When you ask divers about their certification class, no one ever gets excited and says, “Oh, oh, and learning those dive tables was so much fun!” Diving itself is quite fun, yes, but calculating dive tables, tracking repetitive dives, pressure groups and accumulated bottom time has about the same thrill factor as a conversation with your father-in-law. The one that sells life insurance. To old people.
This dislike for dive table calculations is one of the great traditions of diving, much like peeing in your wetsuit to stay warm. In fact, since the very first days of scuba, divers have been building machines to do the calculations for them. As early as the 1950s there were “decompression meters,” “decompression computers,” “deco-meters” and a slew of other devices that have evolved into the present day “dive computer.” Following is a look back at these magnificent devices and the innovations that we often take for granted.
Meter - 1959
Dive computers, for all their present day sophistication, have very humble beginnings. Long before the days of microprocessors and long-life lithium batteries,
engineers built mechanical devices to simulate (rather than actually calculate) the process of nitrogen absorption in the body’s tissues.
The most successful example of these mechanical devices is the SOS Decompression Meter. More affectionately known as the “Bends-O-Matic,” it was sold in the U.S. by Scubapro and manufactured by the Italian firm, SOS Diving Equipment, Limited. This pneumatic device used a ceramic resistor set between two air chambers (one flexible, one constant) to simulate nitrogen absorption and off-gassing in the body. An indicator needle showed the depth to which a diver could safely ascend.
The SOS Meter proved to be more conservative than the U.S. Navy’s diving tables for depths shallower than 60 feet, but considerably more liberal than the Navy tables for deeper depths. But, despite its limited accuracy and questionable reputation, the SOS Meter remained popular through the late 1970s.
Decomputer - 1975
The mid-seventies saw attempts at incorporating electrical technology into dive computers, but the result was
expensive and fragile equipment. So, in 1975 Farallon’s Decomputer was the next stage in the quest for a better mechanical device.
It utilized four semipermeable membranes that represented two theoretical tissue groups (one “fast” and the other “slow”). As the diver moved through the water column, the membranes absorbed and released gas, moving pistons that changed a color-coded display. The green, yellow and red display represented the diver’s decompression status. Surface in the green or low-end of yellow and you were fine. Surface while the Decomputer showed red, and you were not.
The Decomputer's demise was that it was too permissive and seemed to become less-reliable with continued use.
Orca EDGE - 1983
Orca’s Electronic Dive Guide is the granddaddy of the modern dive computer. Also referred to as “the brick,” the EDGE did what no computer did before, it combined a rugged exterior (courtesy of a massive aluminum case) with an intelligent interior. Thanks to the famed microprocessor, the EDGE catapulted dive computers from the dark ages of mechanical systems into the modern era of chips and batteries. It calculated no-deco limits based on depth, time and a pre-programmed algorithm.
The EDGE also combined a graphical and numerical display. A “depth bar” on the left of the screen showed max depth, while a numerical reading on the right gave temperature, depth, dive time and remaining no-deco time. In the center was a bar graph that illustrated nitrogen absorption for 12 tissue compartments. These represent the speed at which different body tissues absorb and release nitrogen. If one of the compartment bars ever exceeded the limit line curve in the middle of the screen, decompression stops were required.
Orca later introduced the Skinny Dipper, which became extremely popular for its small package size.
Datamaster - 1985
Pictured is the Datamaster Sport, actually a generation beyond the original model, but still quite similar in form and function. Its contribution to dive computer history is air-integration.
The Datamaster began the practice of combining the capabilities of a pressure gauge and a dive computer. In addition to simply reading the air pressure, the Datamaster computers could also calculate air consumption and use that to help determine remaining dive time. Interestingly, early models were turned on solely by the increased pressure exerted while submerged, while later units would incorporate the now-common push button for activation.
Orca Phoenix - 1991 / Dive Rite Bridge - 1992
Today, nitrox computers are nearly as common as snorkel keepers, but back in 1991 they were the latest in dive wizardry. Late that year, Orca introduced a nitrox version of its popular Phoenix. It would allow for use of only one nitrox mix (EAN32), but set the stage for a flood of dive computer innovations.
Shortly after the enriched air Phoenix hit the streets, Dive Rite introduced the Bridge. This was the first programmable nitrox computer that would allow the diver to set the fraction of oxygen (FO2) to accommodate a wide variety of nitrox mixes. This programmable feature quickly became the standard, and today, all nitrox computers allow this kind of flexibility.
Cochran Aquanaut - 1993 &
UWATEC aladin Air X - 1993
Air-integrated computers had one drawback, they had to be attached to a hose. So, if you liked the convenience of wrist-mounted instruments, you were out of luck. That is, until 1993, when Cochran and UWATEC introduced hoseless air-integrated computers.
In place of a high-pressure hose, the diver installs a transmitter into the high-pressure port of the regulator first stage. This nifty device senses tank pressure and beams the information out to the wrist-mounted computer. It’s all the convenience of integration without so much as a console to snag the reef.
Cochran, a few years later, also introduced the Nemesis II (pictured). It was the first multi-gas nitrox computer that allowed the diver to use multiple nitrox mixes during a single dive.
Today, there are dive computers that can
support multiple varieties of nitrox and trimix and let you switch between gases at will. They can alter decompression limits based on air consumption rates, water temperature, previous dive history, oxygen exposure and pre-programmable levels of conservatism. All of this information can be downloaded to a PC, so that custom software packages can slice, dice, puree and analyze every aspect for a given dive. And, if that’s not good enough, a computer’s sampling rate can be changed to provide information for, literally, every second a diver spends submerged.
Now, when can we get e-mail underwater?