On 14 April, 2017 - Jef Driesen wrote: > On 2017-04-13 17:04, Jef Driesen wrote: > I tried a different approach yesterday. Instead of adding 1024 to > the calibration value, I simply used the stored value as is, and > calculated the average ppO2 over all three sensors. Then I plotted > all those values against the average ppO2 reported by the device. > And guess what, there is a nice linear relationship between the two! > Doing a linear regression on the data gives a scaling factor of 2.2.
Interesting find. > For the example above this gives: > > Sensor 0: 0.642 = 33 mV * 885 / 100000.0 * 2.2 > Sensor 1: 0.630 = 29 mV * 989 / 100000.0 * 2.2 > Sensor 2: 0.674 = 26 mv * 1179 / 100000.0 * 2.2 > > As you can see, the average ppO2 (0.648) is now very close to the > average ppO2 reported by the device (0.65). This seems to be true > for all samples. The largest difference is now 0.018. > > The next question is of course what's the source of this factor 2.2? Could it be that the calibration value is stored in some odd format, and thats where the / 100000.0 * 2.2 part comes from? > And is correct for all Predators? How did it line up on the petrels? //Anton -- Anton Lundin +46702-161604 _______________________________________________ subsurface mailing list [email protected] http://lists.subsurface-divelog.org/cgi-bin/mailman/listinfo/subsurface
