1. J. Paul Martin, MD Asheville, NC
Dive Computers
J. Paul Martin, MD Asheville, NC

2. 1st commercially available diver-carried electronic dive computer – ORCA Industries’ EDGE – 1983

6. Scott Haldane Scottish physiologist published his dive tables in 1908
Robert Workman, MD researcher in US navy published tables based tissue compartment half times (speed of gas dissolving).
Dr. Albert Buhlmann from Zurich extended the number of TCs to 16 published in 1983
It takes 6 half times to saturate a tissue to 98% saturation.
Scotish physiologist John Scott Haldane is considered to be the father of modern decompression theory. Haldane was the first scientist to apply a scientific approach to predicting decompression and his methods form the basis of the majority of modern decompression theories. Haldane introduced the concept of half times to model the uptake and release of nitrogen into the blood. The half time is the time required for a particular tissue to become half saturated with a gas. He suggested 5 tissue compartments with half times of 5, 10, 20, 40 and 75 minutes.
The approach to decompression modeling proposed by Haldane was used with minor modifications from 1908 through until the 1960s. These modifications were primarily changes to the number of compartments and half times used. The US Navy tables published in 1937 and based on research by O. D. Yarbrough used only 3 compartments as the two fastest compartments were dropped (5 and 10 mins). Later revisions in the 1950’s restored the fast 5 and 10 minute compartments as well as adding a slower 120 minute compartment for a total of six compartments.
It wasn’t until the 1960s that any fundamental changes to the model were considered. Robert D. Workman of the U.S. Navy Experimental Diving Unit (NEDU) was a medical doctor with the rank of Captain in the Medical Corps. It had been observed that tables based on Haldane’s work and subsequent refinements were still inadequate when it came to longer and deeper dives. Workman undertook a review of the basis of the model as well as subsequent research performed by the US Navy.
Workman revised Haldane’s model to take into account the fact that each of the various tissue compartments can tolerate a different amount of overpressurisation and that this level changes with depth. He introduced the term "M-value" to describe the amount of overpresurization each compartment could tolerate at any depth. Workman also added three further slow tissue compartments with 160, 200 and 240 minutes half times.
Rather than present his calculations as a completed table Workman presented his conclusions in the form of an equation which could be used to calculate the results for any depth. He also made the observation that "a linear projection of M-values is useful for computer programming as well" and so was one of the first people to identify the role that computers would come to play in the calculation of decompression tables.
Source of Algorithms

8. Gradient Factors All on gasing Faster compartments saturated
Deep stop only fastest supersaturated
Safety stop most of fast compartments off gasing
When we dive, we always have an invisible ceiling above us. This ceiling is a depth, which we can ascend to without getting DCS symptoms. The ceiling is based on the amount of dissolved inert gas in our tissues. Before the dive, your ceiling is in fact negative depth, meaning that your tissues could tolerate certain overpressure gradient. As the run time increases and diver spends time at the bottom the ceiling depth goes down and starts limiting the ascent possibilities, generating the need for decompression.
The fastest tissues are the lungs, which achieve equilibrium almost instantly. Blood follows in speed, then the brain. The slowest tissues are those that are relatively poorly perfused, such as ligaments and cartilage and bone, or those that have a high capacity for inert gas uptake, such as fat in poorly perfused areas.

9. Dive Computer Algorithms
Buhlmann ZH- L12 Linear 12 Tissue Compartments
Buhlmann ZH-L16 Linear 16 Tissue Compartments
RGBM 100/50 (Reduced Gradient Bubble Model)
DSAT (Diving Safety and Technology)
Dual/Hybrid
Based on theoretic calculations of tissue half-times for nitrogen uptake and off-gasing
Dive Computer Algorithms

10. Dive Computer Algorithms
Buhlmann ZH-L16
Buhlmann ZH – L12
APD Vision Electronics
Atomic Cobalt
Dive Rite NiTek Q / Trio
Liquivision Lynx /Xeo
Shearwater Predator / Petrel
Tusa Element / Zen
VR Tec. NEHeo3 / VRX
Apeks Quantum
Cressi EDV II
Tusa IO-850
Zeagle N2iTiON
Dive Computer Algorithms

11. Dive Computer Algorithms
RGBM
Dual / Hybrid
Hydrospasce HS Explorer
Mares Ico HD / nemo / Puck
Suunto Cobra / D4i / Viper / Zoop
U/W Tech Center UDI
Liquivision X1
Oceanic Atom 3.0 / Geo 2.0 / OC1 / Veo / VT 4.0
DSAT
Aeris CompuMask HUD / Elite 3 /
Epic / Manta / XR-2
Oceanic Datamask HUD / Pro Plus 2.1
Dive Computer Algorithms

12. Sept. 20, 2016

14. The Vision takes the simple operation and clean display from Sherwood’s Wisdoms and adds capabilities including four gas mixes and a digital compass. It’s also more compact, but the display is still sharp and easy to see, with a nice layout and a good backlight. The main screen shows no-deco or O2 time remaining, depending on which is the controlling factor, as well as air time remaining. The three-button navigation is thoroughly intuitive. The 2-D compass is bare-bones but gets the job done. The Vision comes with a locking quick-disconnect and has a user-replaceable battery. Above all we liked the Vision’s plain-spokenness; alt screens say “ALT,” and deco stops are “DECO STOP.” There’s a lot to be said for saying what you mean. The Vision is our Testers Choice in this category.
$920

15. Aqua Lung I300
The i300 keeps things simple and is a very user-friendly dive computer.
“Uncomplicated” is how Aqua Lung describes its i300, and we couldn’t say it better. With big characters and clear cues, the display is easy to see, whether in bright sun or deep dark (with an excellent backlight). The two-button advance/select interface is so simple, it won’t confuse even the newest diver. Selecting a nitrox mix is quick and easy, and doesn’t require changing modes, just increasing the FO2. The safety stop is programmable and clearly marked, but the timer doesn’t show seconds. The alt dive screen is easy to access, though there’s not much data. The tissue-loading and ascent-rate graphs are visible and understandable, and the alarms are very good, with a surprisingly bright red LED between the metal buttons, which are easy on the fingers. Also available in a two- or three-gauge console ($399 and $469), the i300 is thoughtfully designed and well-executed at an attractive price
$399

16. The Perdix isn’t easy to pigeonhole into a category
The Perdix isn’t easy to pigeonhole into a category. It has hairy-chested tec capabilities: open- and closed-circuit modes with five gases in each; programmable for any blend trimix; rated to 850 feet. Yet it’s also a surprisingly friendly rec computer. Its display is one of the easiest to read that we’ve ever used, even in full sun. It helps that the screen is about half the size of a smartphone, but what makes it so readable is the way the crisp, bright characters jump out on the black background. The mix of colors also makes info pop. The bottom of the dive screen toggles through a long selection of info, including a three-color tissue-loading graph and an excellent digital compass. The safety-stop display is perfect, and the two-button navigation, aided by clear screen prompts, makes setup incredibly easy for a computer with so many possibilities. This is a computer for anywhere you dive, even if it’s just 40 feet down on a sunny reef.
$849

17. The full-color screen is what grabs you, but there’s a lot more to the VTX. For a computer with so many settings and options, it’s also one of the easiest that we’ve ever used. The three-button navigation and menus are so simple, you can do almost anything without looking at the manual, although the full-color manual is one of the best in our test. The dive display is excellent, and the prompts and alarms — whether for deep stop, deco stop, safety stop or ascent rate — are impossible to miss or misunderstand. Beautiful as it is, the screen can be hard to see out of the water in bright sun, and the VTX is a little power-hungry (both common issues with other full-color computers we’ve used). The elegant construction of the VTX also earned praise. “A thing of beauty,” wrote one diver . But it turns out that the best parts are inside. The VTX is our Testers Choice in this category.
$ $399.95

18. You probably got this warning before your first computer dive: This is a calculator running a theoretical algorithm and it knows nothing about you. The Mantis 2 changes that. Equipped for “human-factor diving,” the M2 can be paired with a wireless chest monitor (included) measuring breathing rate, heart rate and skin temperature, and uses that data to adjust deco calculations. The M2 can be programmed for three gases, and has a digital compass as well as freedive, swim and closed-circuit modes. Displaying so much data on a screen less than 1¼ inches in diameter is a challenge; some of the units are pretty small, but the data characters are bold and sharp. The four-button navigation is reasonably intuitive, and the buttons themselves are perfect, with a precise action and sealed with triple O-rings. Our test parameters didn’t present an opportunity to explore the limits of the M2’s biometric potential, but it’s exciting technology.
The future?
$1510

19. Dive Computers
Know your computer’s No-Deco calculation – conservative vs. liberal
Adjust the setting to your level of comfort
If your computer dies, wait 24 hours before diving again with a new computer

20. Compare your computer with your buddy’s