The Design Of Transit-time Ultrasonic Flowmeter

Fluid flow is one of the important parameters in industrial measurement. As a non-contact flowmeter instrument, ultrasonic flowmeter has already been widely used with its high accuracy, no pressure loss, wide measuring range.However, because of environmental factors and hardware resources, the methods of data processing about ultrasonic flowmeter are often simple, which causes measurement accuracy and stability difficult to improve. This paper presents an embedded transit-time ultrasonic flowmeter based on ARM, using ARM technology and53H algorithm to achieve the measurement of fluid flow, data processing of the time difference and the stability of the measurement.The content of this paper includes the measurement principle of the embedded transit-time ultrasonic flowmeter, how to build an embedded system platform, how to design embedded software, the data processing methods of time difference and system test.The hardware of the system regarads ARM chip S3C2440microprocessor as the main control unit, that is responsible for the control of measurement process, data processing, communications and so on; CPLD chip XCR3128achieves transmitting and receiving of the ultrasonic pulse signal, the extracted and transmitted control signal; TDC-GP2makes time difference data achieve high accuracy. In the software, firstly, development environment of Linux systems should be built, and the Linux system is easy to make more complex signal processing algorithms come true; through the device drivers program of Linux, ultrasonic flowmeter achieves the meter hardware device drivers, meanwhile, through the application program of Linux, ultrasonic flowmeter realizes the time difference measurement and data processing functions; finally, after cross-compiler, an executable file is generated, which is downloaded to the target system to run and realize function of flow measurement.On the basis of three methods of data processing rolling average filtering, EMD algorithm and53H algorithm and the respective simulation results,53H algorithm is applied to transit-time ultrasonic flowmeter, which improves the linearity stability and accuracy of flowmeter measurement.The testing proves, the measurement error of the meter instrument controls in less than0.8%, which basically reaches the flowmeter measurement requirements and has a good prospect.