超声波液体密度测量的一种声反射系数测定方法

摘要

用超声波测液体密度时,测量声反射系数是重点.提出一种将半波层反射模型简化后,利用相对稳态幅度测量声压反射系数的方法.将一个较薄固体作为半波层置于被测液体中,两侧对称地放置超声波换能器,换能器一个工作在脉冲回波模式,另一个工作在接收模式.调整信号频率使半波层和被测液体交界面的多重反射波达到最大程度干涉,此时被测液体与半波层之间的声反射系数只与两个换能器在稳态下的回波信号幅度比值有关.因此测得换能器的稳态回波信号幅度比,即可得到声反射系数.此方法简化了原来的半波层反射模型,采取对称布局,利用相对稳态幅度法,简化了理论推导过程,降低了测量上的精度要求.最后文章通过实验验证了方法的正确性.%Measurement of acoustic reflection coefficient is the key point when measuring the density of liquid by ultrasonic wave.This paper presents a method for measuring the acoustic reflection coefficient through the relative steady state amplitude based on the simplified model of half wave reflection.A thin solid as a half wave layer is arranged in the measured liquid,and two ultrasonic transducers are placed on both sides of the measured liquid,symmetrically.One transmitter works in pulse-echo mode,and the other works in receiver mode.By adjusting the frequency of signal to make the multiple reflection wave at the interface between the half wave layer and the liquid interfere to the greatest extent,the acoustic reflection coefficient between the liquid and the half wave layer is only related to the amplitude ratio of the two transducers in steady state.So the sound acoustic reflection coefficient can be obtained when the echo signal amplitude ratio of the transducer in steady state is measured.This method simplifies the process of theoretical derivation and reduces the accuracy of the measurement,by simplifying the original half wave reflection model,taking the symmetrical layout and using the method of relative steady state amplitude.At last,experiments are carried out to verify this method.