From 65a11a660ed85deeb63b7808ebfc6e8aa0c037c8 Mon Sep 17 00:00:00 2001 From: "Robert C. Helling" <hell...@atdotde.de> Date: Sun, 18 Jan 2015 13:15:43 +0100 Subject: [PATCH] Don't use current SAC for PSCR calculation
To compute the oxygen drop in a PSCR one needs the ratio of
SAC/o2metabolism_rate. The latter is preconfigured but the former
is known as a function of time. Still, we should use the SAC from
the preferences as (according to wikipedia) the ratio is a constant
even when the SAC is changing as the body increases the SAC to balance
a higher o2 consumption.
Signed-off-by: Robert C. Helling <hell...@atdotde.de>
---
deco.c | 2 +-
dive.c | 17 ++++++-----------
dive.h | 2 +-
planner.c | 2 +-
profile.c | 2 +-
5 files changed, 10 insertions(+), 15 deletions(-)
diff --git a/deco.c b/deco.c
index 14f88f6..9d0ec9d 100644
--- a/deco.c
+++ b/deco.c
@@ -190,7 +190,7 @@ double add_segment(double pressure, const struct gasmix
*gasmix, int period_in_s
int ci;
struct gas_pressures pressures;
- fill_pressures(&pressures, pressure - WV_PRESSURE, gasmix, (double)
ccpo2 / 1000.0, dive->dc.divemode, sac);
+ fill_pressures(&pressures, pressure - WV_PRESSURE, gasmix, (double)
ccpo2 / 1000.0, dive->dc.divemode);
if (buehlmann_config.gf_low_at_maxdepth && pressure >
gf_low_pressure_this_dive)
gf_low_pressure_this_dive = pressure;
diff --git a/dive.c b/dive.c
index 33e3fb2..a5dc152 100644
--- a/dive.c
+++ b/dive.c
@@ -1665,13 +1665,8 @@ int gasmix_distance(const struct gasmix *a, const struct
gasmix *b)
* *mix = structure containing cylinder gas mixture
information.
* This function called by: calculate_gas_information_new() in profile.c;
add_segment() in deco.c.
*/
-extern void fill_pressures(struct gas_pressures *pressures, const double
amb_pressure, const struct gasmix *mix, double po2, enum dive_comp_type
divemode, int sac)
+extern void fill_pressures(struct gas_pressures *pressures, const double
amb_pressure, const struct gasmix *mix, double po2, enum dive_comp_type
divemode)
{
- if (!sac) {
- /* The SAC has not yet been computer, so use the default *
- * We might try harder... */
- sac = prefs.bottomsac;
- }
if (po2) { // This is probably a CCR dive where pressures->o2 is
defined
if (po2 >= amb_pressure) {
pressures->o2 = amb_pressure;
@@ -1687,14 +1682,14 @@ extern void fill_pressures(struct gas_pressures
*pressures, const double amb_pre
}
} else {
if (divemode == PSCR) { /* The steady state approximation
should be good enough */
- pressures->o2 = get_o2(mix) / 1000.0 * amb_pressure -
(1.0 - get_o2(mix) / 1000.0) * prefs.o2consumption / (sac * prefs.pscr_ratio /
1000.0);
+ pressures->o2 = get_o2(mix) / 1000.0 * amb_pressure -
(1.0 - get_o2(mix) / 1000.0) * prefs.o2consumption / (prefs.bottomsac *
prefs.pscr_ratio / 1000.0);
pressures->he = (amb_pressure - pressures->o2) *
get_he(mix) / (1000.0 - get_o2(mix));
pressures->n2 = (amb_pressure - pressures->o2) * (1000
- get_o2(mix) - get_he(mix)) / (1000.0 - get_o2(mix));
} else {
- // Open circuit dives: no gas pressure values available, they
need to be calculated
- pressures->o2 = get_o2(mix) / 1000.0 * amb_pressure; // These
calculations are also used if the CCR calculation above..
- pressures->he = get_he(mix) / 1000.0 * amb_pressure; //
..returned a po2 of zero (i.e. o2 sensor data not resolvable)
- pressures->n2 = (1000 - get_o2(mix) - get_he(mix)) / 1000.0 *
amb_pressure;
+ // Open circuit dives: no gas pressure values
available, they need to be calculated
+ pressures->o2 = get_o2(mix) / 1000.0 * amb_pressure; //
These calculations are also used if the CCR calculation above..
+ pressures->he = get_he(mix) / 1000.0 * amb_pressure; //
..returned a po2 of zero (i.e. o2 sensor data not resolvable)
+ pressures->n2 = (1000 - get_o2(mix) - get_he(mix)) /
1000.0 * amb_pressure;
}
}
}
diff --git a/dive.h b/dive.h
index 327598b..56f38f9 100644
--- a/dive.h
+++ b/dive.h
@@ -143,7 +143,7 @@ struct gas_pressures {
double o2, n2, he;
};
-extern void fill_pressures(struct gas_pressures *pressures, const double
amb_pressure, const struct gasmix *mix, double po2, enum dive_comp_type dctype,
int sac);
+extern void fill_pressures(struct gas_pressures *pressures, const double
amb_pressure, const struct gasmix *mix, double po2, enum dive_comp_type dctype);
extern void sanitize_gasmix(struct gasmix *mix);
extern int gasmix_distance(const struct gasmix *a, const struct gasmix *b);
diff --git a/planner.c b/planner.c
index 8cd786e..d660660 100644
--- a/planner.c
+++ b/planner.c
@@ -749,7 +749,7 @@ static void add_plan_to_notes(struct diveplan *diveplan,
struct dive *dive, bool
if (dp->time != 0) {
struct gas_pressures pressures;
fill_pressures(&pressures,
depth_to_atm(dp->depth, dive), &dp->gasmix, 0.0,
- dive->dc.divemode, dp->entered ?
prefs.bottomsac : prefs.decosac);
+ dive->dc.divemode);
if (pressures.o2 > (dp->entered ?
prefs.bottompo2 : prefs.decopo2) / 1000.0) {
const char *depth_unit;
diff --git a/profile.c b/profile.c
index 05e84cd..026b871 100644
--- a/profile.c
+++ b/profile.c
@@ -945,7 +945,7 @@ static void calculate_gas_information_new(struct dive
*dive, struct plot_info *p
amb_pressure = depth_to_mbar(entry->depth, dive) / 1000.0;
- fill_pressures(&entry->pressures, amb_pressure,
&dive->cylinder[cylinderindex].gasmix, entry->o2pressure.mbar / 1000.0,
dive->dc.divemode, entry->sac);
+ fill_pressures(&entry->pressures, amb_pressure,
&dive->cylinder[cylinderindex].gasmix, entry->o2pressure.mbar / 1000.0,
dive->dc.divemode);
fn2 = (int)(1000.0 * entry->pressures.n2 / amb_pressure);
fhe = (int)(1000.0 * entry->pressures.he / amb_pressure);
--
1.9.3 (Apple Git-50)
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