超声波多普勒流量计的设计

摘要

For the problem that the conventional ultrasonic doppler flowmeter accuracy is low ,the stability is poor ,the dynamic response is slow ,a new type of ultrasonic Doppler flowmeter was developed .Hardware mainly included ultrasonic transducer trans-mitting and receiving circuits ,power amplifier and filter circuit ,mixer circuit,STM32F4 and their peripheral devices .Through adop-ting STM32F4 as the main chip of ultrasonic Doppler flowmeter ,Cortex-M4 core was used in STM32F4 and its hardware FPU unit was built in.DSP instruction set in digital signal processing also increased ,making the capability of digital signal processing was greatly upgraded .The high-precision DDS chip was used in hardware circuit to generate the reference signal ,then the frequency-shifted signal was demodulated 10 kHz using demodulator technology ,which increased the stability of the system measurement and response speed of the flow rate .In the frequency-shifted signal processing ,FFT was adopted to analyze frequency-shifted signal from STM32F4,which improved the measurement accuracy of ultrasonic flow measurement system .Matlab was used to analyze Doppler frequency shift signal spectrum to get its frequency change .%针对传统的超声波多普勒流量计存在的精度低、稳定度差、动态响应慢的问题，研制了一种新型的超声波多普勒流量计。硬件部分主要设计了超声波换能器的发射与接收电路、功率放大与滤波电路、混频电路以及STM32F4及其外围器件。采用STM32F4作为超声波多普勒流量计的主控芯片，STM32F4采用Cortex－M4内核，其内置硬件FPU单元，在数字信号处理方面还增加了DSP指令集，使得它在数字信号处理方面的能力得到大大的提升。在硬件电路中选用高精度的DDS芯片产生基准信号来驱动超声波换能器。在频移信号处理方面，采用中频解调技术将频移信号解调到10 kHz，提高了系统测量的稳定度以及对流速变化的响应速度。运用快速傅里叶变换算法（ FFT）对STM32F4采集到的频移信号进行频谱分析，有效地提高了超声波流量测量系统的精度，并以matlab为分析工具对采集到的多普勒频移信号进行频谱分析，从而得到其频率的变化。