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Gas Integrated Computers

April 25, 2014

Equipment Development and Gas-Integrated Computers.

Let's admit it. We divers are a funny lot. Although we are often seen by others as being very adventurous in what we do, we are usually very unadventurous in the way we do it and that is especially true when it comes to equipment innovation.
Back in the early '70s, divers used tanks with J-valves. When the air in the tank was depleted, the regulator became harder to breathe from. 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. It sounds a bit primitive doesn't it? Can you believe that when submersible pressure gauges (SPGs) were first introduced they were met with some resistance?
Some divers saw them as an additional hazard, an additional failure point. They thought they could easily explode with so much pressure inside them and 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. I haven't ever heard of a pressure gauge so exploding but I'm sure it must have happened - once!
Then we got horse-collar-style buoyancy compensators. These were resisted because it was claimed to be too easy to inflate them and send the diver hurtling to the surface. When conventional BCs replaced them, they too were resisted at first 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 was unconscious. Presumably it was because they had lost control of their buoyancy and hurtled to the surface.
Drysuits were another advance for cold-water diving but again that idea was resisted by some at first. It was true, there was a high profile case of a British scientist snorkelling alone in a Scottish loch, who got helplessly inverted and drowned in a few feet of water. However, few old divers took into consideration that a diver who was warm and comfortable in cold water made better judgements, making it safer over all. They concentrated instead on what happened if air in the suit was not vented efficiently during an ascent.
Then dive computers were invented and did that cause a fuss? Yes, it did. Instead or a diver running his finger along the wrong line of a hard-to-read mathematical table and coming up with the wrong answer, instead of a diver misreading his watch and his depth-gauge, electronics timed the dive accurately and calculated decompression or reducing no-stop times based on what the diver had actually done during a dive.
I remember doing a classic no-stop dive to 100 feet deep for twenty minutes with two other divers. They invited me to use my computer but insisted their traditional table method was safer. They were bemused when I needed to do a stop at ten feet deep and they did not, but it was because my computer had registered that we had gone deeper than they planned and dived for longer than they thought. Back at that time, some divers with computers found themselves having ugly confrontations with other divers about it. This Luddite resistance to the technology is something hard to believe in an age when almost every diver now uses at least one computer.
This hard to understand state-of-affairs probably stems from the fact that newcomers to diving are taught by experienced divers who have their credibility invested in long established ideas. New ideas have got to be adopted by these usually older divers and that can take time to diffuse into normal practice.
It didn't help that the first two electronic computers on the market suffered design problems. The Edge, popular in America, used proprietary 9volt batteries that it chewed through at a rate of knots. Later, around 1986, some suffered faulty pressure sensors that caused incorrect computations of deco times and there were a handful of high-profile Court cases. The Decobrain, more popular in Europe, 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 people 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 that attached to the lower legs and powered by a battery that fitted to the tank in lieu of lead on the belt. I tried a pair and they proved excellent. The inventor was in the UK on his way to a diving safari in the Red Sea.
When I next met him I asked him how he got on. It turned out he hadn't used his devices because the other (European) divers on the boat had laughed at him so much when he strapped them on to his legs. They convinced him to do without them.
Later I got myself a Pegasus Thruster. It too is a diver-propulsion device but instead of needing to hold on to it in the way one does a conventional unit, it straps on to the tank allowing the diver to fly through the water hands-free. It means you have the opportunity to handle a camera and my Thruster has been borrowed by BBC Wildlife cameramen because it gives them the chance to get really smooth tracking shots.
Other divers have often laughed at me when they see me don my rig so equipped 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. They were resisted as well at first. Myths and misinformation grew up surrounding them. Because they made a prognosis of remaining air-time based on a previous breathing rate and the actual depth the diver is at, many who should have known better declared that they preferred to know the remaining pressure in their tank, as if that information was not available as well.
I would say that we all understand the concept of remaining air-time in minutes balanced against the total ascent time required (hopefully the former is always greater than the latter) rather than some pressure reading but it took time for this advance to become accepted. It was caused by a general distrust in technology. That's ironic when we trust technology so much in so many other different ways.
America is often seen as the home of innovation but is noticeable that air-integration of diving computers via a high-pressure hose is more popular still in the USA than it is in Europe. Despite initial resistance, air-integration by radio transmitter finally took off in Europe but it's only just beginning to fly in America.
I was recently doing some deep dives with double tanks in Truk lagoon. Each tank was independent from the other and both regulator's first-stages were linked to separate Suunto computers by separate radio transmitters. Another passenger on the mv.Truk Odyssey stated that he could not believe that I was diving without a 'proper' pressure-gauge.
I think I confused him when I cited all the old reasons given to me for not having a submersible pressure gauge by those old J-valve divers from forty years previously. I retorted that submersible pressure gauges have more failure points in that they have more O-rings and, well, one could even blow up in your face! I was joking, naturally.
Of course there were some defects in gas-integrating transmitters when they were initially invented, 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 under water with one that needed to be paired immediately before diving has faded into the past. There was also talk of photographer's underwater strobe units interfering with the signal. I've never encountered that and I've used a lot of different strobe units as well as a lot of 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 as well, for use as back-up, if you prefer it.
Knowing how long your air will last rather than simply the pressure remaining in your tank makes sense to me and there's always a big safety margin built in too. You are much less likely to find yourself run out of gas if you know that your remaining air is going to last a definite amount of time. I often witness divers looking anxiously at pressure gauges with needles the wrong side of that ominous red line, worrying about running out of gas while close to the surface. Worrying simply increases your heart-rate and with it your breathing rate. The diver that wants to do a five-minute safety stop with a known ten 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's better to off gas gently at six metres than to rush back to the surface because you think your air won't last. Of course, all these computers allow the user to build in a chosen reserve.
Doug Krause of Oceanic/Aeris (AUP) 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 took its time. It's an unusual example of Europeans being ahead for once!

Happy Diving - John Bantin

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