Inexpensive Backup Computer?

Hi all:

I'm going on my first live-aboard and was thinking I might want a redundant
computer. I currently dive with an Aeris 300G and was thinking it might be a
good idea to get a wrist mount one as well, just in case... Any suggestions
on a relatively inexpensive, nitrox-compatible unit? Thanks.

- Dave

If you are going to have a backup computer, make sure you start using it
right away, or else it will give you a false profile.

On my recent trip to Cocoview, one of our party of 4 locked himself out on
his Cobra, he just borrowed another computer for 48 hours, blithely ignoring
the fact that his diving was unsafe. A few days later, he did the same thing
again. Hangovers and headaches were no deterrent, neither was his age of 58
years. A real macho man. He said himself that he was not planning on getting
bent. Very reassuring. Last time I travel with him.

A redundant computer is a good idea.

Make sure you drink lots of water. Hope you have fun. Where are you going?

"David Gintz" <dgintz@gmail.com> wrote in message
news:u9adnRhSFof12zvfRVn-tw@adelphia.com...
> Hi all:
>
> I'm going on my first live-aboard and was thinking I might want a
> redundant computer. I currently dive with an Aeris 300G and was thinking
> it might be a good idea to get a wrist mount one as well, just in case...
> Any suggestions on a relatively inexpensive, nitrox-compatible unit?
> Thanks.
>
> - Dave
>

"Rudy Benner" <newsgroups@rudybenner.com> wrote in message
news:11acj57ct5qh623@corp.supernews.com...
> If you are going to have a backup computer, make sure you start using it
> right away, or else it will give you a false profile.
>


If what you mean is that I should dive with the backup from the beginning,
that's the plan. It'll go on all the dives with me and my primary computer.

The trip is to the Cayman Islands on the Aggressor - my first live-aboard
(and in fact, my first night sleeping on a boat!)

Thanks for the help.

"David Gintz" <dgintz@gmail.com> wrote in message
news:u9adnRhSFof12zvfRVn-tw@adelphia.com...
> Hi all:
>
> I'm going on my first live-aboard and was thinking I might want a
> redundant computer. I currently dive with an Aeris 300G and was thinking
> it might be a good idea to get a wrist mount one as well, just in case...
> Any suggestions on a relatively inexpensive, nitrox-compatible unit?
> Thanks.
>
> - Dave
>

I have the Aeris Atmos 3 and like it alot. You can get it from
http://www.scubatoys.com for about $ 250.00, and since they're a "real"
shop, it comes with a full manufacturer's warranty. I haven't used your
model, 300G, but the fact they'll be both Aeris' should make menu navigation
easier.

Chris

Hi,

Call me silly but I always carry a backup computer with me. It's called my
dive watch, my gauges and a set of
plastic dive tables. I did the Belize Aggressor last fall and forgot to
reset my Nitrox on my computer so it errored
out on me underwater but I was able to go to the dive tables, watch and
gauges (and after 15 minutes or so of
calculations) continue diving the rest of the day. :O) Oh, they're cheap!

r

P.S. I'm a computer guy and I've learned never put all your faith in them.


"David Gintz" <dgintz@gmail.com> wrote in message
news:u9adnRhSFof12zvfRVn-tw@adelphia.com...
> Hi all:
>
> I'm going on my first live-aboard and was thinking I might want a
> redundant computer. I currently dive with an Aeris 300G and was thinking
> it might be a good idea to get a wrist mount one as well, just in case...
> Any suggestions on a relatively inexpensive, nitrox-compatible unit?
> Thanks.
>
> - Dave
>

"scubaran" <bogus@bogus.com> wrote in message
news:mMOdnSvvnuBLeTvfRVn-ug@adelphia.com...

> Call me silly but I always carry a backup computer with me. It's called
> my dive watch, my gauges and a set of
> plastic dive tables. I did the Belize Aggressor last fall and forgot to
> reset my Nitrox on my computer so it errored
> out on me underwater but I was able to go to the dive tables, watch and
> gauges (and after 15 minutes or so of
> calculations) continue diving the rest of the day. :O) Oh, they're cheap!

So you took your maximum depth for each dive and used that to figure your
nitrogen loading on the tables? The obvious problem with your "cheap"
solution is that you're not getting any "credit" for time spent in the
shallows, so you get "cheated" out of bottom time versus someone who had the
sense to carry a backup computer. If all your dives are 60' max for 35
minutes, that's not a problem. But if your dives are closer to an hour each
with maximum depths in excess of 100', recalculating your profiles on tables
would likely show you missed a lot of deco and that you're now dead.

God knows what you meant by "reset my Nitrox" but it sounds like blatant
user error to me. And then you trust yourself to be a backup "computer"?

In article <11ae74b1t1tlte7@corp.supernews.com>, Greg Mossman
<mossman@qnet.com> wrote:

€ "scubaran" <bogus@bogus.com> wrote in message
€ news:mMOdnSvvnuBLeTvfRVn-ug@adelphia.com...
€
€ > Call me silly but I always carry a backup computer with me. It's called
€ > my dive watch, my gauges and a set of
€ > plastic dive tables. I did the Belize Aggressor last fall and forgot to
€ > reset my Nitrox on my computer so it errored
€ > out on me underwater but I was able to go to the dive tables, watch and
€ > gauges (and after 15 minutes or so of
€ > calculations) continue diving the rest of the day. :O) Oh, they're cheap!
€
€ So you took your maximum depth for each dive and used that to figure your
€ nitrogen loading on the tables? The obvious problem with your "cheap"
€ solution is that you're not getting any "credit" for time spent in the
€ shallows, so you get "cheated" out of bottom time versus someone who had the
€ sense to carry a backup computer. If all your dives are 60' max for 35
€ minutes, that's not a problem. But if your dives are closer to an hour each
€ with maximum depths in excess of 100', recalculating your profiles on tables
€ would likely show you missed a lot of deco and that you're now dead.
€
€ God knows what you meant by "reset my Nitrox" but it sounds like blatant
€ user error to me. And then you trust yourself to be a backup "computer"?
€
€

There are some computers that reset the oxygen percentage to a high
number automatically after each dive, and you have to remember to
manually re-set it before you go back in the water. Yes, this is a
"user error" but it's also an easy one to make. I know I have a couple
of times

Using tables as a back-up to a computer is a really bad idea for the
reasons you point out.

Renting another computer is probably the easiest and cheapest way of
having a back-up. You could also get a watch/computer like a Suunto
Mosquito and use that. Of course, if you're diving nitrox and you
forget to re-set your main computer, you're also going to forget to
re-set your back up...

"scubaran" <bogus@bogus.com> wrote in message
news:vqudnYZftZlj_DrfRVn-jQ@adelphia.com...

> Guess I'm lucky in the fact that I can't get an hour at 100' out of a
> tank.

Lucky, or dumb. Or maybe it's dumb luck. Next time, try to not spend the
entire hour at 100'.

Still, even if you only spend 2 minutes at 100' and then do a nice long 2
minute ascent to 40' where you spend another 56 minutes, you do call that a
100' for 60 minutes dive on your tables, don't you?

> I used the
> Nitrox calculations for my numbers to optimize my profiles (Equivalent Air
> Depth, Oxygen
> Partial Pressure, etc. (laminated in my dive log)). Have to say, even in
> diving 5 dives
> that day I still didn't get close to max time in the water with 32-33%.

You were tracking your residual nitrogen and surface interval time, weren't
you? I suppose it's possible if your profiles were shallow enough, but a
couple dives a day over 70' would probably shorten your available bottom
time even on 33%.

Hi,

Guess I'm lucky in the fact that I can't get an hour at 100' out of a tank.
I used the
Nitrox calculations for my numbers to optimize my profiles (Equivalent Air
Depth, Oxygen
Partial Pressure, etc. (laminated in my dive log)). Have to say, even in
diving 5 dives
that day I still didn't get close to max time in the water with 32-33%.

As far as my computer goes, it makes you reset the Nitrox % before each dive
since it
doesn't assume a % between two tanks (safety reason, like you switch back to
an
ambient air after a Nitrox tank). I did the Nitrox reading on the tank and
logged it to my
log book but got distracted for a minute helping someone with their
equipment and didn't
reset my computer before I got in the water. Boy talk about a racket once I
got a depth
but it was too late to reset the % so I dove conservatively and figured out
my numbers
when I got back to the surface. Given that I was on my 2nd of 5 dives that
day, it allowed
me to have confidence that I wasn't going to over do it that day. I guess
I'm a conservative diver
anyway so what I lost in the tables and calculations by not doing a
multi-level profile
wasn't a problem and turned out I had plenty of dive time that day (my
computer showed
that I had only used about 40-50% of my Nitrogen levels for the day the rest
of the week
so it was more of a comfort factor knowing where I was than a safety thing).

Randy

I know a few people who do liveaboards who use Nitrox but keep their
computers or tables on
air profiles to be ultra-conservative in their dives. 'Course they don't do
5 dives a day at depth.

"Greg Mossman" <mossman@qnet.com> wrote in message
news:11ae74b1t1tlte7@corp.supernews.com...
> "scubaran" <bogus@bogus.com> wrote in message
> news:mMOdnSvvnuBLeTvfRVn-ug@adelphia.com...
>
>> Call me silly but I always carry a backup computer with me. It's called
>> my dive watch, my gauges and a set of
>> plastic dive tables. I did the Belize Aggressor last fall and forgot to
>> reset my Nitrox on my computer so it errored
>> out on me underwater but I was able to go to the dive tables, watch and
>> gauges (and after 15 minutes or so of
>> calculations) continue diving the rest of the day. :O) Oh, they're
>> cheap!
>
> So you took your maximum depth for each dive and used that to figure your
> nitrogen loading on the tables? The obvious problem with your "cheap"
> solution is that you're not getting any "credit" for time spent in the
> shallows, so you get "cheated" out of bottom time versus someone who had
> the sense to carry a backup computer. If all your dives are 60' max for
> 35 minutes, that's not a problem. But if your dives are closer to an hour
> each with maximum depths in excess of 100', recalculating your profiles on
> tables would likely show you missed a lot of deco and that you're now
> dead.
>
> God knows what you meant by "reset my Nitrox" but it sounds like blatant
> user error to me. And then you trust yourself to be a backup "computer"?
>

In article <11aeq1f3410ee45@corp.supernews.com>, Greg Mossman
<mossman@qnet.com> wrote:

€ "Alan Street" <agstreet@nonono_san.rr.com> wrote in message
€ news:080620051045418814%agstreet@nonono_san.rr.com ...
€
€ > There are some computers that reset the oxygen percentage to a high
€ > number automatically after each dive, and you have to remember to
€ > manually re-set it before you go back in the water. Yes, this is a
€ > "user error" but it's also an easy one to make. I know I have a couple
€ > of times
€
€ Actually I'd consider such an annoying "feature" to be more computer error
€ than not and that computer would soon wind up lost on the bottom somewhere.

I believe it's a "safety feature" that the manufacturers' counsel
advised them to integrate into their software.


€ But checking and resetting one's nitrox computer, especially if you've got
€ one that resets high, should be as routine as checking the mix after each
€ fill. You don't forget to do that, do you?
€

Yes, but I might do that quite a while before I dive. My computer
"resets" to EAN50 after about 5 minutes at the surface.

€ > Using tables as a back-up to a computer is a really bad idea for the
€ > reasons you point out.
€
€ Unless he's one of those GUE types who "compute" their profile on the fly.
€ Then a good set of tables is probably a decent backup.
€

The "120 rule" plus various fudge factors is a pretty clever idea
(although I think Kane took it a little too far with his recreational
triox class), but I've never gotten anyone at GUE to explain how to use
for anything but one dive per day.