Development Of Gas Ultrasonic Flowmeter With Double Channel Based On Time Difference Method

Since its inception,the market share of the ultrasonic flowmeter has been increasing year by year for its high accuracy and stability of measurement,measurement without pressure loss,wide measuring range,non-contact measurement.The study of the ultrasonic flowmeter started late in China,there is a certain gap in the measurement precision and the measurement range of ultrasonic flowmeter compared with the foreign countries.To the problems of the low measurement precision and the poor stability of the ultrasonic gas flowmeter measurement,this paper puts forward the time measurement method which is the combination of the high precision timing chip TDC_GP22 and the new correlation algorithm for timing measurement chip STM32F407,and designs the double channel gas ultrasonic flowmeter with self-learning function,taking the STM32F103 as the main chip,based on the time difference method.The main research contents of this paper includes the following aspects:Firstly,this paper has a deep research on the measurement principles of the time difference gas ultrasonic flowmeter and comes up with the time measurement methods combining the high precision timing chip TDC_GP22 and the new correlation algorithm for timing measurement chip STM32F407.Secondly,this paper devises the whole design framework of the system and the hardware circuit modules,choosing the 32-bit high performance and low power consumption MCU STM32F103 as the main control chip,and devises the hardware module circuits,such as the ultrasonic signal transmitting and receiving circuit,TDC_GP22 circuit,STM32F407 time measurement model algorithm of time measurement circuit,channel selection circuit.Subsequently,the thought of module design is adapted in designing the software program of the system in the paper.And the paper gives a detailed in designing these programs,such as the main program,TDC_GP22 time measurement program in STM32F407,new algorithm of time measurement procedures,flow value calculation module,and selects the way of program code of single-chip library function to simplify the software program design and improve the efficiency of programming.Then,the new algorithm of the single chip microcomputer STM32F407 is simulated,and the measurement data are analyzed by MATLAB simulation software to judge the reliability and the stability of the new algorithm.Finally,the air is used to measure the flow rate of the two channel gas ultrasonic flowmeter,and the measurement data are analyzed and modified.