hwOS Tech: 2.97 released

[heinrichsweikamp]

That shows that there is no obvious defective hardware in your unit. Hardware faults would show as -4096 likely. Please give a new try and compare the values with the new calibration.

Regards,
Matthias

[Clownfish]

Redid it, close
X: -52
Y: 1270
Z: 529

Will see how it goes.No diving this weekend as big seas, but hopefully next week and over Easter.

[algo]

Hi,

did a OC dive yesterday i noticed two things:
- while doing my last deco stop on 6m it showed me that i should stay 2min on 6m and that my TTS would be 6min. What i understand: 2min (on 6m) plus 1min for the ascend = 3min! Where does the other 3min come from? Or is the ascend rate slower than 6m/min?
(as far as i remember a safety stop is only considered if no deco)
- after surfacing the depth (0.0m) was blinking red and it showed in red "ppo2 0.19bar" - because the red seems very dramatically i suppose it is a warning, but what for?

BR,
Alex

[Ralph]

Hi Alex,

1) right guess - in V2.97 we have slowed down the final ascent speed from 10 m/min to 1 m/min. Two reasons: it's much more healthy to do so, and it adds some safety margin into the gas needs calculation.

2) Which gas mix were you breathing, or were you diving at altitude? The "ppO2 0.19 bar" is the warning that at current depth the gas you are breathing produces a ppO2 that is below warning threshold. The depth is then also shown in red to make the connection with the warning and indicate to you that changing depth can resolve the cause of the warning. The depth will also go red if your ppO2 goes above warning threshold.

Ah, Rob disclosed you were diving at altitude. Then it's the lower surface pressure that causes your ppO2 to fall to 0.19 bar at surface. You can adjust the warning threshold down to 0,16 bar at minimum to get rid of this warning.

BR
Ralph

[Rob]

Hi Alex,

as i told you at the lake, can you use OSTCTools especially OSTCProfile to get the dive from your computer.

Regards
Rob

[algo]

Hi Ralph,

2) i was breathing normal air. Altitude was 400m, Bodensee. Could by, that my pressure sensor is the problem? It always shows lower pressure than there really is. Right now it is showing 952mbar, where my barometers outside shows a pressure of 1005mbar...
(in the past i used Subsurface to adjust the offset of the pressure sensor as much as possible, 20mbar. since this is not possible with 2.97 i will have to wait).

Thanks also for the info about ascent rate. Now its clear...

BR,
Alex

[Ralph]

Yes, it is a combination of both then: lower surface pressure because of altitude plus pressure sensor offset (not good in its own...).

This lower pressure causes your ppO2 to fall to 0.19 bar at surface. You can adjust the warning threshold down to 0,16 bar at minimum to get rid of this warning.

-R.

[heinrichsweikamp]

Hi,

We have changed the ppO2 min to 0.19bar (It was at 0.17bar before) That means in altitude diving you get this (here: useless) warning at the surface. Change the setting to 0.17bar as in the versions before to get rid of this.

Use HWOS Config from http://www.angermayr.eu/ (OSTC Tools) to check if the sensor offset is configured in your OSTC.

regards,
Matthias

[algo]

Hi Matthias,

because i have a Mac i will have to wait until Subsurface can handle the v2.97 version...

BR,
Alex

[Ludo]

Hello team,

I upgraded my OSTC3 some time ago with the latest HWOS v2.97
I then parametered it with the same setting (GF 45/85 and saturation 110/90) as before and as on my OSTC2 with version HW v2.26
The runtimes I get on the OSTC3 are not comparable to previous similar dives, I get deco stops at least 3m lower than expected and longer. Also strange, I had deco stops at 12m but none at 9m for many minutes.
And the OSTC2 with the previous HWOS version gives a runtime consistent with experience.
When I run a simulation, the difference is confirmed as shown in the attached file.
Have you done similar experience? What could explain those strange behaviors from my OSTC3?

Thanks
Ludo

[ClaudeDive]

Hi Ludo,
With your GF 45 / 85 you have to set the SD 100 / 100
you can test this setting with the simulator
Regards

[Ludo]

Hello Claude

I don't really agree with your statement.
And testing it still leads to huge difference in DTR between the 2 computers /HwOS versions, as shown in the attachement.

Kind regards
Ludovic

[ClaudeDive]

Hi Ludo,

My setting is good see parameters and results below

There is a parameter that is not set correctly on your OSTC3

I give you my setup: OSTC3 # 2430> v2.97 latest version 01.03.2018
Depth 51 m - Time 11 mn
GF 45/85 - SD 100/100
Fixed ascent speed: 10 m / mn
Last stop at 3m
PpO2 limits at 1.6 / 1.6 bar
Clean fabrics, no diving for more than 72 hours :
DTR= 21'
15m > 1'
12m > 1'
9m > 2'
6m > 3'
3m > 6'

Regards,

[Ludo]

@HW: which other parameter(s) could make such a difference?

Thank you
Ludo

[Ludo]

Thank you Claude.
You have a 3rd different result too.

Kind regards
Ludo

[ClaudeDive]

Hi Ludo,

Not very different from your OSTC2,

My OSTC3 is set without additional safety stop,

This may be the difference between 2 and 3 minutes with your OSTC2

[Ralph]

Hí all,

in case a dive requires decompression stops, the safety stop will be suppressed so its settings are irrelevant. The deco is affected by the following parameters:

- depth & bottom time - obvious
- the gases - mix, mode (first / travel / deco) & in case of type deco their switch depths (ppO2 settings are irrelevant here, they only control the warnings)
- GF-factors high & low
- saturation & desaturation factors (SD), normally 100/100 when using GFs
- depth of the last stop
- the residual tissue saturation from previous dives (if not long enough ago to have completely leveled out with ambient pressure or if not reset via the reset menu)
- the dive intervall (if set, adds additional time for the tissues to desaturate first before their data go into the deco calculation)
- the current ambient pressure (!!!) - yes, unlike most other offline deco software, the OSTC as a dive computer always factors in all parameters as if you would be really diving here & now.

The salinity setting has _no_ infuence on deco calculation results.

What is new in V2.97 versus before is the reduction of the ascent speed from 10 m/min to 1 min/m for the final ascent, i.e. between the last stop and the surface. This was done for two reasons: you simply should do it as tissue saturation really spikes on the last meter(s) of ascent and to factor in some reserves into the gas needs calculation.
Also reworked is the code that manages the gas changes during the ascent, which among some other aspects removed a rare issue with temporary wired deco predictions while in the mid of a deco phase. Furthermore, each stop requiring a gas change is now made one minute longer to factor in that a) switching may not occure "on the fly" and b) it takes about one minute for the blood to be pumped from the lungs to all the tissues i.e. for the change of the gas mixture inhaled to take effect at the tissues. So V2.97 will produce slightly different results even when all parameters are exactly set equal.

Last but not least to mention: rounding. Stops are always full minutes aka multiples of 60 seconds. If the deco calculation does not clear you for ascent to the next stop level after exactly 60 seconds, you are prompted for 120 seconds even if 61 seconds would have done it. This 59 seconds longer on the stop may cause a subsequent cut of a minute from the next stop then. And as the current surface pressure affects the deco, a few milibar can make the difference between 59 or 61 seconds, resulting in 1 or 2 minutes indicated stop time. So you have to regard deco tables that are in line by +/- 1 minute as equal. And results from deco calculations made at sea level will differ from those made at mountain lake altitude...

BR
Ralph

[ClaudeDive]

Very clear Ralph,
Many Thanks,

[Ludo]

Thank you Ralf for the very detailed description of the parameters of influence!

I still don't get why during diving I had deco stops at 12m and none at 9m.

Coming back to the simulations I compare, there are no gas changes. Deco gas are deactivated. And the 1m/min after 3m doesn't influence the deco stops length themselves.

Do not hesitate if you realize another parameter would lead to that issue.


kind regards
Ludo

[Ralph]

Hi Ludo,

true, the reduced final ascent Speed does not influence the stops - but just the indicated TTS (total time to surface).

A stop depth can get omitted (e.g. stops at 12 and 6 meters, but not at 9) in case the deco on the deeper stop -- always calculated in full minutes so maybe up to 59 seconds longer than required - desaturates the tissues by so far that an ascent by 6 meters instead of just 3 meters is possible. The clue with this is, that each next stop depth is determined by the maximum oversaturation level allowed at that depth. While ascending, the allowed oversaturation increases from stop to stop (when using GF factors and with Gf low < GF high). So at 9 meters more oversaturation is allowed than on 12 meters, but on 6 meters even more is allowed compared to the 9 meters. Thus the "over-clearing" at 12 meters plus the more allowance on 6 meters may render the stop at 9 meters not needed.

Cool, isn't it?
Ralph

[Ludo]

Besten Dank Ralph!

I'm still very puzzled with those new results. I'll have to invest time in adapting the GF to have matching runtimes on both computers.


Schönen Tag
Ludo

[heinrichsweikamp]

Hi,

Let me clarify something:

2 OSTC with the same firmware and the same settings compute the same deco plan. Everything else would be a bug and everybody with two OSTC can do this test. When we pull at batch of computers out of the test chamber here they all run in parallel and show the same TTS or decoplan.

Minimal (One displayed minute (Which can be one second internally)) differences are normal and expected. Reason is, that the real ambient pressure is taken into account as well as the actual tissue data. Fluctuations of the sensor are normal within a few mbar (1mbar equals roughly 1cm of diving).

Two OSTC with different firmware are not expected to compute the exact same deco plan. Especially the 2.97 has minor differences compared to the 2.26. The deco code has been optimised in so many parts (All changes can be accessed via Bitbucket) that some changes in the plan are normal.

Neither the 2.26 or 2.97 compute a false deco plan. There are no known bugs in the deco routine and we consider both version in the default setting of 30/85 a safe deco model. I personally dive at least 2 times/week with our computers. Differences in the plan between the 2.26 and 2.98 are absolutely insignificant in the field.

Comparisons to other brands (Except some quality brands with the ZH-L16GF model like the shearwater) are completely useless. Some brands apply so much Voodoo to their deco model that my brain hurts if I read the ads from them. Please ask the manufacturers of your comparison Suunto (As an example) Computer for details, not us (Since I can't reply in details to such mails or posts). Why are OSTC, Shearwater or Divesoft computers doing the same results while others show only half of the stops or twice as much (Sometimes randomly one or the other)? I can't tell but that shows me that the ZH-L16GF has been understood not only from us but also from others. A good sign that it's safe to say the model is working for the purpose here.

Salinity setting affects the depth reading (But not the deco plan). If you set it to 4% and dive to 100m you'll see whooping 4m of difference on the OSTC to your comparison depth gauge which is set to fresh water. This is to be expected.

Cheers,
Matthias

[swissdiving]

>:D<

[heinrichsweikamp]

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