What To Look For When Buying A Dive Computer March 6, 2020 by lukesheppard

What To Look For When Buying A Dive Computer

As with most sports, when you get into them you often need to invest in your own equipment. Sure you can always rent gear, but it’s rental gear, and rental gear isn’t the best quality and it’s used and abused.  When it comes to buying your own dive gear I recommend starting with mask and fins but when it then comes to the big stuff, a dive computer is right up there as one of the most important thing I’d recommend you invest in because it’s a device that makes your diving safer.

There are countless dive computers out there ranging from small indie startups to well-established manufacturers who have been making dive computers for decades. But when you’re new, and even if you’ve been diving for years, there are features to a dive computer that you may not know to look for or whether it’s worth investing in. Now I’ve used quite a few dive computers in my career so far and there are different grades of computers for different types of diver so a cheap dive computer will do everything you need as a recreational diver, but if you want to progress onto more advanced diving or have better features, then yeah, you have to spend a bit more.

Let’s take a look at What To Look For When Buying A Dive Computer

Face

When you’re first buying a dive computer you can immediately split the range available in two, and that’s large screen vs watch sized. The face on a watch-sized dive computer is, about the size of a large wristwatch, and you can wear it day-to-day without looking odd. This is great but if you struggle with your eyesight then there’s going to be a lot of information packed into that tiny space. And you’ll probably want to see and read all of that info on a dive. Large screen dive computers are much easier to read and can fit more onto one screen, but yup, they’re bulky.

After overall dimensions there’s the screen itself. And much like TVs you can get LED and LCD screens, I’ve never seen a CRT dive computer yet… but the best screens today are colour LCD. Yes they’re the most expensive but they’re colour coded and easy to read at a glance. Cheaper Segment displays are good, and don’t use much power but they’re sometimes hard to understand because the display is fixed as to what it can display where. The best variation of this is a Dot Matrix so if you don’t want to go for the super fancy LCD, look for Dot Matrix at least.

Battery

This decision is often made as soon as you’ve chosen which screen you prefer. Colour screens use a fair amount of power so most of them use a rechargeable battery, just plug it into a USB like your phone and charge it up between dives. They usually get a few days worth of diving, depending on how bright the screen is but you don’t have to worry about bringing spare batteries or opening the computer to change the battery.

Segment display computers tend to have a large button battery that will last a good year or more depending on how much diving you get up to. While definitely cost-effective, you don’t always get much notice when the battery is on its last legs.

Strap

How your dive computer attaches to you is important. Most will come with a traditional watch style rubber strap which is fine, but remember that your wetsuit or drysuit will squeeze and shrink at depth so your computer will become loose. Just make sure it’s strapped on tight. Large screen dive computers will come with a really long strap so it can fit around a drysuit and watch sized computers usually come with an extension strap so you don’t have a big flappy strap day-to-day.

I prefer elasticated bungee straps and a pair of them. Elasticated straps stretch and compress to allow for your suit squeeze. That way my computer stays where I want it. More computers today come with straps but will have four holes in the body so you can use 4mm bungee to make straps. By using two it’s just a bit more redundancy should one strap fail.

Algorithm

The technical thing that most people don’t even think about when investing in a dive computer is the algorithm on the inside. There are a bunch of different algorithms being used today and two or three are the most common and popular; Bühlmann, RGBM, VPM, DSAT. The key point here is that nobody 100% understands exactly what happens in your tissues when you dive and the human body is pretty complicated and if kids cartoons have taught me anything; it’s that we’re all different and unique, so to produce a dive computer that works for anybody is tricky.

So when you’re looking at dive computers look for an algorithm that you can personalise to your own condition because let’s face it; very few of us are in the best physical condition. That way your dive computer will help give you a better representation of a safe dive profile. And try to match algorithms with your buddy. If you’re using two different algorithms then one will tell you to end the dive sooner. Now, I’m not going to go into which algorithm is best here, cos that would be a whole video in itself, and it’s probably impossible to definitively say which is best.

Integration

The last feature that’s worth looking into is air integration. Many dive computers now have wireless air integration where you can fit a transmitter to your regulator and this acts as a wireless beacon broadcasting your tank pressure to your dive computer. This has a few benefits; one, you only need to look at one screen to see your depth, NDL and how much air you have left, so you don’t have to check your gauges. Two, your dive computer will probably work our air time remaining, so it’ll tell you how long your air will last in minutes.

And three you can set alerts so your computer tells you when you get to a certain pressure, so even if you get distracted and forget to check your gauges or something leaks and you don’t notice it will notice for you. There are two kinds of transmitters and there’s an important difference. The common type broadcasts over twenty or thirty different frequencies and you need to pair your computer to that frequency at the beginning of the dive, so if someone else has a transmitter you don’t get mixed signals. The second type is a permanent pairing, where you type in the transmitters serial number into the computer once and that’s it, they’re paired until you delete it. Either way, even if you don’t want air integration right now, it’s worth considering if you’ll want it in the future because you can’t just download a patch you need the hardware, so if you want to upgrade to air integration later, you need to buy another computer.