PADI tables finally going away?

[lowviz]

Please do us a favor and identify the computers that do this. This is the first I have heard of this.

Boulderjohn, don't get too upset about this. Copied from Wikipedia (without permission):

Many computers go into a "lockout" mode for 24 hours if the diver violates the computer's safety limits, to discourage continued diving after an unsafe dive. While in lockout mode, these computers will not function until the lockout period has ended. Other computers, for example Delta P's VR3, will continue to function, providing 'best guess' functionality whilst warning the diver that a stop has been missed, or stop depth exceeded.

-The VR3 comes from England, and a very different legal system. I use a VR3 and accepted the potential consequences...

 

[The Chairman]

That's another neat feature of some computers! If you get in a position where a deep deco stop is required the computer ABANDONS you. It simply pukes and displays "Use Tables". Right in the middle of the dive. There you are, down deep, low on air, totally screwed and your computer pukes. Sure, you shouldn't be there. But there you are...

If you exceed the limits of ANY tool you may well find yourself in unchartered territory. Fact is, PDCs have far greater limits than ANY OW table. Some tables won't even give you deco times.

The scenario you described is not the fault of a table or a computer though: it's a function of inattention by the diver AND his buddy. Today, my buddy and I were hunting lobster off of Ft Lauderdale and decided that we would be incurring deco before the end of our dive. We were both diving Oceanics: he was on a Veo180 and I was on an OC1. Just as I was going to call the dive (we reached our agreed upon deco limit), he tugged on my fin to do the same. We did our deco together and a couple minutes more for good measure. THAT'S what buddies are for! That and for sharing lobster at a friend's house. YUM!

Every dive has three limits: time, gas and depth. A good buddy team knows the other buddy's proximity to these limits throughout the dive. Great buddy skills and communication are essential to being a great diver. Being able to make alphabet soup is not.

 

[DevonDiver]

Translation:

"USE TABLES" = "You screwed up so badly, I can't help you any more"

 

[rstofer]

I think he's just regurgitating info he doesn't understand himself.

It sounds like he is describing the process employed on some computers if you violate decompression.

The computer doesn't abandon you.... it just can't provide you with an ascent profile if you have sufficiently violated its algorythm...by ignoring it.

Maybe...

Read the Oceanic VEO2x0,pdf document on page 57 "Immediate Violation Mode and Gauge Mode"

During a Dive, if a ceiling much greater than 60 feet (18 meters) is required, an Immediate Violation Mode will be entered. This situation would be preceded by entering Delayed Violation Mode #2

The Veo 200/250 would then operate with limited function in Gauge Mode during the remainder of that dive and for 24 hours after surfacing

In other words, if a deep stop is required, this computer reverts to gauge mode. No help whatsoever with deco on the way up. That is not hopeless but it wouldn't be my first choice. I don't do deco dives so I have no idea what it would take to get in that situation.

It's the same story for the VEO100 but the ceiling is at 70 feet.

Same story for the Oceanic Pro Plus 2 at 60 feet.

The VR3 computer goes to "Use tables" if a microbubble stop is missed. It will be displayed for the next 24 hours.

I'll admit that the diver had to mess up badly to get into a position where these deep stops are required. I'm not sure a purely recreational single tank diver could get there. My concern is that the computer literally gives up. Right when you really need it.

I don't promote doing dives that might result in any of these situations. I don't promote the concept of deco dives and prefer to stay strictly within recreational limits.

Richard

 

[The Chairman]

My concern is that the computer literally gives up. Right when you really need it.

Just like recreational tables, only they give up much, much earlier.

"A man's got to know his limits"... Dirty Harry

 

[lowviz]

.............The VR3 computer goes to "Use tables" if a microbubble stop is missed. It will be displayed for the next 24 hours.
..............
Richard

It will still get you home, but tattles on you for a day if anyone glances at your computer. I find it to be a somewhat complicated, really pissy computer that stays on the safe side of things. I can come up clean (non-deco) on my backup with my VR3 whining. However, I'm starting to like it a lot more than I did at first.


Most recreational lockouts are achieved through buoyant ascents. Unlikely that anyone is reading/responding to much of anything while that is happening. As just posted, focus on improving buddy skills rather than looking for a dive computer that thrives on mayhem.

 

[DevonDiver]

Which poses the question... what is a recreational diver doing in deco?

If you don't have the skills and knowledge to dive deco, then it is no wonder that people are violating and 'locking down' their PDCs.

If properly trained and educated... the message "Use Tables" is hardly a killer situation. You just reach for the pre-prepared, dive-specific, back-up tables in your pocket and ascend using the PDC in gauge mode...as every decompression/technical diver is trained and equipped to do.

I'll admit that the diver had to mess up badly to get into a position where these deep stops are required. I'm not sure a purely recreational single tank diver could get there.

Yes...so providing divers don't exceed their no-deco limits without getting the proper training, then this is a complete non-issue.

In the unlikely event that the diver exceeds his no-deco limit to the huge extent that they get a violation, then all they have to do is follow the ascent profile provided from the PDC.

If they massively exceed their no-deco limit...and fail to follow the recommended profile... then what help can the PDC provide?

"USE TABLES" means you've already blown it. A PDC cannot miraculously wind back time and let you have 'another go' at following it's ascent profile.

The PDC is not 'abandoning you'.... it's just that the diver concerned has been such a dangerous muppet that the PDC can no longer compute a safe ascent for them. It cannot magically amend Charles' Law to fix things...

The same is true of rapid ascents. It happens...you've blown it. The PDC can't do anything about it. You sit on the boat breathing O2 and hope that nothing starts aching. The computer stays 'locked out' for 24-48 hours in case you are sufficiently stupid to want to get back in the water during the period when DCS symptoms may arise....

Of course...for recreational divers suffering a rapid ascent... then the "USE TABLES" can refer to the RDP. Think 'Emergency Decompression'... Stay at 5m for 15m or longer (as your air allows) and don't dive for 24 hours.

 

[rstofer]

Clearly the recreational dive tables aren't going to take a person very far into deco. They weren't intended to. Deco diving is for experts. Way above my pay grade...

The thing I find disappointing with the computers that do choke is that unless the algorithms hit a boundary, why should the computer care if I need 30 hours of deco at 30'. As long as I can get the air, the computer should not just quit.

Of those computers that do choke, I don't know what dive profile got them into that state. What I do know is that there is no indication in the NiTek Duo manual that it ever gives up during the dive. No matter what stupid thing the diver has done, the computer will try to help them recover.

But you're absolutely right about the tables (well PADI and NAUI, the Navy tables are different). They only apply to recreational dives and that's the only kind I am qualified to do.

I like my NiTek Duo. Now that my wife has claimed it, I'll have to buy another. No problem! The price is coming down now that there is a new Trio on the market.

Richard

 

[The Chairman]

The computer stays 'locked out' for 24-48 hours in case you are sufficiently stupid to want to get back in the water during the period when DCS symptoms may arise...

Murphy's 3rd Law:

• It is impossible to make anything foolproof because fools are so ingenious.
• Nothing is foolproof to a sufficiently capable fool.
• Make something idiot-proof, and they will build a better idiot.

As a side note, I would like to point out that it was originally "Murray's Law", but there was a typo at the printers.

 

[DevonDiver]

The thing I find disappointing with the computers that do choke is that unless the algorithms hit a boundary, why should the computer care if I need 30 hours of deco at 30'. As long as I can get the air, the computer should not just quit.

I didn't think they did? Although, it seems logical that most computers will have a maximum limit on the deco they can provide.

If you were talking about 30 hours of deco... then you would be firmly into a realm where the computer algorythm was working without any mathematical basis.... and any deco calculations would just be a vague extrapolation of the proven algorythms. From a liability basis, these extreme (boundary pushing) deco schedules won't be provided. People doing that sort of diving, tend to be in a position where they will design and calculate their own algorythms....

The "USE TABLES" issue stems from a violation of the decompression profile.

i.e. The computer wants you to stop at a certain depth, for a certain time.... but you don't do that. You ascend past a given stop...and the computer cannot recalculate a new ascent profile to compensate for that.