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.
Svilainis, L.; V. Dumbrava; Dumbrava, V.; Salazar Afanador, A. (2014). Automatic simultaneous measurement of phase velocity and thickness in composite plates using iterative deconvolution. NDT and E International. 66:117-127. doi:10.1016/j.ndteint.2014
AbstractA new method for the automatic and simultaneous measurement of phase velocity and thickness for thin composite plates was developed based on Ping He's method, without any need of a priori knowledge of the material parameters. Two composites were analyzed: a block of clean epoxy and a thin specimen of glass-fiber reinforced plastic produced by Resin TransferMolding. The proposed method combines cross-correlation functions and iterative deconvolution for accurate measurement of times of flight and gating. The new method has demonstrated to be more accurate than conventional Ping He's method, and can be implemented automatically thus saving processing time and increasing accuracy.
Some factors influence on light emitting diode (LED) far-field pattern (FFP) approximation performance is analyzed. The mean square root intensity error, miscorrelation factor and half power and peak angles variance have been suggested for performance evaluation. The polynomial order, range and the noise influence have been analyzed. The best function candidate has been named.
Analysis of the noise voltage density evaluation procedures of the ultrasonic preamplifier is presented. Ultrasonic testing is demanding low noise reception channel. Techniques and equipment for ultrasonic preamplifier's noise performance evaluation are suggested. Equipment used and measurement technologies applied are described. One of the techniques suggested allows estimating the preamplifier noise with only impedance measurement results available. Sine wave correlation technique was used in the impedance measurement procedure. Another technique, not demanding the spectrum analyzer, was suggested, which uses the analog-to-digital converter (ADC) sampling and the Fourier transform to obtain the noise spectral density. Experimental results for the measured complex gain and the equivalent input noise of the preamplifier are presented. Comparison with traditional noise estimation procedure, using the spectrum analyzer is given. Both direct measurement techniques (ADC record Fourier analysis based and spectrum analyzer) indicated good match. Noise whiteness was estimated: in a region of operation frequencies, 5–7 MHz, noise can be considered as white.
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