Diving with 2 different computers?

[mcohen1021]

Regarding continuing on tables, I would say ‘ehh’ also. The tables unless previously planned out, do not account for multi-level dives, and let’s be honest here, who here doeesn’t go up/down 10-20’ within the same dive? Not an option in 1989-90 for most of us!

Now, if I was diving with two identical computers on identical algorithms and one failed (battery or otherwise), that would be different. But because I do not know the differences between algorithms between brands and models, I personally would not mix and match.

I understand that people have been bent following the rules, and that sucks. I would not call myself overly conservative. I have been deep (137 was my all time deepest), but I typically prefer bottom time over depth. So I prefer to keep it above 100 unless the dive calls for deeper.

 

[outofofficebrb]

Now, if I was diving with two identical computers on identical algorithms and one failed (battery or otherwise), that would be different. But because I do not know the differences between algorithms between brands and models, I personally would not mix and match.

That is the point of this thread, though. It wasn't a debate of whether we need a backup computer or not. It was the logistics of the OP already determining that they want to dive with a backup and how to best integrate it to work together with the primary as seamless as possible given the models at hand. Many of us are saying it is fine to mix and match algorithms between brands/computers/models but use the one with the more conservative algorithm as the primary computer to avoid locking yourself out of the backup. If you dived the more liberal computer and followed those instructions but the more conservative computer is the backup and you ignore required stops and/or blow past NDLs, that would create trouble.There is emphasis on following the instructions of and using one computer consistently unless that one computer fails. That is when you would use your backup.

HOWEVER, if you don't know the difference in conservatism, I would say that it is wise to not mix and match because one could choose their primary incorrectly and defeat the whole purpose of the backup if it locks up.

 

[caruso]

Regarding continuing on tables, I would say ‘ehh’ also. The tables unless previously planned out, do not account for multi-level dives, and let’s be honest here, who here doeesn’t go up/down 10-20’ within the same dive?

Dive tables are more conservative because they assume the entire dive is at the max depth, but that's old news. I doubt there's a single member on ScubaBoard that doesn't know this. In the case of a failure of an only dive computer, if they can figure out their max depths and times of the prior dives (say from their own logs, another divers log or information provided by the charter), they could certainly revert to tables and dive safely for the remainder of their trip, only their dives would be somewhat shorter in duration.

But because I do not know the differences between algorithms between brands and models, I personally would not mix and match.

You might not mix and match but there's no valid reason for it, other than perhaps you're a more conservative diver and prefer a more conservative algorithm in which case it would make no sense to even carry a computer that has a more aggressive algorithm in the first place.

 

[edwants2dive]

Personally I would use 2 computers that calculate the same way. I am currently waiting on my new Aqualung i770r to arrive and plan to buy a lower end Aqualung model to carry as a backup, but hey that's just me.
Along the lines of this thread I was just in Bonaire for a week when my computer flooded 5 minutes into my check out dive so I had to rent one for the week. In this case I did not have enough dive time to worry about the nitrogen load. The thing that I thought about was when I rented the computer it had not been out of the water for 24 hours (some need to be out even longer) so it was still calculating on the last diver's N2 load. That would not be a bad thing as far as being conservative but it could have shortened my dive time (it didn't) but it still could have had an effect on it. So shouldn't operations renting computers try to "cycle" them out so that they are clear of the last renter's profiles? Has anyone else had this issue?

 

[dmaziuk]

The thing that I thought about was when I rented the computer it had not been out of the water for 24 hours (some need to be out even longer) so it was still calculating on the last diver's N2 load. That would not be a bad thing as far as being conservative but it could have shortened my dive time (it didn't) but it still could have had an effect on it. So shouldn't operations renting computers try to "cycle" them out so that they are clear of the last renter's profiles? Has anyone else had this issue?

Read The Fine Manual and do it yourself. On mine reset is buried under "system" menu.

For ones that don't have the button, there is of course the implicit reset function too: remove the battery and wait a bit. But I don't think dive ops would actually do that every time...

 

[Doctor Rig]

I’ve read a number of similar articles/posts about having a primary computer and a backup. In that reading, I don’t recall hearing anyone say the need for a backup computer is situational.... depending on the diving, the number of dives and depths.

From a situational perspective, if a diver is doing several sport dives over the weekend and dives with a SPG and a AI computer, what value does a back up computer provide? Am I missing something?

 

[Blasto]

I wear three different computers.
One monitors my left tank, the other my right tank, the third depends on the dive.

Two of my computers are set for safe conservative diving, the backup is set for an aggressive GF 99 ascent with optimistic assumptions.
If there is a problem that calls for a quick return to the surface (but falls short of an emergency requiring immediate ascent and preparation for a chamber ride), I follow the backup.

When wearing computers with different algos, the rule is to always follow the more conservative of the two (or more). Only exceptions are for emergencies. There's no decision-making involved, and locking yourself out won't be a problem.

 

[dmaziuk]

Am I missing something?

Yes: two is one, one is none, only tables never fail, YOUR GONNA DIE!!! </sarcasm>

 

[jlcnuke]

I’ve read a number of similar articles/posts about having a primary computer and a backup. In that reading, I don’t recall hearing anyone say the need for a backup computer is situational.... depending on the diving, the number of dives and depths.

From a situational perspective, if a diver is doing several sport dives over the weekend and dives with a SPG and a AI computer, what value does a back up computer provide? Am I missing something?

The backup computer has all the profiles of your dives when your primary computer dies on you, so you can continue diving with it instead of going very conservative and calculating everything (including previous dives if you saved the data somewhere) using tables (or abandoning diving for the rest of the planned dives).

 

[dmaziuk]

The backup computer has all the profiles of your dives when your primary computer dies on you, so you can continue diving with it instead of going very conservative and calculating everything (including previous dives if you saved the data somewhere) using tables (or abandoning diving for the rest of the planned dives).

By tables, 6 hours SI and you're clean. Which means when you wake up in the morning, you're in no pressure group. Guesstimating conservatism by tables after the 1 or 3 dives of the day is trivial. So when exactly are you "going very conservative": fifth dive of the day? Sixth?