以單一氣體感測器偵測多種氣體之演算法開發

Abstract

本論文旨在發展一個以單一氣體感測器偵測多種氣體的混合氣體量測系統，應用於偵測下水道對人體有害的混合氣體。量測環境中的混合氣體，同時針對前端的感測器，在加熱器中使用不同的電壓，以改變感測器的溫度，接著利用演算法進行分析，使混合氣體達到定性與定量。對於待測環境，整個系統使用少於待測氣體數量的感測器來完成整個判斷。改變感測器溫度的方式，本論文提出兩種，其一稱為靜態調變，在感測器與氣體反應時，前後各使用一種加熱器電壓，使感測器與氣體反應兩次皆達到穩定狀態；其二稱為動態調變，在感測器與氣體反應時，持續切換加熱器電壓的狀態與時間，使加熱器的電壓呈現週期性方波。由上述兩種調變方式，前端的感測器不需採用多顆感測器來形成陣列，訊號處理時不用額外的演算法進行特徵擷取與圖形辨識，並且直接在時域處理訊號使系統在應用上更為簡單。除了事後分析方法的可行性，也將此方法寫入MCU來驗證其功能，達到即時分析與顯示的目的。

This thesis aims to develop a system of mixture gas measurement which uses single gas sensor to detect varied harmful gas in sewer. Measure mixture gas in the environment; meanwhile, use difference voltage in the heater of front sensor in order to change sensor’s temperature. Then, use algorithm to distinguish mixture gas for achieving qualitative and quantitative. For the environment, the system uses single gas sensor which is used to detect varied mixture gas to complete all analysis. For the approach of changing sensor’s temperature, the thesis proposes two methods. First, when it has a reaction between sensor and gas, use two difference voltage in the heater separately to make the reaction steady both times. It is known as static state modulate. Second, when it has a reaction between sensor and gas, constantly vary voltage’s state and time in the heater to show a square wave of period. It is known as dynamic state modulate. The above-mentioned methods make that front sensor do not need to use multi-sensors to form array, single process do not need an additional algorithm to feature extraction and pattern recognition, and the application of system can be easier in single process in time domain. Besides viability of analysis method after measurement, also verify this method on MCU to achieve real time analysis and display purpose.