Question on SDI Dive Manual

[tarponchik]

The manual has a quiz that asks the students this question in Chapter 3: "What are the 2 main modes of operation of a dive computer?" The correct answer is 1. Surface mode 2. Decompression mode.

I am puzzled, what do these answers mean. If I am diving a normal NDL dive, in what mode is my comp operating? I am below the surface, so this can't be "suface mode". And I did not go into deco, so this can't be "decompression mode" either.

First, the manuals of my dive comps (I have 2, both by Cressi) do not mention anything like this. The word "mode" is used only when referring to the mode button that switches the comp between the "modes". These modes are "time", "gage", "PC". "log" "set" and "hist". The word "decompression" is used only in reference to what happens if you go into deco and how the comp will help you. So there are no such things as "surface mode" and "decompression mode" as far as my comps are concerned.

Second, googling the internets did not help. Nothing of this kind is mentioned here, for example, or even on the SDI page. And this page describes how a comp would lock into "decompression mode" for 24 hrs if you had a deco dive, and this is OK. But then everything else must be "surface mode"? Makes no sense to me.

 

[hotelconucc93]

The best thing to do would be to discuss with your instructor, or email your questions to SDI.

training@tdisdi.com

Best,

Chet

 

[Jim Lapenta]

Anytime you descend the computer is indeed entering decompression mode.

Every dive is a decompression dive!
Every dive you are on gassing and then off gassing.

Too many instructors don't even seem to recognize this.
So, you are decompressing on the ascent.

The decompression time is calculated by the estimated amount of nitrogen you take up based on depth and time and calculated in the algorithm.

That gives you the amount of bottom time you have available for a "no stop" decompression ascent.
This "no stop" decompression is done by ascending at a controlled rate. This ascent is your, to use a simplified driving analogy, rolling decompression stop.

You can't just shoot up. Why?
Because to do so would not allow sufficient time to off gas or "decompress" the nitrogen bubbles in your blood and tissues.

If more people were taught this way, there would likely be less incidents of rapid ascents and people blowing off safe ascent rates.
Just another example of the info that is not taught in order to keep classes as short as possible to maximize profits.

 

[VikingDives]

The manual has a quiz that asks the students this question in Chapter 3: "What are the 2 main modes of operation of a dive computer?" The correct answer is 1. Surface mode 2. Decompression mode.

I am puzzled, what do these answers mean. If I am diving a normal NDL dive, in what mode is my comp operating? I am below the surface, so this can't be "suface mode". And I did not go into deco, so this can't be "decompression mode" either.

First, the manuals of my dive comps (I have 2, both by Cressi) do not mention anything like this. The word "mode" is used only when referring to the mode button that switches the comp between the "modes". These modes are "time", "gage", "PC". "log" "set" and "hist". The word "decompression" is used only in reference to what happens if you go into deco and how the comp will help you. So there are no such things as "surface mode" and "decompression mode" as far as my comps are concerned.

Second, googling the internets did not help. Nothing of this kind is mentioned here, for example, or even on the SDI page. And this page describes how a comp would lock into "decompression mode" for 24 hrs if you had a deco dive, and this is OK. But then everything else must be "surface mode"? Makes no sense to me.

Which course/manual? Also if you go to tdisdi.com and use the chat function, you can chat with an instructor at HQ...

 

[tarponchik]

Which course/manual? Also if you go to tdisdi.com and use the chat function, you can chat with an instructor at HQ...

Problem solved already, the correct answer is 1. Surface mode 2. Diving mode.

 

[ChrisDee]

Which course/manual? Also if you go to tdisdi.com and use the chat function, you can chat with an instructor at HQ...

Page 399, the manual from this site: Scuba PDF Download www.scuba.free-download.net
of the old Knowledge Quest Appendix B OW Scuba diver knowledge,....etc,...

The point was not to dive in some mode like: SLEEP, CHARGING, USB, or something similar. I suspect it is a familiarization question to get people to actually read the manuals. From personal experience, older computers had to be turned on, and manually put into a particular mode, like you had to set the things to "record" if you wanted a record of your dive and stuff like that. Main point: you needed to turn it on, and then make sure it was actually in the right "MODE," otherwise you could have it on, but the display wasn't what you think it was, it could be in "DEMO" mode. Nowadays, many dive computers turn them selves on as soon as they have been in water a certain time and depth AND automaticially go into "DIVE" mode.

That is the correct answere.