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Chapter 1- Diving Equipment Diving Equipment 19 expand the oil and can produce leakage. Underwater Timers Analog and digital dive watches are available, and some watches feature both types of display. An analog dive watch usually has a rotating outer bezel that can be used to indicate elapsed time. A bezel that rotates counter clockwise only is preferred, as the indicated elapsed time can only err on the side of safety, by adding to and not subtracting from underwater time. Digital watches can have additional desirable features such as a stop watch, alarm, timer, light, and even a built-in compass or depth gauge. Bottom timers are pressure-activated instruments that automatically record the time spent below a depth of about 1.5 m (5 ft). Digital and analog types are available, both battery-powered and mechanical springwound. A distinct advantage of a bottom timer over an underwater watch is the automatic operation, since you may forget to set a watch. Many modern bottom timers have a memory to keep track of previous dives, which can be recalled at a later time. Dive watches are now available with advanced features such as a display of depth, temperature, and elapsed time. Some models even have a dive log memory and personal computer interfaces that allow the transfer of many hours of dive profile data to a personal computer. Dive watches and bottom timers should be rinsed with fresh water after diving, and cleaned and inspected annually. Avoid wearing your dive watch in a spa, hot tub, or in the shower. The combination of high temperature and soap can result in damage. Electronic Dive Computers Air-Filled Tube Totally Enclosed Pliable Casing Oil-Filled Water Water Water Water FIGURE 1-15. ENCLOSED BOURDON TUBE GAUGE Dial Sealed Chamber Metal Diaphragm Water Chamber Water Pressure Needle FIGURE 1-16. DIAPHRAGM DEPTH GAUGE FIGURE 1-17. DIVE COMPUTER MOUNTED ON HIGH PRESSURE HOSE FIGURE 1-18. WRIST MOUNT DIVE COMPUTER


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