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OSTC's running hwOS 
OC Gas Configuration >< old firmware
Posted by: derfem ()
Date: September 30, 2017 09:55PM

Hello,

I've just received and try my new OSTC with the new firmware, but I have some trouble to correctly configure the gas for an OC dive.

I make a 3 gas dive: bottom is a 15/60, travel is a NX36, and deco is pure Oxy. Obviously, I start the dive on the NX36.

In my previous 2C, it was very easy to configure it and have ALL THE 3 GAS taken into account for the deco:
G1: 15/60, Activated, Change at 80m
G2: 36, Activated, First, Change at 30m
G3: 100, Activated, Change at 6m

I get some pain to find a clever way to configure these gas in the new HWOS:
G1: 15/60, Travel, change ---
G2: 36, First, change at 0m (not configurable)
G3: 100, Deco, cahnge at 6m.
I run both computers in parrallel on the same dive, and the TTS of the HWOS goes completly weird, and do not take into account neither the 36, neither the 100 (when I was on the 36...)

How can I configure the gas to start the dive on the NX36, and having both gas taken into account for the TTS calculation when I'm on the bottom gas?

Thanks for your answer.
Fred

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Re: OC Gas Configuration >< old firmware
Posted by: ClaudeDive ()
Date: October 01, 2017 01:59AM

Hello,

Ok, Already evoked this in other messages a lot of time,

The problem is that OSTC gives improper gas designations:
First: in reality must be used for bottom gas because there is no gas designation bottom, and moreover there is no designation of travel for the gas travel that one will use in the case of use of a hypoxic bottom gas
Which requires to program the gas travel for the descent in gas deco!

The ideal would be to be able to program a hypoxic dive with:
- Travel: 1 gas travel for the descent,
or better yet:
- Travel & deco: so that this gas can be used for travel and also for deco, otherwise one is obliged to program twice this gas, once for the Travel = to the descent and another time Deco = to the ascent
- Bottom: 1 gas bottom
- Deco : 1 or more deco gases

All this would be very logical for all Trimix divers but is not currently not in the OSTC philosophy that I understand and that I know divert for proper use but the OSTC logic of designation of gases is not currently the most suitable for a program with improper gas designation.

Hoping that Matthias will listen to these requests ...

Best regards,

ClaudeDive ><winking smiley))))°> OSTC3 #2430 <°(((((><

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Re: OC Gas Configuration >< old firmware
Posted by: derfem ()
Date: October 02, 2017 09:58AM

Thanks Claude.

I understand from the manual that Travels are not included in the calculation of the deco. I also understand that HW consider that the dive always starts on the botton gas for a matter of safety.

For my oan use, I mostly do cave diving, and mostly never use the bottom gas first. In the given example, I have to spend at least 15 min on the NX36 before switching to the bottom gas, otherwise the TTS will go crazy.

If I well understand the proper use would be:
G1: TX15/60, FIRST, change --- (unbreathable at the surface ...)
G2: NX36, DECO, Change at 30m (even if it is a real travel)
G3: OXY, DECO, Change at 6m.
Start the dive, and as soon as the computer enter dive mode, I manually force the G2 as the current gas?

Could Matthias confirm this ?

Regards
Fred

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Re: OC Gas Configuration >< old firmware
Posted by: heinrichsweikamp ()
Date: October 04, 2017 07:46PM

Hi Fred,

Travel Gases are taken into account for the deco calculations (As all other gases) but the OSTC can not predict when you will switch to them (Other then deco gases). So, for your setup I'd recommend:

"First": Something you can breathe on the surface (Setup your NX36 twice, one as first and one as deco)
15/60 Travel (<- Switch to this gas during the descent)
"Deco": All your deco gases configured with change depth

Now the more practical approach: Use your NX36 to descend and change to 15/60 in 10m or so. Leave the deco calculations running with 15/60 from the beginning. The difference is minimal for most dives.

regards,
Matthias

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Re: OC Gas Configuration >< old firmware
Posted by: derfem ()
Date: October 05, 2017 10:31PM

Hi Matthias,

Thanks for your answer.

So if I understand well, the confusion comes from my misunderstanding of the gas naming. Correct naming and use is:
- FIRST: the gas on which we start the dive, not included in the calculation of the predictive TTS
- TRAVEL: any gas that could be used during the dive, but not included in the calculation of the predictive TTS
- DECO: deco gas included in the calculation of the predictive TTS

So in my example, if I want to start an hypoxic dive, I would setup the gases as follow:
G1: 15/60 TRAVEL
G2: NX36 FIRST
G3: NX36 DECO
G4: OXY DECO
And the predictive TTS would be correct?

Is there any difference if I setup the gases as follow, and switch to the NX36 at -5m during the descent?
G1: 15/60 FIRST
G2: NX36 DECO
G3: NX36 DECO

[HW]>> Now the more practical approach: Use your NX36 to descend and change to 15/60 in 10m or so. Leave the deco calculations running with 15/60 from the beginning. The difference is minimal for most dives.

Yes I really understand the approach for a normal "open water dive", but in my case, I'm talking about cave diving where I must follow a swallow galery (minus 20-30m) during at least 15 minutes before going deeper with the trimix, and so the difference is really more important, and the TTS is too high (I know it is some kind of additionnal security, but I can deal with it during the preparation/planning)

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