Dive Computer Not Calling for a Safety Stop

[BabyLitigator]

I have a Cosmiq Deepblu, and I've had several recent dives where it did not call for a safety stop. Trying to figure out if there is something wrong, as my next dives are for Deep certification. Will discuss with the shop as well.

This weekend I had two dives, first was a 47 foot max, but an average depth of 21 feet (the second two thirds of the dive was very shallow). Second dive was 54 foot max, average depth of 34 feet, also shallower toward the end (25 minutes because buddy ran out of air quickly), where when we stopped for a safety stop his computer was calling for a stop but mine was not (it looks like we were between 20 and 30 feet the 10 minutes before).

Immediately previously were rescue (all extremely shallow, showed as something like 10 dives under 20 feet), and a 43 minute dive with a max depth of 27 feet and and average depth of 15 feet. All dives prior to that (all averaging deeper and/or longer) called for safety stops.

It could be quirks of the algorithm (the manual says stop if more than 9m and 10 min), and the first dive didn't qualify, and the most recent two would have involved at least 10 minutes shallower than 9m before we started to surface.

Thanks

 

[lairdb]

1. You are in control of the dive, not the computer. If you determine that a stop is advisable, then make a stop.

2. Based on experiences with other computers — not yours — it is fairly common for dives that end with an extended shallow period to be interpreted as having performed the safety stop. If you dive within NDL for X minutes, then ascend and dive at 17ft for 10min, what’s the point in spending an additional 3 minutes? Is it possible the “safety stop” indicator appeared, progressed, and completed without you noticing it?

 

[boulderjohn]

This weekend I had two dives, first was a 47 foot max, but an average depth of 21 feet (the second two thirds of the dive was very shallow).

You did a safety stop. The computer knew it. It will not call for a safety stop if you have already done one. You do not have to be physically stopped to do a safety stop--you just have to be at the appropriate depth.

 

[Belzelbub]

Yeah, I agree. It probably counted time above the safety stop depth as your safety stop. Unless you happened to be looking at your computer during that time, you may not realize that it's doing a safety stop. Depending on your computer, of course. Some will alert (vibrate) when a safety stop is initiated.

With an older computer, I've also seen it where it triggered the safety stop at the first ascent. I'd forgotten something I needed on the boat, so returned to the surface. When I returned and completed the dive, it did not trigger another safety stop. My current computers will, though. As long as my remaining dive would trigger a safety stop based on depth and time, it will start the countdown again.

 

[ofg-1]

1. You are in control of the dive, not the computer.

I, for one, welcome our new computer overlords!

 

[Gandalf-the-Diver]

If at some point on your 1st dive, you hit 20', your computer would prob start a safety stop. You can usually go a little deeper before your computer comes out of SS. But once you go above that depth, the SS countdown will resume. You prob finished your SS obligations, without you having to actually do one; as you swam to exit. Same thing might've happened on 2nd dive. My Shearwater, goes into SS mode when I hit 20', and will go out of SS countdown, if I go below 27', but comes right back on, once I come back up.

 

[dmaziuk]

Seriously though, what @Gandalf-the-Diver said.

My computer will start SS count-down when I hit ~6 msw and will keep counting as long a I stay between ~6.5 and 1.5 msw. Between 7 and 10-ish msw it will suspend the count but not reset it, i.e. it will resume once I come up above 7 msw.

On our typical reef shore dive I usually don't even notice the SS icon. It probably comes on, and disappears long before I'm ready to get out of the water.

 

[BabyLitigator]

Thanks all. Mostly worried about there being something wrong. Been doing a lot of very shallow dives the past few months (shallow locations, Rescue), but doing Deep in less than two weeks and want to make sure my equipment is not malfunctioning. My DM will almost certainly be diving a Perdix so I suspect my computer will scream NDL first.

 

[tursiops]

My DM will almost certainly be diving a Perdix so I suspect my computer will scream NDL first.

Depends on how the two of you have your conservatism set on your computers.

 

[lairdb]

Depends on how the two of you have your conservatism set on your computers.

On which,

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Also, for @dmaziuk