One computer shows safety stop, one doesn't. Why?

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aeweems12

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Location
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I dive with two Suunto computers. I primarily use my D9, but I also have my Cobra 3 as a backup in case the Cobra fails. This past weekend I noticed while diving that my Cobra was showing my 3 minute safety stop countdown while my D9 was not. Why would that be?

I am pretty sure I have both computers set the same as far as deepstop, my nitrox percentage and ppO2, etc.

Here were the details of the dives:

Day 1, dive 1: nitrox 32%, dive time 41 min, max depth 61 ft, average depth ~55 ft
Day 1, dive 2: nitrox 32%, dive time 35 min, max depth 60 ft, average depth ~50 ft

Day 2, dive 1: nitrox 28%, dive time 37 min, max depth 63 ft, average depth ~55 ft
Day 2, dive 2: nitrox 32%, dive time 30 min, max depth 73 ft, average depth ~60 ft
 
Have your read your instructions? Does either one have a SS as an option? Some computers the SS is mandatory and built in. Others, you can turn the feature on or off.
 
What depth were you doing the SS at? It may be possible that one computer had a stop depth set for 20' and one for 15'. If you were doing the stop at ~20 it may be that the computer not counting down had not reached it's stop depth yet.

Mark
 
I have read the instruction manual (again) for the D9, which is the computer that is NOT showing a SS. According to the manual, if I have deepstops turned on, which I do, then the traditional SS is not used UNLESS my ascent rate exceeds 40 ft/min momentarily or 33 ft/min continuously, at which point a mandatory SS is prompted at 10-20 ft. (My Cobra is also set for deepstops.)

On all my dives I was doing my SS at 15-18 ft and the Cobra was showing a SS while the D9 was not. Can anyone from Suunto give me an idea of why?
 
Do the two computers have different safety settings on them?
 
This happened to one of my dive buddies on our last trip together. A few dives after she noticed it wasn't giving her safety stops (when it always had in the past), her computer (Suunto Vyper or Cobra) started acting squirrely and it had to be replaced. Fortunately, it was still within warranty. Can't remember what exactly Suunto determined the problem was, but it was not fixable. I guess that's not really too helpful, but I thought I'd share.
 
aeweems,

There are a few other settings that come into factor. The Cobra 3 and D9 both have an RGBM adjustment in the dive mode settings. Make sure they are both set the same. Also, both computers have an altitude and personal adjustment in the dive mode settings. Please check to see if those are all set the same and let me know.

Best Regards,
Chris from Suunto
 
Very Interesting discussion. I have noticed that my computers, both HelO2's and wrist mounted, display different depths, usually by several feet. This also happened with different Suunto computers, so I assume that there is a variation in the electronics that sense the water pressure and determine the depth. that depth variation could be affecting the safety stop calculations. Secondly, while wearing the computer on your wrist certainly makes it easy to read, arm movement can you some pretty weird readings, especially if you are oriented vertically in the water. Finally, I know Suunto uses different algorithms on different computers. Perhaps that's the case.
 
aeweems,

There are a few other settings that come into factor. The Cobra 3 and D9 both have an RGBM adjustment in the dive mode settings. Make sure they are both set the same. Also, both computers have an altitude and personal adjustment in the dive mode settings. Please check to see if those are all set the same and let me know.

Best Regards,
Chris from Suunto

I went setting by setting with one computer in one hand and the other computer in the other hand tonight. Both are set the EXACT same. While I see the point about arm movement, during my dives my arms are generally tucked under me or holding onto my camera. When it comes time to ascend, these dives were done by coming up an anchor line. I stay very aware of what arm the wrist computer is on and I don't use it to climb the line.

It still just confuses me as to the safety stop. :idk:
 
According to the manual, if I have deepstops turned on, which I do, then the traditional SS is not used UNLESS my ascent rate exceeds 40 ft/min momentarily or 33 ft/min continuously, at which point a mandatory SS is prompted at 10-20 ft.
I think you answered your question here.
You did not exceed an ascent rate of 33/40 ft/min AND had deepstops turned ON.
If you turn OFF deepstops the safety stop should reappear.
 

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