Resetting computer

[gfaith]

BOTTOM TIME WITH BEHAVIOR ERROR
The following errors can occur during an air or EAN dive:
• Uncontrolled ascent
• Omitted deco stop
In this case, PUCK will inhibit the Dive - AIR and Dive - EAN modes for 24 hours, allowing operation in BOTTOM TIME mode only, and will continue to display the error committed during the previous dive.

If I was free diving to 30' there is no doubt I would ascend faster than 60'/min... For sure

 

[doctormike]

Here is another factor to consider. You already know that the computer thinks you are breathing compressed air. Acting on that assumption, it also thinks you are significantly violating the safe ascend speed when you go to the surface. Not only that, it thinks you are doing it again and again and again and again. Many computers will penalize you for violating the ascent rate. Do it multiple times, and you will really get dinged.

I keep forgetting about those computers that think they are the "morality police". My Oceanics don't do things like that.

It is not so much a question of the alarm (another feature thankfully absent on older Oceanics) as much as does it penalize you for such "violations".

I'm not sure I understand this point.

The computer thinks that it's a dive computer. That is, a device that tracks time, depth, mix and ascent rate to estimate DCS risk and try to keep a diver from getting bent. If you use a dive computer for some activity other than the intended purpose, and give it inputs that don't reflect what is going on in the user's body, how is it supposed to accommodate for that? Free divers ascent at rates that would significantly increase the DCS risk for a diver breathing compressed gas at depth. Many computers have a free diving mode (my old Suunto Mosquito had that), or you could use a bottom timer. But the violations are not bugs, they are features.

If you tie your computer to a shot line, drop it to 300 feet and then reel it up as fast as you can, it's gonna complain. It doesn't know that you weren't wearing it.

 

[redacted]

I'm not sure I understand this point.

The computer thinks that it's a dive computer. That is, a device that tracks time, depth, mix and ascent rate to estimate DCS risk and try to keep a diver from getting bent. If you use a dive computer for some activity other than the intended purpose, and give it inputs that don't reflect what is going on in the user's body, how is it supposed to accommodate for that? Free divers ascent at rates that would significantly increase the DCS risk for a diver breathing compressed gas at depth. Many computers have a free diving mode (my old Suunto Mosquito had that), or you could use a bottom timer. But the violations are not bugs, they are features.

If you tie your computer to a shot line, drop it to 300 feet and then reel it up as fast as you can, it's gonna complain. It doesn't know that you weren't wearing it.

I understand that excessively rapid ascents may increase the risk of DCS. What I don't understand is how reducing NDLs for the next dive ameliorates that risk. Where is the science supporting that treatment?

 

[doctormike]

I understand that excessively rapid ascents may increase the risk of DCS. What I don't understand is how reducing NDLs for the next dive ameliorates that risk. Where is the science supporting that treatment?

OK, not sure if we are talking about the same thing... I thought you were saying that it didn't make sense for the computer to estimate an increased DCS risk based on multiple rapid ascents, since they were done by a free diver. Maybe I misunderstood your point... sorry!

 

[Keith.M]

I don't see what the issue is.

You have a puck that you used it for free diving in guage mode.

Now you are confused that it displays no fly time and desat time?

It knows you did some dives. It was either going to give you 18 or 24 hours no fly. So what?

The dsat is going to be more of an issue as you said it was giving less bottom time. I will "assume" that means you were able to get into the planning mode. So in reality, how much less bottom time?

On the puck with air:
39' = 86 minutes
49' = 57
59' = 38
69 = 28
79 = 21
89 = 16
98 = 13
108 = 11
118 = 09
.
.

If I go and have a dive, it is going to have my no fly and my desat times.

I never read that you were locked into guage mode. Are you?

If not, put it in air or EAN and dive!

---------- Post added August 19th, 2014 at 09:56 PM ----------

I also have an Aladin 2G. It has an apnea mode just for freediving.

 

[NAM001]

My aeris locks me into gage mode as i remember. I accidently went in in gage mode and as soon as wet probe was senced i could not exit for 24 hours. The gage mode tracks nothing more than time and depth. no gas issues nothing else. as such it would be fooolish to let you go into normal mode and do a repeditive dive not knowing what the status of the first dive was. I have to looka t my shearwater again but i believe it dies the same thing but you can reset the nitrogen. Whether you can do that in gage mode or normal only i dont know.

I don't see what the issue is.

You have a puck that you used it for free diving in guage mode.

Now you are confused that it displays no fly time and desat time?

It knows you did some dives. It was either going to give you 18 or 24 hours no fly. So what?

The dsat is going to be more of an issue as you said it was giving less bottom time. I will "assume" that means you were able to get into the planning mode. So in reality, how much less bottom time?

On the puck with air:
39' = 86 minutes
49' = 57
59' = 38
69 = 28
79 = 21
89 = 16
98 = 13
108 = 11
118 = 09
.
.

If I go and have a dive, it is going to have my no fly and my desat times.

I never read that you were locked into guage mode. Are you?

If not, put it in air or EAN and dive!

---------- Post added August 19th, 2014 at 09:56 PM ----------

I also have an Aladin 2G. It has an apnea mode just for freediving.

 

[EFX]

You will NOT ongass any N2 during a free dive. What little does is balanced by the same amount offgassing so that over a period of time the average amount is zero. Why is this? First of all it is the ppN2 (partial presure of N2) that matters not the total lung pressure (which is dependent on volume). N2 is not pushed/pulled into/out of the blood by pressure; it diffuses across the lung-blood barrier. This transfer also occurs across the blood/tissue barrier. In order to get flow into or out of the tissues you need a pressure drop (gradient) across the barrier. At the surface your tissues are saturated with a ppN2 equal to 0.79 atm. When you take a lung full of air at the surface your lung ppN2 is also equal to 0.79 atm. When you dive to x feet nothing has changed regarding the ppN2 in either the lungs or the tissues. The pressure drop across the lung-tissue barrier is 0.79 - 0.79 = 0 ppN2. With a pressure drop of zero the flow is zero and your tissues will neither ongass or offgas N2.

I have a Mares Puck dive computer. If you started in air or nitrox mode you need to clear the residual N2 loading before beginning your scuba dive. As others have noted already if you don't the DC will penalize you and give you less dive time. If you were in guage mode you don't need to do anything as the DC doesn't track and store N2 loadings.

The situation I describe above is only if your first dive is a free dive after you've been on the surface a long time. The situation is far different if the first dive was on scuba. In that case your tissues will be at some ppN2 higher than 0.79 and will be offgassing at various rates. If you choose to free dive with yout DC, set your DC to guage mode and periodically exhale during the dive. Since the ppN2 will be building in your lungs due to offgassing you must vent this pp or risk an embolism on ascent.

 

[redacted]

You will NOT ongass any N2 during a free dive. What little does is balanced by the same amount offgassing so that over a period of time the average amount is zero. Why is this? First of all it is the ppN2 (partial presure of N2) that matters not the total lung pressure (which is dependent on volume). N2 is not pushed/pulled into/out of the blood by pressure; it diffuses across the lung-blood barrier. This transfer also occurs across the blood/tissue barrier. In order to get flow into or out of the tissues you need a pressure drop (gradient) across the barrier. At the surface your tissues are saturated with a ppN2 equal to 0.79 atm. When you take a lung full of air at the surface your lung ppN2 is also equal to 0.79 atm. When you dive to x feet nothing has changed regarding the ppN2 in either the lungs or the tissues. The pressure drop across the lung-tissue barrier is 0.79 - 0.79 = 0 ppN2. With a pressure drop of zero the flow is zero and your tissues will neither ongass or offgas N2.

I have a Mares Puck dive computer. If you started in air or nitrox mode you need to clear the residual N2 loading before beginning your scuba dive. As others have noted already if you don't the DC will penalize you and give you less dive time. If you were in guage mode you don't need to do anything as the DC doesn't track and store N2 loadings.

The situation I describe above is only if your first dive is a free dive after you've been on the surface a long time. The situation is far different if the first dive was on scuba. In that case your tissues will be at some ppN2 higher than 0.79 and will be offgassing at various rates. If you choose to free dive with yout DC, set your DC to guage mode and periodically exhale during the dive. Since the ppN2 will be building in your lungs due to offgassing you must vent this pp or risk an embolism on ascent.

You can't have it both ways (red/blue).

Ongassing does occur. Think about a more extreme case where the diver goes to 90 feet in a 5 minute dive. Now couple that with a one minute surface interval and repeat that dive. Not only is the diver ongassing during the dive but she is also not doing a long enough surface interval to do much off-gassing so, over a period of time, the N2 load is building, not balancing at "zero".

Notice, I did not specify whether the diver was doing this this on scuba or freediving. While there may well be a difference due to ascent raters, there need not be. How about 1 minute descent, 2 minutes at depth, 1 minute ascent to 30 ft, and 1 minute ascent to surface.

I reread your post and the problem is in bold. PPN2 does change when you increase the pressure as you descend. And the volume decreased proportionally.

 

[DivemasterDennis]

Patience, patience patience. The computer should/ will reset within a brief period of time.

 

[EFX]

You can't have it both ways (red/blue).

I'm not having it both ways. I included the [blue] sentence to be technically correct. If this confused you I am sorry. At any very small snapshot in time localized tissue sites may develop a very small pressure relative to surrounding tissues due to motion within the body. The effect on the entire lung-tissue system is that N2 will flow into this localized area. But, take another snapshot and the same amount will flow out. The net effect over a longer time span is zero flow. In the context of on/offgassing the amount of N2 is so small it should be ignored completely.

Ongassing does occur. Think about a more extreme case where the diver goes to 90 feet in a 5 minute dive. Now couple that with a one minute surface interval and repeat that dive. Not only is the diver ongassing during the dive but she is also not doing a long enough surface interval to do much off-gassing so, over a period of time, the N2 load is building, not balancing at "zero". Notice, I did not specify whether the diver was doing this this on scuba or freediving.

Ongassing depends on what kind of first dive you're doing: free or scuba. For reasons I mentioned in my previous post no ongassing occurs during a free dive. Ongassing and the associated offgassing is important to the scuba diver because the ppN2 is increasing or decreasing with depth because of compressed air. During a free dive with lungs at a surface ppN2 the pp is not changing with depth only the lung volume is changing. During a scuba dive the pp's of the gasses in the lungs are changing with depth to equalize with the ambient pressure of the water.

---------- Post added August 20th, 2014 at 12:13 PM ----------

Patience, patience patience. The computer should/ will reset within a brief period of time.

After the free dive the fastest tissue compartment will "reset" for all practical purposes after six half-lives or 6(0.5)(5) = 15 minutes for the 5 minute compartment. If we assume a rapid ascent from the free dive the Mares Puck may lock you out of air or nitrox modes upon surfacing. The manual states that if the dive is deeper than 39 feet and the ascent alarm is enabled and the ascent rate exceeds 39 ft/min for greater than a distance equal to 2/3's the depth a lock out will occur. Not a good thing if you want to scuba dive after your free dive. The easiest solution is to set the Puck on "bottom time" (guage) mode. Then, there are no restrictions and no lock outs.