Diving with 2 different computers?

[ThatDogDontHunt]

I've not seen it as a regular thing, not that I'm sure that I would notice. In general I've found most dive crews (especially on LOBs) are pretty aware of who is doing what especially after the first day and they get a feel for the divers. I think they've mastered "peaking" at lots of stuff without being obvious about it.

That is a valid idea. When they double check your depth, time and remaining air pressure for the first few dives they generally get a feeling for "something". I have heard a few holy shits...

 

[Jim Lapenta]

I use a perdix with another perdix as back up. Although this weekend on day one my student wanted to try a perdix so I gave one to her and used my predator as the back up.

 

[BoltSnap]

Maybe reading comprehension isn’t your strong suite. I’m pretty sure I stated that if his primary fails to use his backup, meaning his backup could fail at depth, I re read my post and don’t even see the word “surface” but I’ll check again

This is what you said:

Pick one and use it, if it fails then use the there other as a backup, don’t use both at the same time

Any reasonable person after reading your statement above will understand what I understood from it and will come to the same understanding and conclusion I came with reading your statement. You meant what you said but didn't know that what you said was totally wrong and now you are trying to cover your tracks by attacking others. You just don't know what you are talking about and gave wrong information. The issue isn't my "reading comprehension" as much as your lack of understanding of the issues and your inability to write advice for others with the correct information.

 

[DBPacific]

I can understand why they do it, especially when it was on a liveaboard… If your pc screws up and you’re wearing two of them, how do you know which one is correct?

Imagine you wear 2 PCs, PC #1 screws up, you go on the next dive wearing PC #2, get bent and you’re in the middle of nowhere (like Socorro)… The boat would have to travel 8-10 hrs back to Socorro island from say Roca Partida just to get you airlifter out to get medical attention.

My .02 cents, I’d prefer to err on the side of caution and maintain a spotless safety record while providing the rest of the divers a perfect vacation.

Beyond a computer dying underwater, the difference between computers being 'correct' is the algorithm they use to calculate no deco limits. For a lot of computers, when you breach their NDL limits, it locks you out or changes screens. So one computer could be based off of a more conservative algorithm (your NDL and no deco time will be smaller) while your other computer has a more liberal algorithm which will calculate more time for no deco. Every user manual should say what algorithm they use. If computer one 'fails' that's because you breached the no deco limits set by its algorithm. If you're using two computers at once (one being the backup), then always base your dive off the one with the more conservative algorithm. Yeah, you can still get bent but there's a chance for all of us to get bent using computers or tables regardless of whether or not we have a backup.

 

[FF / EMT]

This is what you said:


Any reasonable person after reading your statement

I must be unreasonable... I bow to your wisdom.

You meant what you said but didn't know that what you said was totally wrong and now you are trying to cover your tracks by attacking others.

you’re right silly me, I actually use both my regulators when j dive as well, even diving with a FFM I’ll take it off because I wouldn’t want my backup to feel lonely.
’

You just don't know what you are talking about and gave wrong information.

Again silly me, I know nothing and my qualifications are hogwash because it’s not the way you do it.

The issue isn't my "reading comprehension" as much as your lack of understanding of the issues and your inability to write advice for others with the correct information.

I’m so silly, I’m just going to ask you if it’s ok to post next time...

 

[caruso]

LOBs ask for max depth and remaining air because it is sometimes required by the government (hello, Queensland, Australia) that they log this for whatever reason. They also use it as a way for divers to "check in" back on a boat so that they know they are not leaving anyone behind, sometimes in addition to an actual "I am here" roll call. Additionally, boats also use it to determine surface intervals and want to know what everyone has dived so they can account for that..

Makes sense. When I was on the Belize Aggressor IV they did that and I sort of took it personally (why are they checking on me, I know what I'm doing!).

Then again I tend to take a lot of things personally that have nothing to do with me.

 

[mcohen1021]

What I was saying in case there was any confusion was that you should only use one computer. There is no need for 2. If your computer fails, you should end your dive. You may disagree with my opinions, but I do have a 31 year accident free track record to back up my opinions.

 

[caruso]

What I was saying in case there was any confusion was that you should only use one computer. There is no need for 2. If your computer fails, you should end your dive. You may disagree with my opinions, but I do have a 31 year accident free track record to back up my opinions.

@mcohen1021 Since you don't have a good argument you fall back on your credentials rather than facts pertinent to the discussion: "I've been diving longer so I know better". Known as argumentum ad verecundiam, something is given more credence than it deserves because of who's saying it. That's no different or any more accurate than a person saying "I have thousands of dives" or "I'm an instructor" therefore "I'm right".

A similar illogical argument (Ad hominem) is insulting your opponent, as has happened on this very thread, with terms such as "you don't know how to read", or simply "you're wrong".

Let your argument stand on it's own merits. That much being said, your argument against a second dive computer is invalid- because as you said yourself, if your one computer fails, it's prudent to end your dive. However if you've got a second working computer, you can clearly continue right on diving, plus you've got your NDL information for a multi day trip and you've got your digital logbooks intact.

And I've been diving since 1984, that's 35 years to your 31 years so I'm right and you're wrong.

 

[mcohen1021]

@mcohen1021
And I've been diving since 1984, that's 35 years to your 31 years so I'm right and you're wrong.

LMAO, now that there is funny. Happy diving to you man.

MC

PS: Question for you - how do you protect yourself when someone tries to cut your regulator hose?

 

[outofofficebrb]

What I was saying in case there was any confusion was that you should only use one computer. There is no need for 2. If your computer fails, you should end your dive. You may disagree with my opinions, but I do have a 31 year accident free track record to back up my opinions.

I think the need for 1 or 2 (or even 3!) is a personal risk assessment. I do agree if you only have 1 and it fails, it’s best to end the dive. You could continue on tables (ehhh) assuming you had been diligent about logging your dives prior to the computer failure or sit out for an extended SI and rent a dive computer with no tissue data (also ehhhh), assuming there is one available to rent given where you are (liveaboard with no spares or all rented out?). However, if you had a second with the proper tissue data that has been on the same dives as the other as @caruso mentioned, you could continue the dive. Given how much time and money I invest on trips and the distance I travel to enjoy so many repetitive dives, that is an easy decision for myself and I'm guessing many others who choose to have at least 1 backup.

No one is saying to continue the dive if your 1 computer fails. I would hope that even a freshly minted open water student would have that opinion and decision, let alone someone who has been diving for 31 years. While it’s great you have been accident free for 31 years, do know that there are incidents of people who get bent and have accidents diving well within limits of their computer that they have been using with no previous issues. It has happened to people with and without PFOs if that is going to be a point. Using 1 or 2 computers does not change this. I am quite sure that even if you spent the last 31 years diving with 2 computers (1 as a backup on every dive but only following the instructions of 1 and only following the instructions for the other only if your primary failed), you would still be accident free. I think your being accident free is a testament to how you dive, how conservative you are diving, your dive profiles, your surface intervals, your No Fly times, your attention to air consumption and air levels, your buddy techniques, your self awareness, good gear maintenance, so on and so forth, etc. You have made decisions and actions that work for you and that is good but it has nothing to do with choosing to dive with a backup computer or in your case, not diving with one.

While you are not stating this, I want to point out there is no correlation with choosing to only use 1 dive computer and a dive accident unless you are talking about a bad judgement call as a reaction to your 1 dive computer failing. At the same time, all those who dive with a backup computer are not more likely to have a dive accident or people who have dive accidents do not always have a backup computer.