Applications of the Piezoelectric Elements on the Ultrasonic Level Indicators

• Main Authors: Chih-Hua Chang, 張志華
• Other Authors: Yu-Kang Lo
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/77532610209726981261

碩士 === 國立臺灣科技大學 === 電子工程系 === 91 === The ultrasonic transducer is a crucial component in a ultrasonic level indicator. The ultrasonic transducer is mainly composed of the piezoelectric device. To solve the “dead zone” problem in measuring the distance, this thesis will focus on the discussions about the basic principles of the piezoelectric elements. Eight equations regarding the piezoelectric effects are introduced. The equivalent electric circuit models of the piezoelectric device are derived. Then an improvement circuit is proposed in this thesis to eliminate the echoes of the driving signal for the ultrasonic transducer. Experiments on a commercial ultrasonic level indicator are conducted to verify the performance of the improvement circuit. Also the equivalent circuit model and the turns ratio of a piezoelectric transformer are presented in this thesis. The relationships among the dimensions and parameters of a piezoelectric transformer and the voltage gain, output power and efficiency are derived. The feasibility of replacing the traditional electromagnetic transformer with the piezoelectric transformer in the ultrasonic level indicator is discussed.