The Apeks Quantum Dive Computer

The Apeks Quantum was my first computer, purchased in November of 2005 just before a trip to the Turks and Caicos. It is Nitrox-capable, accommodating 2 gas mixes. The first gas can range from 21 to 50% Oxygen, while the second (decompression) gas can go all the way to 99%. Other settings include various alarm thresholds, the date and time, and metric vs. imperial. It’s a good idea to commit the method of switching from metric to imperial if you ever have to reset the computer. Put it in Dive Mode and hold both the “A” and “B” buttons down for 5 seconds or more. It logs in 15 or 30 second increments, allowing you to trade off the detail against the number of dives it can record. It also can act as just a bottom timer.

After more than two years of diving with this computer, including some modest (no more than 15 minutes total) decompression diving, I bought a second one as a backup so I could feel more confident on technical dives. The most extreme dives I’ve used them on were a 30 minute drift dive ranging from 160 to 175 feet and 2 hours of bottom time inside the wreck of the Daryaw at about 85 feet. The latter dive required almost an hour of deco on my back gas which was a 35% mix. I used 80% for the deco mix on the drift dive for a total of about 30 minutes, as I recall.

Other team members on both dives were using Cochran Computers, which demand far less decompression time. On the one hand I feel bad when the other divers are waiting around for my computer to clear, but on the other I appreciate the extra safety built into the longer schedule. These same divers are encouraging me to get a Cochran but I could buy half a dozen Quanta for the same price. I’m considering taking a Trimix course at some point, though, so if I want to use a computer rather than tables I’ll be stuck shelling out for something with that capability.

Pair of Apeks Quanta - the one on the left doesn

Unfortunately I have had problems with the older unit (which is out of warranty). I had left it in the drawer for a week and then found it with a blank screen. Of course, the first thing I did was change the battery, a standard CR2032, which had depleted from 3V to about half a volt. However, the replacement didn’t work. A couple of days later the screen came alive but the computer still malfunctioned. Based on the behaviour of the unit I believe that the large central “Mode” button is locked in the pressed position. I’d like to take it apart to see if there is mechanical damage (there was some grit in the battery O-ring cavity and obvious moisture behind the glass) that can be repaired, but the back is fastened by very small diameter Torx screws and I’ve yet to locate a suitable tool for it.

I’m not the only one who has had problems. Others have reported that after 100-150 dives, either the screen dies or the depth sensor fails. The Cochran on the other hand has a reputation of being rock-solid. The one feature that turns me off about Cochran is the lack of manual gas switch. On the Cochran you program in the depth that you switch to a deco gas and the computer automatically switches when you ascend to that depth. I don’t know how you’d do an air break with that, or handle a failure that prevents you from breathing the intended deco gas for a few minutes or more. The only way to switch the Quantum is to hold the “A” button down for 5 seconds.

Aside from the failure I’m very happy with what the Quantum does. The consistency between the 3 units I’ve tried has been impressive in both depth accuracy (all within about 8”) and decompression times (all within a minute). It’s easy to use and easy to read under water, and has never let me down on a dive.

On the Labour Day long weekend I borrowed a friend’s unit to use as a backup and took it tech diving. He has the computer interface and the software produced some very cool charts of my dives. He was half-hoping I’d break it as it was about to go out of warranty, but it worked just fine. I’m not sure I’ll ever buy another one of Quantum because of the reliability issues, but functionally it’s been a good computer at my level of diving. I do recommend carefully cleaning (or even better replacing) the battery compartment O-ring from time to time.