CNS% Issue again.

[Smiler1968]

I've had some odd readings in the past when I use the in built simulator/planner on my OSTC2n. I've created a thread about it in the past.CNS%?

I thought this was resolved but I'm having some odd calculations coming up again.

I'm not Trimix Trained so please don't shoot me down about the mixes used, I was just playing with the OSTC to see if I could work out how to incorporate a travel mix. When I tried I ended up with a CNS of greater than 250%. I would then take the travel gas out and the CNS would calculate to about 76%. Without doing anything I would run the dive again and then it would read about 18% (what I expected). I thought that there may be some sort of nominal surface interval that the OSTC added as a result of the previous plan (>250%). However, I have just picked it up today to run a simulation and it has given me a CNS of 76% again. Without changing anything I ran it again and it dropped back down to 18%.

I have posted some screen shots so you can see what I mean (hopefully I've done it correctly). I had a run time of 21 minutes at 51 meters and I'm using 2.70.

Any ideas?

[img]file.php?2,file=462,filename=13-11-19_CNS_76.png[/img]

[img]file.php?2,file=463,filename=13-11-19_CNS_76.png[/img]

Cheers

Jerry

[Bardass]

How do you set your GF ?

[Smiler1968]

Bardass Wrote:
-------------------------------------------------------
> How do you set your GF ?

30/80

[heinrichsweikamp]

The simualtor takes the CNS (And tissue load) from real dives into account but does not add CNS or tissue load to following simualtions, of course.

Running the same simulation with the same settings and same existing CNS should result in the same results. Seems that the real CNS is not properly backuped here before the simulation. I'll have a look.

Regards,
Matthias

[heinrichsweikamp]

Problem is that I always get 18% CNS for this dive with the 2.70, can you explain a way to reproduce it?

Regards,
Matthias

[Bardass]

same for me, always 18%

[pre]
Modèle Bühlmann ZH-L16C-1a 2002 modifié GRADIENT FACTOR:
* GF_bas (CF32) = 30 %
* GF_haut (CF33) = 80 %
* marge de palier (CF16) = 1.0 m
* dernier palier (CF29) = 4 m
* début de plongée à Pamb = 1013 mbar
* Durée de changement de gaz (CF55) = 0 min

Liste des gaz (circuit ouvert):
* Gaz#1 (premier) = Tx23/26
* Gaz#2 (déco) = Nx32 à 36 m

...
==== Runtime circuit ouvert (OC) ====
21:04 51.0m Déco: ppO2=1.40

51 m 21' 21.0' Gaz#1
36 m ---- 22.5 ' CHANGER Gaz#1 -> Gaz#2
21 m 1' 25.0'
18 m 1' 26.3'
15 m 2' 28.6'
12 m 2' 30.9'
9 m 4' 35.2'
6 m 4' 39.5'
4 m 20' 59.'
0 m ---- 60.8'

DTR = 40 '
SNC = 18%

DTR Réchap @+5' = 54'
RT Réchap @+5' = 80'

[/pre]

[Smiler1968]

heinrichsweikamp Wrote:
-------------------------------------------------------
> Problem is that I always get 18% CNS for this dive
> with the 2.70, can you explain a way to reproduce
> it?
>
> Regards,
> Matthias


Sorry for not getting back to you Matthias, I've been on Nights.

I have run the simulation again and got the same 18%. Then I gave it a crazy mix for the bottom and got >250%. I returned the mixes to something more sensible and ran it again and got 18%.

I sat and changed the mixes around for about 10 minutes or so and kept running the simulation and eventually I got the 76% back. In a nutshell I cannot reproduce it every time but the computer sometimes throws a wobbly after a high CNS%. That being said, I have picked it up fresh from being turned on and got the 76% reading. It does appear that once you have the 18% you can run as many simulations as you want, you will always get 18%. Once you play around with the mixes you stand a chance of getting the 76%.

Screen dumps again.

[heinrichsweikamp]

Not so easy to find this bug I'm afraid.

I now played again some minutes with different mixes and settings and still couldn't reproduce this bug (Which doesn't mean it's not there!)...

Regards,
Matthias

[Smiler1968]

I'll have another play tonight to see if I can reproduce it.

[Smiler1968]

Hi Matthias,

Sorry about the delay. I'm not sure what's going on. I have just picked the OSTC up out of the box and ran a simulation (without fiddling with any mixes). I meant to run it to a depth of 51m for 21mins again but went to 23min by mistake. I ran that anyway and the CNS% came out at 78%. I tried to get a screen dump but wasn't quick enough. I thought I would run it again to 51m 23min just to see what happened. Again 78%. This time I got a screen dump. With the OSTC still attached to the PC and withing OSTC Planner I ran a simulation and got a CNS of 20%.

==== OC Runtime ====
23:06 51.0m Deco: ppO2=1.42

51 m
23 '
23.0 '
Gas#3
36 m
----
24.5 '
SWITCH Gas#3 -> Gas#2
21 m
1 '
27.0 '

18 m
1 '
28.3 '

15 m
2 '
30.6 '

12 m
3 '
33.9 '

9 m
4 '
38.2 '

6 m
5 '
43.5 '

4 m
19 '
62.7 '

0 m
----
63.8 '


TTS = 41 '
CNS = 20%

Future TTS @+10' = 66'
Future RT @+10' = 99'

Any thoughts?

Whilst typing this, the OSTC has turned itself off. I have just powered it up and ran the old simulation - 51m for 21min and it's given a CNS of 76%

[heinrichsweikamp]

Hi,

Can you give the new 2.74 beta a test with your CNS issue?

http://www.heinrichsweikamp.com/?id=57&version=en

We made some minor changes with the simulator (I moved some variables from local to global).

Regards,
Matthias