微处理机-高速采样系统在波速精确测量中的应用

AN APPLICATION OF THE MICROCOMPUTER-HIGH SPEED DATA ACQUISITION SYSTEM TO THE ACCURATE MEASUREMENT OF WAVE VELOCITY

  • 摘要: 本文介绍一种用微处理机-高速采样系统准确测量波速的方法。波速测量的精度取决于走时的确定。但目前大都采用SYC-Ⅱ型波速仪,并靠眼睛判读其示波器上光标的位置来得到走时,由此产生的走时读数误差往往超过0.2微秒。应用本文介绍的系统,这一误差可以大大减少。在测量过程中,走时被一瞬态记录仪用20兆赫兹的最高采样速率(对应的最大读数误差为0.05微秒)记录下来,然后经过一数字接口将数据输入微处理机,由其自动判读波的初动,并立即给出波的走时和速度。 分析表明,对实验室通常采用的样品尺度,该系统的波速测量误差在0.7%以内,波速测量的精度因而得到很大程度的提高。

     

    Abstract: A method is introduced in this paper for precisely determining- wave velocity by means of a microcomputer-high speed data acquisition system. The accuracy of the wave velocity measurement is controlled by the travel-time determination. But this is currently done with a SYC-Ⅱ veloeimeter by determining the, position of a light sealer on its oscilloscope, resulting in a reading error well beyond 0.2 s. With the use of the system presented in this paper, this error can be greatly reduced. In the measurement, the tra-vel-time is recorded by a transient recorder with the highest sampling speed of 20 MHz (corresponding to a maximum reading error of 0.05s), and the data are transferred via a digital interface into a microcomputer which automatically determines the first wave arrival and immediately gives the results of travel-time as well as velocity.For the sample scales commonly adopted in the laboratory, the error in the velocity measurement by this method is within 0.7%. Thus the accuracy of velocity measurement is improved to a considerable extent .

     

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