Constant frequency pulsed phase-locked-loop instrument for measurement of ultrasonic velocity

Publisher Website
Google Scholar
Abstract
A new instrument based on a constant frequency pulsed phase‐locked‐loop (CFPPLL) concept has been developed to accurately measure the ultrasonicwavevelocity in liquids and changes in ultrasonicwavevelocity in solids and liquids. An analysis of the system shows that it is immune to many of the frequency‐dependent effects that plague other techniques including the constant phase shifts of reflectors placed in the path of the ultrasonicwave.Measurements of the sound velocity in ultrapure water are used to confirm the analysis. The results are in excellent agreement with values from the literature, and establish that the CFPPLL provides a reliable, accurate way to measurevelocities, as well as for monitoring small changes in velocity without the sensitivity to frequency‐dependent phase shifts common to other measurement systems. The estimated sensitivity to phase changes is better than a few parts in 107.