Buhlmann ZHL-C / B & Divelogs Divesoft
helling at atdotde.de
Tue Nov 30 06:42:14 PST 2021
> On 30. Nov 2021, at 03:14, Markus Ehmann via subsurface <subsurface at subsurface-divelog.org> wrote:
> One question I have is about the Buhlmann used for planning as well as calculated TTS when analysing a divelog. The settings don't specify if this is the ZHLC or ZHLB.
> Can you tell me which one is used or if I may missed the option to switch to either one?
> Depending on the dive computer used, the differ during the dive and it would be neat to align planning and profile as close as possible.
As you can see in https://github.com/subsurface/subsurface/blob/1e527fb9f01388df2248a90efc7de26c90faec75/core/deco.c#L84
Subsurface uses the ZHLC coefficients as should be the case for dive computers (-B is to generate tables).
For the detailed coefficients, see for example http://www.nigelhewitt.co.uk/stuff/aab.jpg. The a coefficients in the -C model are about 10% smaller in the middle tissues and since
tolerated = (tissue_inertgas_saturation - buehlmann_inertgas_a) * buehlmann_inertgas_b;
this means that tolerated is bigger. That means that for given tissue saturation the ceiling is a higher ambient (tolerated) pressure i.e. deeper. So this version is a bit more conservative, but the difference is not too big.
> Also, having recently added a Divesoft Liberty, I noticed that the import of divelogs works only with the .dlf files.
> With their recent 2021 hardware update, Divesoft added Bluetooth functionality. So I wondered if you have any plans of adding a direct Bluetooth import for this computer to subsurface as well?
I don’t know. As far as I know, none of the developers have such a computer. And implementing this would be helped substantially if there were information on how the protocol is supposed to work (most likely provided by the manufacturer).
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