基于可变阈值和过零检测的四声道气体超声波流量变送器

针对四声道气体超声波流量计,提出基于可变阈值和过零检测的数字信号处理方法,快速、准确定位回波信号,提高系统抗干扰能力。设计了集中采集-集中处理数据的工作模式和双发双收的收发方式,采用FPGA和DSP双核架构,研制了四声道气体超声波流量变送器。利用FPGA擅长并行处理和复杂逻辑控制的优势,实现换能器双发双收、高速DAC和ADC的驱动控制以及数据存储,完成信号的集中采集;利用DSP擅长数字信号处理的优势,实时实现数字信号处理方法,完成信号的集中处理。气体流量标定实验结果表明:研制的四声道气体超声波流量计满足0.5级精度相关技术指标的要求。

Development of Four-channel Ultrasonic Gas Flow Transmitter Based on Variable Threshold and Zero-Crossing Detection

For the four-channel ultrasonic gas flow-meter, a digital signal processing method based on variable threshold and zero-crossing detection is proposed to locate the echo signals quickly and accurately and improve the anti-interference ability of the system. And the working process that centralized sampling-centralized processing of data and the transceiver way that double emission double receive were designed. A transmitter of four-channel ultrasonic gas flow-meter was developed based on FPGA & DSP dual core structure. It realizes the double emission double receive transceiver way, controls the high-speed ADC & DAC and storages the data by taking the advantage of the parallel processing capacity and better logic control ability of FPGA, completing the centralized sampling of data. On the other hand, it realizes the real time digital signal processing method by using the high-speed computing capacity of DSP, completing the centralized processing of data. The gas calibration experiment results show that the four-channel ultrasonic gas flow-meter developed meets the needs of the related technical indicators of the 0.5-level precision ultrasonic gas flow-meter.