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Fix ATM-vs-bar confusion

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SAC should be calculated in relationship to surface pressure, not "1 bar".

I also realize that we have a few other cases where we do the same
mistake: the partial pressure calculations do things like

    po2 = o2 / 1000.0 * depth_to_mbar(sample->depth.mm, dive);

which is wrong as well - the partial pressure is also relative to
standard atmospheric pressures.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
This commit is contained in:
Linus Torvalds 2014-02-11 13:08:29 -08:00 • committed by Dirk Hohndel
parent 92bbed3304
commit e58f54cac1
4 changed files with 16 additions and 6 deletions
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6
divelist.c
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@ -221,7 +221,7 @@ static int calculate_otu(struct dive *dive)
po2 = sample->po2;
} else {
int o2 = active_o2(dive, dc, sample->time);
po2 = o2 / 1000.0 * depth_to_mbar(sample->depth.mm, dive);
po2 = o2 * depth_to_atm(sample->depth.mm, dive);
}
if (po2 >= 500)
otu += pow((po2 - 500) / 1000.0, 0.83) * t / 30.0;
@ -285,7 +285,7 @@ static int calculate_cns(struct dive *dive)
po2 = sample->po2;
} else {
int o2 = active_o2(dive, dc, sample->time);
po2 = o2 / 1000.0 * depth_to_mbar(sample->depth.mm, dive);
po2 = o2 / depth_to_atm(sample->depth.mm, dive);
}
/* Find what table-row we should calculate % for */
for (j = 1; j < sizeof(cns_table)/(sizeof(int) * 3); j++)
@ -338,7 +338,7 @@ static int calculate_sac(struct dive *dive)
return 0;
/* Mean pressure in ATM (SAC calculations are in atm*l/min) */
pressure = (double) depth_to_mbar(meandepth, dive) / SURFACE_PRESSURE;
pressure = depth_to_atm(meandepth, dive);
sac = airuse / pressure * 60 / duration;
/* milliliters per minute.. */