Gas switching and Deco plan somethings not right!

OSTC's running hwOS sport or tech
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Poacher
Posts: 8
Joined: Saturday 11. April 2015, 15:20

Gas switching and Deco plan somethings not right!

Post by Poacher »

Hi All

I've been having a play and running the simulator to familiarise myself with the unit. My usual diving is accelerated deco going from a light nitrox say 26% and switching to a 60% or 80%. I've programmed the travel gas as 26% and deco as 60% running a bottom time of 31 minutes to 42m running +GF at 0% conservatism. When running that dive in the simulator gives me the following: -

18m - 1
15m - 2
12m - 2
9m - 4
6m - 4
4m - 16

Giving me 29m deco plus 3 mins safety and I've set the TTS to 2m so TTS is 34mins. The MOD for the 60% is 13m I've set a switch at 12m, I then switch giving me something like a TTS of approx 29mins, now I'd expect that to be reduced by about 10mins switching to 60% as on my old computer. I'm getting no reduction absolutely none? The NX26 starts flashing yellow and the NX60 is flashing yellow above and to the left, I select using the left button and a ? appears, I select using the right button, NX60 has now replaced the NX26. But there's no reduction in deco/TTS.

On other simulated dives, it's given me a few stops in the deco plan 12m - 1, 9m - 4, 6m - 2, I run the dive and it tells me my first stop is 12m - 1. Once reached it then tells me I've missed a deepstop at 15m what stop!

Something is not right here!

This is my first OSTC and I'm loosing confidence in it fast, I've never had any issues with a dive computer before. What is wrong with this thing?
sailor
Posts: 401
Joined: Friday 11. April 2008, 23:16

Re: Gas switching and Deco plan somethings not right!

Post by sailor »

Hi,

the first thing regarding TTS is a normal behaviour, when all deco gases are set as activ gases.
In this case the OSTC presumes that you are going to use your active gases and calculates the TTS with all active gases.
If you want the TTS to be reduced when switching to a deco gas you have to deactivate this gas.
You can still switch to a deactivated gas but it will not be considered for the TTS calculation.
Once you are switching to the deactivated gas the TTS will be recalculated.

The second thing is also a normal behaviour for the simulator.
This missed deco stop thing will not happen during a real dive with a normal ascent speed.
With the simulator your simulated ascent speed is so fast that you might miss a just developed deep stop.
I have this behaviour all the time when playing with the simulator but i have never seen it during a real dive.

No need to loose the confidence before doing a real dive, the OSTC is a perfect tool from my point of view and works flawelessly for real dives.

Reiner
Poacher
Posts: 8
Joined: Saturday 11. April 2015, 15:20

Re: Gas switching and Deco plan somethings not right!

Post by Poacher »

Hi Reiner

Thank you for your reply.

I'm somewhat lost here none of what you're telling me is mentioned in the manual, plus you're saying the simulator doesn't work properly e.g. it's not simulating a dive and things that are happening wont in a real dive...................this is madness!

What you're saying is I have to deactivate my deco gas and then reactivate it to get deco obligations reduced from gas switching, is that for only simulator or for a real dive too?

As for not normal assent I can't believe they marketed a computer that isn't capable of running a fully simulated dive again to me this is not acceptable, I'm getting less and less confidence as even more flaws are being uncovered, really I am. I've dived a few gas switchable computers all perform perfectly in any mode this is not confidence inspiring, it's almost jump in don’t worry it will be alright!
heinrichsweikamp
Posts: 4376
Joined: Sunday 13. May 2007, 18:07

Re: Gas switching and Deco plan somethings not right!

Post by heinrichsweikamp »

Poacher Wrote:
-------------------------------------------------------
> I've programmed the travel gas as 26% and deco as
> 60% running a bottom time of 31 minutes to 42m
> running +GF at 0% conservatism. When running

Not possible. At least one gas must be the so called "First Gas" (The OSTC sets the "first gas" automatically if required. Please post the exact Gas Setup here and I'll explain it to you.

Regards,
Matthias
Poacher
Posts: 8
Joined: Saturday 11. April 2015, 15:20

Re: Gas switching and Deco plan somethings not right!

Post by Poacher »

Hi Matthias

Yes you are correct I was mistaken with first/travel it defaults to first.

I've now had my eureka moment, and the issue is now solved.

It's was a case of not being able to see the "wood through the trees" to a greater extent and the lack of detailed information in the manual.

All my other computers while in simulation don't assume you will use the deco gas in the TTS/deco as you dive, they carryout the switch at the programmed depth and then reduce the TTS/deco. Therefore you can see the reduction straight after you switch, unlike OSTC which shows the gas switch reduction from the start and then adds the obligation back to TTS/Deco if you don't switch.

So the OSTC was working completely oppositely, I just couldn't see it, it's amazing what you find out at 3am!

Confidence is restored.
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