Bathythermograph

A Bathythermograph (composed of Greek Bathys: deep, Thermos: warm and graphein: carve, write ) is a device for measuring the water temperature as a function of pressure ( or depth in the water, which is proportional to the pressure ). The Bathythermograph is invented by the Americans Spilhaus in 1937 and is mainly used in the Navy to determine the sonar propagation conditions. For temperature determination, a bimetal and for determining pressure serves as a load cell at doses barometer. With these two mechanically acting sensors is scratched with a tip on a coated glass plate, the temperature as a function of depth. These sensors are located in a rugged slim measuring body that is lowered by a wire from the ship.

Despite the heavy robust construction of Bathythermograph is to be used only at low driving speed, so that the ship should almost on top. That's why he has since been replaced by the XBT ( Expendable Bathythermoghraph ), produced since 1960 by the American company Sippican. When XBT temperature is measured with a thermistor. The depth is determined as a function of time at a constant to a good approximation of the free falling rate of descent measuring body. The machine is connected with a very thin insulated wire with a double pen recorder on board the ship. This wire is wound in the measuring body and the on-board device, so that it is relative to the water not moving needs: the movement of the falling test body is unrolled from the local supply spool and the movement of quite fast moving ship from the coil in the onboard device. When the wire is unwound, it breaks and the probe is lost (so far been Sippican of about 5 million probes sold). Nevertheless, this loss is economical because the probe costs less than the fuel consumption for the stopping of the ship.

A further development of the XBT is the AXBT ( Airborne Expendable Bathythermograph ). The AXBT is not used from the ship but by a buoy as a sonobuoy. The measuring signal is transmitted by radio as a sonobuoy to the aircraft.