驻波法与相位比较法声速测量实验的对比研究

Comparative Study on Sound Speed Measurement Experiment Based on Standing Wave Method and Phase Comparison Method

在驻波法声速测量实验中出现了次峰现象,由于次峰的干扰难以准确测量声速;在相位比较法声速测量实验中,也出现了类似现象,在不该出现一三象限直线的地方,出现了幅度较小的一三象限直线,容易导致测量出错.为此,搭建了全自动声速测量系统,通过数据采集卡采集信号,通过单片机和步进电机驱动器控制步进电机的转动,利用步进电机带动丝杠转动,从而实现声波接收器的运动.通过上位机完成绘图和数据存储.分别采用驻波法和相位比较法进行声速测量.在驻波法测量过程中,采用有效值检测模块将声波接收器产生的高频交变电压信号转化为直流电压信号;在相位比较法测量过程中,采用相位差测量模块实现相位测量的数字化.实验结果表明：驻波法和相位比较法各有优缺点.将两种方法得到的数据进行比较,可以更好地发现并消除次峰的影响,实现声速更高精确的测量.

Sub-maximum phenomenon exists in the experiments of sound speed measurement by standing wave method which usually results in mistakes.Similar phenomenon appears in phase difference method.A small amplitude line lie in the 1 st and 3 rd quadrants appears between two standard position of line lie in the 1 st and 3 rd quadrants.So an automatic sound speed measurement instrument was designed.This instrument takes the upper machine as core control unit,uses data acquisition card to acquire data,and controls the rotation of the stepping motor through micro-controller and stepper motor driver.The stepping motor moves the platform through ball screws to realize the scanning of the acoustic receiver.The upper machine completes the functions of drawing and data storage.Sound speed was measured by both methods.An effective value detection module was used to transform the high frequency alternating voltage signal generated by the acoustic receiver into DC voltage signal.A phase difference measurement module was used to measure the phase difference quantitatively.The experiment results showed that both methods have merits as well as demerits.The comparison of the data obtained by the two methods can detect and eliminate the influence of the sub-maximum better and achieve higher accuracy in sound velocity measurement.