Mares Matrix decompression mode

[Valentin]

Hello everyone!

I have just completed TDI Adv. Nitrox Course and I used my Mares Matrix computer.
When we wend beyond the ne-deco limit, the computer showed me to do a deco stop at 3m! which is quite strange and my instructor was also surprised to see a deco stop at that depth, since the usual stop is at 6m.

Has anyone encountered such shallow deco stops with that computer? In the manual there is a image of the screen which shows deco stop at 6 metres. So it will be nice to know whether this is fault of the computer or it always provides for deco stop at 3 metres.

Thank you in advance for sharing your experiences.

 

[Carl_F]

I don't know this computer specifically but a 3 m stop is not unusual from my experience. However, I am more comfortable with 6 m stops so on my computer I have adjusted the shallowest depth for deco to be 6 m. My computer has an adjustable setting for this.

A review of the Matrix computer manual indicates it does not provide this feature. However, if you followed the dive plan you had set up at the beginning of the dive, the computer should clear your deco anyway. This presumed you are using planning software with an algorithm and settings close to the computer algorithm and settings. Otherwise, follow your plan and then if the computer has additional deco, follow that, too, to finish the dive. Or just use the computer as a bottom timer.

 

[g1138]

No experience with it, but I just went ahead and looking online for the manual.
English Manual for Mares Matrix Pg 13-14

Deco Stops are generated progressively as you stay down beyond the No Deco Limit
.....
.....
For Deco Stops, since the duration is a function of the exact depth, only the minutes are shown.
During Deco Stops the following symbols may appear[Paraphrase]

The paraphrase shows arrows point up or down or level.

Going over the obvious IT questions, did you read your manual Cover to Cover? Do you understand the interface & all the symbols that may display?

Page 15 Shows a diagram of Stop Summary Table screen as 1 Deco Stop @ 6m, 1 Deco Stop @ 3m, 1 Safety stop @ 3m.
The Stop Summary Table is available once you surpass your NDL and is Accessible using the Bottom Left Button during your dive. It will show you all stops the computer is planning for you to take on ascent.

To me it would seem normal according to the manual but to the exact reason why, that might be worthwhile to contact Mares directly and see if they can give you an answer.

 

[Steve_C]

Are sure that is a 10 ft stop and not a 10 ft ceiling. On my computers if I use up my NDL by a few minutes it will put in a requried safety stop. THe ceiling is 10 ft and the floor is like 20 (maybe 18). Anyway as long as I keep in the window below the ceiling and above the floor it will count down and view that stop fulfilled after an appropriate time interval.

 

[GrimSleeper]

Hello everyone!

I have just completed TDI Adv. Nitrox Course and I used my Mares Matrix computer.
When we wend beyond the ne-deco limit, the computer showed me to do a deco stop at 3m! which is quite strange and my instructor was also surprised to see a deco stop at that depth, since the usual stop is at 6m.

Has anyone encountered such shallow deco stops with that computer? In the manual there is a image of the screen which shows deco stop at 6 metres. So it will be nice to know whether this is fault of the computer or it always provides for deco stop at 3 metres.

Thank you in advance for sharing your experiences.

This tells me that your instructor has a massive gap in his/her knowledge. 'The usual stop is at 6m'? Utter nonsense. On dedicated technical diving computers such as the Shearwaters, and in most dive-planning software, it is possible to select 3m or 6m (and, in some cases, 4.5m) as the final stop depth. Frankly, if your instructor isn't aware of this, he/she probably shouldn't be teaching decompression diving.

Most recreational dive - and pretend-technical - computers will want you to complete decompression at 3m. Ideally, your instructor should have been able to explain why, and to explain why and when 6m - or any other depth - might be preferable. Your computer isn't at fault, it's just being used for something it wasn't necessarily designed for.


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[admikar]

If you miss deco stop for more than 1 ft (0.3m) alarm will trigger, downward arrow on display and message STOP AT 3m (or 10ft) will be displayed (or whatever depth of the stop is).

From page 12 of Matrix manual.

 

[Remy B.]

Most recreational dive - and pretend-technical - computers will want you to complete decompression at 3m. Ideally, your instructor should have been able to explain why, and to explain why and when 6m - or any other depth - might be preferable. Your computer isn't at fault, it's just being used for something it wasn't necessarily designed for.


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Do you mind to share ?

 

[Steve_C]

Heavy surge can make holding at 3m a yo yo but more stable at 6 m?

 

[GrimSleeper]

Recreational dive computers calculate decompression as an emergency function - you have, for whatever reason, made a dive that has incurred an unplanned decompression obligation. It's reasonable to assume, therefore, that you aren't properly equipped for a lengthy decompression, especially with regard to gas supplies. Consequently, the recreational dive computer is looking to get you as shallow as (reasonably) safely possible as quickly as (reasonably) safely possible, in order to get you out of the water before your limited gas supply is exhausted. To this end, a 3m last stop is utilised to maximise the gradient between ambient pressure and tissue tension and speed off-gassing.

On a properly conducted, planned decompression dive, we are concerned with more than just getting out of the water as fast as possible. We are carrying more gas, and probably different gasses, and that gives us options. If we have higher-oxygen deco gasses, we can now use the gradient between inspired partial pressure of inert gas and tissue tension as a driver for off-gassing, rather than just relying on decreasing ambient pressure. Once we start breathing pure O2, we are not breathing in any inert gas at all, thus making off-gassing as efficient as possible. 6m is the greatest depth at which it is considered safe to breathe pure O2 for any length of time, so this is where we switch.

There are a couple of advantages to staying at 6m rather than moving up to 3m to complete deco. As has been pointed out, wave action is likely to be less. There are also physiological reasons why it's beneficial to have a high inspired gradient and a lower ambient gradient, and so 6m has become the 'normal' last stop in many circles. That doesn't mean you can't finish decompression shallower (once your ceiling is shallow enough) if, for example, you're low on gas, getting cold, concerned about changing sea-state, or just plain bored, so long as you're prepared to accept that you may not feel as good afterwards.


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[Remy B.]

Thanks.

I have a Mares Puck Pro, and I have done two small Deco's on it but it both occasions it tell me 5m that is the safety stop depth as well it just told me to stay longer.

it Happen that one of the Deco dives I was with another diver that had a Matrix but his didn't show nothing of Deco time, (probably a more aggressive setting) I have my DC to normal setting