Gas-Integrated Computer Transmitters

Let's admit it. We divers are a funny lot. Although we are often seen as being very adventurous, we are usually very unadventurous when it comes to equipment innovation. This hard-to-understand state of affairs probably stems from newcomers being taught by instructors who have their credibility invested in long-established ideas. New ideas have to be adopted by these usually older divers and instructors, and that can take time to diffuse into normal practice. For example, why do so many sport divers dismiss gasintegrated computers out-of-hand? A bit of history is in order.

Back in the early '60s, divers used tanks with J-valves. When the air was depleted, the regulator became harder to breathe. The diver then pulled the J-valve release, which allowed access to the last quarter of the tank's supply; the regulator freed up and it was time to ascend. Then came submersible pressure gauges, which were met with similar resistance. Some divers saw them as an additional failure point, thinking they could easily explode with so much pressure inside them. A legacy of that is seen today when trainee divers are still taught to hold the gauge away when they first turn a tank on.

Then came resistance to horse-collar-style buoyancy compensators. Many believed it was too easy to inflate them and they would inadvertently send a diver hurtling to the surface. When conventional BCs replaced them, divers resisted them because they might float an unconscious diver face-down at the surface (unlike the horse-collar that worked more like a life jacket). Nobody asked why the diver would be unconscious. Presumably it was because he had lost control of his buoyancy and hurtled to the surface.

Drysuits were another advance for cold-water diving, but again, some resisted that idea at first. True, there was an internationally publicized case of a British scientist snorkelling alone in a Scottish loch who became helplessly inverted and drowned in a few feet of water. However, few took into consideration that a diver who was warm and comfortable in cold water made better judgments, making it safer overall. They concentrated instead on what happened if air in the suit was not vented efficiently during an ascent.

In the mid 80s, diving computers hit the market, and boy, did they cause a fuss. Instead of a diver running his finger along the wrong line of a hard-to-read Navy dive table and coming up with the wrong answer, or instead of a diver misreading his watch and his depth gauge, computers timed the dive accurately, and calculated decompression or reduced no-stop times based on the diver's actual profile.

I remember doing a no-stop dive to 100 feet deep for 20 minutes with two other divers. I used my computer but they insisted their Navy table method was safer. They were bemused when I made a stop 10 feet deep and they did not, but my computer had registered that we had gone deeper than planned and dived for longer than they thought. This Luddite resistance to the technology is something hard to believe in an age when almost every diver now uses at least one computer.

It didn't help that the first two electronic computers on the market suffered design problems. Orca's Edge used proprietary 9-volt batteries that it chewed through at a rate of knots. Some suffered faulty pressure sensors that caused incorrect computations of deco times, and bent divers brought some high-profile legal cases. The Decobrain used the rechargeable battery technology available at that time, and the gradual build-up of gases within the case during the charging process eventually caused all units to leak. These considerations caused many to shy away from the technology.

Divers have been using conventional diver propulsion vehicles (DPVs) since the times of Cousteau. Many years ago, I met a young man from California who had perfected a system that propelled the diver via propeller nacelles and attached to the lower legs, powered by a battery that fitted to the tank. I tried a pair and they proved excellent. When I next met him, I asked him how things had gone. It turned out he hadn't used his devices because European divers had laughed at him when he strapped them on to his legs. They convinced him to do without them.

Later I got myself a Pegasus Thruster, a DPV that straps on to the tank and allows a diver to fly through the water hands-free, which means you have the opportunity to handle a camera. My Thruster has been borrowed by BBC wildlife cameramen because it gives them the chance to get smooth tracking shots. Other divers have laughed at me when they see me don my rig, but I laugh at them as I piss past them underwater, especially if there is a strong current.

Air-integrated computers have been with us for some time. Of course, they too were resisted at first. They made a prognosis of remaining air-time based on a previous breathing rate and the actual depth, but many divers denied that such information might be useful. They declared that they preferred to know the remaining pressure in their tank, as if that information was not available -- which, of course, it is.

Trained divers should certainly understand the concept of remaining air-time in minutes balanced against the total ascent time required, rather than rely on some pressure reading that requires an estimate of how long it would last. However, it took time for this advance to become accepted because of a general distrust in technology. That's ironic when we trust technology so much in so many other ways.

Old habits die hard. Despite initial resistance, air integration by radio transmitter finally took off in Europe. It's only just beginning to fly in America, where air integration by high-pressure hose, just like a traditional submersible pressure gauge, has been more popular.

I was recently aboard the Truk Odyssey and doing some deep dives with double tanks in Truk Lagoon. Each tank was independent from the other, and both regulators' first stages were linked to separate Suunto computers by separate radio transmitters. Another passenger on board stated that he could not believe I was diving without a "proper" pressure gauge. I retorted that submersible pressure gauges have more failure points because they have more O-rings and, well, one could even blow up in your face! (I was joking, naturally, though there might have been an instance or two years ago.)

Of course, there were some defects in gas-integrating transmitters when they were brought to market, notably an occasional loss of pairing between transmitter and wrist unit. Today's computers pair permanently with their wrist units, so the case of failing to get a tank reading underwater with one that needed to be paired immediately before diving has faded into the past. There was also talk of photographers' underwater strobe units interfering with the signal. I have never encountered that, and I've used many different strobe units combined with many different computers.

If you have insufficient confidence in this modern technology, you could always take the redundant route as you do with other items of diving equipment. Two computers are always a good idea, so why not an extra transmitter? Otherwise, there is usually room on your regulator to have a mechanical pressure gauge for use as backup if you prefer.

You are much less likely to run out of gas if you know how long your remaining supply will last. I often witness divers looking anxiously at pressure gauges with needles on the wrong side of that ominous red line, worrying about running out of gas while close to the surface. Of course, such worrying increases one's heart rate and, therefore, the breathing rate. The diver who wants to do a five-minute safety stop with a known 10 minutes of air-time remaining is far more relaxed, and gas can last a long time for a relaxed diver in the shallows, so safety stops often get extended. It is surely better to use remaining gas at the safety stop than to rush back to the surface. Of course, these computers allow the user to build in a chosen reserve, too.

Doug Krause of Oceanic/Aeris tells me that after a long incubation period, sales of gas-integrated computers using radio links to the tank contents are finally hatching in America. They are finally becoming acceptable. It's an unusual example of Europeans being ahead for once!

If you want to join the 21st century of sport diving, let me suggest some models I've tested and highly recommend. Thanks to the likes of Bruce Wienke and others working on computer algorithms that promise to keep us as safe as possible from a decompression injury even when doing multiple repeat dives, all the computers from major manufacturers test well.

Notable for wireless gas integration are the Suunto Vyper Air and its siblings: the wristwatch-like Suunto D4i to DX range; the Scubapro Galileo Sol with its large, easy-to-read screen; the soon-to-be-available new Aeris gas-integrated computer; and the Oceanic Atom 3, which allows for the possibility of gas integration with multiple tanks. (Be sure to get your dive store expert to show you how to choose one of the dual algorithms of any of these computers to suit the type of diving you'll be doing with it.)

Should you go for something like the Mares Icon HD Air with its engagingly colorful display and rechargeable battery, just be very aware that you must be confident to keep it fully charged between dives because such displays suck up a lot of battery power.

John Bantin is the former technical editor of DIVER magazine in the United Kingdom. For 20 years, he used and reviewed virtually every piece of equipment available in the U.K. and the U.S., and made around 300 dives per year for that purpose. He is also a professional underwater photographer, and most recently the author of Amazing Diving Stories, available at www.undercurrent.org