- 學位論文
利用Fluoropolyol 薄膜與表面聲波元件之氣 體辨識研究
Study of Vapor Recognition by Fluoropolyol on SAW Oscillators
摘要
表面聲波元件(Surface Acoustic Wave, SAW)因其所具之質量負載效 應，使該元件於表面質量變化時，基板波速亦隨之變化，並可藉觀測其中 心頻率變化達到偵測之目的，故當其表面具有氣體可逆吸收之聚合高分子 薄膜時，便可應用於化學氣體感測的偵測辨識。本研究論文即選擇溫度延 遲特性良好的ST-Quartz 為基材，進行表面聲波元件之製作；且於表面聲波 振盪線路設計製作上，則選擇架構適合表面聲波元件的皮爾斯振盪器，以 利製作出雙埠表面聲波氣體感測器，量測頻率響應特性得到的結果其中心 頻率為157.11MHz，輸出振幅為1.51 dB。 除設計表面聲波振盪器外，為有效快速檢測不同薄膜對有機氣體之感 測特性，且減少人力之耗損與人為誤差，亦同步設計以資料擷取卡為控制 擷取介面的自動化擷取系統；另外本研究論文選擇了FPOL、NBR、PIP、 SXFIP 四種不同吸附特性的薄膜，並將之塗佈於表面聲波元件上，且同時 針對待測氣體如酒精、甲苯等..有機氣體進行氣體感測實驗。 經過氣體感測實驗，以30℃、50℃、70℃三種不同的溫量設定，經由 感測薄膜達到飽和點下，可得到氮氣與酒精之間的漂移量，實驗中四種不 同吸附特性的薄膜皆具有穩定及重複性的表現，使其感測結果具有實用性 的價值。 此外，在表面聲波氣體感測器之辨識功能上，利用主成分分析法作為 氣體的辨識及分類，其主要目的是在於將許多變項予以減少，並顯出氣體 之間個別差異及其間的權重關係，為獲得一具辨識氣體種類、分析成分物 質的感測器。
並列摘要
Surface acoustic wave (SAW) devices coated with specified polymer films as chemical sensor have been widely used in detection of a variety of gases. In this thesis, a highly sensitive and simple assembled SAW measurement platform is built. This platform is configured with a SAW oscillator consists of SAW delay line and low pass filter. This stable output frequency has been measured by the 32-bit counter of data acquisition device (DAQ) and linked to personal computer through universal serial bus interface (USB) in order to monitor the frequency shift. This platform has been measured that the frequency accuracy is less than 100Hz with reliable measured results which has capability of monitoring the characteristic of SAW sensor on gas detection. In this thesis, the platform has been used for mass and temperature sensing. Results were obtained by data acquisition system developed by LabVIEW with verities of film SAW devices. Finally, principal component analysis (PCA) is introduced to discriminate gases as a pattern recognition technique. New data of unknown gases are tested and the identification results demonstrate the potentiality of this method.