Choosing A Dive Computer June 6, 2012 by lukesheppard

We all know that Suunto produces two of the most popular dive computers (Zoop Novo and Vyper Novo) currently available that also happen to be entry level computers that do pretty much everything that a recreational diver needs. I’m certainly not knocking them, they are great computers but that doesn’t necessarily mean that they are the right choice for you.

There is an unbelievable number of dive computers on the market these days, at the time of writing this article we hold around 50 different models from 8 or so manufacturers and that is by no means all of them. Add to this the sometimes incomprehensible lists of features and specifications that these computers now have and it’s easy to see how someone could get confused and make a snap decision that turns out to be the wrong choice.

Working for a retail store it becomes second nature to ‘translate’ features between different manufacturers but, as an exercise, I once produced a feature for feature comparison for just two of the bigger brands. I was staggered! In order for the information to be readable, the print out had to be on A1 paper size…nearly a metre wide! So what should you be thinking about when you consider buying a dive computer?

Well…here are some basic questions to get you moving in the right direction. Don’t forget you can use our dive computer comparison chart to help narrow down your choices and also watch our product videos that run through the features and menu systems:

• How far do you plan on taking your diving career?
• Console, wrist or watch?
• Must-Have Features

Your Diving 

As with all equipment purchases, it is important to consider what level you might take your diving to in the future. You don’t want to buy a basic dive computer that you will grow out of in a couple years. On the flip side if you buy a dive computer packed with extra features you will never need, it may confuse you and put you off it…

Do you plan on just sticking to normal recreational no decompression diving or do you plan on advancing through the qualification tree and getting into some more advanced fields such as extended range or accelerated decompression?

If you plan on moving onto technical diving at a later stage it’s worth investing a little more on a more powerful Technical Computer so you can get used to it and its’ features before you reach the Tech Level. For Recreational Diving a more Standard Dive Computer should do everything you will ever need. For Freediving you will need an Apnea Computer with a dedicated Apnea Mode inside.

Computer Style

There are three basic computer styles: Watch Sized, Large Screen & Console. Most divers use a Large Screen dive computer because, as the name suggests, they have a big screen so you can see plenty of information easily. But they are big and clunky so you can’t wear them away from the dive site.

For more active divers Watch Sized computers can be worn at all times, to work, to the gym and when diving. they have smaller screens but still tell you all the information you need to know, just sometimes after a button press or two.

Console mounted dive computers attach to your regulator and replace your SPG. These computers keep all of your decompression and air supply all on one screen so you don’t have to carry extra items or look at two gauges. The downside is that you have no redundancy and if the battery runs out you don’t know how much gas you have left.

What you want the computer to do?

Be conscious of what you want or need the dive computer to do. Go through all of the features you need on a computer and that can quickly rule out some. Here’s a quick glossary on some dive computer modes and features:

Segment Display – the most basic type of digital display where key segments of the screen can darken to display information. Segment displays are limited to the information they can convey so you will need to look up what each symbol and abbreviation means.

DOT Matrix – is an improved version of the Segment Display. Small dots lined up in a grid allow for smaller and more complex information to be conveyed.  Using little power your battery will last a long time but both Segment and DOT Matrix require a backlight to read information in the dark.

Colour Screen – the most modern style of screen with colour coded information. LED, TFT and other modern displays can show very complex information and colour code it to draw your eye where it needs to be. Colour screens use a lot of battery power so they tend to have rechargeable batteries or quick change batteries.

Freediving / Apnea – fancy doing a little snorkelling between dives? A free diving mode will understand that you’re not breathing gas at depth so it won’t penalise you for ascending quickly. Some have specialist alerts for Apnea risks but most will have fast sample rates so your logs are more accurate.

Nitrox & Trimix – Most dive computers have Nitrox algorithms inside them so you can dive on Nitrox and set your gas mix. If you plan to dive to technical depths with Trimix then a computer with Trimix is essential because you can set both O2 and He%.

Gas Switching – if you’re diving with multiple gas mixes then your computer needs to know so it can adjust your dive profile. Using different gas mixes lets you go deeper and speed up decompression stops so you need to input your gas mixes into your computer. Your computer needs to able to manage the number of gas mixes you take with you in the water.

Gauge mode – gauge mode turns the computer into a stopwatch/depth gauge, turning off the Algorithm. Most commonly used by rebreather divers as a backup, gauge mode will not monitor your gas loading but do not use it for recreational diving because you will be stuck in that mode for around 48hrs if used.

CCR / Rebreather mode – dive computers assume you are breathing open circuit gas. If you dive a rebreather you can set some computers to follow your tissue loading based on a fixed setpoint as a backup instead of using gauge mode.

Algorithms – the algorithm inside the computer works out how long you can stay at one depth and when you should ascend. There are a few algorithms out there and each has its pros and cons. Some computers allow the diver to switch between two or more algorithms depending on the type of diving to optimise the bottom time and safety.

Gradient Factor / GF – an algorithm with GF allows you to customise your algorithm and adjust your dive profile. By setting High and Low saturation levels you can speed up deco stops or change where they happen. If you don’t know what they mean then it’s best to leave them at factory settings.

PC interface – dive computers can connect to your desktop or mobile dive to download dives digitally and change settings. Useful if you want to scrutinise your dive profile and stats many computers are fitted with Bluetooth while others require a USB cable or cannot be connected so you have to copy your dives by hand.

Compass – some computers will have a digital compass built in. Digital compasses are arguably more accurate than analogue because you can recalibrate and adjust the declination at each new dive site. 

Battery – all computers are fitted with a battery. Some computers are rechargeable and can be topped up with a USB cable. More traditional computers have single use batteries but look to see if you can change the battery yourself or if a dive centre has to do it for you. Look for available battery kits as you need to replace the O-Ring to maintain a good seal.

Air Integration – either wireless or hose integration, air integration connects your computer to your regulator. This allows the computer to take into account your breathing rate and provide feedback such as estimated air time remaining so you can see how much gas you have left on your computer and it will work out how long it will last in minutes.

The Strap – most computers will come with a standard watch style strap and buckle. Some computers have interchangeable straps so you can personalise or swap your strap to a metal bracelet or a bungee mount. If you’re drysuit diving then you will need a long strap or an extension strap to fit over your sleeve.

Warranty – if you plan on keeping the computer for life it’s worth considering a model that is covered by a lifetime warranty for peace of mind.

Obviously keep in mind that adding extra features does increase the cost.