Tank pressure plots for CCRs

[Jef Driesen]

On 2014-01-06 22:27, Rodrigo Severo wrote:
> I'm trying to understand how to better show tank pressure plots for 
> CCRdives.
> 
> First let me present a few important facts about CCRs for the 
> uninitiated:
> 
>    - CCRs use 2 tanks simultaneously: one called the diluent (usually 
> air
>    but can be some trimix) and the other with oxygen;
>    - the usage pattern of these tanks differ greatly from the open 
> circuit (
>    OC) usage pattern already supported by Subsurface and also one from 
> the
>    other.
> 
> With this in mind I would like to suggest that Subsurface be extended 
> to:
> 
>    1. support multiple tank plots at the same time;
>    2. support different usage patterns besides the current OC one.

In theory, using multiple tanks simultaneously is not unique to CC, but 
also applies to OC diving to some extent. Some examples:

  * While breathing from a secondary tank (e.g. deco gas), your BCD or 
drysuit is probably still connected to your primary tank. Thus both can 
be used at the same time.

  * Several dive computers support multiple (wireless) tank sensors. So 
in theory you can already get multiple tank pressures per sample. 
Libdivecomputer definitely supports this, and in theory some of the dive 
computer data formats can certainly support this as well. But in 
practice I have never seen it. So far, all dive computers with multiple 
tank sensors seem to "suspend" the other sensors when switching to 
another one.

Note that I don't have any data (at least not that I'm aware of) from a 
device with several pressure sensor *in use*, to really confirm this. If 
anyone can provide such data, that would be great! I guess the majority 
of divers only uses a single tank, and the ones that frequently do use 
multiple tanks (e.g. tec divers) tend to prefer analog pressure gauges.

  * Some dive computers take this one step further and support monitoring 
your buddy's tank pressure. Unfortunately I don't know if or how the 
buddy tank pressure gets recorded.

Jef