气体超声流量计回波信号的自适应阈值法研究

The Self-Adaptive Threshold Method of Echo Signal for Gas Ultrasonic Flowmeter

时差法超声波流量计常采用双阈值法确定特征点,测量到达特征点时间,从而计算渡越时间。相比于单阈值法,双阈值法一定程度上提高了流量计的准确性,然而超声回波信号在传播时易受到温度、压力以及换能器特性的影响,导致双阈值法在一定工况下特征点产生错误判断。针对此问题,提出了一种自适应的双阈值方法并设计硬件电路。该方法可在较低的采样频率下获得回波信号各个波峰幅值,实时更新第一阈值,判断特征点是否一致并进行自动补偿,从而提高渡越时间的测量精度。最终实验结果表明,与传统双阈值法相比该方法具有较好的适应性和计量特性。

The ultrasonic flowmeters with time difference method usually use the double threshold method to determine the characteristic point,measure the time of the feature point and calculate the flight time.Compared with the single threshold method,the accuracy of the ultrasonic flowmeter can be improved by using the double threshold method.However,the ultrasonic echo signals is easily to be affected by temperature,pressure and the characteristics of transducer,which can lead to wrong judgment of the feature point under certain operating condition.To solve this problem,an adaptive double threshold method is proposed and the corresponding circuit is designed.This method can obtain the each peak amplitude of echo signal at a lower sampling frequency,update the first threshold in real time,determine the consistentance of the feature point and compensate the time automatically.The experimental results show that the method has better adaptability and measurement characteristics than the traditional double threshold method.