the amount of this error for accurate results. In 

 order to determine the amount of correction to 

 apply to depth for accurate work, the following 

 ])rocedures can bo used in an emergency : 



With tlie sleeve all the way back, im- 

 merse the thermal element in a cold and 

 then in a warm (less than 105° F.) bucket 

 of water. This will cause a long zero depth 

 line to be drawn across the slide. The slide 

 is then placed in the viewer and the differ- 

 ence, in feet, of the trace above or below the 

 zero depth line on tlie grid is the error for 

 which corrections must be made at all 

 deptli readings. 

 BT"s that have a depth eri'or of more than 10 

 feet for a 200-foot instiiunent, 20 feet for a 450- 

 foot instrument, or 40 feet for a 900-foot in- 

 strument should be replaced. 



C-10 The Expendable Bathythermograph 



or XBT. — An expendable bathythermograph 



system (XBT), built by the Sippican Corp., is 

 used aboard ship for measuring the temperature 

 of sea water in the water column from the sur- 

 face down to a depth of 1,500 feet. (Measure- 

 ments to depths of 2,500 or 5,000 feet can be 

 obtained with special probes and recorder mod- 

 ifications.) Tlie XBT can be used while the ship 

 is liove to, but it is especially designed to be used 

 wliile the sliip is underway. Tlie XBT includes 

 three components: the launcher, the recorder, 

 and the expendable probe (fig. C-15). 



The launcher (fig. C-16) includes the dis- 

 charge tube, tlie breech, the stanchion, and the 

 launcher/recorder cable. 



The recorder (fig. C-17) is a conventionl 

 type, 120 VAC, 60HZ, analog recorder with a 

 temperature scale from 28° to 96° F or —2° to 

 35° C. Special depth/temperature scaled chart 

 paper is used in the recorder. 



The expendable probe (fig. C-18) includes 

 the canister, the probe with calibrated thermis- 



DISCHARGE TUBE 



Figure C-15. Expendable bathythermograph (XBT) 

 system. 



Change 1—1970 



CABLE TO RECORDER 



Figure C-16. XBT launcher, Sippican model LM-2A. 



C-9 



