標題: | 微小化非色散式二氧化碳氣體感測器氣腔設計 A Small-sized Non-dispersive Infrared Carbon Dioxide Sensor Chamber Design |
作者: | 吳承泰 趙昌博 Wu, Cheng-Tai Chao, chang-po 光電系統研究所 |
關鍵字: | 比爾-朗伯定律;氣體感測器;二氧化碳;中空波導;Beer-Lambert law;gas sensor;carbon dioxide;hollow waveguide |
公開日期: | 2016 |
摘要: | 本論文提出一微小化非色散式二氧化碳氣體感測器之氣腔設計,其微小化的目的為將一高精準度的二氧化碳感測器整合於智慧型手機中,隨時監控使用者周圍之空氣品質。基於朗伯-比爾定律,單色光照射於介質後,部分光能會被介質吸收,因此透射光強度就會減弱,以減弱的光強度推斷出氣體濃度的方法稱為非色散式氣體感測。一非色散式氣體感測器包含紅外線光源、氣腔、光感測器及驅動與讀取電路,本論文專注於氣腔之設計,其中氣腔使用的是有高反射係數的鋁材質,以及尺寸如同光纖具有高反射率的中空波導。氣腔之設計分為軟體模擬和實際測量兩部分,在軟體模擬部分,使用COMSOL軟體,模擬氣腔的氣體擴散速度,以及使用光學模擬軟體TracePro,針對氣腔的大小、形狀及材質,模擬紅外線光在裝有二氧化碳氣體的氣腔內,其氣腔內紅外線光的反射強度和吸收程度,找出較適合整合於智慧型手機中的,微小化非色散式二氧化碳氣體感測器之氣腔設計,並將其氣腔實體化,並進行實際測量。本論文所設計的金屬氣腔,為長度5公分、內徑5毫米、厚度0.5毫米的鋁製氣腔,而本文所設計的中空波導氣腔,大小則為長度6公分、內徑1毫米、厚度0.25毫米的中空波導氣腔。其所對應之CO2濃度為0~3000 ppm,準確性為100 ppm±5%,Time constant 5秒內。本文設計的鋁製氣腔和中空波導氣腔,其大小都小於市面上的氣體感測器,並可以整合於智慧型手機中。 A new types of miniaturized non-dispersive infrared (NDIR) sensors for CO2 are designed, fabricated and optimized. Non-dispersive infrared sensors (NDIR) have been proven effective in sensing ambient concentration levels of CO2, which can serve as the indicators for air quality. A typical NDIR sensor as shown in the figure below consists of three main components; an infrared light-emitter (light source), a gas chamber, a photo detector (PD, light receiver), and associated drive/readout circuit. In operations of such NDIR sensors, as the infrared emit through the gas chamber, the gas molecules of CO2 in the designed chamber absorb the energy of the infrared light in specific wavelengths --- CO2 (4.26μm). Since the amount of absorbed energy depends on the level of CO2 concentration in the gas chamber, the output voltage level of PDs reflects successfully the ambient gas concentrations of CO2 for sensing. The optics of the emitted light in the designed gas chamber will be simulated based on race tracing with the goal to minimize the chamber size, while maintaining required thermopile sensitivities, in order to fit in the confined inner space of a larger-sized cell phone. |
URI: | http://etd.lib.nctu.edu.tw/cdrfb3/record/nctu/#GT070158024 http://hdl.handle.net/11536/139199 |
顯示於類別: | 畢業論文 |