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Chapter 5- Decompression, Dive Tables, and Dive Computers Decompression, Dive Tables, and Dive Computers 145 ation before you begin your dive. If you must turn your computer on with a switch, do not turn it on at depth, or after you have started your descent, because your dive will not be recorded accurately. You can damage some computers by turning them on at depth. Scrolling All computers can scroll before diving (after they are initialized) and between dives. Between dives, the computer accounts for your residual nitrogen and the time you have been on the surface. It shows your Allowable Maximum Dive Time for your next dive for each depth programmed in the computer. This is called scrolling. Some computers will scroll continuously while you are on the surface. Once they have scrolled through the maximum dive depths that they are able to calculate they show your last dive or series of dives. Other computers will scroll only if put in Planning mode. Read your dive computer’s manual to learn how to make your computer scroll. Dive Mode When a computer is in dive mode, it will display data such as your current depth, maximum depth, water temperature, actual dive time, and the time you have left at your current depth (figure 5-25). Some computers will also show a graphic representation of the nitrogen in your body or in various theoretical tissues. An air-integrated computer will show the air pressure in your cylinder. It might also indicate how much time you have left at your current depth based on your air consumption. Some dive computers will compare your remaining air time with your remaining dive time and display whichever is the shorter, limiting factor. As your bottom time lessens and you approach decompression status, some computers give you a visual warning message such as “GO UP.” When this occurs, you must begin your ascent immediately, but at the proper rate. FIGURE 5-25. WHEN A COMPUTER IS IN DIVE MODE, IT WILL DISPLAY DATA SUCH AS YOUR CURRENT DEPTH, MAXIMUM DEPTH, WATER TEMPERATURE, ACTUAL DIVE TIME, AND THE TIME YOU HAVE LEFT AT YOUR CURRENT DEPTH. Most computers require that you use an extremely slow ascent rate. Some models have different ascent rates for different depth ranges. All dive computers give a warning signal when you exceed the ascent rate (figure 5-26). Some computers warn you with a flashing screen stating something similar to “SLOW” or will warn you with a flashing red light. Other models warn with a beep or a synthesized voice. No matter what the signal, you must slow down or possibly stop your ascent until your computer tells you to ascend. Any time you violate your computer’s ascent rate, you increase your risk of DCS. Always monitor your computer carefully during ascent. If you exceed your computer’s maximum depth range, your computer will warn you with a message FIGURE 5-24. A DIVE COMPUTER DISPLAY WILL LIGHT UP COMPLETELY DURING INITIALIZATION.


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