基于离散信号相关性的超声波回波信号动态阈值研究  

Research on Dynamic Threshold of Ultrasonic Echo Signal Based on Discrete Signal Correlation

作　　者：陈倩 李跃忠[1] CHEN Qian;LI Yuezhong(School of Mechanical and Electronic Engineering,East China University of Technology,Nanchang 330013,China)

机构地区：[1]东华理工大学机械与电子工程学院,江西南昌330013

出　　处：《仪表技术与传感器》2023年第12期105-110,共6页Instrument Technique and Sensor

基　　金：国家自然科学基金(61663001);江西省科技厅重点研发计划(20212BBE53033)。

摘　　要：超声波燃气表具有精度高、量程宽、压损小、低功耗等特点,逐渐应用于天然气贸易计量与城市燃气计量领域。然而超声波信号受管道内气体流速、温度与压力等因素的影响,回波信号幅值波动大且伴随水平方向偏移,在满足系统低功耗运行的要求下,实现对回波信号的高精度峰值采集与特征点的正确选取是后续流量处理的关键。为此,文中通过二次插值处理高速ADC采集的离散序列以得到回波信号的峰值,依次对静态和动态条件下的回波信号峰值序列进行离散信号相关运算,以相关性计算结果为判断依据实现阈值电压的动态调整,从而保证了特征点定位的稳定性与传播时间的精确性。该动态阈值设定方法应用在以低功耗STM32L073为主控芯片,TDC-GP22为高精度测时芯片的超声波燃气表样机上,检定结果表明:在0.025~4 m^(3)/h的流量范围内,该样机满足国家1.5级精度仪表对相对误差和重复性要求。Ultrasonic gas meter has the characteristics of high precision,wide range,small pressure loss and low power con-sumption,and is gradually applied in the field of natural gas trade measurement and city gas measurement.However,ultrasonic signals are affected by factors such as gas flow rate,temperature and pressure in the pipeline,and the amplitude of echo signals fluctuates greatly and is accompanied by horizontal deviation.In order to meet the requirements of low-power operation of the sys-tem,it is the key to realize high-precision peak acquisition of echo signals and correct selection of feature points for subsequent flow processing.Therefore,in this paper,the discrete sequence collected by high-speed ADC was processed by quadratic interpo-lation to obtain the peak value of the echo signal.The discrete correlation operation was carried out on the peak sequence of the echo signal under the static and dynamic conditions successively.The dynamic adjustment of the threshold voltage was realized based on the correlation calculation results,so as to ensure the stability of the feature point positioning and the accuracy of the propagation time.The dynamic threshold setting method was applied to the ultrasonic gas meter prototype with low power con-sumption STM32L073 as the main control chip and TDC-GP22 as the high precision timing chip.The test results show that the prototype meets the national requirements for relative error and repeatability of 1.5 electrode precision instrument in the flow range of 0.025~4 m^(3)/h.

关 键 词：超声波燃气表 二次插值 离散信号相关性 动态阈值 

分 类 号：TH701[机械工程—仪器科学与技术] TN98[机械工程—精密仪器及机械]