diff options
Diffstat (limited to 'dive.c')
| -rw-r--r-- | dive.c | 110 |
1 files changed, 96 insertions, 14 deletions
@@ -1525,23 +1525,105 @@ int gasmix_distance(const struct gasmix *a, const struct gasmix *b) return delta_he + delta_o2; } -/* Compute partial gas pressures in bar from gasmix and ambient pressures, possibly for OC or CCR, to be extended to PSCT */ +/* 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. + * 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) { - if (po2) { - /* we have an O₂ partial pressure in the sample - so this - * is likely a CC dive... use that instead of the value - * from the cylinder info */ - if (po2 >= amb_pressure || get_o2(mix) == 1000) { - pressures->o2 = amb_pressure; - pressures->he = 0; - pressures->n2 = 0; - } 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; + 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; } - } else { + 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. + 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; pressures->n2 = (1000 - get_o2(mix) - get_he(mix)) / 1000.0 * amb_pressure; |