surface interval countdown question

mason · Feb 4, 2006

I searched, and didn't adequately get the answers I was looking for.

I don't have a computer yet, but I was reading the manual on a buddy's Cyber Aqualand NX yesterday, as I'm considering buying it. It states there's a no-fly countdown, but it appears the SI isn't a countdown, but just a timer. I've never used a computer, and don't know much, but another buddy has a Cochran and he said his does a countdown. I've only used tables, and would really like the countdown feature. Which ones countdown and which ones don't?

--Eddie

Rick Murchison · Feb 4, 2006

mason:
I searched, and didn't adequately get the answers I was looking for.

I don't have a computer yet, but I was reading the manual on a buddy's Cyber Aqualand NX yesterday, as I'm considering buying it. It states there's a no-fly countdown, but it appears the SI isn't a countdown, but just a timer. I've never used a computer, and don't know much, but another buddy has a Cochran and he said his does a countdown. I've only used tables, and would really like the countdown feature. Which ones countdown and which ones don't?
--Eddie

Count down to what?
In the case of a time-to-fly the computer (depending on the computer) has a simple countdown to a set time after diving - typically 24 hours - or it calculates a time-to-fly based on a cabin altitude of 8000'.
What would you be counting down to during a SI? The computer is keeping track of how long you can stay down at any given depth, which you can scroll through with the planning mode. Unless you want to set some specific dive parameter (I want to go to 70 feet and stay for 25 minutes) then the computer has no way of knowing what to give you a countdown for.
Or am I missing your question entirely?
Rick

mattroz · Feb 4, 2006

ditto

Rick Inman · Feb 4, 2006

Actually, some computers countdown to (supposed) zero saturation. I own (don't use anymore) one that does that. You get one screen timing up the surface interval, one screen counting down the no-fly, and one screen counting down to zero-sat. It's just counting down to "A".

A totally worthless function if you ask me.

docmojo · Feb 4, 2006

Computers are great but they don't replace your tables and safe diving. I agree with Rick on this one..

cinder4320 · Feb 4, 2006

The only countdown mine does is a three minute safety stop countdown. When i hit 18ft-13ft my computer will begin the 3min countdown.

Surface interval is a simple timer. As the timer goes up your N2 saturation goes down. Since you don't wait until your back to an "A" group before getting in the water a countdown doesn't make sense. Mine is all on one screen, surface interval timer, N2 saturation.

alcina · Feb 4, 2006

Yup, as above...

As you haven't used a computer before, maybe think about the Surface Interval timer as showing you the same thing as the surface interval table that you are used to using. As you scroll on the computer through how long you get at each depth it is showing you the same thing....as you increase SI time, you simply move to the next box on the table. The computer does this continually and you simply hit the Dive Plan function on it to see how more time on the surface will impact your dive time.

Some computers also have an interval setting. So if you know you are going to spend another 30 minutes on the surface, you plug that in and then run Dive Plan - that will show you how long you get at your chosen depth for the next dive. You can run this repeatedly if you are unsure of how much SI you need (though your tables should be with you, too!)

Have fun!

mason · Feb 4, 2006

O.K., maybe it wasn't clear, but maybe that's why I am also confused. Using just tables, anyone can figure down to a zero sat, and get you back to an "A", or any other group to figure on repetitive diving with nitrogen residual. My buddy's Cochran has a countdown to show SI with nitrogen residual and without, so you know how long until you're at an "A". Maybe it's exclusive to Cochran, I don't know. I really don't think it's a worthless thing to know. So either every other manufacturer thinks it's a worthless thing to know, or Cochran thinks it's worthwile. Whatever. Thanks.

--Eddie

mason · Feb 4, 2006

On an ocean dive, one divemaster had an Atom, another had a console (think it was a Wisdom), and some of the clients had ones i wasn't familiar with. The lead divemaster used my buddy's Cochran to time our SI.

--Eddie

Walter · Feb 4, 2006

mason:
I searched, and didn't adequately get the answers I was looking for.

I don't have a computer yet, but I was reading the manual on a buddy's Cyber Aqualand NX yesterday, as I'm considering buying it. It states there's a no-fly countdown, but it appears the SI isn't a countdown, but just a timer. I've never used a computer, and don't know much, but another buddy has a Cochran and he said his does a countdown. I've only used tables, and would really like the countdown feature. Which ones countdown and which ones don't?

--Eddie

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