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標題: | 音叉物位計之驅動電極設計 The Driving Electrode of Tuning Fork Level Sensor |
作者: | Bo-Xuan Huang 黃柏瑄 |
指導教授: | 張培仁 |
關鍵字: | 音叉物位計,振動,有限元素法,圓形壓電薄板,電極設計,等效電路, Tuning fork level sensor,Vibration,Finite element method,Circular piezoelectric plate,Electrode design,Electrical equivalent circuit, |
出版年 : | 2017 |
學位: | 碩士 |
摘要: | 現今的傳統大型工業如食品工業、石化相關產業、化學工業等,都會在儲存槽或聯通的管線中放置工業用的感測器,以監控內部原物料在產線上的狀況,達到工廠自動化的目的,其中以超聲波型、雷達型、音叉型等物位感測器最為常見。本研究主要研發新型的音叉型物位感測器,以單一壓電致動/感測層搭配不同幾何設計的上電極,來取代市售之音叉型物位感測器所使用之多層堆疊壓電層的設計,可大幅縮小音叉物位計的體積並拓展其應用範圍。本文以有限元素法分析音叉結構之應力與應變分佈;續根據應力與應變的分佈,在單一壓電薄板上設計了同心圓與三片式兩種電極設計,並探討電極面積和位置的影響。為了解音叉物位計的電訊號特性,本文首先量測所有電極設計之感測端電壓與電流,以及透過雷射位移計量測音叉在共振頻下之振動位移;接著,透過精密阻抗分析儀量測,找出壓電致動/感測元件的等效電路參數進而證明感測電壓與電流的量測結果,並且與美國專利US 6920787 B2所提出的四等分電極設計做比較。實驗結果顯示,同心圓電極與三片式電極在多種驅動電壓下,存在一個最佳的致動電極寬度,而最佳寬度即為音叉根部內側的間距。本研究設計的三片式電極在單位驅動電壓下會產生0.53 V的感測電壓、0.18 μA/mm2的感測電流密度及3.9 μm的振動位移。相較於美國專利的四等分電極設計,其在單位電壓下產生0.19 V的感測電壓、0.045 μA/mm2的感測電流密度及0.95 μm的振動位移。從實驗結果中可以看出,本文之三片式電極設計可以使音叉結構在共振時產生較大振動位移以及較大的感測電壓與電流訊號,因而利於音叉物位計之感測訊號的分析以減少錯誤的判讀。 In traditional heavy industries, such as food, petrochemical, and chemical industries, industrial sensors have been applied to the storage tank or connecting pipes to achieve accurate control or immediate monitoring. Among these sensors, level sensors are used to monitor the condition of the raw materials in the production lines, realizing automation. In this research, we develop a new type of tuning fork level sensor. This sensor is composed of only one single piezoelectric material with a proper geometrical design of electrode. To minimize the size of tuning fork, the traditional stacked-type piezoelectric film is modified. We simulate the system, and find that the region of maximum stress and strain is located at roots of tuning fork, and the maximum amplitude of displacement is also between the roots of fork, indicating this is the optimal zone for sensing. Based on these results, we propose two designs of electrodes, three-piece and concentric circle. The maximal displacements are 3.9 μm and 1.7 μm, respectively, compared with 0.95 μm from the device designed with an equally-quartered electrode (U.S. Patent 6920787 B2). Besides, the tuning fork with three-piece electrode has a significant gain, which is verified using equivalent circuit model. This significant gain allows higher accuracy of signal. The smallness and high output gain allows our new design much more competitive than many commercially available applications. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/77739 |
DOI: | 10.6342/NTU201702667 |
全文授權: | 未授權 |
顯示於系所單位: | 應用力學研究所 |
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ntu-106-R04543018-1.pdf 目前未授權公開取用 | 39.87 MB | Adobe PDF |
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