REDUCING THE INFLUENCE OF NOISE ON THE ACCURACY OF ULTRASONIC PULSE ONSET DETECTION

An essential component of ultrasonic nondestructive testing is determining the delay time between the transmitted and received signals. Therefore, the accuracy of determining the onset of both the transmitted and received pulse affects the accuracy of all subsequent calculations. The main measuring transducers are usually piezoelectric. A relatively new approach involves using small-aperture magnetostrictive transducers as a generator and receiver of the ultrasonic signal. Such magnetostrictive sensors have low-current excitation coils, resulting in low amplitudes of received signals. Therefore, it is an urgent task to develop algorithms for determining the onset of a pulse that could reduce the noise present in the signal or not be sensitive to it. In this paper, a method for determining the onset of an ultrasonic pulse is proposed based on utilizing a standard function from the LabVIEW library to determine the position of the peak value of a periodic pulse. The mathematical expressions for modeling transmitted and received pulses were obtained. Based on these mathematical expressions, a modeling experiment was conducted to verify the accuracy of determining the beginning of the probing pulse by the proposed method. The simulation experiment was performed with noise following a Gaussian distribution for the range of standard deviation (SD) values from 0 to 10. According to the modeling results, it was found that the proposed method allows determining the beginning of the probing pulse with a relative error not exceeding 3.5 % for the values of the SWR less than 2. Keywords: ultrasonic signal, magnetostrictive sensor, signal-to-noise ratio.