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Hello,

I recently purchased an OSTC plus. My dive buddy has an OSTC2C.

I have observed that with the same parameters configured, the decoplan obtained are different. I give a simple example:

Bottom time: 29'
Depth: 30 m
GF: 30/85

Decoplan with OSTC plus:

15m 1'
12m 1'
9m 3'
6m 5'
3m 12'

TTS: 28'
CNS: 8%

Decoplan with OSTC2C:

12m 1'
9m 3'
6m 4'
3m 9'

TTS: 21'
CNS: 8%

This is a simple example and there is already 7 'difference in the TTS

I would like to know why these differences. They are supposed to use the same decompressive algorithms.

If it is necessary to give you some more parameters, please ask me.


Thanks in advance.

Regards.

Hi,

i don't now the deco calculation routines of the 2C in detail, but those of the recent OSTC 2 / plus. Which firmware are you using on the plus?

BR
Ralph

Hi Ralf,


On the plus I am using hwOS Tech v2.97
On the OSTC2C v2.80 is the current versión.

Both of them set to Bülhmann 16 with GF factors.

OSTC2C set by default saturation factor to 110% and desaturation to 90%. I suppose with ZH-L16+GF decotype saturation factors are not taken into account.

OSTC plus set saturation factors to 100% for both.

BR

Hi,

sorry, i forgot to ask for a few other things:

- are you using the deco calculator from the simulator menu or are you running the OSTC in dive simulation and than look at the display after 29 minutes of dive tiem?

- single gas, air?

-

Besides possible differences in the configuration, there are a few differences in the ascent and deco calculation code as well which likely will influence the results. For example V2.97 calculates the final ascent with 1m per minute whereas the previous code took 10 m/min. With a last stop at 3 meters, this adds 3 minutes to the TTS and thus (thats why it was done) also pulls the gas needs prediction towards the safe side.

The Sat/Dest factors are not used in GF mode, if they would had, the 2C would have given the longer deco of the two.

Last but not least: there's quite some time between the coding of the last 2C firmware and the 2.97 (which is brand new), with many in-detail improvments, rework of safety margins, etc since then. Anyhow, i'll try to at least reproduce your 2.97 results as i have no 2C at hand...

BR
Ralph

Hi Ralph,


- I am using the deco calculator from the simulator menú in both computers.

- Yes, single gas, air. Just to make a simple test.


I understand the few differences in the ascent and the increase of the gas need prediction. I have also notice that the rate of ascent in the OSTC2C is a constant value for all depths.

But these differences are supposed to increase the TTS and that the deco time should be the same in both computers.

However, if we look at decotimes the differences are already 5', having differences in times of the shallower stops and depth at the first stop.In fact, the difference by ascent rate is 2'

I worry that in more technical dives these differences will increase much more.

Obviously, in this type of dives we will carry our dive plan written in the wetnotes, but it is a pity not to be able to take the OSTC as a backup and with the same decoplan in both computers.

Please, tell me if your results are the same.


BR

Hi,

sorry for the delay, have been (too) busy the last days...

On my OSTC2 after reset all, on single gas air, GF30/85, 30 m for 29 mins it says:

15 m 1 min
12 m 1 min
9 m 2 min
6 m 5 min
3 m 12 min

TTS 25 min, CNS 8%

So it's again a little bit different. Hmmm.... Current surface pressue while i'm doing this is 988 mbar - that also has a bit of influence on the results. So one stop more (one deeper one, for a minute) and/or deviations of +/- 1 minute on a particular stop depth is within natural tolerance band due to varing surface pressures, slight changes of the code, rounding (internal computation uses float numbers, for displaying they are converted to integers) and not to forget the slowed ascent speed from last stop to the surface.

BR
Ralph

Well, i don't think the different computers will deviate by too much during a longer / deeper dive. Fact is, there have been many small improvements in the deco calculations between the V2.26 and the V2.96, last but not least in the code that calculates the ascent (and gas-switching). So

Hi Ralph,


I have just done the same simulatorwith OSTC plus. Current surface preasure 954 mbar.

Surprisingly, the dive plan is different even with the one previously done with this same computer. Just 1' with mine and 4' with yours.

On single gas air, GF30/85, 30 m for 29 mins it says:

15 m 1 min
12 m 1 min
9 m 3 min
6 m 5 min
3 m 13 min

TTS 29 min, CNS 8%

Is it v2.96 on your OSTC2?

Could someone else do this simulation and write the results, please?

BR

My OSTC is running V2.98...

Anyhow, there is no difference in the deco/ascent code between 2.97 and my 2.98.

You have a different ambient surface pressure and as said +/- 1 minute is "at random" due to rounding. A stop can e.g. be internally 1 minute 59 seconds or 2 minutes 01 seconds, which is quite the same. Anyhow, as on the display there are only full minutes shown, it's 2 mins in the first case and 3 in the later (rounding is always up to the next full minute in this case).

-R.

Hi to everyone

I have done the same on my OSTC+ Tech #15717 FW Ver. 2.97

GF 30/85
Bottom Time 29' max. depth 30m
Deco Plan:
15m - 1'
12m - 1'
9 m - 3'
6 m - 5'
3 m - 12'

TTS: 28'
ZNS: 0 -> 8%

Pressure 955 mbar