Use a Computer or BT?

[EFX]

I haven't seen a computer that will allow you to download your custom tables, but as has been mentioned, this is not really necessary as many tech computers and deco software programs share the same algorithms and allow you to match the Gradient Facotrs and degree of conservatism.

Can the computer be programed for multiple waypoints where it alarms or tells you to ascend to the next level according to your pre-planned profile? Can it also tell you when and which gas to switch to?

 

[Nasser]

Can the computer be programed for multiple waypoints where it alarms or tells you to ascend to the next level according to your pre-planned profile? Can it also tell you when and which gas to switch to?

Yes some computers can. I would suggest you go to the Shearwater Research site and download the manual for the Petrel. It is a very good example of the current state-of-the-art in tech dive computers and will give you a clear idea of it's capabilities:

Petrel Downloads | Dive Computer Firmware & User ManualShearwater Research

You can also check out some video demos on their site and on Youtube.

 

[rongoodman]

Can the computer be programed for multiple waypoints where it alarms or tells you to ascend to the next level according to your pre-planned profile? Can it also tell you when and which gas to switch to?

I don't understand where the idea of downloading a profile to a dive computer is coming from. There was at least one dive computer, made by Cochran as I recall, that automatically switched deco gases in it's calculations, based on depth. This could cause big problems if the switch wasn't actually made, or was undesired, such as a cave dive in which the diver was temporarily forced shallow but then had to descend again. The Shearwater will change the color of the gas display to remind you to switch to a richer active deco gas if you haven't done so already when it thinks you should. When you have cleared a deco stop, the display will change to show the next stop, and time required.

 

[EFX]

Yes some computers can. I would suggest you go to the Shearwater Research site and download the manual for the Petrel. It is a very good example of the current state-of-the-art in tech dive computers and will give you a clear idea of it's capabilities.

Thanks. I'll read the manual.

I don't understand where the idea of downloading a profile to a dive computer is coming from.

I have no experience with Tech diving procedures or with the computers so it's just me wondering and thinking out loud.

 

[Nasser]

You're welcome.

Just on a side note, you misquoted on your second reply in the above post. The original quote should be credited to rongoodman as posted below not (me) Nasser

I don't understand where the idea of downloading a profile to a dive computer is coming from.

 

[Michael Guerrero]

Maybe a more concrete example using a computer for tech diving will help.

So lets say I'm going to do a 150' dive on air for 30 minutes. I will select a deco algorithm (ZHL-16C w/ GFs for me), a conservatism level (probably 50/80 GF Lo/Hi or something), input that into my desktop software with whatever deco gas I've elected to use (80% or 100% usually), and then hit the run button.

The software will tell me what my deco obligation is, how much of each gas I will use (based on the preferences I've set in the software), what CNS% I will have, OTUs, and when I will need to switch gases (though it's pretty standard based on the deco gas you choose). So, I will "cut tables" using the schedule the software has computed based on the algorithm, conservatism, and gases defined. Usually I'll have two contingency tables for longer runtime and deeper depth just in case. I take these tables and tape them to my slate so I have them with me during the dive.

Next I have a recreational computer set to gauge mode, that will act as my backup should my primary computer fail. If the primary computer fails, then I rely on my gauge mode computer and tables to complete the dive.

Lastly, I make sure my tech computer is configured for the same conservatism and deco gas(es) and jump in the water. During the dive I mainly pay attention to my tech computer for run time, depth, etc. I reference it regularly so I will be able to make a decent guess of where I am in the dive if all of a sudden the screen goes blank and I have to resort to my BT/tables. I do the deco schedule prescribed by my tech computer, because it's calculating that on the fly, and it lets me know when I'm carrying a more efficient deco gas than the one I'm currently using. At the same time, I make sure to stick closely to my cut tables in case I have to employ them instead due to a malfunction (plan the dive, dive the plan comes to mind).

Anyway, this is how I incorporate a tech computer into my deco dives. There's plenty more involved in the planning process, but that's pretty much how the computer fits in.

Mike

 

[PfcAJ]

I always find it curious how many people print such limited tables for their diving. 2 contingency tables is quite a small range of potential eventualities (deeper, shallower, shorter, longer, varying degrees of each of those variables). Also curious is that it appears that people re-do this process over and over.

 

[TSandM]

AJ, I think that's about the best argument for using a computer . . . I have limited technical experience, but I plan my dives using a tool that does allow me to adjust what I do on the fly. However, I am also aware that that tool has limitations. It is very useful within a certain set of parameters, and becomes more dubious outside of them. Sawtooth profiles and very long, shallow dives are two of the places where it may or may not work well, so I don't at all mind having V-planner on my wrist to give me a second opinion on what I conclude ought to be my deco. I have perfect freedom to follow my original plan, but if the computer is telling me something very different from what I think I ought to do, I should at least step back and examine the possible reasons why.

 

[EFX]

Thanks Michael. It's a good explanation until I got to the following:

...., and it lets me know when I'm carrying a more efficient deco gas than the one I'm currently using.

I have no idea what you mean by this. Can you elaborate?

 

[PfcAJ]

AJ, I think that's about the best argument for using a computer . . . I have limited technical experience, but I plan my dives using a tool that does allow me to adjust what I do on the fly. However, I am also aware that that tool has limitations. It is very useful within a certain set of parameters, and becomes more dubious outside of them. Sawtooth profiles and very long, shallow dives are two of the places where it may or may not work well, so I don't at all mind having V-planner on my wrist to give me a second opinion on what I conclude ought to be my deco. I have perfect freedom to follow my original plan, but if the computer is telling me something very different from what I think I ought to do, I should at least step back and examine the possible reasons why.

I'm not sure those arguments are valid. You still need SOME sort of table to use in event of a computer failure. My argument is that that making a special little table for every single dive is silly. Make a set of tables that covers a wide range of depths and times and you never have to do it again.

In regards to sawtooth dives, I've posted some downright nutty sawtooth profiles on here before. Hard to argue that avg depth isn't an effective tool for managing those exposures. A lack of experience in averaging depth could lead to an issue if the computer craps out.