COMPUTER Apeks Quantum
I went diving in the Red Sea. So what you say. I dived with two standard 12 litre tanks twinned as independents, as a lot of people choose to do nowadays. I used air in one tank and nitrox 36 in the other.
ÂÂÂÂ Why Because I could dive to 50m on the air but, once I got back within its operating depth range (say 30m), I swapped over to the nitrox 36 to speed my decompression.
ÂÂÂÂ How did I monitor that I used a new Apeks Quantum two-mix dive computer.
ÂÂÂÂ Suddenly deep dives over the lower tongues of the reefs at the Brothers, Daedelus and the Elphinstone were not so challenging, and once I had sucked the nitrox 36 down to 30 bar I could always swap back to the air (nitrox 21) and toggle back to it on the Quantum to extend my dive time further.
ÂÂÂÂ That came in useful when the oceanic whitetip shark turned up in the shallows just as I was about to climb back on board the liveaboard. Thank goodness I still had a couple of frames of film left in my camera. The Quantum tracked my decompression status all the way.
ÂÂÂÂ It has a particularly clear-to-read, self-illuminating display, very much in line with the Cressi Archimede which, I bet, comes from the same factory somewhere in Japan. It has time, dive, dive-planning, logbook, dive-profile, PC-download and time-setting modes. These are easily understood and set with the aid of three buttons: one for mode, one for detail and one for adjustment. You can switch between imperial and metric measurements.
ÂÂÂÂ In dive mode you can set up to two nitrox mixes, and any that are not set to air revert to worst-case-scenario (99% O2, 79% N) at midnight each night. This means that you must set your computer for the nitrox mix you use each day at least. You should be doing this anyway immediately before each dive after analysing the gas in your tank. Or you can of course leave the computer set permanently to Air.
ÂÂÂÂ You can only use a set ppO2 of 1.4 on mix No 1 and 1.6 bar on mix No 2. The Quantum will not allow you to switch to a richer mix setting if you are beyond the maximum operating depth at 1.6 bar ppO2 for that particular mix.
ÂÂÂÂ You can also choose to set it with one of three personal safety factors and dive profiling taking waypoints every 15 or 30 seconds, and calibrate it for either sea or fresh water.
ÂÂÂÂ So what of its algorithm, that all-important mathematical calculation that tries to second-guess how much nitrogen you have actually absorbed Im told its a 12-tissue model Swiss algorithm modified by Randy Bohrer. All I can tell you is that it sat alongside a well-thought-of Suunto Vytec on my wrist for a weeks diving, with both set at the minimum personal safety-factor, and the remaining no-stop time and stops demanded by the Apeks Quantum seemed to be almost exactly in step with the Suuntos.
ÂÂÂÂ The Quantum has a particularly easy-to-understand ascent-rate indicator which ties into an ascent-rate variable between 16, 12 and 8m/min. It has the usual oxygen-limiting-fraction display, which I rarely saw get far from the starting blocks. Other audible warnings are supplemented by a flashing display if you exceed any of the parameters of diving thought to be safe limits.
ÂÂÂÂ You can also use the instrument as a straight depth-gauge and timer (with electronic recording) in Gauge mode.
ÂÂÂÂ In line with most computers now, this Apeks model includes a voluntary safety stop between 6 and 3m. In this case the countdown is in minutes and seconds, which enables you to see how quickly the time actually passes. And the strap is long enough for use with a drysuit.
Im not sure that the computer interface and software is available yet, but at only £249 the Apeks Quantum is remarkably inexpensive for a mix-switching nitrox computer, and it uses a common user-replaceable 3V lithium coin-cell battery too. As so often, the Japanese have come up with a winner.
  • Apeks Marine Equipment 01254 692200,

  • Divernet
    The Apeks Quantum has a particularly clear-to-read self-illuminating display
    + Easy-to-read display
    +Option to switch nitrox mixes during the dive