Cobra Water Temp's Not Right

[Pete1961]

I've been noticing that the Dive manager and possibly the Cobra is not saving my temp. at max. depth. Whenever I upload to Dive manager the surface temp and temp at max depth. are always the same. Today surface was 57 and bottom was 44. Both temp's in dive manager were 57. Also air temp is always way off. Anyone else have this problem ? What's the scoop ?

 

[RichLockyer]

Same thing with my Vyper.

 

[ShoalDiverSA]

I have checked my SDM now and my Cobra is registering different air, bottom and water temperatures on the dives, though they differ by 7 degrees Celcius at most.

I have noticed that the temperature displayed during the dive is about 2 or 3 degrees higher than the actual temperature. I have not taken down an independent thermometer, but I have compared the readings to other instruments in the group, and I know what a 17 degrees dive feels like (not 20 like the Cobra says)!

Cheers,

Andrew

 

[RichLockyer]

Mine is showing three different numbers... air temp, max depth, and "end of dive", however, the temp does not change on the display on the graph as I scroll through the dive.

WHAT it is recording as max depth temp, I don't know. It's hard looking through the profiles, but most of my deeper dives involve at least one thermocline, and the max depth temp appears to match the coldest, but air temp is WAY off.

Ya... most readings do tend to be about 2 degrees high. A lot of the locals joke about "Suunto Degrees" as if they have their own version of the metric system.

 

[ShoalDiverSA]

SDM does not appear to save temperature profile information for the dive.

The temperature information in the exported files only appears as single entries in columns W, X and Y in MyDive.csv. There is no temperature information in MyDive$PRO.csv. So it would appear that the computer only stores the temperature upon entering dive mode, the temperature at max depth is updated as the max.depth increases and it stores the temperature at exiting dive mode. This makes logical sense, but will result in dodgy readings if you want actual air temperatures. You will most likely be in the water when the computer enters and exits dive mode, so the readings will be incorrect as "air" temperatures.

This is my take on it anyway...

Cheers,

Andrew

 

[jamiei]

On a dive to 75' at which the bottom temp was 50 F, my cobra saved a max depth temp of about 66F and the end of dive temp was around 72 F. I know the max depth temp was 50 F because I read it several times at depth on the display and the water was definately in the lower 50's... not mid 60's. My sample rate is also set at 10 seconds. Who knows what's going on... it works perfectly other than that. We went through two thermoclines on that dive. The temp below 30' was below 66 F.