Logging CCR dives

Anton Lundin glance at acc.umu.se
Tue May 9 05:18:18 PDT 2017

On 08 May, 2017 - Robert Helling wrote:

> Davide,
> > On 8. May 2017, at 17:15, Davide DB <dbdavide at gmail.com> wrote:
> > 
> > I've logged the first few CCR dives with a Shearwater Petrel and a SF2 unit.
> > I discovered that most fields get filled by data coming form the
> > Petrel and some doubt arose on how to correctly log these dives.
> > Basically I find the equipment tab filled with my default cylinder (3
> > liter) and the CC gas set on my Petrel. i.e 3L 18/45 and a column
> > called "use" with the value "OC Gas".
> > I can only change it with "no use". What does it mean?
> > I would expect "CC use". It's my diluent. Of course in my Petrel I
> > have the same mix set as bailout gas but I guess it isn't.
> > Moreover for each dive I have to add another cylinder to record my
> > Oxygen tank setting initial and final pressure.
> > Once I go in the stats tab I find gas calculation only for the 18/45
> > mix, no trace for the oxygen consumption.
> > Why I do not find any data for the Oxygen? Would it be very useful add
> > these tanks by default. I don't know CCR units without a Oxygen tank
> > and actually Oxygen consumption is the most important parameter. Isn't
> > it?
> > If I understand correctly the logic behind I guess I should add my
> > bailout tanks marking them as "no use".
> > 
> > If someone is already using Subsurface proficiently with CCR logs
> > could you give me some hints?
> as was recently discussed on github “OC gas” is a misnomer, the text should be changed to “gas used”.
> To be honest, Subsurface currently does not really do any reasonable gas calculations for CCR dives. As always, it only considers gas used if it is ever switched to and has the implicit assumption that at any moment in time, the diver is only breathing a single gas. Both is of course wrong for CCR dives. Apart from displaying the initial and final pressures of the cylinders anything more advanced is really hard to do (like interpolating pressures for example). For oxygen in CCR dives, I would only make a linear in time interpolation (independent of depth) while predicting diluent use as a function of the depth profile is really hard to do right.

We actually do handle the diluent and o2 consumption simultaneously,
via the MkVI import.

I don't know if you can "activate" that functionality manually.

You can all see it in action when importing the test data


Anton Lundin	+46702-161604

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