Possible Bug with Stats and Info

[Ryan McLean]

Attached log.

Would a semi-correct model be to allow a the user to specify the 1st switch
in bar so to take 35bar as an example on 2 cylinder charged to 200
1st switch is at -35bar (165bar remaining)
2nd cylinder then at 2x35bar (-70bar) from full (130bar remaining)
1st cylinder then at -70bar from last use (95bar remaining)
...
continue until end of dive.


It's not perfect but would kind of follow established practice for indy
cylinders. I know it doesnt account for the bias of trying to leave more in
the long hose cylinder in case you need to donate but it may be a good
start.


I've probably not understood gas compressibility correctly but I took a 10L
cylinder to hold 2000L at 200bar. So if I had used 80 bar in each cylinder
then I had used 1600L total...
For the SAC i used the avg of 5m for the calc (so SS may have got this
correct if it has used the actual profile.) However divelogs.de has 17.1 (i
think my calc came in at 16.9) https://en.divelogs.de/dive/2075948

Thanks for the quick response.

Ryan

On Mon, May 8, 2017 at 9:02 PM, Linus Torvalds <
torvalds at linux-foundation.org> wrote:

> On Mon, May 8, 2017 at 11:47 AM, Ryan McLean <pvtryan100 at gmail.com> wrote:
> > I performed a side-mount dive with 2x10L 232 Bar Steel Cylinders added in
> > the Equipment Page as two separate line items
> >
> > On both tanks:
> > Starting Pressure: 200
> > Final Pressure: 120
> > Dive Time (62m 20Sec)
> > Max Depth 7.2m
> > Avg Depth: 5m
> >
> > Looking at the info Page I see:
> > ********
> > Gases Used
> > Air
> > Air
> >
> > Gas Consumed
> > 720L
>
> Yeah, you don't have a gas switch event, so subsurface thinks the
> second tank is basically unused.
>
> > When I look at the Stats Page I see
> > ********
> > Gas Comsumed:
> > 720L
>
> Same thinghere.
>
> You can add a fake gas switch event on the profile, and you'll get the
> expected numbers, I think.
>
> I do *not* know what the right model for "use two cylinders at the
> same time" is, although the other hack (right now) is to simply
> consider your dual cylinders to be one single one (of twice the size).
> But that only works when the beginning/ending pressures match (like
> they happen to do for you), ie when you can basically consider the
> side mount cylinders to be one single combined manifold.
>
> Although your expected numbers are kind of wrong:
>
> > Gas Consumed
> > 800L
> > 800L
> >
> > SAC
> > 17
> >
> > Gas Comsumed:
> > 1600L
> >
> > SAC
> > 17
>
> Your 800l is wrongly calculated.
>
> You seem to think that one atmosphere is 1 bar. That's not true.
>
> You also don't take the compressibility of air into account.
>
> I suspect the subsurface number of 720.9l per cylinder is actually the
> correct one. You can hover over the equipment fields to see the actual
> conversion to liters at the pressures in question.
>
>                      Linus
>
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