ℃ . Thus, this device has to actualize the
temperature compensation of chlorine gas signal. The temperature adopts 18B20, which converts 12-bit temperature to digital word.
Fig. 13. The relation between temperature and output signal
5. Software system design
The software of the system is developed under IAR,
with the C language [8].
5.1. Host instrument software system design
Fig. 14. Main program flow of the host instrument
Fig.14 shows the main program flow of the host instrument. The initialization program realizes the initialization of watchdog and real time clock, USART, timers, I/O. System self-check program realizes the function of checking communication, SD card and real time clock. RS485 communication program realizes the communication with chlorine gas transmitters one by one. The host instrument sends the request, and transmitters answer. Data processing program realizes the temperature compensation of chlorine gas signal, alarm judgment. HMI program realizes the functions of display and keyboard code detecting. Data storage program realize the function of saving data of Chlorine Gas density into the SD card. GPRS communication program realizes the function of communication with the control center.
5.2. Chlorine gas transmitter software system design
Fig. 15. Main program flow of the chlorine gas transmitter
Fig.15 shows the main program flow of the chlorine gas transmitter. The initialization program realizes the initialization of watchdog and real time clock, asynchronous serial communication interface, timers, I/O. System self-check program realizes the function of checking chlorine gas sensor, temperature sensor and communication. Measuring chlorine gas program realizes the function of measuring Concentration of Chlorine Gas. Measuring temperature program realize the function of measuring temperature of the monitoring area. RS485 communication program realizes the communication with the host instrument. As the MSP430F2013 do not have USART, asynchronous serial communication is realized by software.原文请找腾讯752018766,辣-文^论,文.网
http://www.751com.cn6. Conclusion
It is proved by experience that this device can realizes detecting concentration of chlorine gas in the monitor area. The measurement range of the device is 0~20 ppm, resolution is 0.1ppm, response time is less than 30 sec and the detecting error is less than 2%. This design can meet the real application in papermaking industry, textile industry, pharmacy, plastic industry and water treatment industry. This device is feasible and has wide application prospects. After changing the type of gas sensor, this device can detect other poisonous and harmful gas.
7. Acknowledgment
This paper is supported by the National Natural Science Foundation of China （ NSFC-60604024 ） , the Key Science and Technology Plan Program of Science and Technology Department of ZheJiang Province(2008C23097), the Scientific Research Plan Program of Education Department of Zhejiang Province (20060246) and the Sustentation Plan Program of Youth Teacher in University of Zhejiang Province (ZX060221).
8. References
[1] Wang Huibin, "The Effect of Low Concentration Chlorine on Workers' Ventilation Function ", Chinese Journal of Radiological Health, vol 16,(2)2007, pp.227. [2] Wang Zipu, Chen Gongbei, Chen Fei, A chlorine gas detecting alarm instrument, China Patent, 91214946.9.
[3] Zhou Yongqing, "Design of pocket Cl_2 alarm device", Journal of Transducer Technology, vol 23,(11)2004, pp.41-42.
[4] OLDHAM GROUP, MX 48 : measurement and alarm unit,
[5] He Xicai, Xue Yongyi,Sensor and Its Application,China Machine Press, Beijing, 2003.
[6] Liu Kuixue, Chen Lihua, Lv Qinghua, Quan Baofu, "Portable wireless toxic gas detection system", Chinese Journal of Scientific Instrument, vol 27,(6)2006, pp.1302-1304.
[7] Cao Ye, Zhang Guangyou, Hu Wenxiang, "Automatic Monitoring Techniques for toxic, harmful and combustable gases and their Applications", Modern Instruments, (2)2001, PP.41-43.
[8]Hu Dake, C Language Programming and Development of MSP430, BeihangUniversityPress,2003.上一页 [1] [2] [3] [4] 下一页
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