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A device for obtaining a record of temperature against depth (actually, pressure) in the ocean from a ship underway. Abbreviated BT. Also known as bathythermosphere.



an instrument lowered from a ship in motion for measuring the distribution of the temperature of water relative to depth. The body of a bathythermograph has a streamlined shape and is equipped with tail fins for stabilizing the instrument’s attitude when it is lowered into the water; the instrument is lowered by means of a steel cable.

The temperature sensor is a hot-wire anemometer, consisting of a long copper capillary tube mounted on the tail fins. One end of the capillary tube is sealed and the other is connected to the fixed end of a manometric coil spring. The capillary and spring are filled with toluene. When the temperature changes, the volume of toluene and, consequently, the pressure within the manometric system change. With an increase in temperature the free end of the manometric spring is untwisted at an angle proportional to the amount of temperature change, and it is twisted with a decrease in temperature. The pointer attached to the free end of the manometric spring records the temperature on a smoked-glass plate, which is shifted by a hydrostatic depth sensor as the instrument is lowered in the water. Hermetically sealed Sylphons function as the depth sensors. Modern bathythermographs record water temperature with a minimum accuracy of 0.1°C. They are used in oceanographic research and on fishing survey vessels.


Rukovodstvo po gidrologicheskim rabotam v okeanakh i moriakh. Leningrad, 1967.
Deriugin, K. K., and I. A. Stepaniuk. Morskaia gidrometriia. Leningrad, 1974.
References in periodicals archive ?
Conductivity, temperature, and depth (CTD) or expendable bathythermograph (XBT) casts were conducted every 55 km (30 nmi) along the survey transect.
We leverage national and international data sources like satellites, oceanographic buoys, expendable bathythermographs, surface observing systems/networks, and other sources of critical environmental data.
Water column data were collected with conductivity-temperature-depth (CTD) profilers 1 h before sunrise and 1 h after sunset on each survey day and with expendable bathythermographs (XBTs) during daylight hours at intervals of ~55 km.
According to measurements by an array of autonomous free-floating ocean floats called Argo, as well as by earlier devices called expendable bathythermographs, or XBTs, that were dropped from ships to obtain temperature data, ocean heat content has increased over the last 16 years.
The sailors received the awards for overhauling the AM-3729/SR amplifiers, LS-474/U speakers, Type G telephones, AN/BQH bathythermographs and electrical workbenches aboard Eisenhower, rather than sending them to contractors for overhaul or purchasing new equipment.