O2 sensor values on CCR dives

[Anton Lundin]

On 01 December, 2017 - John Smith wrote:

> 
> 
> On 1 Dec 2017, at 20:39, Davide DB <dbdavide at gmail.com<mailto:dbdavide at gmail.com>> wrote:
> 
> Yes I know perfectly how calibration works. I meant how po2 is calculated from downloaded data.
> 
> Sorry, I wasn’t making myself clear. The point I was trying to make was wondering how libdivecomputer takes the individual cell calibration into account as there doesnt seem to be any calibration values in the log file.
> 
> It's a completely different story.
> 
> Am I the only one with a Petrel controller here? Maybe other user can confirm if their pO2 values are correct.
> 
> I was thinking about whether I could time match data from my AP handset - which shows PPO2 for each cell against my ext petrel  data. The following graph shows the data extracted from subsurface.
> 
> 
> [cid:c2b9af0b-0980-493c-b296-7c51e8aff908]
> 
> I know there is a small difference between the two computers, I see that during calibration, but I cannot see anything major in this particular dive.
> 
> 
> davide at mobile
> 
> Il 01 dic 2017 7:38 PM, "John Smith" <noseygit at hotmail.com<mailto:noseygit at hotmail.com>> ha scritto:
> 
> What I do not understand is how this conversion was made the very first time. I mean how did you reverse engineered those values? I mean did you have a reference data set (mV, calibration K and resulting po2) to compare against?
> Surely every time you run the calibration routine on the shearwater there should be a new calibration value (calibration k) for each cell. The PPO2 is then a linear calculation based on this.


In the data we have sensor1-3 mV , calibration values for sensor 1-3,
sensor status after voting and the computed average p02 between the used
sensors.

After steering at those values and playing around with a bunch of
different formulas we figured out how to use the calibration values so
it matched the data we had from 10 or so different units.


Thats how I and Jef reverse engineered it.


//Anton


-- 
Anton Lundin	+46702-161604