Mark loves to go scuba diving, but he’d like to take his computer along. He compares products that let him do that.
We started scuba diving and got certified about 16 years ago, and then for various reasons, we stopped. Over the years we talked about starting again, but there was always something that was more important, so we put it off.
Finally, about a month ago while we were on holiday, the opportunity to go diving presented itself and, well, we got hooked all over again.
Now after a few equipment upgrades and a few repairs, we’re good to go. But there’s one piece of equipment we need that wasn’t around when we got certified: a dive computer.
Dive computers measure how long you stay underwater and how deep you dive. From this data, they tell you how fast you can return to the surface so you can avoid decompression sickness, otherwise called the bends.
The bends are caused by pressure changes. When you are scuba diving, your air supply delivers air at the pressure required to let you breathe comfortably. The pressure increases the deeper you go, which causes your body’s tissues to absorb more nitrogen. When you ascend, the pressure decreases so the nitrogen comes out of your tissues. Unless you carefully control the rate at which the nitrogen comes out of solution, it will form bubbles in your body.
These bubbles can cause a variety of symptoms, ranging from itching and rashes (skin bends) and joint pain (the bends) to sensory failure (blindness, loss of tactile sense), paralysis and death. In short, you don’t want to get your ascent wrong when you dive.
Traditionally divers use decompression tables to figure out how to ascend safely, but dive computers do the same thing more accurately.
The most-sophisticated devices are integrated with your air tank and monitor how fast you are using up air and track how much “bottom time” you have left, given how deep you have gone and how long it will take to ascend safely.
What’s really cool for us computer geeks is that you can download dive data to your PC so you can keep records. Quite a few dive computers support downloading.
We initially looked at the Sherwood Wisdom ($780), which is considered a fine dive computer. But it seems Sherwood really didn’t put much thought into how downloading would be done and how the PC software would look and work. The proprietary plug on the USB data cable for connecting the PC to the Wisdom device is awful – flimsy, doesn’t locate positively and can be inserted upside down. The software is very poorly documented (even the built-in help gets details wrong), is thin on features and has a very poor user interface). The software and cable is outrageously priced at an additional $150.
We’re considering purchasing a Suunto Vytex DS ($1,300), which does everything the Wisdom does (although some would argue its decompression algorithm is superior) and monitors tank pressure with a wireless connection.
Where Suunto is more advanced than Sherwood by orders of magnitude is its software. Dive Manager has a very good, easy-to-use user interface, and you can download and test the program before you buy (note that Sherwood doesn’t even make screen shots of its software available).
Like the Sherwood Wisdom, the Suunto Vytec uses a USB cable with a proprietary plug (priced at about $100), although it is a rather more robust design. Note there also are numerous sophisticated hacks online for building your own interface for the Vytec.
There’s some interesting technology in the wireless connection between the dive computer and the air tank. Because more than one diver might use the same system, you sync up the dive computer and the sensor sync by holding them close together at power-up so they can select an unused channel. Subsequent syncs by other units discover the used channels and select from available ones.
Do you dive? Do you use a dive computer? Decompress on Gibbsblog or link to gearhead@gibbs.com.
