The main purpose of a dive computer is to help scuba divers measure the duration (and various other statistics) of their dives, then guide them safely back to the surface.
A dive computer watch, is a dive computer packed into the size of a regular sports watch. Consumer dive computer watches offer the readings of a traditional analog diving watch in a digitalized form, as well as a bunch of extra features and functions that are beyond the abilities of an traditional analog watch.
Dive computers offer an alternative way of calculating the information that was traditionally the job of decompression tables and as a computer can perform continous calculations based on real-time data of the partial pressure of inert gasses in the body, depth of the dive and time, the computer readouts can be computed in real-time, offering the diver up-to-the-minute information that accounts for any changes in dive schedule.
The information offered by a modern day dive computer watch varies from model to model. Typically it can display the following information:
- Current depth, in easy-to-read LCD format
- The maximum depth achieved in the current dive
- The time taken to reach the current depth, excluding decompression stops
- Cumulative dive time
- Required decompression stop depth and time
- Current water temperature
- Rate of ascent in this dive
- Diving profiles (useful when transfering your diving information to a personal computer)
- Time to Fly – how long a diver must wait after a dive before boarding an airplane
- Diving history – all information gathered in previous dives
- Maximum non-decompression bottom times time of the last dive
Advanced diving computers are capable of linking to a diving cylinder pressure meter, allowing them to display information such as gas pressure and estimated breathing time based on current consumption and gas remaining.
In many brands of dive watch computers, audible alarms can be configured to sound when the diver has missed a decompression stop, exceeded his maximum operational depth, is ascending excessively fast or when oxygen toxicity limits have been exceeded.
One disadvantage of dive computer watches, over analog dive watches, is that they consume battery power as opposed to many popular scuba diving watches that rarely need a recharge. Computer dive watches work by measuring time and the surrounding pressure to estimate the partial pressure of gas accumulation in the diver’s tissues. From this the diving computer is able to create an estimate of when a direct ascent is no longer possible and will then come up with a strategy that includes one or more decompression steps to ensure a safe ascent to sea level. A good dive watch computer can even account for dives that take place in water above the normal sea level, in places where a slower ascent rate is required.
Some examples of the algorithms used to determine decompression include the Varying Permeability Model, the Reduced Gradient Bubble Model, Bühlmann tables and the Multi-Tissue Model.
While modern day dive computer watches are capable of generating an ascent plan on-the-fly, for safety reasons, it is still recommended that divers plan their dives well in advanced and unless the dive is altered due to unexpected circumstances, stick to the original plan. The plan should always be within the limits of established decompression tables.
A problem with dive computer algorithms is that pressurized release and aborbtion gas in the human body is still not understood completely. Another cause of error is that the fitness, health and physiology of an individual diver varys from person to person.
A diver is recommended to undertake the following precautions to reduce the chance of decompression sickness:
- If relying on dive computers, try and use a conservative decompression model
- Factor in common environmental discrepencies that the dive watch may not be programmed to compensate for (e.g. high altitude)
- Add extra deep safety stops when undertaking a deep dive
- Never be afraid to make your ascent slower
- Add more shallow safety stops
- Ensure you spend a long period of time at the surface between dives
Some dive watch computers even have a “lockout” mode that renders the watch unsuable for a 24 hour period, whenever a diver violates the computer’s programmed safety limits, the idea being to prohibit further dives after the user makes an unsafe dive.
Special Purpose Dive Computers
Specialized diving computers have the ability to determine decompression schedules when the diver is breathing gasses other than regular air. Pure oxygen, heliox, nitrox and trimix are such common gas mixtures. The majority of these types of diving computers determinine compression for ‘open circuit’ SCUBA where proportions of gasses are at a constant level. These are called “constant fraction” dive computers. Others use ‘closed circuit’ SCUBA (rebreathers), where constant partial pressures of the gasses vary. These are called “constant partial pressure” dive computers.
Dive Computer Watch Manufacturers
The following companies are makers of dive computer watches:
- Benemec Dive Computer Watches
- Citizen Dive Computer Watches
- Cochran Undersea Technology Dive Computer Watches
- Delta P Technology Dive Computer Watches
- HeinrichsWeikamp Dive Computer Watches
- HTM Sports: Mares and Dacor Dive Computer Watches
- HydroSpace Engineering Dive Computer Watches
- Liquivision Dive Computer Watches
- Pelagic Pressure Systems: Aeris and Oceanic Dive Computer Watches
- Shearwater Research Inc. Dive Computer Watches
- UWATEC Dive Computer Watches (child company of Johnson Outdoors)
- Underwater Technology Center Dive Computer Watches
- Seiko Dive Computer Watches
Others companies sell clones of the major manufacturers. These are:
Seiko Clone Computer Watches
- Apeks Dive Computer Watches
- Cressi Dive Computer Watches
- Dive Rite Dive Computer Watches
- ScubaPro Dive Computer Watches
- Tusa Dive Computer Watches
- Zeagle Dive Computer Watches
Pelagic Pressure Systems Clone Computer Watches
- Beuchat Dive Computer Watches
- Genesis Dive Computer Watches
- Seemann Dive Computer Watches
- Sherwood Dive Computer Watches
Benemec Oy Clone Computer Watches
- A.P.Valves Dive Computer Watches