- 學位論文
攜帶式脈衝調控型氣體感測系統與電子鼻系統校正平台之最佳化
Optimization of a Portable Pulse-Modulated Gas Sensing System and a Calibration Platform toward Electronic Nose
摘要
電子鼻是一種模仿嗅覺感測與智慧分析功能的氣體感測系統，以用於辨識或量化某些氣體濃度或其成分組成。在此論文研究中，我們設計了一套利用脈衝式電壓調變進行量測的可攜帶式氣體感測器，用於環境氣體的監測，同時建構一套氣體校正平台用以評估對於各種氣體種類及濃度變化的反應作為電子鼻系統的基礎。這套攜帶型感測系統是以低耗能的微處理器 (MSP430FG439) 為核心，其優點除了低耗電量、體積小外，亦可做即時運算。氣體感測器的部分是以二氧化錫 (SnO2) 為感測材料的金屬氧化物型氣體感測器，並有液晶顯示器做即時的資訊顯示以及 ZigBee 無線傳輸模組可將資料傳送到電腦端分析處理或儲存。金屬氧化物型的氣體感測器其感測材料需被加熱才具有最佳感測活性，為能控制工作溫度與效率，設計使用脈衝式循環加熱工作模式，其優點是可以固定感測器的工作溫度，達到良好的再現性，避免因為連續的加熱方式使感測器的工作溫度持續提升，影響到其再現性，除此之外，亦可延長感測器的使用年限以及減少系統的耗電量(減少67%的耗電量)進而達到長時間監控的目的。我們也利用調變循環加熱的參數，如控制加熱時間的長短，控制電壓的大小而改變加熱的溫度，進而使系統的表現達到最佳化。 校正平台是一個以鋁合金材料為底座並在其上蓋上一個玻璃鐘罩所構成，並且將此裝置放於化學抽氣櫃內。我們可以利用這套校正平台量測出氣體感測系統的靜態與動態校正曲線。目前共可進行丙酮、乙醇以及甲醇三種氣體的測試，並利用體積稀釋法調配各種不同的濃度，分別為5、10、20、30以及40 ppm。實驗結果發現，此氣體感測器對於酒精感測最為靈敏，對於丙酮感測則最不靈敏。除此之外，此系統可以量化這三種氣體的濃度，並且其反應趨勢在氣體濃度10到40 ppm之間有很強的線性關係。
並列摘要
An electronic nose is a gas sensing system which mimics the mammalian sense to distinguish and quantify some components of odors. In this thesis, a portable gas sensing system based on the cyclic heating method modulated by voltage was implemented to do environmental monitoring and a calibration platform was set up to evaluate the response of the gas sensing system to some odors. This portable gas sensing system was based on the microcontroller MSP430FG439 which advantages were low power consumption, small size as well as real-time processing. The gas sensor of this system was tin oxide (SnO2) gas sensor. Furthermore, there were a liquid crystal display (LCD) to show some information about odors in real-time and a wireless communication module, ZigBee to transmit data to a terminal computer to store or analyze. Because the SnO2 gas sensor would be activated by heating the sensing material, the cyclic heating method was used to heat the SnO2 gas sensor so as to achieve better reproducibility. Moreover, the cyclic heating method could avoid increasing the operation temperature due to the accumulation of heat. Otherwise, it could also extend the lifecycle of the SnO2 gas sensor and lower the power consumption of the gas sensing system (67% off) to do long-term monitoring. The parameters of the cyclic heating method such as the duration of heating or operation temperature controlled by the voltage were modulated to optimize the performance of the gas sensing system. The calibration platform was constructed by an alumina stage covered with a glass cylinder chamber and it was put inside a fume exhaust hood. The static and dynamic calibration curve of the gas sensing system was evaluated by this calibration platform. Three samples, acetone, ethanol and methanol with the concentration of 5, 10, 20, 30 and 40 ppm were introduced to the gas sensing system and the gas sensing system was the most sensitive to ethanol but less sensitive to acetone. Otherwise, the gas sensing system could quantify the concentration of these three samples and it had good linear relationship between the reactive intensity and these three samples with the concentration from 10 to 40 ppm.
參考文獻
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