基于DPS技术的超声波多普勒流量计的设计

【作者】 丁丽晶；

【导师】 李明伟；

【作者基本信息】 大连理工大学 ， 通信与信息系统， 2002， 硕士

【摘要】 超声多普勒流量计主要用于污水类非纯净液体和混有固体颗粒的两相流的流量测量，其优点是：分辨率高，对流速变化响应快；对流体的压力、粘度和温度等因素不敏感。但就当前测量水平来说，其精度及其它性能都有待于进一步提高，因此，超声多普勒流量计的研究无论是对于自动化测量技术的提高还是对于环保事业来说，都将是一项极有意义的研究课题。 本课题设计的超声多普勒流量计引入先进的数字信号处理技术，在频域上对多普勒信号进行有效的处理，主要处理技术是以快速傅里叶(FFT)变换为基础的周期图法和峰值逼近算法。具体方法是首先对多普勒频移信号进行采样，再进行FFT变换，进而得到该信号的功率谱，在功率谱上应用峰值频率的逼近算法，加上适当的数字滤波技术，从而得到频移信号所对应的频率值，在此基础上，根据多普勒效应原理，求取管道中流体流速及其它数据量。为进一步提高精度，在进行数据采样时，采样率的选择根据频率值进行了分段设置，提高了FFT变换的频谱分辨率。由于要进行大量的数据处理，硬件电路采用TI公司的TMS320F240 DSP作为核心处理器件，从而满足系统实时性的要求。硬件电路除了核心器件外，还辅以其他滤波及放大电路等，最终推出一款结构简单、系统完善的新型超声多普勒流量计。 该系统除了具有一般流量计的显示功能，如瞬时流量、累计流量、累计时间、瞬时流速的显示等，还引入了频谱的动态显示，有利于实时观测信号状态，特别是对于多普勒流量计的安装非常有利。在仪表精度和稳定性方面，也有了进一步的提高。更多还原

【Abstract】 Ultrasonic Doppler flowmeters are mainly applied to measure flux of sewage or other liquid with solid grain. They are of high resolving power, and can respond quickly with the variety of velocity. Moreover, they are insensitive to the pressure and temperature of liquid. But now, technique in this field will be improved, so the task is significative not only to automatic measurement but to environment protection.Hardware and software of ultrasonic Doppler flowmeter are designed in this paper. Digital signal processing is introduced to analyze Doppler signal, for example, FFT is used to convert Doppler signal from time domain to frequency domain, and then the algorithm of approaching peak value is put into practice. After this, filter software is in use. Thus Doppler frequency shift is obtained. According to Doppler effect, velocity and flux can be calculated. Because of mass-calculation, TMS320F240 DSP is chosen as core part in hardware design. And in hardware design, low-pass filter, amplifier, D/A convector and other circuits are included. The whole system is simple and intelligent.The system designed is improved in precision and stability. It has a distinct characteristic in display - the function of dynamic spectrum display, which is advantageous during it’s installation.更多还原