IF SCUBA-DIVING IS A RELATIVELY YOUNG ACTIVITY, technical diving using gases other than air is almost newborn! We are sometimes in danger of forgetting that many of the pioneers are still with us and very much active.
Kevin Gurr is one of these pioneers, and over the past few decades he has been supplying equipment that helps technical divers to achieve their aims.
Some of his ideas have been far ahead of their time. He has seen a raft of small companies that he owned fall victim to his over-optimism about what divers were prepared to buy.
He was probably the first to introduce a computer that was linked to tank pressure. It was hard-wired to a connection in the regulator. It came and went.
You have to kiss a lot of frogs before you meet your princess, and Kevin had his fair share of frogs before he introduced the VR3 computer. It suffered, if you like, from association with Kevin’s extremely complex thought-processes.
Nobody would claim that it had a user-friendly method of setting up but it was probably the only computer that was available for a long time to manage a multi-gas dive,
and it became standard issue among technical divers and the growing band of closed-circuit rebreather divers.
Inevitably, as the technical-diving and tech-diving wannabe market grew, the VR3 faced growing competition from other manufacturers, not least those of CCRs.
Kevin responded by introducing the VRX, in the belief that it would be far more user-friendly. A derivative is used in combination with VR Technology rebreathers such as the Sentinel.

MEANWHILE, WIRELESS INTEGRATION of diving computers with the diver’s tank had become almost commonplace. The patent was held by a single major manufacturer, so the others had to pay a royalty to use the idea.
Another recent development has been the possibility of using an organic LED (OLED) system for the computer display. This is self-illuminating and allows colour to be introduced.
A further interesting development has been the synergy between Kevin Gurr’s VR Technology and the US giant manufacturer headed up by an older pioneer diver, Bob Hollis.
One of Bob’s sons wanted to develop a technical-diving arm of the Hollis empire, and rebreather technology, especially in the area of those units that meet PADI Recreational Rebreather criteria, was ready and waiting with Kevin back in the UK.
So Hollis now manufactures the Explorer rebreather and markets a VR Technology technical-diving computer, the DG05. This has an OLED display plus wireless gas-integration, just like the Oceanic computers from an associate company.
Synergy works both ways. Kevin sent me his latest and otherwise identical VRX OLED with (Oceanic-style) wireless gas-integration to try.
I stole the following words from the Hollis catalogue and adjusted them into English accordingly: “Whether you are advanced nitrox looking towards trimix or CCR or already there, the VRX OLED will provide you with the platform to modify based on your diving needs.
“Benefit from a vibrant OLED display, wireless monitoring of up to four different gases and the freedom of a variable decompression model ‘VGM’ all encased in a rugged mil-spec aluminium case.”
The VRX can be supplied ready to dive with anything from air and straight nitrox to trimix, and in open, semi-closed or fully closed-circuit mode.
It can accommodate open-circuit bail-out gases should the closed-circuit diver switch during a dive. It is also compatible with the OPTOCON infra-red optical interface available with the Sentinel CCR (and some other devices), can display tank pressures and PO2 simultaneously, and side-steps electrical connection problems under water.

OLED Screen
I’m told (rightly or wrongly) that OLED displays have been adopted from the medical equipment industry and are now available in only two sizes. This computer uses the smaller of the options but all the information needed is squeezed in agreeably.
It is set up using the two buttons with single, short or long push, as will be familiar to anyone who has used a VR3. It uses a rechargeable lithium battery, and the charging cap is removed by unscrewing and without the use of any special tools. A charger is included in the package and will recharge a completely flat battery in about three hours.
The screen itself has numbers and icons in the rather blocky form that is characteristic of
VR Technology computers.
Older divers will need their reading glasses for some of the mini-menus, something to consider if diving from a small boat.
It should also be noted that although the OLED display glows loud and proud at depth
or at night, or in otherwise low-light conditions, once you get near the surface somewhere like the Red Sea with bright Egyptian sunlight it becomes very difficult to read indeed.

Algorithm
The VGM (Variable Gradient Model) algorithm allows you to adjust the mandated decompression by adjusting the gradient factors for different sections of the ascent. This has the effect of adding variable safety factors or the converse, and demands a degree of knowledge by the user, as it is possible to design your own decompression curve. It should not be done in ignorance of the associated risks.
There is also the option to use a derivative of the Buhlmann ZHL-16 when mandatory
two-minute deep stops are required.
You can preset up to 10 different gases so that you can switch to what is appropriate at any given time. It is fully programmable even while under water, and you can even switch between algorithms between dives.

Gas Monitoring Display
Because this computer is sold both in the USA and elsewhere, it has the option of both metric and Imperial displays. It can be linked to up to four different transmitters.
I had only one transmitter, and initially I used it for some simple single-tank nitrox diving in the middle of the Pacific Ocean.
With me was a Finnish national, Mika, who was a computer whizz-kid from the Oracle software company, working in Germany.
He had his own earlier-model VRX.
The instruction manual for the VRX is supplied as a CD. This is less than convenient when sitting in a wobbly little boat and about to go diving, and I wish I’d gone to the trouble and expense of printing it out before I’d set off.
I was able to get the wireless icon displayed, but neither my Finnish friend nor I was able to get the VRX OLED to display my tank pressure during a dive. This proved very annoying.
It took only a brief phone-call to VR Technology to get it working properly, but of course I had to wait until I’d flown the 7500 miles home. I think that indicates the problems of understanding the menus of VR Technology computers. Experienced VR3 and VRX users might sneer at this suggestion. I know I’m a Luddite, but Mika certainly is not.
Once it was up and running, the tank pressure was displayed clearly in the top right-hand corner of the screen. It changes colour from green through yellow to red as the supply diminishes to 30bar or less.
When the tank is not turned on, the last pressure is displayed in an attractive violet colour, indicating a poor or bad radio link.

Setting Up
Setting up the gas list was where my misunderstanding came in. Far from home, Mika told me that “B” indicated back-gas, when in fact it was bail-out gas. “Tick” selects the gas and a separate highlighted blob indicates whether that gas is to have a transmitter dedicated to it.
“CC” indicates that a gas is specific to closed-circuit, and an empty box means that it has not been selected.
Gases are shown in the list in order of their ascending MOD (maximum operating depth) with used gases at the top.
The tank pressure is aligned to the gas list too, and alternates with the MOD of each gas.
If tank pressure is 30bar or lower, it is displayed in red. If the batteries of any transmitter are low, this is shown up on the tank-pairing page in yellow.
You can also switch between three optional final decompression-stop depths, 3m, 4.5m and 6m. I set mine to 6m to tie in with the safety-stop function of another computer I was using alongside the VRX OLED.

In the Water
The display shows current depth, dive duration, tank pressure and time to surface in large figures. In much smaller figures you’ll see the depth of the deepest stop required and its time.
The OLED mode shows coloured figures on a black background. This is less cluttered than the classic VRX display, and you can get all this information during a dive by means of
a short press on the left button, and it appears for around 10 seconds.
It also automatically switches to large graphics mode. The menu bar disappears after
a few seconds, and the primary dive information fills the screen.
In G-mode, a natty little graph of your dive profile appears. There is also a deco bar to enable a “curved” decompression schedule to be achieved, and an ascent-rate monitor bar.
Gas-switches are prompted during the dive in red as you reach the MOD you have set for each gas during an ascent. If you are unfortunate enough to need a gas “handed-off” by another diver that is not on your preset list. you can amend the current gas as you go.

The Onion
Like all of Kevin Gurr’s computers, the VRX OLED is very much like an onion, in that there are layers of displays and functions to be peeled away.
I sometimes think those who buy them must spend hours at home on winter evenings discovering more things about their computer.
The dive-simulation program included is certainly good, and I suggest that anyone new to this type of computer should devote many evenings to getting familiar with it before taking the plunge. Do this with the help of the VR Technology CD and a PC.

COMPARABLE COMPUTERS TO CONSIDER:
Shearwater Predator, £1156
Liquivision Xeo, £736

SPECS
PRICE from £945
ALGORITHM VRM or Buhlmann ZHL-16
VERSIONS Nitrox, Trimix, OC and CCR upgradeable
DISPLAY OLED
CONTACT www.technologyindepth.com
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