Types of dive computers

There are ALLOT of types of dive computers. Just about any manuffacturer of diving equipment has his own brand of dive computer.

Here are some of the producers: Uwatec/Scubapro (with their Aladin series computers), Sunnto, Cressi sub, Genesis, Aeris.

The following table shows some of the computer models, the companies that produce them and some features

More about three of these computers, study and text by Rodale’s Scuba Diving magazine.

Aeris 500 AI

Strenghts

Easy to see, read and understand; Clear graphs with three-color highlighting; Easy adjusting of NDLs at any time with a bar graph; Handles multilevel and repetitive diving well; Excellent backlighting for both surface and underwater use; Multiple user settings that are easy to use; Good instructions and prompt card; Oxygen default in nitrox mode can be turned off; Audible alarms can be turned off; Has user-adjustable sampling rate for dive profiles; Makes use of alternate screens; Displays both remaining gas time and NDLs at the same time; Has a turnaround point alarm.

Weaknesses

Time to fly is an arbitrary countdown. Some letters, symbols and numbers are very small. Building on the success of other Aeris dive computers, the 500 AI adds several significant features to this already strong line of dive computers, including the dependability of hose-mounted gas integration and the ability to display both gas time and NDLs at the same time. Of course, much of the 500 AI's easy, clear usage comes from the color-highlighted graphs for nitrogen, oxygen and ascent rate.

Other positive features include providing total ascent time when in decompression; gas time remaining that provides for ascent time, any decompression and your preset reserve; extensive data in the log function; and a quick high-pressure disconnect so you can separate the computer from your regulator.

Also available are lens protectors, retractors and clips, plus a compass can be added to the 500 AI.

Usage Notes

• If it has been over two hours since the last dive, you need to reactivate the 500 AI, even if there is information, such as time to fly, on the screen.
• The 500 AI counts dives by dive day, so you will have several dives of the same number, but each dive will also be labeled with the date and time of entry.
• All Aeris dive computers are calibrated for salt water below 2,000 feet elevation and for fresh water at higher altitudes.
• By changing the user-adjustable sampling rate for the dive profiles, you can increase the PC download memory to 254 hours, but of course with far less detail.
• If a violation occurs, the 24-hour lockout is from the time of last use, not from the time of the violation.
• The time to fly is an arbitrary countdown, but you can use time to desaturation as time to fly, if you wish.
• Even though the owner's guide tells you that decompression is an emergency, and then tells you how to decompress, decompression is not an emergency.

Aqua Lung/SeaQuest Cobra by Suunto

Strengths

Compact, small size; Intuitive bar graphs with three-color highlighting; Excellent backlight for both surface and underwater use; A great wealth of features and functions; User-friendly for such a feature-rich computer. High degree of adjustability; with both personal and altitude settings before the dive, and the use of graphs during the dive; Provides for both mandatory and optional safety stops; Wealth of user settings; User-selected gauge mode for special tech situations; Displays both remaining gas time and NDLs at the same time; Only Suunto computers can scroll dive profiles without a PC; Makes use of alternate screens; Excellent decompression mode; Has a bookmark feature to mark events during the dive; Most extensive memory and dive history available among today's dive computers; with 36 hours of logged details.

Weaknesses

If violated, goes into gauge-only mode for 48 hours; Nitrogen and oxygen share the same bar graph; Ascent rate indicator is not "buffered," so it shows fast ascents too easily.

The Suunto Cobra packs the most features and functions into a small space of any dive computer we have ever tested. The bringing together of three push buttons with water contacts, graphs and color highlighting, on-screen prompts, dependable hose mounting and the most extensive memory available, make this an outstanding dive computer.

Additional positive features include:

• Oxygen default to 21 percent after two hours of non-use.
• The decompression mode is continuous, so as you ascend, the ceiling moves progressively upward, giving you credit for outgassing and providing an hourglass symbol for the optimum deco zone.
• During decompression, the total ascent time is also displayed.
• The PC sampling rate can be set by the user.

The Cobra is more conservative than older Suunto dive computers. And it can be set to be even more conservative by the use of the personal and altitude settings. The instruction manual states that "the no-decompression limits ... (in the most liberal setting) ... are slightly more conservative than those permitted by the U.S. Navy tables." In fact, the limits range between 56 percent to 80 percent of the Navy tables, depending on depth within the recreational diving range. The leading scientists in the decompression field all agree that the Navy no-decompression limits should be reduced, and Suunto's algorithm does just that, therefore reducing the risk. But by making the Cobra even more conservative with the personal and altitude settings you can reach a point of impracticality: these settings can reduce the no-decompression limits to between 22 and 40 percent of the Navy tables.

Usage Notes

• The Cobra is set for salt water.
• Logged dives are numbered in series until the no-flying time reaches zero. So there will be multiple dives with the same number, but each dive is also identified by date and time.
• Fast ascents can cause a "Mandatory Safety Stop," therefore, you should slow down or stop; if you do not, the no-decompression limits of the next dive will be reduced.
• Take the instructions and prompt card with you on dive trips, as it can be tricky to remember all the button pushing sequences if you do not use the Cobra frequently.
• The nitrogen loading bar graph indicates the time available at depth, not the total impact of the nitrogen loading, as other dive computers do.
• Time to fly is 12 hours plus desaturation time.

The excellent safety stop feature can confuse dive guides who are not familiar with it; so tell your dive guide about it before the dive.

Scubapro/Uwatec Aladin Air Console, Air Z& Air Z O2

Strengths

Clear and easy-to-read displays; Time-to-fly actually calculated and displayed; Also provides desaturation time; Excellent dive profile with PC interface; Long-life batteries; Excellent battery indicator with reserve; Variable ascent rate indicator; More realistic approach to decompression; Gas time remaining and NDLs both displayed at the same time.

Weaknesses

Complete lockout, no gauge mode, no access without a PC; Some settings and data are accessible only with a PC; No planning mode provided in the Air Z O2; Electrical contacts are not labeled.

Even though these three Uwatec Aladin dive computers have very different capabilities, they operate on the same basic algorithm with the same fundamental functions. The Air Console uses a hose, while the Air Z and Air Z O2 are both hoseless. The Air Console and Air Z do not have nitrox functions, while the Air Z O2 does. The Air Z O2 is actually a very sophisticated, high-tech dive computer that can also be paired with an Uwatec OXY-2 (SCR O2) for monitoring the oxygen function of a rebreather. The Air Z and Air Z O2 replace the Air X, Air X Nitrox and Air X O2 in the Uwatec Aladin line.

Other positive features of these computers include:

• Log book and dive planning functions are easy to access.
• Ascent time is provided when in decompression.
• The Air Console has a quick high-pressure hose disconnect on the console end, so it can be removed from the regulator.
• The Air Console also can be fitted with a compass.
• The data displayed on the Air Console is all on the same surface, making it easier to read.
• The PC interfaces provide for 37 logged dives and 175 to 200 minutes of dive profiles, but this can be increased with the use of the optional Memo Mouse to nearly 60 hours of profiles.
• The Air Z and Air Z O2 both have backlights, plus removable/replaceable screen guards.
• The Air Z O2 has excellent oxygen warnings.
• Both the Air Z and Air Z O2 will work without the transmitter, but, of course, will not then display the gas function.
• The oxygen function of the Air Z O2 does not default.

Usage Notes

• The reserve gas setting can only be made with a PC and uses certain odd increments—435, 508, 580, etc. This is due to the calculations being done in metric, but displayed in imperial units.
• A rapid ascent can cause a decompression stop, and, if not heeded, will cause a violation and lockout.
• After the 24-hour lockout period, a desaturation penalty can be added by the computer program for as much as 72 hours.
• The variable ascent rate indicator (faster when deeper and slower when shallower) uses a percentage display, but as it has no "buffer," it jumps around a good deal.
• In the dive plan mode, there is a dive simulator that allows you to change the surface interval and plan no-decompression or decompression dives.
• There are no user adjustments, but Uwatec computers are programmed with a self-adjusting function that increases the conservatism based on temperature, work load, ascent rates and dive profiles.
• The Air Z O2 can be programmed for oxygen from 21 to 99 percent in 1 percent increments.
• Uwatec computers are set for fresh water; therefore, they read 3 percent deeper in salt water; 100 feet reads as 103 feet, etc.

Having no push buttons, Uwatec dive computers do not have alternate screens during the dive mode and are limited as to the data that can be viewed and the settings that can be made on the surface without a PC.