What's the difference between a dive computer and a bottom timer?

[PvtStash]

I use a cheap digital armitron from Target in stop-watch mode for anything up to 90' , square profiles are fine...

If I'm doing anything over 90' where I'll be approaching NDL's tho' I break out the ol' Dacor Microbrain (I'll upgrade eventually, but hey it still works an I'm chea..er Frugal)

 

[gcbryan]

An example: a 'camping on the Yukon' dive. I'm rusty (and new to iDeco), so feel free to verify my numbers/correct me.

100 ft, double AL80, 3000 PSI - on air (I know... see below).
40 minutes at depth - wreck is big and there is plenty to see (rule of third with iDeco seems to be 44' - I'm lazy and will trust it for that post). It's a square dive unless you really want to do a thesis on the mooring line.
Nothing especially technical there (actually, tech divers would probably be smarter and use trimix to avoid that long deco).

Total ascent time:

• US Navy tables: 20'
• iDeco: 29'
• Vyper: 39' - and you're breaking thirds (and it takes forever to pry that number out of the computer)

Isn't the bottom timer option more tempting now?
(And yes, I still love my Vyper - in computer mode - thank you very much).

Adding helium (trimix) would lessen the narcotic effect not the deco time. A high O2 deco mix would lessen the deco time.

 

[fnfalman]

A high O2 deco mix would lessen the deco time.

100% O2 at 25-ft, baby!!!

 

[rongoodman]

One problem with dive computers is that the decompression algorithm used might be proprietary, so you're not really sure of how it's making its calculations. Others specify the exact model they're using. There are higher end tech computers, such as the Liquivision X1, that require you to choose and install the software separately. That way, you know exactly what you're running, which might well be the same software you'd use on your home computer to cut tables for use with a bottom timer.

 

[Cave Bum]

100% O2 at 25-ft, baby!!!

Don't you mean 20 foot? See the formula in my avatar...

((1.6/1.00)-1)*33=19.8 Feet

{1.6 is the max PO2 for deco & 1.4 for the working portion of the dive}

Which, of course, brings up the issue of having a computer that can switch to a deco gas...

Be safe and have fun in the water! Bruce

 

[elan]

I cannot imagine anyone wanting a bottom timer over a dive computer unless they have an issue with the price of the computer. They may be trying to conserve their monies by using a bottom timer instead.

No need to imaging I got a bottom timer and put my computer on sale. One of the reasons was that my comp was gauge not wrist. But I like my BT more. Very simple and straightforward. Time, depth, temperature and ascent rate which I hardly ever use. Will I switch it for a simple computer ? I doubt. I does place more demand on the brain but after my 10th dive approx I memorized all NDL limits of my PADI air table. I donnot know why I like it but I do. And yes it forces you to plan the dive ahead and dive the plan which I believe is good.

 

[elan]

I've seen several posts praising bottom timers over dive computers, but what's the difference between the two? I'm assuming that a dive computer has more functions so why would you want a b.t. instead?

I'm especially interested because I'm looking at getting a computer in the near future, most likely an AI Oceanic VT3 or ATOM 2.0. And yes I do realize that I'm sticking my neck out there by admitting it. :guillotine: Thanks.

Jason

it also depends on what you want. I have changed to BT just because I want to figure out all those things myself inside out, tables, deco stops, time tracking etc.

 

[fnfalman]

Don't you mean 20 foot? See the formula in my avatar...

((1.6/1.00)-1)*33=19.8 Feet

{1.6 is the max PO2 for deco & 1.4 for the working portion of the dive}

Which, of course, brings up the issue of having a computer that can switch to a deco gas...

Be safe and have fun in the water! Bruce

I was just making a funny. I'm not certifiied and trained to do anything but regular rec Nitrox.

 

[H2Andy]

Don't you mean 20 foot? See the formula in my avatar...

but what about FRESH WATER????

 

[Riger]

1.6 is the recommended maximum PPO₂. It is my understanding that not too long ago, it was not uncommon to dive to 2.0 PPO₂.

I have only been diving for 18 months, so if there are any divers out there with more information in this regard, I'd be happy to hear about it.

Thanks in advance

Best Regards
Richard