Is a super computer needed for gas switching?

[FPDocMatt]

As a rank beginner, I'm not anywhere near wanting or needing to do gas switching yet. I'm just curious about something.

If you are switching to a different gas mix (such as switching from air to EAN50 to decompress), do you have a special type of dive computer that allows you to enter in at that point that you're switching mixtures? Because if you didn't, then it seems to me that you'd basically be "off the computer" from then on.

Just curious.

 

[rongoodman]

Most of the tech computers require you to manually switch gases when you reach the proper depth, although I think the Cochran computers do it automatically. The Uwatec Aladin 2g is one of the least expensive models which will allow you to switch to a rich nitrox mix for decompression.

 

[Pullmyfinger]

You would enter your gas mix for gas #1, #2, and #3 (if the computer has it) pre-dive.

On my Dive Rite Nitek Duo, I switch from gas#1 to gas #2 at the actual gas switch. This is if I were using this computer in computer mode.
I have it in Gauge mode, with another bottom timer as a back up. I plan my dives with v-planner, and follow the run times/depths, and gas switches according to that plan.

To answer your question, you would assign the gas mixes pre-dive. Back gas and deco mix(es).

-Mitch

 

[Wookie]

It's a good question, and if you are shopping for a computer, I'd say to get the very best you can afford. That might be a Shearwater, or a VR-3 (horrors) or a Liquivision or a Nitek Q. My Shearwater actually allows me to change my preset mixes underwater (which would indicate piss poor pre-dive planning) if I want. I still suggest you should learn to dive using a dive planning software such as V-planner and make your first hundred or so gas switches manually before you learn to rely on a computer. My 2 cents.

 

[IanBrit]

Yes, you need a multi-gas computer that factors in the gas mixes and by design, these will support the switching of gas (the process is 'switch gas then tell the computer') and most will prompt the diver with various alarms, including a depth warning should the diver descend back past the MOD. These need to take into account the opportunity for skipping the gas (which could include the fact you lost the gas somewhere along the way, some equipment failure or simply due to diver choice (indicating a radically changed dive plan)) as well as predicting the decompression stops along the way. There are many on the market, with support from 2 gases to many. For instance, my Galileo Sol supports 10 gases of various oxygen and helium percentages. The classic dive computer purchases seem to be Air/Nitrox single mix -> Multiple gas -> Trimix ready. Where you start in the evolution depends on how honest your dive store was (or the budget).

 

[waterpirate]

As mentioned there are a lot of options to look at in regard to features when buying multigas computers. From a training standpoint most instructors require you to use tables only to commit you to the discipline of "plan the dive, dive the plan". After that most people start with the nitek duo or one of it's clones. It is a good 2 gas computer that makes a good bottom timer in gauge mode. After the 150fsw is crossed there are a lot more forks in the road. To many to concern yourself with untill you are there.
Eric
Do you do any ocean diving in Ocean City?

 

[HowardE]

Many of the Oceanic (Aeris) Computers, and some Suunto computers also support gas switching, with accelerated Deco.

I've done deco dives with gas switches on a Shearwater and Oceanic OC1 at the same time, and the deco profile was pretty much the same.

 

[gsk3]

if you are shopping for a computer, I'd say to get the very best you can afford.

I'd actually recommend the exact opposite, for a few reasons:

1. Computers seem to be a very personal preference. You could buy that fancy computer and then when it comes time to make full use of its capabilities down the road, discover you'd rather have a different one.
2. Computers are technology, and thus depreciate rapidly. $1k is a lot of money to spend on a technical computer that isn't going to deliver any more capabilities than a $150-500 computer for half or more of its life.
3. You may not wind up doing any tech. diving down the road (there's plenty to see in this world within NDLs).
4. Even if you do wind up doing technical training, you may wind up using ratio deco or similar methods, which only requires a bottom timer, not a computer.

 

[SeaCobra]

As a rank beginner, I'm not anywhere near wanting or needing to do gas switching yet. I'm just curious about something.

If you are switching to a different gas mix (such as switching from air to EAN50 to decompress), do you have a special type of dive computer that allows you to enter in at that point that you're switching mixtures? Because if you didn't, then it seems to me that you'd basically be "off the computer" from then on.

Just curious.

I am sure that anyone wishing to do gas switches, etc., would indeed have the proper training. Using a computer to handle your gas switches is one way to do it. You can also do it by preplanning your dive with software or tables and then executing the dive with a bottom timer and depth gauge. This method works well for square profile dives

 

[FPDocMatt]

Yes, you need a multi-gas computer that factors in the gas mixes and by design, these will support the switching of gas (the process is 'switch gas then tell the computer') and most will prompt the diver with various alarms, including a depth warning should the diver descend back past the MOD. These need to take into account the opportunity for skipping the gas (which could include the fact you lost the gas somewhere along the way, some equipment failure or simply due to diver choice (indicating a radically changed dive plan)) as well as predicting the decompression stops along the way. There are many on the market, with support from 2 gases to many. For instance, my Galileo Sol supports 10 gases of various oxygen and helium percentages. The classic dive computer purchases seem to be Air/Nitrox single mix -> Multiple gas -> Trimix ready. Where you start in the evolution depends on how honest your dive store was (or the budget).

I'm amazed that my beginner-level dive computer (Mares Puck) actually has nitrox capability. The instructions talk about MOD, which I didn't understand when I first read it. Of course, this basic computer wouldn't be able to handle a gas change during the dive, I bet. On the other hand, it'll be a good long while before I'll be even considering technical diving.

Note: After practicing medicine here in rural Maryland for 13 years, asking patients how long they've had symptoms, I finally learned what these terms mean:

• Awhile: 2 months
• A good while: 6 months
• A good long while: 1 year

:shades: