Sea-Bird Electronics SBE 45 MicroTSG, Руководство пользователя

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We draw the following conclusions from the research papers listed above:
1)
Investigators using specialized equipment under scrupulously controlled laboratory conditions report
measurements of SV vs. changes in temperature, salinity, and pressure which differ by
0.5 meters/second and more.
It is unrealistic to expect that commercial direct-measurement
instruments will be more accurate under field conditions than the laboratory equipment used by
successions of careful researchers.
2) The
claimed accuracy of commercial direct-measurement SV probes probably more legitimately
represents their precision (compare with CTD/SV uncertainties tabulated above) rather than their
absolute accuracy. The relationship between what these instruments read and true sound velocity is
probably just as dependent on the same vagaries that are also the only significant sources of error
when employing the CTD approach.
3)
Because of the uncertainties in the time-delays associated with the acoustic transducers and
electronics (and because of the difficulty of measuring with sufficient accuracy the length of the
acoustic path), direct-measurement probes must be calibrated in water. As suggested by the research
under controlled laboratory conditions, this is not an easy task, especially over a range of
temperature, pressure, and salinity. On the other hand, a CTD probe can easily be calibrated using
accepted methods.
4)
A CTD can predict absolute SV to something better than 0.5 meters/second (a judgment seconded
by Professor Millero in a private conversation), while its relative accuracy (precision) is probably
better than 0.05 meters/second under the most demanding conditions of field use.
5)
The very high precision associated with CTD measurements and the existence of an internationally
accepted relationship (even if imperfect) between CTD and SV permits very consistent
intercomparison and a high degree of uniformity among CTD-derived SV data sets, no matter when
and where taken.
Bibliography
C-T. Chen and F. J. Millero, 1977, Speed of Sound in Seawater at High Pressures. J Acoust Soc Am, 32(10),
p 1357.
V. A. Del Grosso, 1974, New Equation for the Speed of Sound In Natural Waters (with Comparisons to
Other Equations). J Acoust Soc Am, 56(4), pp 1084-1091.
J. M. Pike and F. L. Beiboer, 1993, A Comparison Between Algorithms for the Speed of Sound in Seawater.
The Hydrographic Society, Special Publication No. 34.
Wilson W D, 1960, Equation for the Speed of Sound in Seawater. J Acoust Soc Am, 32(10), p 1357.
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