Computer-watches SUUNTO gas-integrated D4i, D6i & D9tx

THERE’S BEEN A LOT OF FUSS RECENTLY about a new type of lightweight hp hose, with lots of discussion on the Internet as to whether it is safe or not. I haven’t really got involved either way, because I haven’t used anything as crude as a hose connected between my tank and a mechanical pressure gauge in years.
Why would I? It’s as daft as having your phone connected to the exchange by a copper wire!
It was Guglielmo Marconi who said that radio transmissions were here to stay, and I guess he has been proved right over the years. Ever since Dr Crippen rued the day it was invented, people have been taking advantage of wireless links.
This is why I’ve been using wirelessly connected gas-integration of at least one of the diving computers on my wrist, and I’ve never had to worry about looking at a pressure gauge since. These gas-integrated computers not only tell you your decompression status and current tank pressure, but also calculate how long that gas is likely to last at the depth you are at, and at the rate you have been breathing it.
Of course, you can program in a reserve pressure too. If you keep your remaining gas time longer than your total time to the surface, you shouldn’t get into trouble.
I’m on record as saying that this feature has been one of the most important and successful advances in keeping divers out of harm’s way.

Misinformation
So let’s lay to rest some of the myths about these magical bits of kit. Firstly, your camera’s flash will not cause the computer to lose the transmitter’s signal. This might have happened once, to one of the first radio-linked computers, when used with a flashgun that employed an electronic vibrator to indicate recycling of the capacitors, but underwater flashguns haven’t used those in yonks. Usually they were eaten by the sharks that were attracted to them.
Secondly, you get an actual tank-pressure display as well as the gas-time prognosis, so you are always aware of the basic information.
Thirdly, there are fewer O-rings to offer failure points in a radio transmitter than in a hose and pressure gauge.
Fourthly, radio has been proved reliable. Even aircraft captains use it!
I’ve been in the habit of diving with two gas-integrated computers with two different transmitters. I admit that in the past I have backed up a single transmitter with a high-pressure hose and gauge.
Now I don’t need to, and having one fewer hose to deal with is a godsend. This is especially true when I twin up independent cylinders.

Problems
So what are the drawbacks? Well, you have to get the battery in the transmitter changed every few years. You could do this yourself, but diving computer manufacturers have proved that not all divers are sufficiently dextrous to do this successfully.
The transmitter, screwed into the regulator first stage, looks like a convenient handle for a helpful boat crew-member when hauling a tank on board. I’ve found that yelling: “Don’t hold it by that!” the first time it happens helps develop muscle memory for these people.
The other admitted problem with the Suunto computers of the past was the need to pair the computer successfully with the transmitter every time you are about to dive.
An unsuccessful pairing results in a display that, instead of giving your tank pressure, declares: “Fail.” That’s a bit boring when you’re already on your dive.

Suunto Solutions
The new range of Suunto computer-watches pair permanently the first time, and unless you choose to change a transmitter code because, for example, another diver on your boat is using the same one, they stay paired.
The “Fail” feature has been discontinued. Not only that, but all the computer-watches in the new range can be paired to give a wirelessly integrated tank-pressure display. The “i” suffix indicates this with the new D4i and the new D6i, and they are no bulkier than they were before.
I say this because the first gas-integrated Suunto computer-watch, the D9, was a little
on the chunky side. For this reason, I chose to wear a D6 as a day-to-day watch instead.
Let’s address another myth about computer-watches, the one about the display being too small to read, or that you don’t get a full spectrum of information.
The dot-matrix display of the LCDs give figures as big as any full-size Suunto computer. You need to push a button to get peripheral information, but all the crucial stuff is there, loud and proud.
Setting up one of these computer-watches is even more intuitive, thanks to some changes in the software, now called “DM4 with Movescount”. The displayed abbreviations are more obvious now, including those for that all-important transmitter pairing.

Deep Stop/Surface Interval
The manufacturer tells me that the latest pressure sensor employed offers a much more accurate depth measurement than before, but how would I notice that? Deep stops can be selected, although a diver can choose to ignore them when the time comes, so I guess these are just an add-on and not crucial to the algorithm, rather like the three-minute safety stop at 5-3m.
Now you get both displayed, rather than one or the other. You used to have to pre-select one or two minutes as a deep stop, but now the algorithm calculates what is appropriate, and credits you in the shallows.
Countdowns are now in minutes and seconds. which is a bit more comforting than displaying a one-minute stop when perhaps only 25 seconds is required.
The actual surface interval is also now displayed between dives, and time-to-fly has been relegated to an icon. The memory logbook shows the average depth as well as the maximum depth achieved on a dive, and there’s bar-graph representation of the dive.

Suunto D4i & D6i
These computers, designed for use with air or nitrox, are rated for a maximum depth of 100m and 150m respectively. The D6i looks slightly more robust in its stainless-steel case, and it can be programmed for two different nitrox mixes, as well as being usable in freedive mode. Sampling rates are increased to a choice of seven, from every second to every minute.
I’ve rarely used more than two nitrox mixes when open-circuit diving, but I often do use two.
I’m often castigated by Internet warriors for diving with two independent tanks with differing nitrox mixes (using the richer mix for the shallower part of the dive) but I do this only for dives where others might make do with a single tank.
Dives on the wreck of the Rosalie Moller in the Red Sea or the Bianca C in Grenada are good examples. The D6i is perfect for this.
I’m pleased to note that the electronic compass display is switched on when you want it and stays on until you decide you need it no longer – unlike the annoying compass of the old D6. Now it is three-dimensional tilt-compensated too.

Suunto D9tx
The new Suunto D9tx is just as bulky as its predecessor, but now uses the same Suunto/ Wienke algorithm as the Helo2. This means that you can add a helium percentage, and use it for open-circuit trimix diving.
It may have the same dimensions as the D9, but the titanium case has a serious gunmetal finish and less bling. It’s rated to 200m deep.
You can preset up to eight different gas mixes with oxygen percentages of 21-99% and helium percentages of 0-92%. It comes with a USB interface cable for downloading dives to a PC.
Like the D6i, it features a stopwatch mode that can be activated during the dive.
If I have a complaint about the D9tx, it’s the strap. This might sound trivial, but it is not made of the same material as its siblings and, although it comes with an extension strap just like the others, it’s made of a different elastopolymer.
I found it difficult to thread through the buckle loop over a bulky drysuit-clad wrist.
See, Suunto? You’re not perfect!

Audible Alarms
The new-sounding alarms attempt to be reminiscent of what they are trying to tell you. For example, if the computer thinks you should be going up, it has a series of beeps with a rising note, and vice versa. There is also a different beep for gas-switch alerts.
I was reminded of something iconic diver Stan Waterman replied to a young diver on a liveaboard when he informed him that he had heard his computer beeping on a dive: “Oh my goodness. Does my computer beep?”
The fact is that when wearing a hood you need very good hearing to notice these audible alarms.
I left one at my bedside in my hotel because I failed to hear the alarm-clock feature. I turned the audible alarms off.

Model-Finder
There is a very useful features comparison function for the D9, D9tx, D6, D6i, D4 and D4i
on the Suunto website.

COMPARABLE COMPUTERS TO CONSIDER:
Oceanic OC1 with transmitter, £850