Incorrect Po2 shown on dive log

[agar...@gmail.com]

Hello!

I'm diving a CCR with Petrel2 head.

Unfortunately, it looks like the po2 shown on my dive log does not match the actual dive po2. Most dives show a pO2 of 1.5ish, whereas the set point (and the shearwater cloud report as) 1.3.

One dive actually shows the po2 as 0.7 on the info box too, even though it's shown at that 1.5ish on the graph!

Any thoughts/suggestions?

Cheers,

Alex

[Michael Keller]

Hi Alex.

On Wed, 1 Oct 2025 at 13:52, agar...@gmail.com <agar...@gmail.com> wrote:

I'm diving a CCR with Petrel2 head.

Unfortunately, it looks like the po2 shown on my dive log does not match the actual dive po2. Most dives show a pO2 of 1.5ish, whereas the set point (and the shearwater cloud report as) 1.3.

One dive actually shows the po2 as 0.7 on the info box too, even though it's shown at that 1.5ish on the graph!

In the absence of a log file to look at I am guessing here, but I think that you are using a 'DiveCAN' Shearwater CCR controller, and not an analogue monitor / controller unit?

This would explain the too high readings in the profile graph - the scaling for 'DiveCAN' units has been improved in newer versions of Subsurface and you should upgrade to the latest version.

As for the data overlay, my suspicion is that the tank used at this point in the dive is set to 'OC' in Subsurface instead of 'diluent', so the ppO2 shown is that of what you'd get if you were breathing the gas in the tank in open circuit bailout.

Ngā mihi

  Michael Keller

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