dealing with unused tanks

[Jef Driesen]

On 30-12-12 22:18, Linus Torvalds wrote:
> On Sun, Dec 30, 2012 at 12:52 PM, Jef Driesen <jefdriesen at telenet.be> wrote:
>>
>> Are there any devices that allow switching to inactive gasmixes during the
>> dive. That would be very counter intuitive. If the answer is yes, then
>> what's the purpose of marking a gas as inactive?
>
> One obvious purpose for marking it inactive would mean that the dive
> computer wouldn't use it for any future deco calculations (ie the
> "minimum time to surface" number).
>
> For example, if you have a bail-out bottle with 50% O2 or something
> that you do *NOT* want to use except in emergencies, you may well want
> to list it in the dive computer (in case you have to use it you can
> switch to it and get deco info using that knowledge), but you'd want
> to mark it as "inactive" to make sure that the dive computer doesn't
> think you're going to use it for your deco stop.

I see, but in that case the meaning of the inactive flag is different from what 
we have been discussing so far. Inactive in this discussion would mean something 
like not present, and thus not possible to switch too. At least that's what I 
had in mind. For example a device that stores the gasmix percentages as 0xFF to 
indicate an inactive gas. It could equally well be stored as a flag next to the 
percentages of course.

The inactive flag as you describe falls into our used/unused category. And 
that's something very different.

Jef