Chapter 5 — BATHYTHERMOGRAPH 



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Figure 5-9. — Grid mount assembly and slide viewer. 



20 feet for the 450-foot model, and 40 feet for 

 the 900-foot model; the BT slide shows double 

 traces over the entire trace length; more than 

 18 months have elapsed since last calibration. 



BT SLIDES 



To make proper use of information on the 

 slide obtained by lowering the BT, an under- 

 standing of how to interpret the trace and its 

 meaning is of as much importance as the lower- 

 ing and raising process. To read the trace 

 properly, two pieces of equipment are necessary. 

 They are the BT grid and the slide viewer. 



GRID AND VIEWER 



Notice in figure 5-8 that the grid has a block 

 in the lower right corner containing certain 

 information. Included are the BT serial number, 

 the type (OC-2/S, meaning that it is the medium, 

 or 0- to 450-foot depth model), and the date of 

 manufacture. 



The grid is mounted in a grid mount assembly 

 that attaches to a slide viewer. Both of these 



items, needed for reading BT slides, appear in 

 figure 5-9. The grid mount assembly in the 

 illustration is a bottom view and shows the grid 

 as it is mounted in the assembly. Putting it in as 

 shown (backwards) allows it to be read correctly 

 when viewed through the slide viewer. The BT 

 slide fits behind it with the etched side toward 

 the grid, and is held in place by a spring clamp. 



Loading Slide into Grid 

 Mount Assembly 



To load the BT slide into the grid mount 

 assembly, set the slide loosely in the holder. 

 It should be positioned with the coated surface 

 down and the beveled corners on the right side, 

 just clearing the stop pin. Hold the assembly 

 as shown in figure 5-10. With a thumb motion 

 like that used in rolling a cigarette, push the 

 slide against the spring until the slide drops 

 flat against the grid. Then push the slide to 

 the right firmly against the stop pin. The coated 

 surface should lie smoothly against the grid. 



The prescribed method prevents the grid 

 from scratching or rubbing against the coated 

 surface. When the holder and slide are placed 



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