Journal of Oceanography

, Volume 61, Issue 5, pp 905–912

Inter-manufacturer Difference and Temperature Dependency of the Fall-Rate of T-5 Expendable Bathythermograph



The fall-rate of the T-5 expendable bathythermograph (XBT) produced by Tsurumi Seiki (TSK) Co., Ltd and that by Sippican Inc., are intercompared by a series of contemporaneous and colocated measurements with conductivity-temperature-depth (CTD) profilers. It is confirmed that the fall-rates of the two manufacturers' T-5 differ by about 5 percent, despite the fact that they had been believed to be identical for many years. The cause of the difference is discussed on the basis of a detailed cross-examination of the two T-5 models. It is found for the first time that the two models are different in several respects. The manufacturer's fall-rate equation is only applicable to the Sippican T-5, for which Boyd and Linzell's (1993) equation seems to be slightly more accurate. Kizu et al.'s (2005) equation gives a clearly less biased depth than the manufacturers' equation for the TSK T-5. It is also found that the fall-rates of both T-5 models are dependent on water temperature, perhaps because of viscosity. The temperature-dependency of the fall-rate of the TSK T-5 is larger than that of the Sippican T-5.


T-5 XBT expendable bathythermograph fall-rate equation time-depth conversion equation temperature measurement VOS monitoring water viscosity 


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Copyright information

© The Oceanographic Society of Japan/TERRAPUB/Springer 2005

Authors and Affiliations

  1. 1.Department of Geophysics, Graduate School of ScienceTohoku UniversityAza Aoba, Aramaki, Aoba-ku, SendaiJapan
  2. 2.Tohoku National Fisheries Research InstituteShinhama-cho, Shiogama, MiyagiJapan
  3. 3.National Research Institute for Far Seas FisheriesShimizu Orido, ShizuokaJapan

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