Research On Vital Techniques Of Ultrasonic Flow Measurement

This article' s research is based on "three-meters in one long-distance meter reading system". Ultrasonic water meters are widely applied in industrial measurement field for its many advantages. However, it also has some disadvantages, for example, ultrasonic is easily attenuated in the flow, the pipeline must always be full and meters are sensitive to flow field and temperature. There are some ultrasonic meters types: transit-time ultrasonic meters, Doppler meters, open-channel water meters and so on. Transit-time is choosed after various factors are analyzed.In this paper, velocity-distribution discipline of the pipe-flow, concludes velocity curve and studies bow pipelines and coarse pipelines are analysed; plane-wave' s wave theory, principle of the ultrasonic sensor and selection of the sensor frequency are introduced; the mechanics principle of ultrasonic water meter is introduced, primary reasons of influencing measurement precision are analyzed, and a new method about improving measurement precision is put forward; hardware design of the meters is studied, including ultrasonic emission circuit, reception circuit, communication circuit; precision of the A/D switch of the DSP is improved and a new digital signal method(wavelet transform) is used to accurately measure arriving time of the ultrasonic wave.Main innovation of this paper is that:1. Velocity-distribution discipline of the pipe-flow is analysed, velocity curve is concluded, bow pipelines and coarse pipelines are studied, and an academic foundation is provided for measuring pipeline average velocity of flow.2. Main factors of influencing measure precision are studied, and a new method about improving measurement precision is put forward. This method overcomes disadvantage conventional transit-time ultrasonic.3. Improvement arithmetic of TMS320F2812 inner A/D precision is studied, wavelet transform technology is used to replace cross-zero check method and threshold check method, ultrasonic signal arriving time is accurately confirmed and measurement precision is improved.The measurement method of using wavelet transform technology to detect ultrasonic signal arriving time can be used to other ultrasonic detection field and at the same time provide a new study method and thought to other signal detection technology.