Bathythermograph

bathythermograph [¦bath·ə′thər·mə‚graf]

(engineering)

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.

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Bathythermograph 

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.

REFERENCES

Rukovodstvo po gidrologicheskim rabotam v okeanakh i moriakh. Leningrad, 1967.
Deriugin, K. K., and I. A. Stepaniuk. Morskaia gidrometriia. Leningrad, 1974.