Measurement and Identification of Liquid Loadings Using SAW Liquid Sensors

• Main Authors: Chang, Shi-Yuan, 張世源
• Other Authors: Ro, Ru-Yen
• Format: Others
• Language: zh-TW
• Published: 1998
• Online Access: http://ndltd.ncl.edu.tw/handle/39506115614577152134

碩士 === 義守大學 === 電機工程研究所 === 86 === 　　Propagation characteristics of surface acoustic wave (SAW) produced by the interdigital transducers on piezoeletric substrates, are functions of electric and acoustic properties of liquid loadings. The SAW liquid sensor is designed to detect variations of propageation characteristics and furthermore to recognize liquid loadings. In this thesis, a SAW liquid sensor for measuring and identifying liquid loadings is developed using a measurement system which can chacterize propagtion characteristics of SAW along with the utilization of principal component analysis nad the neural network method for pattern recognition. The accuracy of the measured phase velocity of the metal surface is 0.13%. Deionized water and aqueous solutions with different mass concentrations of potassium chloride (KCl) and sodium sulfate (Na2SO4) are characterized using the measurement system. Effects of conductivity and frequency on the fractional velocity change and transmission coefficient change are investigated. The relaxation phenomena are observed in the curves of the fractional velocity chagne and transmission coefficient change. The principal component analysis and neural network method then is applied for classifying and identifying aqueous solutions with different conductivities. Good recognition results are obviously observed. Results obtained cae be used for the design of SAW biochemical and biomedical sensors.