Design of ultrasonic imaging system is presented. System has a modular structure with main acquisition and front end electronics separated in order to have minimal path for host PC connectivity and shortest path to ultrasonic transducer. Such acquisition modules placement allows reducing the induced EMI and increasing the flexibility of the system. Positioning module is also separate and allows various scanning equipment configurations. Evaluation of excitation and reception electronics parameters is presented. Essential measurement procedures outlined. Signal digitization parameters (sampling frequency, clock jitter and quantisation) were chosen to balance time of flight estimation random errors versus interpolation bias errors.
Study on the accuracy of the ultrasound velocity application for chemical process monitoring is presented. Cure degree of epoxy resins was monitored in order to establish the percentage of the final cure based on ultrasound velocity of longitudinal waves. Time of flight estimations by correlation processing were used to estimate the velocity. Sources of error in the velocity measurement and their influence in the sensitivity and accuracy of the results have been studied. In order to improve the accuracy and reliability of the measurements, the use of Spread Spectrum instead of conventional excitation signals have been evaluated. Experimental results indicate that random errors of propagation time estimation are lower than velocity fluctuation over the chemical process. Spread spectrum signals provide more reliable measurements.
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