低濃度室內環境氨氣偵測儀器原型機之開發

Abstract

本實驗搭配由國立交通大學光電所所提供的氨氣傳感器元件與Arduino 一並使用，建立低成本的可攜式環境氨氣偵測儀，分析學校廁所周圍的環境氨氣濃度；並架設氨氣濃度生成系統作為實驗室內各濃度氨氣來源。由交大光電所所提供的氨氣傳感器元件是由有機半導體作為傳感器主要的感應材料來進行氨氣的感測，當有還原性氣體通過時，會吸附在表面上並造成半導體的背景電流下降，由量測電流下降的幅度推算氣體濃度。原型機的建立主要分為架構部分與氣體管線部份，透過 Arduino 程式控制電磁閥與收取類比訊號的功能來儲存訊號並分析。實驗一開始先進行氨氣生成系統的建立，透過標準氨氣氣體鋼瓶與質量流量控制器來調整至所需的氨氣濃度，並使用衝擊瓶將氨氣通入水中量測 pH 值變化來記錄實際生成的氨氣濃度，之後完成原型機的組裝並進行測試與實際採樣分析。視傳感器元件的狀態，目前能夠偵測到濃度低至 100 ppb 、高至 2500 ppb 的氨氣。實現以低成本與低技術要求完成室內氨氣濃度分析的功能。日後藉由Arduino 的擴充可能性與便利性，能夠做到無線傳輸的功能，實現實時大範圍即時環境監測，建立雲端監測網。

In this study, we’ve combined Arduino with the ammonia sensor unit, which provided by NCTU Department of Photonics Institute of OE Engineering to constructed a low-cost portable environment ammonia sensing device for analyzed ambient ammonia concentration around the school toilet, and built an ammonia concentration generating system as the ammonia source in the laboratory. The ammonia sensor unit used Organic semiconductor as key material for sensing ammonia. When the reduction gas contacted with the sensor unit. The decrease of background current caused by the absorption of the reduction gas, then computing the concentration of ammonia by the variety of background current. The establishment of the prototype was mainly divided into the structure part and gas pipeline part. Controlling the solenoid valve and saving the analog signals by Arduino. At the beginning of the experiment, the ammonia concentration generating system was built. The concentration of ammonia was adjusted by standard ammonia cylinder and the mass flow controller, aerated to H2O by impringer and measured the pH value, and estimated the concentration of ammonia formed by generating system. After the completion of the prototype assembly and correction and real sampling analysis. According to the state of sensor units, we could measure successfully the concentration of ammonia as low as 100 ppb, and up to 2500 ppb. Demonstrated that we could complete to analyze the indoor ammonia concentration in the low-cost and low- technical requirements. In the future, arise from the extension possibility and convenience of Arduino and modules, it can also realize the wireless transmission, achieve the real time large-scale environment monitor.