Cochran Commander depths???

[coop1]

I know this isn't the equipment forum but deep and caves are where I'm using it... I've got a generation II commander 2 gas option that is reading about 3-5' shallower than my my Vytec. The vytec is new but reads the same as my other computers (except the commander) as well as my buddy's computer. Anyone experienced this problem before? I'm not getting much off the Cochran website so a contact there would be appreciated. I know 3-5' doesn't sound like much but it could mean the difference in a 30 minute stop and a 45 minute stop. Any help would be appreciated. Thanks

coop

 

[teknitroxdiver]

Is the Cochran calibrated for fresh and the Vytec for salt water?

 

[coop1]

Is the Cochran calibrated for fresh and the Vytec for salt water?

This was my first guess also. According to Cochran, the unit is self calibrating for salt or freshwater. It has to do with the conductivity between the contacts. It has no menu for manually setting the unit to salt/fresh either. I don't think this should be the problem. Obviously I'm not diving with the unit as a primary or back-up now but I've carried it along to see what the difference is a few times now...

 

[padiscubapro]

I know this isn't the equipment forum but deep and caves are where I'm using it... I've got a generation II commander 2 gas option that is reading about 3-5' shallower than my my Vytec. The vytec is new but reads the same as my other computers (except the commander) as well as my buddy's computer. Anyone experienced this problem before? I'm not getting much off the Cochran website so a contact there would be appreciated. I know 3-5' doesn't sound like much but it could mean the difference in a 30 minute stop and a 45 minute stop. Any help would be appreciated. Thanks

coop

from experience the cochran is usually the most accurate depth guage out there.. the automatic adjustment based on "salinity" will make things vary a bit.... if its 3-4 feet at 100fsw, and you are in salt water it makes sense... a fresh water calibrated computer would read about that deeper than one that knows set for salt water..

The depth REALLY isnt a big issue as long as you follow the plan for the computer you are using.. depth is a pressure reading not a linear distance and as long as its calculated based on its scale all should be fine..

Just because 3 computers read different nubers say 100, 104 and 106, doesnt mean they are giving different answers.. it all depends on what scale they are using internallly and as long as they base their calculations on it all is fine...

for example the european norm defines the pressure units based on a specific salinity of waterso that 10m of water = 1.0bar, while the us navy uses a totally different salininty so that 1atm=33.066fsw, while another US standard uses 1atm=33.000 fsw.. and the depth is a measure of pressure which depends on the specific gravity..

 

[Bwanar]

You didn't say weather you were diving salt or fresh or both? Most computers are calibrated for salt water. Until recently, it was my understanding that the Cochran's were the only computer that self tested and could tell the differance between salt and fresh. I have 2 and have always found them to be very accurate. I am not sure about the Vytec though. Does it have a manual adjustment? I just got a new VR3 and will be diving it in the next few days (weather providing). I'll let you know how the Cochrans stacks up and the new king of the hill.

I know this isn't the equipment forum but deep and caves are where I'm using it... I've got a generation II commander 2 gas option that is reading about 3-5' shallower than my my Vytec. The vytec is new but reads the same as my other computers (except the commander) as well as my buddy's computer. Anyone experienced this problem before? I'm not getting much off the Cochran website so a contact there would be appreciated. I know 3-5' doesn't sound like much but it could mean the difference in a 30 minute stop and a 45 minute stop. Any help would be appreciated. Thanks

coop

 

[Aquanaut4ata]

The Cochran doesn't have a "calibration" per say to set for salt or fresh. Most computers just simply read in FSW. The Cochran reads the appropriate depth for whatever water it's in by detecting salinity. Computers aren't actually sensing depth. They sense ATA, and convert it to feet or meters.