The Development Of An Ultrasonic Industrial Water Flow Meter

In recent years, with the development of national economy, the accurate measurement of large flow becomes more and more necessary in many industries. In order to meet the needs of industry, ultrasonic flow detection technologies have been widely applied. It uses the liquid velocity information carried by the ultrasonic to measure the flow of liquid. The advantages of the meter are non-contact, no pressure loss, low cost, simple structure, wide measuring scope; it is especially acceptable for measurement of large flow. In this paper, by absorbing and referring to the domestic and foreign advanced technology, the author developed an ultrasonic industrial water flow meter based on transit time difference method and MSP430 MCU. And it can measure fluid flow accurately.The paper studies the basic principle of ultrasonic flow detection technologies, analyzes the main factors which affect the measurement accuracy of the ultrasonic flowmeter, gives some technical measures to improve stability and measurement accuracy of the meter such as: designing precise time measurement circuit by CPLD to improve the accuracy of measuring time; controlling the signal scope to shield noise interference; improving the accuracy of signal detection by compare dynamic threshold voltage and detect the width of the signal pulse; using software error correction and digital filtering technology to improve the system stability and anti-jamming capability.In the design, the core processor is MSP430F149 produced by TI; it is used to process the flow data, control the timing and external module of the meter. And the design uses the CPLD-XC2C128 as the digital circuit system module; it is used to modulate the ultrasonic pulse for pulse drive block, and measure the transit time of the ultrasonic pulse accurately. Basis on this, the paper designs the modules of filter circuit, amplifier circuit and comparison circuit etc. The paper gives the design of PCB, and completed the work of debugging the PCB. The software design for MSP430 in C language is given and CPLD in Verilog language is developed. In order to monitor the meter, paper develops the program for communication with PC in VC++ language.Experiments show that the system is stable and reliable; test data has good repeatability. The system lays a good foundation in developing the practical, high-performance ultrasonic flowmeter in the future.