Design And Realization Of Time-difference Ultrasonic Flowmeter Based On Phase Shift Modulation Technology

When measuring the flow rate with ultrasonic flowmeter,the loss of pipe pressure can be ignored,the flow of different pipe diameter can be measured,it has no requirement for medium,It can be used to measure the flow of dangerous medium,and it is convenient to install and maintain,and has a great market share.In 1960s,China's ultrasonic flow meter industry began to start,and technological level in the field of ultrasonic flow measurement has a relatively large gap compared with Germany,the United States and other countries.Therefore,designing an ultrasonic flowmeter based on innovative technology is in line with the development requirements of China's flow measurement technology.In order to solve the small flow measurement problem of small pipe diameter,the design of ultrasonic signal processing based on phase-shifting modulation detection technology is proposed.The time difference method is used as the basic measurement principle,by studying the model and method of phase shift keying modulation identifying corresponding wave,a time-difference ultrasonic flowmeter based on the phase-shift modulation technique was designed.The phase detection technology in this measurement system is used to process the received signal,the measurement error caused by uncertainty of the arrival time of the received signal has been solved.In order to extend the sound path,the U-shaped method was used for the pipe design,two alloy baffles were installed inside the measuring pipe section as reflection devices.This thesis first introduces the research background of the project and the development of ultrasonic flowmeters at home and abroad,it analyzes the measuring principle of the ultrasonic time-difference flowmeter,introduces the measurement principle of the design proposal proposed in this paper.And the algorithm is improved by analyzing the flow measurement algorithm,eliminates the effect of temperature on measurement accuracy.By analyzing the flow field in the pipeline,the flow rate correction coefficient is given.Secondly,according to the design proposal proposed in this thesis,through the circuit simulation,the hardware circuit module test and the module circuit assembly,the hardware system design of the measuring instrument has been completed.The timing chip selects TDC-GP22,the microcontroller uses MSP430F449 chip,and the phase-shift detection chip adopts high-speed CMOS phase-locked loop 74HC7046 chip.At the same time,a threshold detection module,a transceiver control module,an ultrasonic transducer matching module,a filter amplification module,an analog-to-digital conversion module,and a phase detection module are designed.The measurement system is powered by a 3.6V battery.Under the IAR Embedded Workbench IDE programming environment,the system software program is programmed.Finally,the production of the prototype was completed,several characteristic flow points were selected to calibrate the ultrasonic measurement system made in this paper.According to the experimental results,the ultrasonic flowmeter was designed in this paper reached the secondary accuracy requirement stipulated by the General Administration of Quality Supervision,Inspection and Quarantine.