Development and Evaluation of DUT Vibro: A High-Precision Vibrating Wire Sensor Readout

Abstract

This study presents the development and evaluation process of a vibrating wire sensor readout named DUT Vibro, with both hardware and software entirely developed by Vietnamese researchers. The primary objective of this paper is to evaluate the efficacy of two methods to determine the resonant frequency of the vibrating wire to facilitate precise strain calculations.  In this study, parabolic interpolation is investigated to improve the accuracy of the resonant frequency of a steel wire, addressing the limitation of Fast Fourier Transform (FFT) constrained by the storage capacity of the microcontroller. In addition, the determined resonant frequency of DUT Vibro is compared with a commercial DIGIANGLE (DAS). Furthermore, two stimulation signals—sine and square waves—were employed to compare their impact on measurement accuracy. The results indicate that the parabolic interpolation method yields the lowest standard deviation, closely aligning with the DAS readout, and demonstrates stability across both low and high load conditions. In contrast, the FFT method exhibits greater error variability, particularly in the medium load range, due to the influence of noise and non-linearities in the response signal. The sine wave stimulus combined with parabolic interpolation achieves the highest accuracy. The measurement system maintains high linearity, with linearity errors below 0.5% of full scale (FS), and the lowest linearity error is 0.129% FS when using a sine wave stimulus. Linear regression analysis reveals a slope coefficient of approximately 0.052, reflecting a linear relationship between load and measured strain. Based on these findings, the parabolic interpolation method has been integrated into the DUT Vibro readout, meeting stringent accuracy requirements for strain measurement applications.