Research And Design Of Intelligent And Pipe-state Liquid Ultrasonic Flowmeter

In the field of industrial flow detection,ultrasonic flowmeter is playing an important role with its advantages including non-contact character,high accuracy,low cost,easy installation and so on.The domestic research of ultrasonic flowmeter starts relatively late.And there still exist a large gap in the aspects of accuracy,stability and reliability compared with the research level of well-known foreign corporations.So our ultrasonic flowmeter market is currently dominated by foreign products.In order to further improve the research and development level of domestic ultrasonic flowmeter and enhance the market competitiveness of domestic brands,in this paper,with the MCU and CPLD as the core,a liquid ultrasonic flowmeter based on time difference method is designed.This thesis makes an in-depth analysis on the main aspects of ultrasonic flowmeter,including hardware platform,time-measurement technique,software processing methods and experimental results verification.The hardware design of ultrasonic flowmeter mainly includes the design of the sensors and circuits.Using a Z-type tubular structure design,sensors can complete transmitting and receiving ultrasonic waves by containing a piezoelectric ceramic transducer wafer.The design of hardware circuits adopts modular method,and the modules include ultrasonic transmitter,echo reception and microcontroller peripheral circuits.The system generates a pulse signal of 1MHz by CPLD.After power amplifying,the system drives the transducer to emit ultrasonic waves.AGC circuit is used to adapt the complex field environment of pipe caliber and the impurities being measured and adjust the echo gain automatically when echo reception comes.MCU peripheral circuits include OCT output,485 communication,display output and other modules.Loose measure and exact measure are designed in CPLD.Loose measure is counted through the entire clock cycle.Based on delay line interpolation method,exact measure of under whole clock cycle is completed by using a way of negation gate combination to build a delay chain.The combination of the two methods can make the temporal resolution achieve grade ps.On the software processing,the complex filtering method for noise reduction of time difference data is not only accessible,but also has a good filtering effect.Finally,with the application of water flow calibration device of ZhonghuanTianyi corporation,calibration method is used for calibration verification of different caliber flowmeters under different flow points.Experimental results show that this prototype has a high repeatability and the error level of this prototype is 1.Thus,this prototype can meet the practical needs of industry scene.