O2 sensor values on CCR dives

Anton Lundin glance at acc.umu.se
Sun Dec 3 00:10:57 PST 2017

On 02 December, 2017 - Davide DB wrote:

> On 2 December 2017 at 22:29, Anton Lundin <glance at acc.umu.se> wrote:
> > Can you save the same dive from Shearwater Desktop so I can take a look
> > at the mV values they report there, so see of they are out by about -8
> > or so?
> >
> >
> Sorry I forgot I shared it privately with Jef
> It's attached now.

This file was from subsurface, but what I was looking for was a log file
from Shearwater Desktop. I would like to see if it saves the "raw" mV
values, or if it corrects them and then saves them.

> >
> > Your Sensor 3 reads a bit high towards the end of the dive, but you're
> > probably already aware of that.
> >
> >
> Should be the number 2 actually. It's nearly time to change them all.
> Thank you for your effort on solving this.
> Is it possible that I am the only one who noted this? Pushing the oxygen at
> 1.5 during the last part of the deco brings inevitably the graph in the red
> area.

My guess is that you are the only one with a such high correction factor
that it actually shows. I also guess most divers won't look at their
logs close enough to actually notice a .1 difference.

I'm a bit worried when i see that the correction factors for all 3
sensors are att max. Have you ever double-checked the mV values with
either a simple signal generator or a multimeter?

You could just check what a sensor actually reads in mV with a
multimeter, and what your DC reads from the same sensor during the same
conditions. I doubt that there is something wrong, but a maxed out
correction factor makes my spider sense tingle...

On to another topic, I would like to see that we had a interface between 
libdivecomputer and subsurface to report the computer calculated "true"
ppo2 to, and not just the raw sensors.

That would have made this way easier to spot.

The raw mV values would have bin nice to have to.

Heck, even subsurface saving the raw binary dive as a blob in the git
tree would be awesome to be able to debug parser oddities on old dives.


Anton Lundin	+46702-161604

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