On Oct 27, 2014, at 03:42 PM, Rodrigo Severo <rodr...@fabricadeideias.com>
wrote:
Bill,
I agree: 1/2 foot is noise, 10 m is significant.
What value do you think we should use as limit? I just proposed 1 m on
my previous email to Robert but I'm not sure if this value is big
enough.
What do you think?
It'd be interesting to put some code together, run it on real dive data and see
how the predicted number compared with the measured one. Until you do I think
it'd be difficult to know where the noise filter level needs to be set.
> Would tracking only the size of the counter lungs be sufficient?
I don't think any of this is necessary, neither counter lungs volume
nor loop volume as I mentioned on my previous email.
Without knowing has much gas is in the loop (note: not counter lung size, which
is part of the maximum loop volume) you can't know how much diluent to add to
maintain it*.
Example: 5l of gas in the loop. Decend from surface to 10m (2bar). I need to
double the mass of gas in the loop to maintain volume, hence I need to add 5l
(surface equivalent mass**).
Counter lung (maximum) volume is irrelevent, because divers try not to run
maximum volume. In fact they try to run minimum volume (i.e. 1 human lung full)
because doing so uses less gas and is easier to control (buoyancy). You
probably need to work out an average of what this diver tends to do (like SAC)
and use that in predictions.
Paul
* Similarly, You can't know how much O2 to add to raise the ppO2 by some amount
without knowing how much gas is in the loop. Hence ascents are tricky too
** Terminology when talking about amounts of gas under pressure is hard. Really
we should talk about masses of gas, but we don't.
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