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Dive Computers

Dive Computers. UMAINE Scientific Diving Program. Dive Computers. Increasingly common in the diving community Almost all recreational divers use computers Some recreational agencies train only with computers Increased reliance on computers for dive planning/ tracking.

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Dive Computers

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  1. Dive Computers UMAINE Scientific Diving Program

  2. Dive Computers • Increasingly common in the diving community • Almost all recreational divers use computers • Some recreational agencies train only with computers • Increased reliance on computers for dive planning/ tracking

  3. History of Dive Computers • More than 30 years • First commercially available computer • Orca EDGE

  4. Advantages of Dive Computers • Increased Dive Profile Precision • Use of more complicated / multiple algorithms • Allow Multi-Level Profiles • Increased Dive Time vs. tables • Increased Information / Dive Profile Data • Dive Logging Aids / Reporting • Fewer Calculation Mistakes

  5. Disadvantages of Dive Computers • Precision, NOT Accuracy • May reduce safety margin • Provide false sense of security • May encourage risky behavior/ diving to limits • Hidden Assumptions • Semi-autonomous = less incentive for diver planning • Malfunctions / Power Loss

  6. Precision vs. Accuracy Precisely calculates / tracks dive PROFILE Eliminate estimates Eliminate rounding Applies data directly to algorithm Does not accurately measure N2 Absorption / Elimination NO DIVE COMPUTER CAN ACCURATELY MEASURE YOUR PHYSIOLOGIC CONDITION OR ACUTAL NITROGEN EXPOSURE All based on THEORETICAL models.

  7. Misuse of Dive Computers • Failure to account for Residual N2 from previous dives • Failure to plan for contingencies • Ascent Rate Violations • Multiple Diver Sharing • Switching OFF / Clearing Memory • Improper Time/ Depth Profiles • Excessive confidence in computer algorithm

  8. Before Diving with a Computer • Working knowledge of: • Dive Tables/ Decompression Theory • Computer assumptions, guidelines, hazards • Proper computer use/ implementation • Type/model of computer to be used • UMAINE / AAUS Dive computer guidelines • Approval from UMAINE DSO / DCB

  9. Computer Training Requirements • DCB Approved Training Session • DCB Make/Model Approval • Diver Authorization is Make/Model Specific • Annual testing / service / calibration • Knowledge and Proficiency Evaluations • Written Exam • Practical Dive session(s)

  10. AAUS Dive Computer Guidelines 1. Only those makes and models of dive computers specifically approved by the Diving Control Board may be used. 2. Any diver desiring the approval to use a dive computer as a means of determining decompression status must apply to the Diving Control Board, complete an appropriate practical training session and pass a written examination. 3. Each diver relying on a dive computer to plan dives and indicate or determine decompression status must have his/her own unit. 4. On any given dive, both divers in the buddy pair must follow the most conservative dive computer. 5. If the dive computer fails at any time during the dive, the dive must be terminated and appropriate surfacing procedures should be initiated immediately. 6. A diver should not dive for 18 hours before activating a dive computer to use it to control their diving. 7. Once the dive computer is in use, it must not be switched off until it indicates complete out gassing has occurred or 18 hours have elapsed, whichever comes first. 8. When using a dive computer, non emergency ascents are to be at a rate specified for the make and model of dive computer being used. 9. Whenever practical, divers using a dive computer should make a stop between 10 and 30 feet for 5 minutes, especially for dives below 60 fsw. 10. Multiple deep dives require special consideration.

  11. UMAINE Dive Computer Requirements(Section 3.2) Timing Devices, Depth and Pressure Gauges • Each diver must have an underwater timing device, an approved depth indicator, and a submersible pressure gauge. Gauges shall be inspected and tested before first use and every twelve months thereafter.

  12. UMAINE Dive Computer Requirements(Section 3.2) Determination of Decompression Status: Dive Tables, Dive Computers • a) A set of diving tables, approved by the Diving Control Board, must be available at the dive location. (Approved no-decompression tables are listed on the UMAINE Personal Diving Log, Appendix 9) • b) Dive computers may be utilized in place of a depth gauge and timing device, and must be approved by the Diving Safety Officer. AAUS guidelines for dive computers are available in Appendix 14. • c) Each diver must plan and monitor their dive individually, according to the method employed to calculate decompression status (i.e. depth gauge, timing device, and tables; or dive computer). A single depth gauge and timing device or a single dive computer may not be used to monitor decompression status for more than one diver. • d) A written record of the diving activity as described in Section 2.70 will be filled out at the dive site in a timely manner to ensure an accurate account as possible of the diver's dive profile.

  13. One Diver, One Unit Each diver must have a specific and separate unit dedicated to his/her use for the duration of the dive series.

  14. Only 1 Computer = Use Tables If either member of a buddy pair does not have a computer, the dive will be planned and executed using University approved dive tables.

  15. Dive Profiles • Proper Profiles • Deepest portion of dive first • Progressively shallower • Slow ascents • Improper Profiles • Reverse Profiles • Sawtooth Profiles • Repetitive Bounce Dives All increase DCS Risk

  16. Ascent Rate Ascent rates shall be no faster than the rate indicated by the computer.

  17. Safety Stops Whenever practical, divers shall make a safety decompression stop between 10 and 30 fsw for 5 or more minutes, especially for dives deeper than 60 fsw.

  18. Multi-Day/Multi-Deep - Be Conservative - Models not well tested. - Suggest Day Off every 3-5 days

  19. Computer Failure = Dive Terminated In the event of a DC failure at any time, diving will be terminated immediately, using proper ascent procedures.

  20. 24 Hour Rules Pre-Dive- A diver shall not dive for 24 hours prior to activating a dive computer to control decompression status. Computer Stays On- For computers with manual on/off switches, the computer shall not be switched off for 24 hours after end of diving. Failure / Switch Off- If a diver’s computer fails, or the computer is switched off before it indicates completeoutgassing , the diver shall not dive for 24 hours. One-ceiling per day- Only one dive shall be made in any 24 hour period in which a decompression ceiling is incurred.

  21. AAUS REVERSE PROFILES • 1999 AAUS Workshop • “Is doing a deeper dive after a shallower dive a risk factor for DCS? • “What exactly is a Reverse Profile?” • Panel of Experts • All Industry Segments • Theory and Practice Review

  22. WORKSHOP FINDINGS • Artifact of USN Tables • TIME Advantage for Deep First • Communication Error • Reverse Profile not a risk IF: • Depths < 130 fsw • No Decompression • “Delta-D” < 40 fsw SAFETY STOP IMPORTANT

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