NDL staying at 0 for a while after deco completion

Legacy OSTC's
Titus
Posts: 23
Joined: Thursday 19. June 2014, 10:36

NDL staying at 0 for a while after deco completion

Post by Titus »

Hi,

I'm a pretty new user of OSTC 2C.
I did a deco dive (max depth 32m) this week and get a deco stop indicator at 3m for about 2min (TTS was about 6min, TTS@+1 = 7 min).
When ascending, we made a stop of about 12min at 15m to explore a small wreck. The deco stop disappeared, NDL returned to 0 (TTS = 2min; TTS@+1 = 2min).
The NDL time stayed at 0 during about 5 to 10 more min before to switch directly to 240min

So my first question is : if I have a NDL of 0, it means for me that if I continue at this depth, deco stop(s) will appear. In this case it is not true because the TTS@+1 was the same than the TTS and I stayed at this depth for a fex minutes more (about 10) and NDL still indicated 0; so what ?

Second question : why the NDL stays so long at 0 and then going directly to 240min. I would expect to see my NDL going from 0 to 240min by steps (I do not mean minute per minute, but at least per large steps)

Thanks for sharing ...

Titus
Titus
heinrichsweikamp
Posts: 4370
Joined: Sunday 13. May 2007, 18:07

Re: NDL staying at 0 for a while after deco completion

Post by heinrichsweikamp »

Hi Titus,

Can you please download this dive with the "OSTC Tools" and post the .dive file of this dive here?

regards,
Matthias
Titus
Posts: 23
Joined: Thursday 19. June 2014, 10:36

Re: NDL staying at 0 for a while after deco completion

Post by Titus »

Hello Matthias,

I will do my best because I do not know how to do it with "OSTC Tools".
I will download the software and will check how to dump a dive. Any manual (in UK) I might download that could help me ?

Thanks
Titus
Rob
Posts: 362
Joined: Thursday 12. May 2011, 18:12

Re: NDL staying at 0 for a while after deco completion

Post by Rob »

Hi Titis,

i think you dont need a manual,
just run OSTCConfig, click on "Get dfata from OSTC"
select the port, check "with status and profile" and click on download.
you wil find the profiles in your home folder ( my documents/OSTCTools/Serialnumberofyourostc/Profiles )

Regards
Rob
Home: http://www.angermayr.eu
email: ostctools@angermayr.eu
Home of OSTC Tools: http://ostctools.angermayr.eu
HWOSConfig for Android: https://play.google.com/store/apps/details?id=eu.angermayr.hwosconfig
Titus
Posts: 23
Joined: Thursday 19. June 2014, 10:36

Re: NDL staying at 0 for a while after deco completion

Post by Titus »

Thanks. I have attached the dive dump.
Hope to hear/read you soon
Titus
heinrichsweikamp
Posts: 4370
Joined: Sunday 13. May 2007, 18:07

Re: NDL staying at 0 for a while after deco completion

Post by heinrichsweikamp »

Hi Titus,

This happens in the non-GF deco model if the difference between the ambient pressure and the pressure in the leading tissue is near identical (no on- or off-gasing). It's an (unwanted) effect of the Bühlman algotrithm in the OSTC.

regards,
Matthias
Titus
Posts: 23
Joined: Thursday 19. June 2014, 10:36

Re: NDL staying at 0 for a while after deco completion

Post by Titus »

@Matthias,

So it means that we are at the very limit between deco and no deco (with respect of th CF 11 & 12 that add additional conservatism in the non GF model).

Is it save to go surface in this state (I mean being at the very limit) ?

This being said, I had difficulty to believe that someone could stay at the exact depth where there is no on- or off-gasing during a great time (even several minutes). this looks for me quite unbelievable.
i also do not understand why the GF or non GF might play a role, knowing that the GF is just a way to change the position of your M-Values line.

Thanks
Titus
Vortax
Posts: 23
Joined: Thursday 28. June 2012, 13:50

Re: NDL staying at 0 for a while after deco completion

Post by Vortax »

heinrichsweikamp Wrote:
-------------------------------------------------------
> Hi Titus,
>
> This happens in the non-GF deco model if the
> difference between the ambient pressure and the
> pressure in the leading tissue is near identical
> (no on- or off-gasing). It's an (unwanted) effect
> of the Bühlman algotrithm in the OSTC.
>
> regards,
> Matthias

Well, I had a similar problem, while diving mi CCR unit using GF model:

I went for a dive with a CCR rebreather. Main controller was a shearwater predator (GF 30/85), and secondary as a stand alone, my OSTC 2N (firmware 2.8,GF 30/85, fixed ST 1.3).

While diving, I hit the "0 NDL" mark in my OSTC (not my predator), but I DIDNT WENT INTO DECO.
After that moment, the ostc stayed at 0 NDL regardless of the actual depth, for almost 20 minutes!!!. At divetime 46 (depth 13m), the jumped straight to 240 NDL.

The OSTC was on GF mode... and whats more, I had used it for a while in OC diving tek. In previous firmwares never showed this behaviour, on GF, neither ZHL-16 without GF.

Not sure if is a bug, but if it is, is a really serious one...

Best regards.
heinrichsweikamp
Posts: 4370
Joined: Sunday 13. May 2007, 18:07

Re: NDL staying at 0 for a while after deco completion

Post by heinrichsweikamp »

Vortax Wrote:
> Not sure if is a bug, but if it is, is a really
> serious one...

No, it's not. In the end it does not make much difference if you have 0min NDL or 1 min of deco. If the difference between the ambient pressure and the pressure in your leading tissue is very low, the deco situation (0min NDL in your example) does not change. Even for 20min.

Regards,
Matthias
Vortax
Posts: 23
Joined: Thursday 28. June 2012, 13:50

Re: NDL staying at 0 for a while after deco completion

Post by Vortax »

Im afraid I explained the problem incorrectly. The problem is not "since there was almost no difference in pressure, the NDL stayed at 0". The problem was: "even there was difference in pressure, and my NDL was rising in my other computer, the OSTC showed me an incorrect "0 NDL" when it should be "40 min", for example.

I thought you previously said that this only happens in the non-GF deco model... well, I was diving in GF model. My Other computer was also in GF 30/85, and it DID NOT get stuck in a fixed NDL number... the NDL was growing as I started diving shallower. My OSTC, on the other hand, was stuck at same NDL.

Same deco model, same diving profile (one in each of my arms), same parameters... only the OSTC showed this behavior.

How can the GF model be blame then?

- At 26min (27m) I hit "0 NDL" on my OSTC. My other computer was "7 NDL"

I stayed a little time about that depth, OSTC NDL was always 0 NDL, the other computer continued lowering the NDL till "1 NDL" at 31:40 min (24m).

Then i went shallower.

- At 34 min (21m) my other computer showed "15 NDL". OSTC was 0 NDL
- At 35:30 min (19m) my other computer showed "82 NDL". OSTC was 0 NDL
- At 38 min (21m) my other computer showed "35 NDL". OSTC was 0 NDL
- At 40 min (19,5m) my other computer showed "54 NDL". OSTC was 0 NDL

etc etc

Only at 42 min (13m) when my other computer showed "99 NDL" (that´s the "max NDL", as OSTC is "240" ), then, my OSTC jumped straight from "0 NDL" to "240 NDL" (again, "max" NDL).

The fact is that the other computer was constantly updating the NDL, while the OSTC was not, until max NDL was reached. I Don´t know if the problem was the OSTC not beeing able to accurately calculate the NDL, or if it was doing it correctly, but not showing the data on the screen. That problem did not happen in the other computer (again, same profile, same deco model).


I can upload both diving profiles or make snapshots, if needed.

Best regards.
Vortax.
divinglog
Posts: 181
Joined: Tuesday 15. January 2008, 00:14

Re: NDL staying at 0 for a while after deco completion

Post by divinglog »

Hi Vortax

Can you download this dive with Diving Log and post the logbook file here or send me to info (at) divinglog.de? I would like to use it to test the build-in deco calculator.

Thanks,
Sven
Diving Log 6.0 - https://www.divinglog.de/
Vortax
Posts: 23
Joined: Thursday 28. June 2012, 13:50

Re: NDL staying at 0 for a while after deco completion

Post by Vortax »

divinglog Wrote:
-------------------------------------------------------
> Hi Vortax
>
> Can you download this dive with Diving Log and
> post the logbook file here or send me to info (at)
> divinglog.de? I would like to use it to test the
> build-in deco calculator.
>
> Thanks,
> Sven

Hello sven, I´ll do my best to upload it ASAP, but I´d like to note that I in fact am using diving log (last ver.) to "see" the NDL as was shown in the OSTC.

In the "deco calculator" option, you can select showing the NDL as it would be calculated by the diving log software, or by the OSTC computer. When you select the OSTC profile, the "0 NDL" problem is shown... but if you switch to diving log calculations, the "0 NDL" problem desappears... that´s another reason to think the problem is on the OSTC, not in the deco model.

Regards.
Ziggi
Posts: 1
Joined: Monday 21. July 2014, 17:04

Re: NDL staying at 0 for a while after deco completion

Post by Ziggi »

The other option I believe is to "switch" to air before the designated stop depth
I.e when on air at 20m perform a switch and choose air again

I did this recently and it recalculated my deco therefore I think the computer now assumes you will not perform the switch at designated switch depth.
Titus
Posts: 23
Joined: Thursday 19. June 2014, 10:36

Re: NDL staying at 0 for a while after deco completion

Post by Titus »

Vortax wrote :
"
In the "deco calculator" option, you can select showing the NDL as it would be calculated by the diving log software, or by the OSTC computer. When you select the OSTC profile, the "0 NDL" problem is shown... but if you switch to diving log calculations, the "0 NDL" problem desappears... that´s another reason to think the problem is on the OSTC, not in the deco model.
"

This is worring me much and making a "fake" gas switch (like suggested by Ziggi) to force the OSTC to recalculate or at least to force a screen refresh of the NDL is not for me a valid when being under the water.


So, reading the Vortax post, I'm indeed thinkink that it is more a problem of screen refresh or screen refresh programing and not a deco algorithm programing bug.

What does Matthias think about this ?

Cheers
Titus
heinrichsweikamp
Posts: 4370
Joined: Sunday 13. May 2007, 18:07

Re: NDL staying at 0 for a while after deco completion

Post by heinrichsweikamp »

Titus Wrote:
>
> What does Matthias think about this ?

I'm waiting for the log file....

If the NDL was logged correctly but not displayed correctly it should be easy to fix.

regards,
Matthias
wrobell
Posts: 105
Joined: Wednesday 28. January 2009, 16:28

Re: NDL staying at 0 for a while after deco completion

Post by wrobell »

i had similar experience last saturday, but on no-deco dive:

- hit 39m
- wait till 2min ndl
- start ascending slowly (< 10m/min)
- ndl drops to 0min (expected)
- continue ascent
-- my buddy's dive computer increases ndl (different computer, different deco model)
-- ostc keeps ndl at 0min
- at depth around 20m (or maybe 16m?), ostc suddenly jumps from 0min to 18min ndl

firmware 2.50, dive on air, gf 20/90, last stop 6m. logs maybe next week.
swissdiving
Posts: 815
Joined: Saturday 30. July 2011, 07:30

Re: NDL staying at 0 for a while after deco completion

Post by swissdiving »

Yes mine does that too. It always has. I don't see the problem. You're not supposed to bounce around 0 NDL. Ascend and you will get the NDL time counting up. The same with the Aladin, only difference is it'll start counting up immediatly. But then if its so importante to you Titus, that it starts counting up immediatly, by all means Matthias please fix it.

It hasn't made a shred of difference to my NDL diving. I know I can rely on my OSTC 2 and have for the last three years.
Cheers,

Hansjoerg

--> 2N ¦ 2201 / 3892
--> OSTC4 ¦ 257 / 392 / 424 / 647/1324 Fischer

RTFM
wrobell
Posts: 105
Joined: Wednesday 28. January 2009, 16:28

Re: NDL staying at 0 for a while after deco completion

Post by wrobell »

swissdiving Wrote:
-------------------------------------------------------
> Yes mine does that too. It always has. I don't see
> the problem. You're not supposed to bounce around
> 0 NDL. Ascend and you will get the NDL time
> counting up.

but... I was ascending :) i tried to follow your "rule"
(not documented by any diving org, isn't it?), just
OSTC begged to differ.

also on some wrecks, with this possible bug, you will
have to cut your dive short or enter deco to know
that you really are out of time. so quite inconvenient or
in second case a risk, which is not big deal on its own
if your run on gradient factors, but your insurer might
have different opinion.
swissdiving
Posts: 815
Joined: Saturday 30. July 2011, 07:30

Re: NDL staying at 0 for a while after deco completion

Post by swissdiving »

Again, diving at the NDL limit is risky in itself. If you have to abort your dive at that stage for one reason or another, and you have to surface straight away you shouldn't be surprised if you get DCS.

If you get DCS in a situation like this its not the computer that is the cause but your physical/mental condition and you choosing to dive to the limit.

I know of no diving organisation that sanctions diving at the NDL limit, be it with tables or computer.

@Matthias
I've extracted a profile with OSTC Tools and sent it to you via email.
Cheers,

Hansjoerg

--> 2N ¦ 2201 / 3892
--> OSTC4 ¦ 257 / 392 / 424 / 647/1324 Fischer

RTFM
wrobell
Posts: 105
Joined: Wednesday 28. January 2009, 16:28

Re: NDL staying at 0 for a while after deco completion

Post by wrobell »

what is the limit to ndl limit then? :)

again, if ostc displayed the ndl properly, then the problem you rise would not exist.
swissdiving
Posts: 815
Joined: Saturday 30. July 2011, 07:30

Re: NDL staying at 0 for a while after deco completion

Post by swissdiving »

Instead of complaining, provide HW with the profile as per request from Matthias...
Cheers,

Hansjoerg

--> 2N ¦ 2201 / 3892
--> OSTC4 ¦ 257 / 392 / 424 / 647/1324 Fischer

RTFM
wrobell
Posts: 105
Joined: Wednesday 28. January 2009, 16:28

Re: NDL staying at 0 for a while after deco completion

Post by wrobell »

do not worry, for sure i will be sitting on this bug shorter time than you :p :)
heinrichsweikamp
Posts: 4370
Joined: Sunday 13. May 2007, 18:07

Re: NDL staying at 0 for a while after deco completion

Post by heinrichsweikamp »

Hi all,

I got an example of this effect. Here at time=16:00 the NDL has reached 0min

[img]file.php?2,file=570,filename=start.PNG[/img]

At time=22:00 the NDL jumped to 33min

[img]file.php?2,file=571,filename=stop.PNG[/img]

Between these two images a (more or less) constant ascend happened, dt=6min, dDepth=33,87m-14,25m=19,62m, mean-velocity=19,62m/6min=+3,27m/min

If you stayed at 33m for a few seconds/minutes more we would have seen 1min@3m for the same period.

Regards,
Matthias
swissdiving
Posts: 815
Joined: Saturday 30. July 2011, 07:30

Re: NDL staying at 0 for a while after deco completion

Post by swissdiving »

As I said, no big deal to me. Its wrobell who's "worried".
Cheers,

Hansjoerg

--> 2N ¦ 2201 / 3892
--> OSTC4 ¦ 257 / 392 / 424 / 647/1324 Fischer

RTFM
wrobell
Posts: 105
Joined: Wednesday 28. January 2009, 16:28

Re: NDL staying at 0 for a while after deco completion

Post by wrobell »

I am attaching two files.

First file is the full bin dump of the OSTC memory. The dive I am talking
in one of the previous posts was the first dive on 2014-07-26.

Second file, debug output from Kenozooid for this dive, which shows (deco
time to be interpreted as in OSTC docs - it is NDL time when depth is 0):

[pre]
DEBUG:kenozooid.driver.ostc:deco time 1, depth 0
DEBUG:kenozooid.driver.ostc:sample 91 info: depth = 28.90, pfb = 0, size = 0, data: b''
DEBUG:kenozooid.driver.ostc:sample 92 info: depth = 28.35, pfb = 0, size = 0, data: b''
DEBUG:kenozooid.driver.ostc:sample 93 info: depth = 28.25, pfb = 0, size = 0, data: b''
DEBUG:kenozooid.driver.ostc:sample 94 info: depth = 27.78, pfb = 0, size = 0, data: b''
DEBUG:kenozooid.driver.ostc:sample 95 info: depth = 27.31, pfb = 0, size = 0, data: b''
DEBUG:kenozooid.driver.ostc:sample 96 info: depth = 26.33, pfb = 6, size = 6, data: b'480000000003'
DEBUG:kenozooid.driver.ostc:deco time 0, depth 0
DEBUG:kenozooid.driver.ostc:cns b'03'
DEBUG:kenozooid.driver.ostc:sample 97 info: depth = 25.94, pfb = 0, size = 0, data: b''
DEBUG:kenozooid.driver.ostc:sample 98 info: depth = 25.39, pfb = 0, size = 0, data: b''
DEBUG:kenozooid.driver.ostc:sample 99 info: depth = 24.58, pfb = 0, size = 0, data: b''
DEBUG:kenozooid.driver.ostc:sample 100 info: depth = 23.79, pfb = 0, size = 0, data: b''
DEBUG:kenozooid.driver.ostc:sample 101 info: depth = 23.64, pfb = 0, size = 0, data: b''
DEBUG:kenozooid.driver.ostc:sample 102 info: depth = 23.05, pfb = 3, size = 3, data: b'000000'
DEBUG:kenozooid.driver.ostc:deco time 0, depth 0
DEBUG:kenozooid.driver.ostc:sample 103 info: depth = 22.55, pfb = 0, size = 0, data: b''
DEBUG:kenozooid.driver.ostc:sample 104 info: depth = 22.18, pfb = 0, size = 0, data: b''
DEBUG:kenozooid.driver.ostc:sample 105 info: depth = 21.81, pfb = 0, size = 0, data: b''
DEBUG:kenozooid.driver.ostc:sample 106 info: depth = 21.81, pfb = 0, size = 0, data: b''
DEBUG:kenozooid.driver.ostc:sample 107 info: depth = 21.47, pfb = 0, size = 0, data: b''
DEBUG:kenozooid.driver.ostc:sample 108 info: depth = 21.21, pfb = 6, size = 6, data: b'520000000004'
DEBUG:kenozooid.driver.ostc:deco time 0, depth 0
DEBUG:kenozooid.driver.ostc:cns b'04'
DEBUG:kenozooid.driver.ostc:sample 109 info: depth = 20.73, pfb = 0, size = 0, data: b''
DEBUG:kenozooid.driver.ostc:sample 110 info: depth = 20.32, pfb = 0, size = 0, data: b''
DEBUG:kenozooid.driver.ostc:sample 111 info: depth = 19.96, pfb = 0, size = 0, data: b''
DEBUG:kenozooid.driver.ostc:sample 112 info: depth = 19.58, pfb = 0, size = 0, data: b''
DEBUG:kenozooid.driver.ostc:sample 113 info: depth = 19.53, pfb = 0, size = 0, data: b''
DEBUG:kenozooid.driver.ostc:sample 114 info: depth = 18.96, pfb = 3, size = 3, data: b'000000'
DEBUG:kenozooid.driver.ostc:deco time 0, depth 0
DEBUG:kenozooid.driver.ostc:sample 115 info: depth = 18.10, pfb = 0, size = 0, data: b''
DEBUG:kenozooid.driver.ostc:sample 116 info: depth = 18.16, pfb = 0, size = 0, data: b''
DEBUG:kenozooid.driver.ostc:sample 117 info: depth = 17.76, pfb = 0, size = 0, data: b''
DEBUG:kenozooid.driver.ostc:sample 118 info: depth = 17.83, pfb = 0, size = 0, data: b''
DEBUG:kenozooid.driver.ostc:sample 119 info: depth = 17.06, pfb = 0, size = 0, data: b''
DEBUG:kenozooid.driver.ostc:sample 120 info: depth = 16.67, pfb = 6, size = 6, data: b'630000000004'
DEBUG:kenozooid.driver.ostc:deco time 0, depth 0
DEBUG:kenozooid.driver.ostc:cns b'04'
DEBUG:kenozooid.driver.ostc:sample 121 info: depth = 16.17, pfb = 0, size = 0, data: b''
DEBUG:kenozooid.driver.ostc:sample 122 info: depth = 15.96, pfb = 0, size = 0, data: b''
DEBUG:kenozooid.driver.ostc:sample 123 info: depth = 15.88, pfb = 0, size = 0, data: b''
DEBUG:kenozooid.driver.ostc:sample 124 info: depth = 15.55, pfb = 0, size = 0, data: b''
DEBUG:kenozooid.driver.ostc:sample 125 info: depth = 15.72, pfb = 0, size = 0, data: b''
DEBUG:kenozooid.driver.ostc:sample 126 info: depth = 15.77, pfb = 3, size = 3, data: b'001300'
DEBUG:kenozooid.driver.ostc:deco time 19, depth 0
DEBUG:kenozooid.driver.ostc:sample 127 info: depth = 15.53, pfb = 0, size = 0, data: b''
DEBUG:kenozooid.driver.ostc:sample 128 info: depth = 15.55, pfb = 0, size = 0, data: b''
DEBUG:kenozooid.driver.ostc:sample 129 info: depth = 15.59, pfb = 0, size = 0, data: b''
DEBUG:kenozooid.driver.ostc:sample 130 info: depth = 15.64, pfb = 0, size = 0, data: b''
DEBUG:kenozooid.driver.ostc:sample 131 info: depth = 16.18, pfb = 0, size = 0, data: b''
DEBUG:kenozooid.driver.ostc:sample 132 info: depth = 16.59, pfb = 6, size = 6, data: b'6b00000d0004'
[/pre]


As you can see the NDL was 0 minutes between 26m and 16m. Quick reminder,
my buddy's dive computer was showing increasing NDL while we were
ascending (see my first post).
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