interesting oddity in SAC rate display in profile infobox

[Anton Lundin]

On 08 September, 2021 - Dirk Hohndel via subsurface wrote:

> Simple to reproduce.
> 
> Manually add dive - let's just use the default 15m / 40min
> Add a tank - 10.0l, start 200bar end 100bar
> 
> Dive overall has a SAC of 9.9l/min
> 
> Because there is no sensor data, we are creating a constant SAC rate theoretical gas consumption line (at least I thought we did).
> But as you hover over the profile from start to finish, you'll see the SAC rate increase from 7.9l/min to 10.7l/min
> 
> 
> 
> Am I misunderstanding what I'm seeing?
> Admittedly, I haven't looked at the code, yet. I just saw this underlying problem reported on Scubaboard and figured I'd share the simple demonstration of the issue here

This has bin like this ever since we started to gas computations based
on non naive p-v-t calculations.

We still extrapolate the sac rate based on the naive formula, and later
use those extrapolated values to calculate a real sac, so due to
compressibility we think we consume less gas in the beginning and more
towards the end.


A long time ago I took a stab at fixing this but it turned real messy
and I just left it.


//Anton


-- 
Anton Lundin	+46702-161604