吳政忠臺灣大學：應用力學研究所吳俊億Wu, Jun-YiJun-YiWu2007-11-292018-06-292007-11-292018-06-292006http://ntur.lib.ntu.edu.tw//handle/246246/62532With the development of industries, there is a growing need for sensitive, accurate, and inexpensive sensors of measuring relative humidity. Humidity sensors are expected for a broad spectrum of applications in meteorology, chemical industry, process control, medical instrument, agriculture, and etc. A good sensor should be characterized by high sensitivity, wide dynamic range, fast response, good reproducibility, easy interface electronics, small size, and minimum cost. It is hard for single sensing system matches all these criterions. However, surface acoustic wave ( SAW) sensing devices are promising candidates to pursue the above goals. In this thesis, the 145MHz based SAW resonator is fabricated and integrated with the amplifier to form a SAW-based oscillator. To function as a humidity sensor, hygroscopic polymer polyethylenimine is coated on the delay line of the resonator as sensing film by airbrush method. Moreover, dual delay line configuration is constructed for the common mode rejection for external influences such as temperature, drift, etc. Then, the sensing devices are exposed to repeated cycles with various relative humidity to investigate the performances including sensitivity, reproducibility, and repeatability. The results reveal good linearity between frequency shifts and various relative humidity and enough short-term repeatability.Acknowledgements I Abstract II Lists of Notations III Table of Contents V List of Figures VII List of Tables IX Chapter 1 Introduction 1 1-1 Research Motivation 1 1-2 Classification of Humidity Sensors 2 1-3 Literature Review 3 1-4Contents of the Chapters 4 Chapter 2 Abbott COM & Principles of SAW Sensor 7 2-1 Coupling-of- Modes Model 7 2-1.1 First Order Wave Equations 7 2-1.2 Propagation Loss 9 2-1.3 Reflectivity Coupling 10 2-1.4Transduction Coupling 13 2-1.5 [P] Matrix 15 2-1.6 Simulation of Two-Port SAW Filter 19 2-2 Principles of SAW Sensor 22 2-2.1 Mass Loading Effect 23 2-2.2 Chemically Interactively Film 24 2-2.3 Sensitivity 25 Chapter 3 Preparation of SAW Sensor System 32 3-1 Principles of SAW-based Oscillators 32 3-1.1 Oscillators with Two-port Resonators 33 3-1.2 Fabrication of the SAW Resonator 34 3-1.3 Design of the Amplifier 36 3-2 Dual Delay Line Configuration 38 3-3Deposition of Chemically Interactive Film 39 3-3.1 Selection of Sensing Film 40 3-3.2 Spray-Coated Polymer Filmr 40 3-4 Gas Flow System for Various Relative Humidity 41 Chapter 4 Construction of SAW Sensor System & Humidity Measurements 51 4-1 Fabrication of SAW sensor 51 4-1.1 Measurement of SAW oscillator 51 4-1.2 Measurement of Dual Delay Line Configuration 52 4-2 Deposition of Hygroscopic Film 52 4-3 Temperature Effect on SAW Sensor 53 4-4 Interface of Data Acquisition & Real-time Visualization 54 4-5 Measurements of Sensors toward Various RH 55 4-5.1 Repeatability 55 4-5.2 Sensitivity 56 4-5.3 Noise & Limit of Detection 58 Chapter 5 Conclusions and Future Work 71 5-1 Conclusions 71 5-2 Future work 72 References 731677991 bytesapplication/pdfen-US表面聲波共振器溼度感測器聚乙基亞胺噴槍靈敏度Surface acoustic waveResonatorHumidity sensorPolyethylenimineAirbrushSensitivitythesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/62532/1/ntu-95-R93543010-1.pdf