Open AccessAn ultrasonic frequency sweep interferometer for liquids at high temperature: 2. Mechanical assembly, signal processing, and application
Author(s) -
Ai Yuhui,
Lange Rebecca
Publication year - 2004
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2004jb003062
Subject(s) - interferometry , ultrasonic sensor , speed of sound , optics , materials science , signal (programming language) , acoustics , transducer , maxima and minima , acoustic interferometer , physics , wave propagation , longitudinal wave , computer science , mechanical wave , programming language , mathematical analysis , mathematics
The design and application of a frequency sweep (FS) interferometer for sound speed measurements on high‐temperature silicate liquids, with the potential to be applied to liquids at high pressure, are presented. FS interferometry differs from variable path length interferometry in that no mechanical movement of a buffer rod is required. Instead, a wideband pulse spanning 1–2 MHz is transmitted down the upper buffer rod, which allows maxima/minima in the returned signal to be evaluated as a periodic function of frequency. Measurements may be made at several different centered frequencies (from 3 to 7 MHz with the transducer used in this apparatus) in order to test whether the liquid sound speed is frequency‐independent and thus relaxed. This paper describes the mechanical assembly and the algorithms for signal and data processing, which are based on the solutions to the wave equations in a rod‐liquid‐rod interferometer. The precision and accuracy of the FS interferometer is demonstrated by measuring the relaxed sound velocities in six liquids (NaCl, a sodium silicate, two sodium aluminosilicates, CaMgSi 2 O 6 , and Fe 2 SiO 4 ) with well‐known sound speeds from the literature.