SUUNTO Cobra Issues?

[Rick Murchison]

Took a new Cobra to the springs this weekend. First dive, it was reading 25% shallow! Never seen a computer that far off. The next seven dives it was correct!
Interestingly, one of the other instructors was diving a Viper, and it did the 25% shallow trick on one dive too. (no, it wasn't the same dive, and we didn't get our landmarks confused)
We're writing SUUNTO with our observations for possible explanations, but in the meantime I will not dive either of these computers without backup.
Rick

 

[Warhammer]

Let us know how it turns out, Rick. My Cobra has only been down 4 times and zero problems so far. I checked the depth reading against my buddies analog gauges on 3 of those dives and it was within a couple of feet of it. Maybe I should pick up an analog depth gauge to carry for awhile just in case.

 

[DameDykker]

How unlucky and scarry for you! I have 30+ dives on my Cobra - never a problem. A the reg + computer just came back from service. The depth readings are accurate within a foot according to the service report. I sure hope these problems will not re-surface.

 

[Rick Murchison]

While awaiting an answer from SUUNTO, we think the problem is that the water sensing contacts aren't picking up submersion quite right because of the purity of the fresh water (water is actually a sorry electrical conductor - it has to have impurities in it to effectively conduct electricity) we were diving in. If this is the case, ocean diving shouldn't be affected, but this line of computers (Cobra/Viper) will be unsatisfactory for Florida caving.
We'll see what they say.
Rick

 

[bio guy]

I'll be interested to hear what Suunto's response is Rick. I dive the Vyper in freshwater without any problems, but purity is another matter altogether. I'm not sure of the exact electrolyte properties of the water around here, but it isn't pure, nowhere near the purity of a cave I would imagine. In fact, after seeing how much salt was put down on the roads this winter, we'll have to see if the lakes are still freshwater after the spring shock...lol. Seriously though, let us know how you make out with Suunto.

 

[large_diver]

...Which begs the question --

How often does this happen wth ANY brand of computer?

 

[Rick Murchison]

I haven't seen this happen with any other brand. I have seen outright failures, floods, lockups etc, but never one that's intermittently way off. It is disturbing... I'd rather have one that's just plain bad. This looks like we may have a design problem. As I said, we'll see what SUUNTO thinks.
Rick

 

[Warhammer]

What would the water contacts have to do with it? It looks to me like that if it wasn't making connection then it would simply shutdown. I haven't had mine out of the console yet, so I'm not sure, but isn't it possible that something just got in the way of the depth sensor? I seem to remember reading something in the manual that said it was paramount that it remain clean and free of obstruction.

 

[tomcat]

I agree with warhammer. The purpose of the contacts is to allow the computer to sense that it is submerged in water (and perhaps prepare to automatically enter dive mode when further submerged). The depth sensor, located on the underside of the computer does the actual sensing.

What i find is that whenever depth sensors are "covered up", e.g. by the protective boot, they can get a bit off because water pressure may not be evenly distributed to it somehow (for example, trapped air bubbles?). This happens to some extent with my vyper although at greater depths (>5m), there are no problems.

Not sure what you can do about this, but I bet my booties that it has nothing to do with the contacts and conductivity of the water.

tomcat

 

[OKI_GI]

Everytime I open up this board, I'm gladder I found it. What else is out there on the Cobra?