Trouble with SDA after flying

[Pyromancer]

I had the same problem after a flight from UK to Malta, but my SDA read a constant depth of 1.1 metres and unable to access any other functions.

Tried running the battery down and re-booting, but that didn't work.

Washed the depth sensor a lot (constant running water for several hours) didn't appear to correct the problem, but might have helped.

Took it on some Tec dives to 'exercise' the sensor (I used another dive computer and tables - didn't rely on the SDA), after the third dive it started working - showing a 0.9 metre deeper reading than the other computer - As this was less than 1 metre it meant that the SDA zeroed on surfacing and the other functions were once again accessible.

On the fourth dive this dropped to 0.3 metre deeper than the other computer.

Fifth dive saw the SDA agreeing with the other computer plus or minus 0.1 metre.

It now seems to be working just fine.

 

[Scubacastor]

I wonder if this problem comes from the sensor or from a bug in the firmware.

If it's not a sensor related problem, while flying the SDA might activate and start to believe to be somewhere in altitude. And then when the plane goes back to ground pressure, the SDA on some occasion switches to dive mode as pressure is higher than what it was during flight in the cabin.

So the question might then be : how to reset that activation.

And I also wonder if traveling with the computer in an airtight box is not the best solution to avoid this problem.

 

[Pyromancer]

An airtight box may well be the best solution, however anyone trying this will need to make sure that the box is airtight and that there is a vacumme release on the box (the screw with an 'o' ring on a pelli case).

I speak from experience, as I had my camera in a cheap pelli copy without vacumme release - it was not completly air tight, so it lost pressure on a flight. Once back on the ground the increased external pressure forced the box shut making the seal tight.

Couldn't get the box open for two days - ended up drilling a hole in it and later inserted a brass fitting in the hole to create a vacumme release screw!

 

[Scubacastor]

Well, after I had noticed the atmospheric pressure was unrealistically high after a dive (after the SDA had been rinced "properly"), I decided to take my computer for a long bath in fresh water. The unit lost something like 25 hpa before and after the bath. So I guess I will simply leave my unit in some fresh water for some time after each dive.

My point here is to show that a way to prevent self-activation is to have the computer rest in fresh water to remove any deposit on the sensor. I am right now in the mediterranean sea which is a sea with higher salinity and I am pretty sure some salt was on the sensor despite the regular cleaning.

I would be nice to see the pre-post dive log of the dive prior the computer self activated to see if the problem is not related to sensor cleaning.

 

[CRITIDOC]

Anyone know if there is a master reset procedure for the SDA? ie which switch sequence would reset it?
Still looking for a vacuum chamber to desat and surface my unit to see if it will work, still stuck at 28 feet with a 20 foot deco stop for 432 minutes (down from 434).
Depth changes with pressure just is plus 28 feet.

 

[iztok]

Try those vacuum bags for packing clothes or food storage vacuum container?

Sent from my MB860 using Tapatalk

 

[CRITIDOC]

Did that, now I get a reading that there is 480 minutes of deco needed at 10 feet. Ran a few cycles of charging, vacuum battery goes dead and recharging, still get 28 feet when it comes back to life and 10 feet for 480 minutes deco stop.

 

[iztok]

Did you soak it in fresh water?

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[CRITIDOC]

Yes it was soaked in freshwater. With the vacuum cycles have managed to get the depth down to 24 feet, it seems to be dropping about 1 foot per cycle ( charge it , place it under fresh water in a vacuum canister, slowly increase the vacuum so the units reads 10 feet ,it shows 480 minutes of deco needed at 10 feet and this has not changed) allow it to deplete under pressure, when recharged it is 1 foot less in starting pressure, it started doing this a few days ago.

 

[iztok]

You put it in the water in the canister then vacuum air out? This will not do much of a pressure decrease in water I would think.