Reaching deco quickly
Posted by: Manohulu ()
Date: June 02, 2019 10:26PM

Hello there,

I upgraded my OSTC3 to the latest version when it was released, but since I found out that my dives are reaching the deco quickly than before and also comparing with other buddies who have OSTC or other brand.

I checked my GF with my wife, 30/80 for me 40/80 for her, but even changing this parameter I can't stay as long as she can do.

Any advices?
Thanks

OSTC3 #2315 v3.01
Switzerland

Re: Reaching deco quickly
Posted by: Ralph ()
Date: June 03, 2019 07:35AM

Hi,

what's your setting on the Saturation & desaturation factors? If using GFs, they should be set to 100% each, else you get an extra penalty (shorter NDL, longer deco).

Re: Reaching deco quickly
Posted by: Manohulu ()
Date: June 03, 2019 08:23AM

Hi ralf,

Both saturation set to default, 100%
I reread the manual to be sure I didn’t made a mistake.
As I wrote only GF are set to 30/80 and also tried 40/80 as my wife has.
But she don’t have OSTC, I’ll check with a friend this afternoon who has a OSTC, during the next dive.

Cheers

OSTC3 #2315 v3.01
Switzerland

Re: Reaching deco quickly
Posted by: Kehrmaschine ()
Date: June 03, 2019 01:13PM

Hi

A higher GF low won‘t make a big difference. Just the first Deco stop will be shallower.

Best regards
Mario

Re: Reaching deco quickly
Posted by: Manohulu ()
Date: June 19, 2019 02:24PM

Sorry for the late answer, it can be from a poor battery. During the dive I saw a battery warning but soon I finished it my battery percentage increase to 72%. one hour later, 26%...
Battery changed let see next dive.

OSTC3 #2315 v3.01
Switzerland

Re: Reaching deco quickly
Posted by: Ralph ()
Date: June 19, 2019 05:57PM

Well, as long as the OSTC stays alive, it will do its calculations in a propper way...

Re: Reaching deco quickly
Posted by: Manohulu ()
Date: June 19, 2019 07:18PM

I may have a big issue since 3.01 update

It worked fine for the update one month ago, but now, I put a brand new SAFT LS 14500 and it's written Batt:0% ; In system information I have 3.445 (T0)

Another thing is when it reboot (batterie replacement) it's written Successfully Update to 3.01, but every time.

So I would try to reflash my computer but I can't connect to it on OSTC Companion 3.00 beta 8 I got this message:
OSTC3 selected.
Connecting...
Bad identity reply (1)
Port tty.usbserial-A4SHCQSJ: Bad identity reply (1)
Error: Port tty.usbserial-A4SHCQSJ: Bad identity reply (1)

Any idea...

OSTC3 #2315 v3.01
Switzerland

Re: Reaching deco quickly
Posted by: Manohulu ()
Date: June 19, 2019 08:11PM

So I did a reset battery and re set to T1 3.6v disposal, all back to normal, 100%.
Also reflash from my Linux computer instead of Mac, connection OK, I could reset all things.

OSTC3 #2315 v3.01
Switzerland

Re: Reaching deco quickly
Posted by: Manohulu ()
Date: July 13, 2019 12:12AM

I remove GF from the algorithm and all went back normal...

Did something change? I always had GF since I have this computer.

OSTC3 #2315 v3.01
Switzerland

Re: Reaching deco quickly
Posted by: Ralph ()
Date: July 13, 2019 04:58PM

Within the last and current release versions 2.99 and up, nothing fundamental has changed with the deco algorithm, including the GFs. Only the 3.03 published as beta has largely refactored code, but it is not recommended for productive use yet. Actually, there will be an updated beta soon.

Re: Reaching deco quickly
Posted by: Manohulu ()
Date: July 13, 2019 05:27PM

Thanks Ralph,

I don’t remember which version I had before the one a have but probably before 2.99.

Anyway I don’t think GF are very useful for recreational dive, just have to remember to re add it soon I’ll have to do technical dive with deco tanks.

All the best.

OSTC3 #2315 v3.01
Switzerland

Re: Reaching deco quickly
Posted by: Ralph ()
Date: July 14, 2019 12:01PM

Well, without GF and with Sat/Desat at 100%, staying a little bit away from the absolute NDL limit would be wise. Doing the safety stop will help in doing so. Alternatevely, you can also set the Sat/Dsat to say 95% as these factors where on purpose introduced to add conservatism in a none-GF regime.

BR
Ralph

Re: Reaching deco quickly
Posted by: Manohulu ()
Date: July 14, 2019 07:19PM

Hi Ralph,

Set the Sat/Dsat to say 95%, heuuu my lower value is 100% and up to 140%.
GF are, but not activated
Low 30%
High 80%
I’ll try with my buddy who have a OSTC 2n with GF disabled just to see some adjustments.

Thanks,
Manu

OSTC3 #2315 v3.01
Switzerland

Re: Reaching deco quickly
Posted by: Ralph ()
Date: July 15, 2019 07:45AM

Hi Manu,

sorry, 95% for Sat was in error from my side, it would be 105% for this value. So: calculated saturation taking place 5% faster than in "real" and desaturation 5% slower than in reality.

There is a lot of debate on which GFs to set, with current bias to set the GF low not too low. If you are air diving with going into little deco only, a GF low of 30% is probably not working well, values in the range of 50 or even 60% are increasingly belived to be more appropriate. A GF high of 80% will do quite good, giving some safety margin. Just for comparison: other brand's "sport" computers, although not providing possibility for GF adjustment and/or not using Bühlmann but some other algorithms, seem to do things that can be matched with Bühlmann on a 90/95 GF setting...

BR
Ralph

Re: Reaching deco quickly
Posted by: jb2cool ()
Date: August 12, 2019 03:34PM

I was seeing similar behaviour and that led me to find this post, using the advice I found in this thread (https://forum.heinrichsweikamp.com/read.php?6,20642) I found that my conservatism being set on 0 was not what I wanted, I actually wanted this set to conservatism = GF. This makes the new OSTS Plus with the sport firmware behave much more like the older OSTC Mk.2 that I have.

Re: Reaching deco quickly
Posted by: Manohulu ()
Date: August 21, 2019 11:44PM

Thanks JB2Cool for your input...

I also discuss with two other divers close to where I live and both stop upgrading there OSTC3 because of different symptoms.

What I remember is my last "good" firmware, 2.98.
1 - Is it possible to downgrade from 3.01 to 2.98?
2 - Is it possible to have a link to download it?

Many thanks,
Manu

OSTC3 #2315 v3.01
Switzerland

Re: Reaching deco quickly
Posted by: jb2cool ()
Date: August 22, 2019 10:11AM

There should be no need to downgrade, just set conservatism to GF and it should behave like you expect.

Re: Reaching deco quickly
Posted by: Manohulu ()
Date: August 22, 2019 10:28AM

I didn’t change anything since I bought (2014) this computer and never had to change and never had that kind of issue.
Less than 5 years and I am disappointed with.
Already think about buy something else.

OSTC3 #2315 v3.01
Switzerland

Re: Reaching deco quickly
Posted by: Arno ()
Date: August 22, 2019 01:28PM

Manohulu Wrote:
-------------------------------------------------------
> I didn’t change anything since I bought (2014)
> this computer and never had to change and never
> had that kind of issue.
> Less than 5 years and I am disappointed with.
> Already think about buy something else.


Although I do understand your issues with the firmware changes, most (if not all) of them are pretty neatly announced in the release notes on this forum. You can use those to 1) decide whether or not to upgrade and 2) which settings you might need to alter after upgrading.

Deco has never been exact science and especially the last few years a lot of new insights have come to our knowledge. I prefer that my divecomputer follows these new things rather that still using my first uwatec aladin dive computer which still uses the same principles as it did 20 or more years ago.

Re: Reaching deco quickly
Posted by: Ralph ()
Date: August 22, 2019 09:20PM

There's been a lot of fine-tuning in the code since the V2.9x series of firmwares, with lots of improvements not only in the NDL and deco calculations, but also in e.g. battery handling, power consumption and other internals normally not directly visible to the end user. So from the manufacturer's point of view, it is recommended to keep the OSTC up-to-date with the latest stable releases available.

Coming back on the topic "reaching deco quickly", i just made a test run with the latest 3.04 beta, which is also the basis of the latest Sport Firmware already released. Settings are single gas air, clean tissues, straight Bühlmann (Sat/Desat = 100% each, GF = 100/100), at sea level. Here's what i got using the dive mode simulator:

20m -> NDL 55 mins
30m -> NDL 19 mins
40m -> NDL 10 mins

When i compare these times with the good old PADI RDP, it looks like this:

20m -> OSTC 55 mins, RDP 45 mins
30m -> OSTC 19 mins, RDP 20 mins
40m -> OSTC 10 mins, RDP 9 mins

So it doesn't seem the OSTC is giving too short NDL times.

-Ralph

Re: Reaching deco quickly
Posted by: Manohulu ()
Date: August 22, 2019 10:30PM

So I can say I have a big issue with my OSTC because at 40m I cannot stay more than 3 minutes.

Next time I’ll dive I’ll try to do a video to show you if you want

OSTC3 #2315 v3.01
Switzerland

Re: Reaching deco quickly
Posted by: jb2cool ()
Date: August 23, 2019 02:39PM

It's likely just some settings that are wrong. What are the deco parameters you have set on your computer?

Re: Reaching deco quickly
Posted by: Manohulu ()
Date: August 24, 2019 03:39PM

My Settings:
Dive Mode: OC
Deco Type: ZH-L16+GF
PPO2 settings: Max 1.4, Max Deco 1.6, Min 0.17, Min loop 0.4
Deco parameters: Sat 100%, Desat 100%, GF Low 35%, GF High 80%
Bottom and Deco Gas: 20L/Min
Last Deco: 3m
Ascent speed: 10m/'
Gas Change: +1'

One dive from this morning in attachment as all can see 18 minutes to reach 33 meters (because of a buddy ears) and 4 minutes remained, normal?
[www.dropbox.com]

My wife still had almost 15 minutes (same dive)

So my question, because last year it was more easy to dive with my OSTC in version 2.98, How can I downgrade my OSTC? Otherwise I'll take my Suunto as primary because it became less preservative.

Best regards

OSTC3 #2315 v3.01
Switzerland

Re: Reaching deco quickly
Posted by: Ralph ()
Date: August 24, 2019 05:17PM

Well, while all the way down you are using up NDL time. 33 meters has some 18 minutes NDL at depth, which you can actually only have at depth in full if you are dropping down like a stone. With your slow descent, quite a portion has been eaten up while on the way down...

Instead of taking a Suunto, you can also set the GF high to about 95%, that will do about the same job as Suunto's RGBM takes you quite to the edge of Bühlmann or PADI RDP limits.

Also your GF low probably doesn't fit your dives.

Whithout sharing your wife's comuter settings, can't comment on that, sorry.


BR
Ralph


PS: the formular how to calculate the NDL limit has not changed in all the updates, it's by Bühlmann book and Eric Bakers GF paper

Re: Reaching deco quickly
Posted by: Arno ()
Date: August 24, 2019 05:20PM

I reproduced this dive in Subsurface diveplanner (looks like you used the same programm for your uploaded image) and with your settings it is about correct that NDL was about 4 minutes at the time you arrived at 33 meters (when diving on normal Air).

If you still have 15 more minutes left you get the following profile.

profile

and that means deco with first stop at 12 meters.
So every computer with air giving 15 more minutes NDL (until total BT of about 28 minutes) I would quickly discard of.

Even with Nitrox 32 this would require a minimal deco obligation of 2 minutes at 3 meters.

Re: Reaching deco quickly
Posted by: Ralph ()
Date: August 24, 2019 06:08PM

That's also in line with Multideco:

with 4 minutes at depth (18 mins descent + 4 mins BT = 22 mins RT)

MultiDeco 4,14 by Ross Hemingway,
ZHL code by Erik C. Baker.
Dekompressionsmodell: ZHL16-C + GF
TAUCHPLAN
Oberflächenpause = 5 Tag(e) 0 hr 0 min.
Höhe über N. N. = 0m
Konservatismus = GF 100/100

Abst. 33m (16) Air 2m/min Abstieg
Tiefe 33m 5:30 (22) Air 0,88 ppO2, 33m ead
Oberfl. (28) Air -5m/min Aufstieg

with 5 minutes at depth:

Abst. 33m (16) Air 2m/min Abstieg
Tiefe 33m 6:30 (23) Air 0,88 ppO2, 33m ead
Aufst. 3m (29) Air -5m/min Aufstieg
Stop 3m 1:00 (30) Air 0,27 ppO2, 3m ead
Oberfl. (33) Air -1m/min Aufstieg

--> DECO, outside NDL !!!

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