calculating the "No Stop Time"

[igor p]

do you have any web page about you uw computer?

No, sorry never got the time to put it together....
Started learning like you by studying deco models, than slowly going throught time decided to build one.

Igor P

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[dberry]

Sorry I can not agree. I have built my own decoplanner and UW computer. It implements known decompression algorithm with clasical safety settings. It's results are in line with most known Shearwater tech computers. I believe they are quite good in calculating safe deco profiles for different (a lot of different) divers. The conservatism or safety settings are normal algorithm settings and no added further paddings even for CCR dives used there.

But on the other side, it is true, decompression models are only mathematical models that try to describe/simulate what happens in the divers body.

More or less, I believe, they are quite succesful as the injury incidence is quite low.

Igor P

It never occurred to me that the OP actually wanted to build his own computer to be used on dives. I'm definitely impressed if you have built a DIY dive computer, since now we're talking about miniaturized electronics, transducers, and non-trivial packaging for a hostile environment. I'm not sure I'd dive without a commercial backup PDC (or tables), but I'm still impressed.

We're largely in agreement on the other issues; there is no reason one can't reproduce the results of a model (or output of a PDC based on a given model) on a laptop or smartphone, given the equations, assumptions, and reasonable initial values. Then it largely becomes an exercise in programming. It won't yield anything more accurate or individualized than the underlying model, since the variability in each person's anatomy and physiology is a major factor limiting every model. Unless you have a way to monitor N2 loading in a person's body compartments in vivo, in real time. THAT would be the ultimate! Time for N2 sensing nano-bots and near field RF?

Just out of curiosity, are you doing this for fun, or to create a new commercial product (PDC or software package)?

 

[EFX]

.... It won't yield anything more accurate or individualized than the underlying model, since the variability in each person's anatomy and physiology is a major factor .... Unless you have a way to monitor N2 loading in a person's body compartments in vivo, in real time. THAT would be the ultimate! Time for N2 sensing nano-bots and near field RF?

Some time ago I started a thread on advanced technology which included two major topics: real-world sensing of inert gas levels and are you ready for this: TLV (total liquid ventilation). The former may become a reality sooner than we think. Getting sensors in the body takes the uncertainty away from using models which although have been safe enough, cannot prevent DCS when precursor conditions are stacked against the diver. On the other side divers who have favorable conditions can dive longer than the model calculates. We may eliminate the models but we can't eliminate the decompression.

To eliminate decompression we have to go liquid. "Breathing" a liquid eliminates the uptake of inert gasses and hence eliminates deco. If the sinus cavities can be flooded with liquid it also eliminates limiting descent/ascent rates (no need to clear). Another idea in that thread posted by someone in the health care industry was to use a portable blood scrubber that would filter out the CO2 and N2 and add O2 as needed. The N2 (and H2 if breathing mixed gasses) would be filtered out of the blood before returning to the body to eliminate tissue loading. Interesting stuff.

 

[igor p]

It never occurred to me that the OP actually wanted to build his own computer to be used on dives. I'm definitely impressed if you have built a DIY dive computer, since now we're talking about miniaturized electronics, transducers, and non-trivial packaging for a hostile environment. I'm not sure I'd dive without a commercial backup PDC (or tables), but I'm still impressed.

We're largely in agreement on the other issues; there is no reason one can't reproduce the results of a model (or output of a PDC based on a given model) on a laptop or smartphone, given the equations, assumptions, and reasonable initial values. Then it largely becomes an exercise in programming. It won't yield anything more accurate or individualized than the underlying model, since the variability in each person's anatomy and physiology is a major factor limiting every model. Unless you have a way to monitor N2 loading in a person's body compartments in vivo, in real time. THAT would be the ultimate! Time for N2 sensing nano-bots and near field RF?
Just out of curiosity, are you doing this for fun, or to create a new commercial product (PDC or software package)?

Helped some other deveopers betatesting and checking model impementations in their comercial products,
Doing this for fun.
Otherways agree with you - model try to mimic tissue saturation and desaturation, but it does not know what reality is. It calculates limiting supersaturation limits based on empirical data, but does not know what reality is.
Need to write again, I believe deco models and their implementations brought as into actual reality where only fewe incidens happen, so seem they are safe to certain degree.

Igor P

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[dmaziuk]

Well, how much accuracy do we need?

The other question is how much accuracy do you have? The pressure sensor may give you a cm resolution to begin with.

 

[JohnnyC]

Measure it with a micrometer, mark it with chalk, cut it with a chainsaw.....

That's the phase mentioned earlier in the thread. I think the theoretical stuff is way cool, but realistically the available data already implemented (in a commercial aspect) is more than adequate for actual use when diving. While you may be able to do all of this theoretically, as mentioned, there are so many other variables involved that short of a very tightly controlled chamber divem where all of the variables are perfectly tuned to the model, there's going to be variation that the simple calculations don't account for.

Don't let this deter you from doing the math, it's very neat stuff, and by all means enjoy your time doing the work. I'm just pointing out that the practical application is far more complicated than the simple equation would lead one to believe.