Info Two New Dive Computers from Scubapro for 23! LUNA 2.0 (with & without Air Integration with GF) with aggressive pricing

[Wibble]

I keep wondering why some divers are so concerned with being locked out after a decompression stop is violated for more than the maximum time allowed by their computer.

I have a few over 2250 dives since 1997, all with at least one of my computers being an Oceanic that would lock me out for 24 hours if I violated a deco stop for more than 5 minutes. Most of my dives are no stop, but about 5% are light deco, generally less that 10 min. I have never been locked out in violation gauge mode. I have also never run out of gas.

I have dived a backup computer most of the time, some Oceanic, but some other brands. There was no lockout on my Cochran EMC-14, it was a bit more liberal than DSAT. My Dive Rite Nitek Q had a 24 hour lockout, My backup has been a Shearwater Teric since 2019, obviously, no lockout.

I would find some computers too conservative for my liking, but I believe I could make any of them work.

As I understand your diving -- and please correct me if I'm wrong -- most of your diving is non-decompression diving.

When most of your dives are deco dives, you need to be aware of tweaking your profiles if there's some extraordinary issue. There's a ton of scenarios which have been mentioned here, but any time that you "must get out ASAP" then you need to be able to make the decision as to how much decompression you can blow off. I dive with 50:80 and know that it takes about 5 minutes for the SurfGF to get from 90% down to 80%. As long as it's not been a stressful dive, I'd be more than happy to surface with 90% and would be extremely confident that I would not be bent.

The computer -- a digital abacus -- knows so little; just the depth time and gas (assuming that's correct). What we don't want is to have a wrist-mounted brick

 

[OMyMyOHellYes]

If one takes three computers on a trip and only dives two of them at a time, then you can just swap out the fresh one if you get locked out.

JK

 

[Belzelbub]

I keep wondering why some divers are so concerned with being locked out after a decompression stop is violated for more than the maximum time allowed by their computer.

For me, it's mostly the principle of it. I've owned a couple Oceanics that would lockout, and I never made them lockout. So, I understand that it is not a huge issue the majority of the time.

The Oceanics were also on the liberal side running DSAT, so a violation is likely a real violation. I don't find it ideal, but understand it, and could make it work.

I can't, however, understand the logic of doing a lockout based on a user selected conservatism buffer. Especially if that violation wouldn't have even been a violation if the user had selected a less conservative option.

I can't, for the life of me, understand why a computer would lock out underwater. Which is exactly what some do.

But, like I said, it's the principle of the thing. I paid good money for my dive computers. I want them to function. I don't want them to switch to a mode where they only display depth and time and no longer track N2 loading. If the point was to keep the diver out of the water, why then would gauge mode be available. Makes no sense.

 

[scubadada]

As I understand your diving -- and please correct me if I'm wrong -- most of your diving is non-decompression diving.

When most of your dives are deco dives, you need to be aware of tweaking your profiles if there's some extraordinary issue. There's a ton of scenarios which have been mentioned here, but any time that you "must get out ASAP" then you need to be able to make the decision as to how much decompression you can blow off. I dive with 50:80 and know that it takes about 5 minutes for the SurfGF to get from 90% down to 80%. As long as it's not been a stressful dive, I'd be more than happy to surface with 90% and would be extremely confident that I would not be bent.

The computer -- a digital abacus -- knows so little; just the depth time and gas (assuming that's correct). What we don't want is to have a wrist-mounted brick

Yes, my comments apply to my diving and my experience, that I detailed in my post. My Oceanic computer, a VT3, would never be considered a technical computer, whereas my Teric is.

 

[dmaziuk]

I can't, however, understand the logic of doing a lockout based on a user selected conservatism buffer. Especially if that violation wouldn't have even been a violation if the user had selected a less conservative option.

Because it's too simple: when you change the conservatism, you change the M-values. If you exceed the M-values, you go into VGM lockout.

What you are asking about is the additional layer of logic that treats the conservatism setting as a "soft" M-values that can be dismissed until you hit the "hard" M-values. There is a number of problems with it, but conceptually: how do you know that all/most of your users want it that way? There's like 5 people in this thread that do, and not one of them actually has the computer being discussed.
(Because nobody does.)

 

[stuartv]

I keep wondering why some divers are so concerned with being locked out after a decompression stop is violated for more than the maximum time allowed by their computer.

Should everyone carry a jack in their car? Most people have never used theirs and never will. If they have a flat, they'll call AAA or similar. So, why even carry one?

I've never done anything that would lock out a computer. Nevertheless, I can imagine the possibility and so, I don't want a computer that will lock me out.

Imagine this (just one scenario of many I can imagine that seem plausible):

You are just about to hit your NDL on a dive at 100'.

You see a diver that is non-responsive, but their reg is still in their mouth.

You perform a rescue ascent to get them to the surface as quickly as possible, while holding their reg in.

It takes 6 minutes on the surface to get the diver onto the boat and free you to look after yourself.

Now, your computer has locked you out because of a too fast ascent, followed by more than 5 minutes on the surface. You want to go back down, do a long safety stop and a slow ascent. But, your computer is no longer giving you any info about what to do.

That seems unsafe.

Same situation, except you're doing "light deco" (and based on conservative settings). You have a small deco obligation, but you blow it off to get the diver to the surface. Your computer locks you out because of an omitted deco stop.

You may feel like your deco was "light" enough that you don't really need to descend and do any stops. You may feel like you should do that. Either way, your computer will no longer help you do that. Nor will it allow you to dive again that day or the next, even though you know that you would be fine to do so.

If you had a Shearwater, maybe you were diving with GF Hi of 70 and you hit the surface with a GF99 of 85. You might know that you're fine with that and don't need to go back down and do stops. Instead, you're using a computer that will lock you out. It also doesn't give you as much info as a Shearwater, so you don't really know how close the model predicts that you are to being "bent". And you can't descend and let the computer tell you what to do to re-ascend "safely" - because it went into Violation Gauge Mode after your 5 minutes on the surface.

Like I said earlier. I want my fuel gauge to continue working, no matter how I was driving my car. Hopefully, I'll never be in a situation where I need that. But, I want to be prepared in case I am.

 

[stuartv]

Because it's too simple: when you change the conservatism, you change the M-values. If you exceed the M-values, you go into VGM lockout.

What you are asking about is the additional layer of logic that treats the conservatism setting as a "soft" M-values that can be dismissed until you hit the "hard" M-values. There is a number of problems with it, but conceptually: how do you know that all/most of your users want it that way? There's like 5 people in this thread that do, and not one of them actually has the computer being discussed.
(Because nobody does.)

More nonsense. The M-values do not change. Period. (unless you change to a different algorithm altogether) Look 'em up on the Internet. They are what they are. They don't change based on anything you do on your dive computer.

 

[stuartv]

From a strictly Rec diver point of view, M-values are the border between their diving and Pretzelland.

Conservatism settings on your dive computer are where you tell the computer how close you are willing to get to Pretzelland. Am I 10 feet from the border when I surface? Or am I 50 feet from it?

If I set it to keep me 50' from the border and I decide to take note of my computer's warning, but proceed to 40' from the border, does that mean I'm an illegal immigrant? No. Thus, my computer should continue to tell me where I am.

Everyone just needs to understand that the computer's "GPS" that determines how far you are from the border to Pretzelland is its best guess - but ONLY an educated guess. Just like a real GPS, it can be off, in any direction, by a little bit or a lot. So, if you set it to take you within 10' of Pretzelland and it happens to be off that day by 20' in the wrong direction, you are going to be well into Pretzelland because you were not sufficiently conservative in your choices.

 

[dmaziuk]

More nonsense. The M-values do not change. Period. (unless you change to a different algorithm altogether) Look 'em up on the Internet. They are what they are. They don't change based on anything you do on your dive computer.

Sorry Stuart, but for someone who did software, you appear to be quite bad at Algorithms and Data Structures 101: a deco model is a function of 3 inputs: pressure, time, and "safe overspressure margin" aka "M-values". By changing the conservatism setting, you are changing the 3rd input. That's how it works in the Computer Science universe.

 

[stuartv]

Sorry Stuart, but for someone who did software, you appear to be quite bad at Algorithms and Data Structures 101: a deco model is a function of 3 inputs: pressure, time, and "safe overspressure margin" aka "M-values". By changing the conservatism setting, you are changing the 3rd input. That's how it works in the Computer Science universe.

I "do" software every day. I have downloaded Erik Baker's original Fortran code that implements Gradient Factors and reviewed the code. I used to write Fortran for a living a long time ago. I feel like I understood his code reasonably well.

M-values don't change.

The 5 inputs to the algorithm are GF Hi, GF Lo, pressure, time, and breathing gas. The M-values are built into the algorithm. They are not inputs provided by the user of the algorithm.