Method for accurately measuring of acoustic time difference based on optimal threshold

Abstract

The measurement accuracy of acoustic time difference directly affects the reliability of ultrasonic stress test results. The threshold method was proposed to be used for measuring acoustic time difference. The new method compares the time at the optimal threshold of two periodic signals with definite time-delay, the time interval at an optimal threshold is the acoustic time difference. The mathematical model of error analysis for measuring acoustic time difference by threshold method was established, and the optimal threshold value is determined according to the model. The noise is inevitable in the process of stress measurement; the ultrasonic signals with different signal-to-noise ratios were stimulated to verify the reliability of the optimal threshold method. The simulation results show that the method has a high antinoise capability, higher detection accuracy, and better adaptiveness to the ultrasonic signal of the time change.