Confused: Suunto D4 Safety Stops

[danuka]

Hi All,

I did 2 dives yesterday with about 1 hour in between. These were not deep dives, i.e. 70 feet for the first dive for about 45 minutes and 60 feet for the second for about 50 minutes.

My D4 gave the warnings that can be seen in attached images at the end of second dive. And, I got confused by these and wanted to ask:

1. According to the D4 manual, if there is a safety stop recommendation or a mandatory safety stop, it should display "STOP" there, but it only displayed CEILING and ASC TIME, and there was no STOP on the display??? What does this mean?

2. It gave 8 minutes for the ascend time at around 9 feet, which seemed a lot. My wife's oceanic gave only 3 minutes, and 8 minutes is a lot more. And, we had to finish diving due to currents after 6 minutes of a safety stop (as always, she is the master and we do what she says), and D4 errored out (it is only showing ER on screen now).

What i don't understand is that even though it did not give a stop, it kept giving warnings and errored out even though these were pretty regular dives and we did not push limits in any way.


Thanks in advance.

 

[DevonDiver]

Check the level of conservatism you have set. It's quite possibly giving you less NDL than your wife's if you have a higher threshold set. Either that, or you were deeper for longer than she was on the same dive/s.

1. According to the D4 manual, if there is a safety stop recommendation or a mandatory safety stop, it should display "STOP" there, but it only displayed CEILING and ASC TIME, and there was no STOP on the display??? What does this mean?

Read the section of the manual that describes 'Deco Mode'. You were in deco.

The newer Suuntos also go into this mode if you violate the ascent speed. I'm guessing they'll penalise you with stops appropriate for the severity of that violation, but I've only seen them give 3 minutes. Overstaying NDL is most likely, given what you describe. The CBT graph (left side) seems to substantiate that assumption.

2. It gave 8 minutes for the ascend time at around 9 feet, which seemed a lot.

Because, in Deco Mode, the ascent time includes a mandatory stop. It is the total time to surface - accounting for safe ascent speed and deco stop. The 'Ceiling' is the minimum depth that you cannot ascend above, until permitted. In this case it was 3.5m. If you ascended above that depth, before the deco was finished, your computer would lock-down after the dive.

My wife's oceanic gave only 3 minutes, and 8 minutes is a lot more.

You were in deco, she wasn't.

... D4 errored out (it is only showing ER on screen now).

Computer enters 'error mode' if the required deco is not completed. It will lock out for a prescribed period of time (24-48hrs).

 

[Hatul]

As DevonDiver stated you went into deco. The ceiling of 3m means do not ascend above this deco stop. The ascent time is the deco stop time + ascent time + safety stop of 3 mins. It's also showing your ascent was too fast. It should be all in the manual.

Adam

 

[FinnMom]

If you set the deep stops on a Vytec DS it disables the recommended safety stops option.
I suspect the D4 is the same in this respect.

Picture 1 says you should spend 8 seconds rising from where you were just then to above 3m. It also tells you you should not rise above 3m until told OK. Photo 2 shows you at 3.3 m and the computer saying you should stay below the ceiling and above the floor for 3 more minutes. The Suunto recalculates your decompression needs constantly based on how long your are down, at what depth and (this last one is news to a lot people) how fast you ascended. You apparently came up faster than your computer would have liked. With a different computer brand, ascending faster than recommended and spending time even 4-6m below your buddy during this 45 min dive, getting some significantly different stop times is not surprising.
If you rise above the ceiling more than 3 min or more before the Suunto says OK, it will go into ERROR for 24 hours because you should not dive for 24 hours.
All of this is in the manual. Read it a few times over so it percolates in and saturates the memory cells. You want to be able to remember even when your thinking is a little fuzzy.

 

[ElChe]

The difference between Oceanic's DSAT and Suunto's RGBM algorhythm is well known: the Suunto is much more conservative, you'll experience your wife have more no deco time. (And you dive safer, certainly, but some people says Suunto is too conservative.) In this case I recommend to dive together following the more conservative computer's rules.

 

[DiveNav]

your D4 was in deco ....

I suggest you read the manual and take the D4 online class too to see the D4 in action during a deco situation.

Also you can use our simulators to create deco scenarios and see how the D4 responds to them.

http://www.scubaboard.com/forums/images/attach/jpg.gif​

Alberto (aka eDiver)

 

[DevonDiver]

I suggest you read the manual and take the D4 online class too to see the D4 in action during a deco situation.

+1 Further education would be beneficial. I've seen a few divers omit deco because they've not understood what their computer was telling them in that situation. It's a major over-sight (and something that should be addressed in dive training, now that the agencies are getting more computer-focused).

Also: Download the dive onto your Suunto Dive Manager software. That will allow you to 're-play' the dive and study your nitrogen loading in comparison with your computer display. Some screenshots from that (especially from the moment when the display indicated 'ceiling') will allow a definite diagnosis.

 

[Hatul]

In an ironic twist, what saved you from getting bent was the large safety margin of the Suunto. If you violate the more liberal Oceanic DSAT you more likely would get bent.

 

[DiveNav]

.....something that should be addressed in dive training, now that the agencies are getting more computer-focused.....

indeed.
In fact, two major agencies (PADI and SSI) are already providing Specialty Courses for model-specific dive computers: they include online theory (our classes) and an open water dive with a qualified instructor.

 

[ElChe]

I know a not major local agency who teach computer diving for 10 years during the OW course because majority of the divers use them instead of tables. So they have to know tables AND computers too even if they are only beginners. This agency don't ask money for an extra course...