Research And Implementation Of The High-accuracy And Low-power Dual-channel Ultrasonic Flow Meter

Over the last decade, with the rapid development of the high-speed digital signal processing technology and microprocessor technology, the ultrasonic flow measurement technology has made considerable progress, and its engineering application has become increasingly mature, which plays an important role in the field of Industrial fluid measurement and trading calculation. However, as the flow field distribution of pipeline fluid is different in dissimilar flow state, and because of the interference of the external environment and their own factors, there is so much noise in the measurement results of the single-channel ultrasonic flow meter, which inevitably affects the accuracy and stability of the measurement. Therefore, based on principles of transit-time ultrasonic flow meter, by consulting a large number of domestic and foreign documents, and referring to the problems associated with the measurement process, the paper studied and achieved the high-accuracy, low-power design of the dual-channel ultrasonic flow meter. The main work and innovation are as follows.First, it analyzed the principles of transit-time ultrasonic flow meter; mainly studied the theoretical formula of the flow velocity under different flow state and the correction factors, and its impact on the measurement accuracy; explored the measures to raise the flow rate and the measurement accuracy; and using the theory of Gauss-Legendre numerical integration, modeled a meter of the dual-channel ultrasonic flow meter.Second, it introduced the design of the hardware and software systems of the dual-channel ultrasonic transit-time flow meter in detail. The hardware mainly includes the choices of the chip and the component, the establishment of the hardware circuit and specific functions of each module. The more important modules are:such as the time measurement module, the transducer matching circuit module, the ultrasonic echo signal processing modules and the interface modules. However, the software gives a functional flow chart of the hardware module, such as the main program flow chart, the time measurement flow chart, the pulse output interface flow chart, the buttons and display flow chart, and the interrupt service flow chart.Third, according to the high accuracy requirements of the ultrasonic flow meter, it achieved the endpoint detection to the ultrasonic echo signals with a lot of research and experiments, by designing and using the method of zero threshold comparison; using the algorithms of median filter, moving average filter, weighted filter, compound digital filter constituted by Peters algorithm, processed the measurement data; and actualized a dynamic tracking of the correction factor by Newton interpolation theory, and improve the measurement accuracy of the flow meter effectively.Fourth, it accomplished the independent power designs of the microprocessor module, the timing module, and the amplification module, which is in order to achieve the control of the system to the various functional software modules. At the same time, on the basis of the principles of ultrasonic flow meter, controlled the MCU system clock and low power modes reasonably, and ensuring measurement accuracy, meanwhile reduced the power loss as much as possible to reduce the system power consumption.