Max Depth

[Stephen McMullan]

Hi,

I see from the manual that the OSTC MK2 device is rated to a max depth of 120m. What is this based on? Is it the limit to which the device has been tested due to available methods of testing or has the device failed at pressures exceeding 13bar in test or during dives?

I've dived the MK2 to 125m with a 20min bottom time without issues but only on one occasion. Has anyone else brought the device deeper than 120m? I'm the only diver in my group that has the MK2 but there is a lot of interest from my buddies. They are asking about the max depth compared to other devices however.

Thanks for any info.

Regards, Stephen

[heinrichsweikamp]

Hello Stephan,

The OSTC Mk.2 uses a pressure sensor for about 130m maximum. Depth readings beyond 130m are interpreted as a defective sensor and the OSTC shuts down. So you have some safety margin but the OSTC is not intend to be used for depth below 120m, sorry.

regards,
Matthias

[Stephen McMullan]

Thanks for the quick and clear response Matthias.

Its not a problem for 99% of my dives and I still love the device.

Keep up the good work.

Stephen

[Solodiver]

Hm, interessting news. I'm quite sure I asked this before and was told, that "just" the deco algorithm is designed/limited to 120m but is calculating even deeper dives on a "inofficial" calculation.

What happens if one is going deeper than 130m, the OSTC shuts down and is going up again? Is it switching on again? What about the decoplan? Is it reseted?

Is there a warning before switching of so one can stop going deeper (f.i. if one depends on the decoplan)?

[Solodiver]

May I push up my questions from the last post?

Stephen, do you have any practical experience concerning this topic now?

[peppe.marsala]

As I know, if the Mk2 detects a depth below 130 mtrs it shuts down and a hard reset (with magnet) is required to restart it. Matthias can definitely provide the correct answer.

[smcmullan]

Hi solodiver,

No, no more deep dives until July-Sept. I do all my diving in Ireland so have to wait for the weather and water temperature. The dive to 125m was HMS Curacoa which is almost 80km offshore - we needed a sat-phone for emergency cover. To be honest there are not that many wrecks deeper than that which are accessible by day-boat charter. So the 130m limit of the device doesn't really concern me. If I get an opportunity to dive deeper then I might leave the OSTC at home for that particular dive and just take a slate.

I'm more interested in whether the dive planner on OSTC is giving me good information in the 60-99m range I still have my doubts

Regards, Stephen

[dmainou]

Hi mate,

I presume that the algorithm will be pretty much the same as the one on the DR5. (since there is no indication that they have modified it for very deep diving).To confirm this it may be best if you send a pm to Matthias or Jean Do. Or you could even download a copy of both the DR5 and the MK2 algorithms. The deco routine is written in C so even without programming skills you can see where they are coming from.

I think that part of your answer will be in the sensor. Rather than me giving you the wrong info please take a look in here:

http://www.intersema.ch/index.php?optio ... format=raw

The sensor is rated to a maximum of 14 bar so, I believe, it should be more than fine for the range of diving you seek.

D


PS. I don't think that the sensor will explode shortly after 1.4ATA has been reached its just that it will become quite inaccurate and it may stop working at some point in time. However just like HW has said 120m max depth when the sensor could give 130 I'm "sure" that intersema designed it for more than 1.4 ATA but its only comfortable publishing 1.4. Thus why it still worked in the dive you just did.

[dmainou]

BTW, If you read the manual of the DR5 it states that it could go down to 350-500 meters but that the ZHL model is only good to 220.

Also the intersema document shows a maximum overpressure of 30 Bar. So it won't explode it will just become highly inaccurate (thus why the DR5 has two sensors one for the shallow and one for the deep)

It's not a straight answer but pieces to the puzzle.

D

ps may I also suggest that the glass on the screen may have a certain rating and therefore why the one used in the DR5 is thicker.

[Solodiver]

Thx for all the replies, but the question is still not answered. Matthias states "[...] and the OSTC shuts down".

Will there be a warning before?
What happens when ascending above -130m? Will it switch on again? Is there any decoplan left? Or will the unit break completely?

I do not feel so comfortable if I know that my backup unit is going to switch off and I've to rely on this shearwater thing only...

Thx,
Jan

[peppe.marsala]

Solodiver,

why don't you try to plug the Mk2 to your pc, run a simulation within Jdivelog, push it below 130 mtr. and see what happen? Nevertheless, IMO the Mk2 is intended (and sold) to dive up to 130 mtrs, so if your dives are below that depth I belive this is not the right tool to use. It was widly discussed in the forum that the pressure sensor works up to that.

Just my 2 cents.

[dmainou]

Disclaimer *** I am no programmer, so take what I will write below with a pinch of salt. This is NO advice explicit or implied.***

Out of curiosity I have read, to the best of my capabilities, the current OSTC code.

Although it doesn't mean its not there, I was unable to find a single line of code that says if pressure is higher than ABC then XYZ (such as exit). So I couldn't find evidence that it will shut down. (again it doesn't mean it's not there just that I couldn't find it)

However, I did find a number of lines to adjust the pressure reading when it is over 100m. I presume to cater for a the known reading error at extreme depths.

I also found that there is a limit for where the deepest stop must take place (93m)

So, if you are interested in pushing the limit you may wish to call intersema and find out what happens after 14 bar. If the sensor itself sends an error message to the ostc rather than continuing to provide an innacurate reading then it is quite possible that the deco calc will stop at the worst possible time.

The further q is if the deco calc will be worth anything at all if given that the sensor will be providing inaccurate data to the decompression engine?

Another possible problem arising is that once you surpass certain depth, certain gradient factors could call for a deeper stop than the 93m maximum set on the code which could lead to an error and then exit.

Truth is, that the sensor is not rated past that depth, there is no public specification for the glass and I don't believe that any of the programmers are fool enough to comment on a public forum. It would simply be legal suicide.

So, in my opinion, if you need something capable of depths greater than 130m then for the sake of your safety buy a DR5 or similarly capable computer.

D

[JeanDo]

Such a code do exists. Overpressure is fatal error 3: search source for fatal_error_code

[dmainou]

JeanDo Wrote:
-------------------------------------------------------
> Such a code do exists. Overpressure is fatal error
> 3: search source for fatal_error_code


Jean Do,

Thanks for your input.

I think that that sums it up.... if you go over 14 bar then error code #3 then exit and you loose your bacup pc at the worst possible time.

D