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CCR patch: Reorganise the oxygen partial pressure calculations

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This patch responds to the side effects that the CCR code has had with
respect to ceilings in OC dives and dive plans. Dive ceilings are now
calculated correctly again.

The following were performed:
1) remove the oxygen sensor and setpoint fields from the gas_pressures
   structure.
2) Re-insert setpoint and oxygen sensor fields in the plot_data structure.
3) Remove the algorithm that reads the o2 sensor data and calculates the
   pressures.po2 value from function fill_pressures() in dive.c and save
   it as a separate function calc_ccr_po2() in profile.c.
4) Activate calc_ccr_po2 from function fill_pressures() in profile.c.
5) Move the relative position of the call to fill_pressures() within the
   function create_polt_info_new() in profile.c.

Signed-off-by: willem ferguson <willemferguson@zoology.up.ac.za>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
This commit is contained in:
willem ferguson 2014-10-13 21:19:21 +02:00 • committed by Dirk Hohndel
parent 5d1bc11ab7
commit c8eb2dccc5
4 changed files with 136 additions and 129 deletions
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99
dive.c
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@ -1526,106 +1526,27 @@ int gasmix_distance(const struct gasmix *a, const struct gasmix *b)
}
/* fill_pressures(): Compute partial gas pressures in bar from gasmix and ambient pressures, possibly for OC or CCR, to be
* extended to PSCT. This function does the calculations of gass pressures applicable to a single point on the dive profile.
* The structure "pressures" is used to obtain data and to return calculated gas pressures to the calling software.
* extended to PSCT. This function does the calculations of gass pressures applicable to a single point on the dive profile.
* The structure "pressures" is used to return calculated gas pressures to the calling software.
* Call parameters: po2 = po2 value applicable to the record in calling function
* amb_pressure = ambient pressure applicable to the record in calling function
* *pressures = structure for communicating o2 sensor values from and gas pressures to the calling function.
* *mix = structure containing cylinder gas mixture information.
*dc = pointer to divecomputer structure.
* 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, const struct divecomputer *dc)
extern void fill_pressures(struct gas_pressures *pressures, const double amb_pressure, const struct gasmix *mix, double po2)
{
double sensor_j, sump, midp, minp, maxp;
double diff_limit = 100; // The limit beyond which O2 sensor differences are considered significant (default = 100 mbar)
int num_of_diffs; // The number of unacceptable differences among the ogygen sensor partial pressure measurements
int i, j, np;
bool maxdif = false, mindif = false;
if (dc->dctype == CCR) { // for CCR rebreathers..
// Estimate the most reliable PO2, given the different oxygen partial pressure values from the O2 sensors
switch (dc->no_o2sensors) {
case 2: { // For 2 sensors: take the mean value of the two partial pressure sensors.
np = 0;
sump = 0; // This calculation allows that for some samples (especially at start of dive) with
for (j = 0; j < 2; j++) { // an inactive sensor, the sensor(s) with zero values are not used.
sensor_j = pressures->sensor[j];
if (sensor_j) {
np++;
sump = sump + sensor_j;
}
}
if (np > 0) // if there is at least one sensor value
pressures->o2 = sump / np; // then calculate the mean, else
// else pressures->o2 = po2; // if there are no valid sensor values, the use the po2 parameter.
break;
}
case 3: { /* For 3 sensors: diff_limit is the critical limit indicating unacceptable difference (default = 100 mbar).
* a) If all three readings are within a range of diff_limit, then take the mean value. This
* includes the case where reading 1 is within diff_limit of reading 2; and reading 2 is
* within diff_limit of reading 3, but readings 1 and 3 differ by more than diff_limit.
* b) If one sensor differs by more than diff-limit from the other two, then take the mean
* of the closer two sensors and disregard the 3rd sensor, considered as an outlier.
* c) If all 3 sensors differ by more than diff_limit then take the mean of the 3 readings. */
for (minp = 9999999999, maxp = -1, sump = 0, j = 0; j < 3; j++) {
sensor_j = pressures->sensor[j];
if (sensor_j < minp)
minp = sensor_j;
if (sensor_j > maxp)
maxp = sensor_j;
sump = sump + sensor_j; // Find min, max and mid of p-values
}
midp = sump - minp - maxp;
num_of_diffs = 0;
if ((maxp - midp) > diff_limit) {
num_of_diffs++;
maxdif = true;
}
if ((midp - minp) > diff_limit) {
num_of_diffs++;
mindif = true; // Find no of unacceptable differences
}
switch (num_of_diffs) {
case 0:
;
case 2: {
pressures->o2 = sump / 3; // 0 or 2 unacceptable differences: find mean of three values.
break;
}
case 1: {
if (maxdif) // 1 unacceptable difference: find mean of two closer values
pressures->o2 = (minp + midp) / 2;
if (mindif)
pressures->o2 = (maxp + midp) / 2;
break;
}
} //switch no_of_diffs
}
default: { // if # of sensors is 1 or unknown, simply take the value of the first sensor
if (pressures->sensor[0])
pressures->o2 = pressures->sensor[0];
else
pressures->o2 = po2; // if no sensor value found, then go to next section, esimating PO2 using depth.
}
} // switch dc->n0_o2_sensors
pressures->he = (amb_pressure - pressures->o2) * (double)get_he(mix) / (1000 - get_o2(mix));
pressures->n2 = amb_pressure - pressures->o2 - pressures->he;
} // if dc->type == CCR; Now pressures->o2 should be defined, based on direct measurements.
if (po2) { // If we had a CCR dive (above) then pressures->o2 is defined, therefore this option is a fallback,
if (po2 >= amb_pressure || get_o2(mix) == 1000) // dependent on the po2 parameter in the call to this
pressures->o2 = amb_pressure; // function and applicable to non-CCR dives.
if (po2) { // This is probably a CCR dive where pressures->o2 is defined
if (po2 >= amb_pressure || get_o2(mix) == 1000)
pressures->o2 = amb_pressure;
else
pressures->o2 = po2;
pressures->he = (amb_pressure - pressures->o2) * (double)get_he(mix) / (1000 - get_o2(mix));
pressures->n2 = amb_pressure - pressures->o2 - pressures->he;
} else if (!pressures->o2) { // Open circuit dives: no gas pressure values available, they need to be calculated
pressures->o2 = get_o2(mix) / 1000.0 * amb_pressure;
pressures->he = get_he(mix) / 1000.0 * amb_pressure;
} 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;
}
}