Trouble with SDA after flying

[CRITIDOC]

Actually the vacuum is enough to bring the unit to the surface. After about 12-15 cycles, I manages to clear the deco requirement and desat the unit. Un fortunately, it still resets to a pressure offset when recharged. This time the pressure offset has reduced to 15 feet. When I tried with just air in the canister it made no difference. I also used vacuum bags but when enough vacuum is created to bring the unit to surface pressure, I am unable to slide the control switches without puncturing the bag. Will need a high mountain to try the reset procedure mentioned in this thread.

 

[T-Fish]

I just encountered the same problem. 67 happy dives with my SDA, and lots of air travel, both long and short distance. My last two dives were in the Mediterranean. The computer ended the dives just fine, entering surface mode, allowing me to log details about the dives, etc. After the return flight, the computer is now stuck at 2.5m of depth. I experimented with letting the battery run out and with vacuum bags, like lots of people on here. I found that the former compounds the problem: the computer locks up even more (when you finally get it to surface mode) because it has now logged incomplete dives and wants to clear the maverick diver of all possible issues. Eventually, I rigged up a vacuum cleaner with a small hose that fits snug into the pressure sensor opening (the round hole on the back with the metal cross inside). This allows me to surface the SDA (but doesn't let me bring it to all-green condition yet, as I can't let the vacuum cleaner run for 26+ hours). The hose has a slider on it that lets me open and close an air gap, thereby controlling the amount of vacuum the SDA is exposed to, and therefore the ambient pressure it thinks it's in.The vacuum cleaner gets the air pressure to about 800 hPa (down from slightly less than 1000 where I live). This lets the SDA exit dive mode. It stays in surface mode as long as the pressure doesn't exceed 831 hPa. When it gets to 832, the unit briefly displays "732" (!) and then enters dive mode at 1 m depth. This leads me to believe the following: the SDA doesn't enter dive mode based on some fixed pressure threshold. Instead, two things need to happen: First, a pressure change of 100 hPa (the difference between 832 and 732) has to occur, which is consistent with jumping to 1 m of depth in dive mode. When this happens, the unit takes the last value before the pressure change as the surface air pressure (in my case 732). This approach would allow for automatic consideration of different diving altitudes, as it doesn't use a fixed assumption of air pressure at sea level of 1013 hPa (roughly 1 bar). Second, this pressure change has to happen in a certain (short) amount of time, so that it doesn't get confused with a regular change in altitude while driving or flying. And that's where the problem is - for whatever reason, several flights did not cause an issue, but the last one did. Maybe the cabin pressure increased more quickly than normal, enough to trigger dive mode. Now, my SDA believes the correct surface pressure is a ridiculously low 732 hPa, and it wants to sit in that environment to finish its decompression. Even when I surface it artificially with my vacuum, it won't let me run a firmware update (to hopefully reset it all), because it's still decompressing. And I can't keep the vacuum running for that long ...I do believe the solution is to get the SDA to its imaginary surface pressure and to then gradually increase ambient pressure until back to normal. If this can be done at a slow enough rate, the computer should think it's just coming down from a high mountain, without triggering dive mode. I could try to go up a mountain to do that (as has been suggested), but my back-of-the-envelope calculation suggests that I would have to get above 2000 m from the 400 m where I live. And I'd have to stay there a while... (if I don't want to "change owner" and lose all my log entries, which don't exist online anymore thanks to Uemis' bankruptcy). Or maybe I should just take it on another flight?Any suggestions regarding how long the SDA might need to stay at it's imaginary surface pressure and how fast or slow the rate of approaching normal can be?Sorry for the long post, but I thought it might be helpful. And maybe I can get my questions answered too.Thanks!T.

 

[ijdod]

Would it be somehow feasible to rig some sort of (household)container to keep it in under lower pressure? My parents used to have these plastic bags you could pull vacuum, and then heat-seal. I know of at least some containers that should hold a mild underpressure like that; although the hard part would be to get the device in, and potentially operate it too. Perhaps your local highschool might have some vacuum items you could use over the weekend.

 

[Scubacastor]

It sounds like the problem is linked more to some programming decision that fails in a given situation (like rapid pressure increase) rather than a sensor failure. An airplane cabin is pressurized at around 750-800 hpa which is pretty much the pressure for which the SDA switches back to diving.

The cure is problably to do some vaccum to go back
- to the surface at 750-800 hpa
- wait for the desat to be complete or force a firmware update to clear deco (maybe the reset will reset the sensor)
- As long as the desat is done, the unit might consider diving again if ambiant pressure increases
- slowly increase the ambiant pressure to 1013.

As for the vacum container, I built a pressure pot from water filter cardrigde holder. The SDA won't fit into mine. Another thing is to get an old ikelite housing and adapt some plumbing to it to remove the air. You may use a big seringe or something like that: Chapter 6: Aerodynamics: Homemade vacuum pump and water pump

 

[T-Fish]

Would it be somehow feasible to rig some sort of (household)container to keep it in under lower pressure? My parents used to have these plastic bags you could pull vacuum, and then heat-seal. I know of at least some containers that should hold a mild underpressure like that; although the hard part would be to get the device in, and potentially operate it too. Perhaps your local highschool might have some vacuum items you could use over the weekend.

Been experimenting with that. I'm still shying away from buying one of those food vacuum packaging devices, so I'm toying around with food storage boxes, bicycle valves and vacuum cleaners. It works in principle, but I can get enough suction - I get the SDA to 1m of depth, but not higher. :-( it only takes a little more ... Trying to think of another way to get that extra vacuum power.

Btw, I took my SDA on a flight with me today. I learned that cabins get pressurized to different degrees depending on floght duration (or rather altitude). The SDA went from 2.5m to 1.5m - just not enough. If I can't figure out this vacuum container thing, I may have to wait for my next long-haul flight. Or I do go a high mountain and put it in a box up there ...

However, in addition to getting enough vacuum in the first place, the key challenge will be to then be able to reduce that vacuum gradually in very small steps. That's why I was thinking bicycle valve (mounted backwards).

 

[T-Fish]

I FIXED MINE!

Simple process without vacuum chambers and mountains: Attach a piece of hose to the pressure sensor opening (round hole on the back). I found that the piping for Gardena's Micro Drip system works well, although it's a bit stiff. Remove the sensor guard (cross-shaped metal piece) first by rotating it 1/8th of a turn and then shaking it out. This allows the hose to be pushed in further and sit more tightly. Seal the area around the hose with a bit of silicone and let cure. The silicone can fairly easily be removed again later. Then simply apply suction to the hose with your mouth, and when the unit has surfaced, close the hose tightly with a strong (but light) clamp. Don't suck too hard - this will only further raise the altitude the SDA thinks it's at. Fill the end of the hose with a bit of silicone to keep the vacuum inside. Allow the SDA to sit and fully desaturate, until all-green on the home screen. Keep it connected to power, to be sure. When all clear, run a firmware update. While the firmware is being INSTALLED (lower progress bar on the screen), remove the silicone and the clamp from the end of the hose to expose the unit to full ambient pressure. Keep the hose in place for now, in case you have to start over again. The firmware being in an update process prevents the unit from reacting to the sudden pressure change. When the SDA re-boots, it comes back normal and fully happy with the actual ambient pressure. Voilá!

Now, if someone could tell me how to get my SDA to sync with the website again after my data has been removed from the server... I don't want to do "change of owner" as this will erase the data on my SDA, and there's no more backup. My old login data don't work anymore - the site seems to remember that there once was a profile by that name. I created a new account, but it doesn't have my SDA associated with it. But my SDA knows it's been registered already, so it doesn't give me the option of doing it again, so I can't get it linked a to a new account. Any ideas?

 

[Scubacastor]

Thanks for sharing the info T-Fish

Regarding the SDA sync,
- unless you ask your data to be removed, they should be there.
- the only way is to write to uemis (they have a new email address) and ask them to delete completely your former account including your profile... and then create the same one than the one into your dive computer.

For both ways, write to the UEMIS people as your problem is beyond what you can do with their online system. Someone has to manually change things in the database...

 

[b3v]

Thank you from me too, t-fish and the rest of you. It also happened to me after a flight to Malta (what is it with Malta, there was another guy having this problem flying from UK to Malta). Had to use my considerably less fancy but also more reliable suunto backup dive computer. After the flight home the problem doubled, from 2.5 m to 5 m.
I have prepared a piece of plastic tube to the sensor hole and I will follow the procedure described by t-fish. So glad it can be saved, I was ready to ditch it, thinking the sensor had failed. My Zurich SDA and its bright display has always been the focus of much appreciation from fellow divers and I was so happy with it, apart from this embarassing software bug. We do fly a lot as divers, so it really is something that should'nt ever happen. I will report back as I attempt the procedure.

 

[Pyromancer]

I was the guy who had this problem when going to Malta - But having taken my SDA on a few dives it cleared itself - it was only on a 1.1m false dive, so almost at the surface.

I think it was a budget airline problem - too faster increase in pressure when approcahing landing that caused it.

Had the same problem coming back from Egypt a month or so back.

Built myself a pressure chamber to try and cure the 1.8 metre dive my SDA was on.

Made the mistake on putting my SDA under vacumme and then it stuck on a 6.3m dive!

I'm currently trying T-Fish's solution, it's working so far - I've managed to sync my SDA to the website and download all my dives - now going to try and download them into the beta release of the stand alone SDALog I'm testing for Fabien.

I'll report back on the success or failure of my re-setting attempts.

---------- Post added ----------

Just finished re-setting my SDA using T-Fish's procedure.

IT'S ALIVE !!!!

Very happy now that my SDA is usable again - thanks T-Fish.

One thing I would add to the procedure though - delete all the bogus dives from your SDA before syncing with MyUEMIS

All those 720 minute shallow dives take an age to upload, then you have to go through and delete them from your MyUEMIS log - easier to delete them on the SDA first.

Thanks again T-Fish.

Off to try and re-inset that little brass cross!

 

[b3v]

And I fixed mine!!! So happy, thank you all and especially T-fish. I did it with a variation of the T-fish procedure.

I was the guy who had this problem when going to Malta - But having taken my SDA on a few dives it cleared itself - it was only on a 1.1m false dive, so almost at the surface.

I think it was a budget airline problem - too faster increase in pressure when approcahing landing that caused it.

Older planes fly with lower pressure but it is OK as long as the increase is not too fast. I will certainly use an airtight box next time.

But really, such a bug is intolerable in a high end product. We should decompile the software and fix the bug, without or preferably with the revived company. If anything should be done differently this time with uemis, it should be to embrace help from the users and opening of the software or they will just bite the dust once again.


t-fish procedure with o-ring seal, plastic pipe glued to sensor hole, sustaining negative pressure for days until it desaturates.