Dive computers... SO many choices!

[Rred]

Interesting that NAUI, PADI, and NOAA all are using different numbers. Each 5 minutes apart at 60' msw. And while NOAA is giving the longest times..one could argue they might be the folks who are most in tune with the medical issues, with no other considerations (litigious resort students) to influence the numbers they choose to use.

Incidentally, DAN's email this week led me to a web article they have, which states there are currently no dive computers using ambient temperature. Since the issue is problematic, I think it comes down to the individual using the "personal factor" and remembering to add a +1 whenever they anticipate whatever they call a 'cold" dive.

And somehow despite the huge number of varying algorithms and computers in use, the percent of DCS in recreational divers apparently has remained the same over the last decades.

 

[Gary Johnson]

1. Compass=battery drain, i've got one on my computer and never use it.
2. Algorithm; provided you are diving within conservative limits it should NOT lock you out. It may complain and beep if you do something wrong but having it lock on you is unlikely. I've been diving for 24 years and never had one lock me out.
3. Upgrade-ability; not a huge fan of it unless you have aspirations of learning technical diving. I'm advanced Trimix and have been since 2002, keep it simple.
4. Cost; my opinion, keep it conservative, it's like any piece of equipment, great when you have it but hurts when you need to replace it, if it falls off the side of the boat, gets trodden on, stollen, flooded, or otherwise stops working you’ll be glad it didn't cost 1000's of $€£¥ or whatever you spent on it.

However, I do think the options you should be choosing between are watch size or larger "zoop" size, I have both, my watch is my dive computer which means I'm never without one if a dive comes available. That said, for planned dives I tend to rely on my larger screen computer, just easier to read.

So, my opinion for what it's worth, pick the one you like the look of!! I've been using Suunto for years, got 4 of them and regularly dive two at the same time, at this stage of you diving most of the major brands should be fine....

 

[KenGordon]

I just realized I'm a doofus and what I said above is dumb. There is no interpolation required. At the point you go into deco, the depth at which you exceed 30% (or whatever your GF Lo is) of the M-value (in your leading compartment) is whatever it is. It can be calculated directly, without regard to what GF Hi is. And, the only way your depth would affect the calculation is if you choose to factor ascent time into the calculation.

If you choose to calculate it the way Baker does, which is to say ignore ascent time, then current depth would not be a parameter in the calculation at all. At that point, you are doing a somewhat simple calculation to answer the question "at what depth will my current tissue loading have at least one compartment that is greater than or equal to 30% (or other GF Lo value) of the M-value for that compartment?"

Of course, my ideal computer would factor ascent time into that calculation, so that it doesn't show me a stop that I will never hit (assuming I ascent at 30 ft/min). I believe the Perdix does work this way and, for example, my SeaBear H3 does not. I believe my H3 would show me a stop, as I ascend, that will disappear before or just as I get there. But I digress...

Anyway, I think the answer to @KenGordon's question would be that the anchor is set at the time you go into deco, by calculating the ceiling at that time, based on your current tissue loading and your GF Lo setting. As your tissue loading increases, it would be constantly recalculated. If your tissue loading decreases, it would stay set at whatever value it has. At least, that's my guess.

My question was for LandonL. I know how it works in the Erik Baker scheme. I was asking because something he said didn't match my understanding of that.

Why do you want the computer to factor in offgasing during the ascent to the first stop? That, and continuous ceilings or small stop intervals, makes the profile more aggressive. Since what you get from GF is a history of use leading to an assumption of 'safeness' surely you want to stick with the way it has been used.

Of course if what you really want to do,is claim to some DM that your 90 minute air dive was within NDL, as seems to be the main criteria for SBers to chose a computer, then sure, assume some slow ascent rate and call it no stop...

 

[MasterMindDiver]

Short Bio about me first..
Open water diver
Nitrox certified
Live in Florida (which means I dive alot)
I plan on taking the advanced open water course. No cave, or tec diving, ever.

However computer shopping has never been so difficult.!
I was going to get something cheap at first, like the old Suunto Zoops that my dive buddies, who are advanced divers haave, and it fpretty much does the job, how's your depth water temp, has the safety stop countdown, and how long you've been down.

Then I saw the cressi giotto.. Discontinued, but large screen, easy to read, also very basic and does the job, read all the reviews, everyone likes it. It's discontinued...
Then I see the Oceanic 2.0/3.0 it can match other computer profiles and you can add a second tank and is also one of the more affordable ones.
Then then I see the Suunto D4i novo.. Which is air integrated (yes I do understand that the extra part that you have to buy, the transmitter, used to get the tank and the computer to "talk" to each other is another few hundred dollars.)
Then I see the d6i (and other pricier models) that is air integrated AND has a built-in digital compass.
And I see aloft of people using shearwater petrel.
And then while researching the petrel I learned about the Mares Icon HD (looks like the petrel.. LED screen, air integrated, compass..) Love the LED screen and the colors.

Then at the dive shop me and some students entered a debate about how you do (or don't) need a wrist computer when you can just buy the console (One and Done.) and not have to read both a console and your wrist. I don't even have my own regulator yet, so a console is Off the list.

So my question is:
Exactly what type of *wrist* computer is appropriate for an advanced diver?
I want to buy something nice and suitable so that I don't feel the need to have to UPGRADE later on.

The extra features (digital compass, air integration, etc...) they sound very convenient but is it really worth the extra money?

Hello Nikole,
Actually I was having the same situation you have few months ago till I decided what fits me well.
The difference is that I am currently getting my dive master certification + planning for tech diving and that makes a huge difference ..
and based on that i went for perdix AI .. andI am very happy with it.

in your case , i would recommend something cheaper like ostc sport OSTC sport since you are not planing for tech , as well as liberal like perdix for using Bühlmann Model ZH-L16C Algorism and firmware supports upgrades.
also Amazon.com : ScubaPro Aladin TEC-3H Dive Computer : Sports & Outdoors is using Predictive Multi-Gas ZHL8 ADT MB algorithm accommodates three gases (21-100% O2)... with is a above what you want .. but a kind of liberal like perdix/ostc.

on the other side , I have some AOW instructors/students who are very happy with Mares Smart Amazon.com: Mares Smart Wrist Dive Computer, Black: Sports & Outdoors .. even some dive instructor using it within the courses.

Sunnto dive computers are very cool as long as you are staying within safety limits and following it .. accidental behaviors of going DECO and not doing deep stops will lock you out . specially if you are in a boat trip and got it in your first deep dive, you will not be happy staying and watching others dive..

also oceanic pro-plus 2.1 seems to be cheaper then above options Oceanic Pro Plus 2.1, Air/Nitrox, Air Integrated Computer with Compass .. but bulky and i don't think it is as liberal as ostc/perdix..

the main point while diving with dive computer is to be safe .. so with whatever option you will go for .. specially with the liberal dive computers .. make sure you follow deep/safety stops and taking it smoothly to avoid hurting yourself.

Hope that information help you deciding the best computer that fits your needs and budget.
Regards

 

[stuartv]

Incidentally, DAN's email this week led me to a web article they have, which states there are currently no dive computers using ambient temperature.

But there are ones that use the diver's skin temperature...

 

[Diving Dubai]

Sunnto dive computers are very cool as long as you are staying within safety limits and following it .. accidental behaviors of going DECO or not doing deep stops will lock you out specially if you are in a boat trip and got it in your first deep dive. you will not be happy staying and watching others dive..

The way this is written is very misleading, I assume in intentionally so I will clarify for others reading

Suunto WILL not lock you out for missing deepstops, you can turn the deepstop requirement off. If you have it enabled and miss the deepstop it may add time onto your Safety Stop - maybe a minute

The Suunto will not lock out if you go into Deco, If however you don't carry out your deco obligation or break the deco ceiling for 3 minutes on a stop then it will lock you out

Those Suunto's which run their Fused RGBM can be more liberal than the Perdix depending on the settings.

All RGBM computers do not like short SI. If you are on a boat, do a deep dive and then drop back in again after an SI of 60 mins or less, you will get a reduced NDL on that dive - depending on your personal settings.

OSTC, unless they have recently changed their policy, they do not sell their computers into the USA, but they are fine computers. In my area they are just as popular as the Shearwaters. The Sport is a fine model and will suit all recreational divers as you say, the plus allows for Trimix upgrade for those who want it. I'm currently lusting after an OSTC 4.

 

[MasterMindDiver]

The way this is written is very misleading, I assume in intentionally so I will clarify for others reading

Suunto WILL not lock you out for missing deepstops, you can turn the deepstop requirement off. If you have it enabled and miss the deepstop it may add time onto your Safety Stop - maybe a minute

The Suunto will not lock out if you go into Deco, If however you don't carry out your deco obligation or break the deco ceiling for 3 minutes on a stop then it will lock you out

Those Suunto's which run their Fused RGBM can be more liberal than the Perdix depending on the settings.

All RGBM computers do not like short SI. If you are on a boat, do a deep dive and then drop back in again after an SI of 60 mins or less, you will get a reduced NDL on that dive - depending on your personal settings.

OSTC, unless they have recently changed their policy, they do not sell their computers into the USA, but they are fine computers. In my area they are just as popular as the Shearwaters. The Sport is a fine model and will suit all recreational divers as you say, the plus allows for Trimix upgrade for those who want it. I'm currently lusting after an OSTC 4.

Hello Diving Dubai,
Thanks for clarifying that point in details .. Yes , you are absolutely right .. i did a small correction in my post to avoid any confusion.
Regards

 

[stuartv]

Why do you want the computer to factor in offgasing during the ascent to the first stop? That, and continuous ceilings or small stop intervals, makes the profile more aggressive.

I believe this is incorrect.

Assume you're using 30 for GF Lo.

Calculate your first stop without factoring in ascent time. Let's say that puts your first stop at 100'. You next stop would be at 90' with some higher GF value. So on and so forth until you arrive at the surface with a GF equal to the GF Hi value that you had set.

Calculate your first stop factoring in ascent time. With off-gassing during the ascent, your first stop might still be at 100'. But, for the sake of this discussion, let's say that you off-gas enough during your ascent that you don't actually get to 30% of your M-value until you get to 90', so 90' is your first stop.

Your way (the first way) results in getting to 90' with some GF that is higher than 30% of the M-value. I.e. the value that is calculated for 90' by interpolating from 30 at 100' to GF Hi at 0'. If you're using GF 30/70, and your first stop is at 100', then at 90', I believe your GF would be 34.

The second way results in getting to 90' with a GF of 30 or less.

So, your way, GF 34 at 90'. My way GF 30 at 90'.

It seems to me that factoring in offgassing during the ascent makes the profile more conservative, not more aggressive.

Since what you get from GF is a history of use leading to an assumption of 'safeness' surely you want to stick with the way it has been used.

Okay. So, how about the way Shearwater does it?

 

[KenGordon]

In one case you stop at 100 and in the other not until 90. I contend that the second one is more aggressive.

By factoring in travel time when calculating the ceiling you will end up with a shallower ceiling as you will have been shallower in the mean time. That can make a surprising difference to the ceiling depth, like a couple of metres for a dive without much deco.

This line of though leads back to an interesting (ish) question about computer implementations. Where should the first gf lo be applied? At the first projected stop or the first time the diver reaches a stop? What happens if a diver does a multilevel dive and never hits any stop until quite shallow? Should that 'first' shallow stop anchor the gf lo-hi line, or the one they would have had if they had done an ascent at the time of the deepest ceiling?

More implementation choice. Lucky it is all so open and non proprietary eh?

 

[stuartv]

In one case you stop at 100 and in the other not until 90. I contend that the second one is more aggressive.

Being at 90' with a GF of 34 is more conservative than being at 90' with a GF of 30???

Let me point out an additional feature of this theoretical dive.

The off-gassing that occurs during the ascent means that, if you calculate the first stop using my way, you first stop is at 90' with a GF of 30. That's not a question. That's an observation of the conditions I already described.

Same dive, same ascent. Since you would actually not hit GF 30 until 90' (per the specifics of the example), that means that, with your way of doing it, when you arrive at 100', you will be less than 30, so your stop would end up being for 0 time. It would clear before or as soon as you get there. So, you would actually ascend non-stop on up to 90' (no matter which way you calculate the first stop). And, at 90', the GF value being used to determine your stop time is GF 34, instead of GF 30 (if done my way).

So, your way would still have you directly ascend to 90', same as my way. But, your way would clear your 90' stop based on GF34, where my way would clear you based on GF30.

Do you still claim your way is more conservative?

Let me express it again, going back to general terms. Your way anchors GF Lo at a deeper depth. That means that at every depth from your first stop on up, the GF value you will use as the gate for that depth is a higher number than the GF value my way would use. That means that at every depth of the ascent, your diver will have a higher GF value than my diver.