How important is a depth gauge as part of a reg set?

[CT-Rich]

The only way tables are meaningful is if you preceding were done with square profiles and you knew your group after the first dive. A Dive computer is a watch and a depth gauge and a set of tables. Analog gauges are about as accurate and reliable as a computer, provided the batteries are changed regularly. They also take out the human element when figuring out where you are in relation to the NDL at any given moment.

if you have a nice watch and want to wear it diving, god bless, but it isn’t going to replace the functionality of even the cheapest computer. The only analog devices I would keep as back ups to the electronic versions are a SPG if you have a wireless AI computer and a compass. TBH, I just like using a real compass because I have always used one and I don’t need to learn how to operate them.

 

[boulderjohn]

I'm not going into the water before I know clearly what is my max time for my max depth according to the table.

I computer will tell you the same thing before the dive. On the first dive, it will tell you the same thing the dive table will, assuming they have about the same algorithm. The difference is that on the second dive, the computer will tell you the maximum depth and time while taking into consideration your gas loading from the first dive. If you wait 10 minutes, it will give you a different answer because of the greater surface interval. If you are using the tables, you can do that as well, but you must go through the full table calculations from the first dive plus the surface interval, and if you did a multi-level dive on the first dive, then those calculations will not be accurate.

 

[Zef]

if you did a multi-level dive on the first dive, then those calculations will not be accurate.

Bbbbb...but what about the wheel?


-Z

 

[CycleCat]

...if you use a computer and pretend like it’s a tables dive, then your computer grants you some extra time beyond the NDL of the table (which it most likely will) then you’re violating the table and are now doing a computer dive.

I get it. The light just came on after Jcp2's post. All this time I was imagining the computer would take a dump INSIDE my table time limit. I had not considered that due to the calcs of the computer I could be way past table times for the same dive when it quits working. But getting that extra time is what a computer is for. So I guess knowing table times would only help salvage my dive day if the computer dies before my table time limit is reached.

 

[halocline]

This whole thread started because I wondered if an analog depth gauge should be part of my setup in addition to the computer. I will be diving with a good ol' dive watch along with my computer because I LIKE dive watches. I've worn one since I was a teenager (early 80's). I'll lose bottom time that way but at a minimum, time in the water and max depth is all I need to know to use a dive chart, isn't it?

I also use a dive watch, no back up computer. For recreational, NDL diving, that is more than sufficient.

It's great that you are going through this intellectual exercise. You might think about a couple of things:
1) The dive computer only tracks your depth and time, it does not have any idea what your actual tissue loading is.
2) It then spits out numbers that are theoretical representations of your N2 exposure. Different computers will spit out different numbers, and some numbers (like NDL on the ascent at the end of a dive) have no actual relevance.
3) There is no magic line between a dive that is perfectly safe to surface from, with no possibility of DCS, and one that is not safe. There is a very large 'grey area' where some divers would be fine ascending on some days, and others diving the same profile might suffer DCS. You probably want to avoid this grey area as a new diver, and learn to mitigate any risk you might have on longer, deeper dives, especially repetitive ones. This is best done through greater understanding of the factors in DCS exposure (some of which have nothing to do with your dive) and acting accordingly.

Here's an example of this last bit. If you follow what happens with some dive planning software (a great tool for learning BTW) you will learn that usually, the initial required deco stops, as a diver slips from an agressive NDL dive into a required deco, are shallow. Often an extended stop at 10 feet is the first deco requirement, although some software or computer settings will set the stop at 20 ft. So lets say you are on a dive, your computer stops working, and you are concerned that you might have 'stepped over the line' into some required deco. You could simply do your normal safety stop at 15 feet, then do an additional, longer stop at 10 feet. Or you could do your safety stop at 20 feet for 3 minutes and then proceed to 10ft. How long? As long as you want, maybe 10 minutes if you have the air and time. It's not necessary, but it might make you feel better. Better psychologically about a surfacing without the computer's ok, and better physically, because long shallow stops are known to be very effective at reducing N2 loads in recreational diving.

This long post is really about learning not to be a slave to the computer. It's your dive behavior (and topside behavior as well) that determines your risk for DCS. The more you learn about this, the better equipped you will be to dive safely, and mitigate the risk if you eventually decide to dive deeper, longer dives.

 

[CT-Rich]

I also use a dive watch, no back up computer. For recreational, NDL diving, that is more than sufficient.

It's great that you are going through this intellectual exercise. You might think about a couple of things:
1) The dive computer only tracks your depth and time, it does not have any idea what your actual tissue loading is.
2) It then spits out numbers that are theoretical representations of your N2 exposure. Different computers will spit out different numbers, and some numbers (like NDL on the ascent at the end of a dive) have no actual relevance.
3) There is no magic line between a dive that is perfectly safe to surface from, with no possibility of DCS, and one that is not safe. There is a very large 'grey area' where some divers would be fine ascending on some days, and others diving the same profile might suffer DCS. You probably want to avoid this grey area as a new diver, and learn to mitigate any risk you might have on longer, deeper dives, especially repetitive ones. This is best done through greater understanding of the factors in DCS exposure (some of which have nothing to do with your dive) and acting accordingly.

Here's an example of this last bit. If you follow what happens with some dive planning software (a great tool for learning BTW) you will learn that usually, the initial required deco stops, as a diver slips from an agressive NDL dive into a required deco, are shallow. Often an extended stop at 10 feet is the first deco requirement, although some software or computer settings will set the stop at 20 ft. So lets say you are on a dive, your computer stops working, and you are concerned that you might have 'stepped over the line' into some required deco. You could simply do your normal safety stop at 15 feet, then do an additional, longer stop at 10 feet. Or you could do your safety stop at 20 feet for 3 minutes and then proceed to 10ft. How long? As long as you want, maybe 10 minutes if you have the air and time. It's not necessary, but it might make you feel better. Better psychologically about a surfacing without the computer's ok, and better physically, because long shallow stops are known to be very effective at reducing N2 loads in recreational diving.

This long post is really about learning not to be a slave to the computer. It's your dive behavior (and topside behavior as well) that determines your risk for DCS. The more you learn about this, the better equipped you will be to dive safely, and mitigate the risk if you eventually decide to dive deeper, longer dives.

No diving device tracks your N2 load, A dive watch also does not track it or your depth. A dive computer is an assemblage of date collection devices that converts the data into a computer model of your N2 load and makes recommendations about the safe execution of your dives. The only real difference between a DC and using tables is that you become the aggregator of the data and the processor. Both can be safely used for diving, one of them is far more precise and reliable.

 

[Hoyden]

Two is one; one is none. I carry two computers on every dive. No depth gauge, just computers.

 

[Jcp2]

The only reason I have a gauge is because it’s part of a console with my SPG.

 

[Zef]

No diving device tracks your N2 load, A dive watch also does not track it or your depth. A dive computer is an assemblage of date collection devices that converts the data into a computer model of your N2 load and makes recommendations about the safe execution of your dives. The only real difference between a DC and using tables is that you become the aggregator of the data and the processor. Both can be safely used for diving, one of them is far more precise and reliable.

Could you be a little more pedantic please.


-Z

 

[halocline]

Bbbbb...but what about the wheel?


-Z

It's funny, I was going to bring up the PADI wheel, which I used to use back in the day. I actually liked it, although I'm sure they've long since relegated it to the trash heap. I'd bet someone could find one on one of the auction sites, it might be fun for the OP to play around with if he wants to work with dive tables.