Hands-on Review of Ratio iX3M2 Dive Computer

FEATURES

This is an oversized, chunky dive computer with a 2.8″ screen that looks like a Shearwater Perdix on steroids (or maybe it’s just eaten a Perdix for breakfast?), and is designed for both recreational diving and tech diving, with a heavy emphasis on tech-friendly features. 

There are 2 variants of the iX3M2 dive computer – one with a built-in GPS and one without.     Within each of these variants, there are 3 models lines:  the Pro, the Deep and the Tech.    The unit I have is the Pro but most of the details of the review also apply to the other models as well. 

 

Like virtually every computer these days, the IX3M2 Pro has gauge, freediving and nitrox modes.   It also has a built-in compass with some nice features like lockable directions and 85% tilt compensation.       And it comes with 3-factor alarm – visual, acoustic and vibration, thereby reducing the chances of the diver missing an alert – you can set alarms for ascent speed, MOD, gas reserve (if using a transmitter), NDL, deco violation, time and depth.     And the computer also offers automatic altitude adjustment.    

In addition, the computer lets you use up to 3 gas mixes, which is covers most air-based open circuit tech diving.     

And while on the topic of decompression, the iX3M2 uses the modern Buhlman ZHL-16C algorithm, which is suitable for both recreational and tech.   You can, of course,  change the conservatism of the unit via 6 settings, as shown below.

         

 

It has an NDL planner that will let you plan a dive and show you how much NDL you will have left at the end as well as how much air is needed for that dive.     In addition, it also has a deco planner too, which uses your planned profile and gas mixes to prepare a run table (albeit without validation of CNS, potential of counter diffusion or gas volumetric availability).

And then there are some neat little add-ons that make it super interesting.

For one, you can purchase an optional analyser accessory that plugs into the unit and lets you set the computer directly from the testing unit – attach one end of the accessory to the computer and use the analyser on the other end to test your Nitrox mix, and the number will show up on your computer, for you to save.      Super cool!

There are also some neat features for tech divers diving with multiple gases (3 allowed in the Pro model):  the computer actually gives you an alert when a better mix is available (based on your depth and entered gas mixes), and you have the option of approving or rejecting the switch.      In addition, once you go into deco, the computer shows you a table with your entire decompression schedule listed in a single place, so you know the overall plan.

Lastly, there is the integrated gas blender app – here, you enter into the iX#M2 what’s inside your tank and what your desired mix is, and it tells you how to obtain that chosen mix – both for nitrox and trimix!   A very convenient feature indeed!

The iX3M2 series all offer air integration, letting you add up to 3 wireless transmitters to each computer.

The Deep version of the dive computer adds the following features:  normoxic trimix, ability to choose between multiple algorthims (Buhlmann Z12/Z16B/Z16C and VPM-B)

The Tech version adds:  full trimix, ability to use up to 10 gas mixes (!!), user settable Gradient Factors and user settable Critical Bubble Radius

About the only downside is that you need the top-end version in order to get user-settable gradient factors when even an entry-level Shearwater Perdix or Garmin lets you do so, but in the end, the 6 settings available cover pretty much all the common settings recreational divers will use.  For trimix, however, having the option to choose your own gradient factors is quite nice even with normoxic trimix, so it is a bit vexing that Ratio left this only for the highest version of the computer.

Speaking of the different version:   if you want to upgrade the features, simply plug the unit into Ratio’s Toolbox app and you can apply an upgrade code (purchasable online) to do so.        The Toolbox app also lets you customise the unit a little, download/view your dives, install app upgrades. see the location of the dives (on GPS-enabled models) and more.   Do note that the upgrade is only from the Pro to Deep to Tech models, but you cannot do a software upgrade from a non-GPS version to a GPS version.

Lastly, the unit comes with a rechargeable battery that uses a USB cable with a proprietary locking connector on the other end.      This connection is very secure and ensures that the unit won’t accidentally come loose.     However, one thing that would have been nice would have been to have a more standard charging mechanism as well – eg, wireless charging, as with the Shearwater Peregrine.     That would reduce the risk of being dependent on a proprietary cable while out on a dive trip.

USE

Out of the box, the interface was easy enough to understand – the four buttons with context-sensitive labelling, made it very intuitive to figure out what did what.    It took a couple of minutes to get a sense of the menu structure and what was where, that’s it.      Setting the nitrox mix was super easy, and required only a few button presses.

But the display itself took my surprise when I first turned it on, simply for the sheer amount of information there.   I mean, look at this screen.   Why is there so much stuff there??    This is like extra pineapple on a pizza!

But once I thought about it, I realised that this is simply because I am used to the relatively spartan displays of other dive computers and the info on the Home Screen of the Ratio is fairly useful to ensure your computer settings are up to the mark:  eg, you can see what mix you are diving, what your computer’s mode is as well as conservatism setting.

That said, I’d still prefer if they changed the prominence of some of the displays:  eg, I felt that the ambient pressure / temperature displays took up a disproportionate percent of the screen view compared to other, more relevant bits of info like Mode and Gradient Factor.          

As an aside, a neat touch is that by using the Ratio Toolbox app, you can actually replace the “RATIO” on the main page with your name – a good way of ensuring your computer doesn’t get mixed up with someone else’s.

Once you start diving, however, the display becomes a lot more intuitive and to the point.        The top row gives you your depth, time and either NDL or time to surface (depending on whether you are in deco or not).    In addition, a color coded arrow indicates your ascent rate (green, yellow or red, depending on whether you are slower than, at or faster than 9m/min).

 

The bottom row provides ancillary information, such as maximum depth, PPO2 and current mix being breather.      

By pressing one of the buttons, the bottom panel can also show other ancillary information such as water temperature, ascent rate, average depth, gradient factors, oxygen toxicity units, total CNS and time.   And here, you also get access to a stop watch – which is a really, really cool feature.    Another button also toggles the display to show tissue saturation as well as a deco table showing your entire remaining deco obligation (if applicable).       And you can also get a compass display.     It is worth knowing that in all of these screens, the top row, showing depth, time and NDL/TTS is always visible.

And speaking of the compass display, you can program a direction to follow and then get a visual display telling you if you have turned away, as well as prompts for a reciprocal heading – all of which makes navigation super easy.

And that brings us to the middle row – this is going to be empty for most of the dive, only showing info once the diver is at the safety stop or in deco.   Initially, this felt like a waste of space:  my initial thought was that this space could have been better used to make the NDL more visually obvious.      However, there is a significant benefit to this implementation as well:   recreational divers aren’t always familiar with the deco screen and what it means (I have actually seen recreational divers mistakenly think their deco time is their NDL and continue to dive when they are well into double digit deco).   So having this info clearly presented is a big plus – and it most certainly is clearly presented:   indicators tell you whether you need to ascend or at the optimal depth, and an equally obvious countdown on how much time you have left.

That middle row is also used to show various alarms (such as depth alarms or MOD alarms). 

So all in all, it actually is fairly well-thought out display which presents information in a sensible manner to the diver.

A couple of noteworthy points about the display:    while the Ratio iX3M2 does have a multicoloured display, the use of those colours is very sparse.    As a default, all information is presented in the same colour scheme – blue for the labels, white for the data, with other colours (red, green) only coming into play during prompts or when specific limits have been exceeded. 

And the last point is battery life – I used it for 2 days, for 5 dives, and then spent a week or so playing around with different features, etc, and the computer still has 87% battery life left.     So I’d say getting 30-35 dives out of a single charge should be very reasonable, which would put it more or less on par with my Perdix with a wireless transmitter.      That’s more than enough to cover a week’s diving vacation, which is my minimum threshold for a dive computer.

THE WIRELESS AIR TRANSMITTER

One very unique feature about the Ratio dive computers is the wireless air transmitters that pair with them, and are available as an optional purchase.

The transmitters have a a bright LED that flashes green until 100 bar, then yellow until 50 bar is reached, at which point it flashes red.     This feature allows the dive guide or buddy to also monitor the air of a diver, and reduces the risk of divers unknowingly running out of air.

Also of interest to side-mount divers will be the fact that the dive computer has a Multi Transmitter mode.   Here, the dive computer will automatically track tank switches and display the air pressure of the tank that is currently being breathed, but will provide an air time remaining that takes into account the air in both the tanks.    That’s a really smart feature!

Lastly, this air transmitter unit is rechargeable via USB, which is a godsend, as it doesn’t require you to run around looking for hard-to-find batteries when your transmitter runs out of air on a dive vacation (because OF COURSE that is when it will run out of batteries).

Summary

I was very pleasantly surprised by the overall experience with the Ratio iX3M2.     My initial reaction to the main screen and then the menu structure was lukewarm but a large part of that is because I am used to the menu structure and display of the Shearwater Perdix.    

Once I got past this, however, I found that the Ratio has its own menu structure that is consistent and logical in its own way, and the computer itself is super easy to use, both in terms of pre-dive settings as well as during the dive itself.    

That being said, here were 2 issues that I noticed with the computer:

• First, the safety stop implementation is quite strict – you really do have to be within a fairly narrow window of depth around 5m for the timer to count down.    Shearwater, on the other hand, will happily count off a safety stop as long as you are anywhere between 3-8m.   I quite appreciate this, especially if I want to avoid the crowds of divers all clustered at the 5m mark

• Second,  the straps of the computer are a little hard to adjust one-handed, atleast for me.    I find the Shearwater Perdix straps quite easily to pull tight or loosen with one hand, whereas the Ratio straps were a lot finickier and often required me to remove it, adjust and then put back on.

But other than this, the overall use experience with the unit was very positive.  

To start with, the feature set of this computer is fantastic, both for recreational divers and for tech divers.     The LEDs on the air transmitters, the intuitive display, the ability to plan both NDL and deco dives in more detail and a really intuitive compass are all features I enjoyed. 

But all the features in the world are useless if the ergonomics are rubbish – and I am glad to say that this is most certainly NOT the case here.    The computer was easy to set and easy to use, with a legible display with all the information presented in a very intuitive manner – you won’t need to memorise the manual to learn what does what.

In short, this is an excellent choice for divers looking for a full-featured dive computer which can scale up as their involvement in the sport grows, and a viable alternative for someone looking for an alternative to Shearwater.