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

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 .