Bottom Timer Vs. Dive Computer

[LVX]

Can someone please go through the advantages of using a bottom timer alone instead of a dive computer and then possibly go through a senario where you are making 6 dives in a weekend only using a bottom timer and tables. Do you use the square profile for all dives? If so, does this not limit how long you can stay down compared to a dive computer that recalculates your depth and time.

thanks in advance.

[peter_steinhoff]

I'm assuming you're thinking of rec diving since you mentioned using a computer.

Take your table of choice (I use this: http://dir-diver.com/en/download/ ). Write down the maximum allowed bottom time for all depths in your wetnotes and try to remember them if possible.

Make your first dive and during the dive check your time and depth now and then and try to memorize them. If you diving a square profile it's easy. If not you're probably starting deep and moving up shallower in which case you can use your average depth. It doesn't have to be super accurate - deco theory is a blunt tool.

Anyway, for the second dive you take the depth from the first dive, the bottomtime and the surface interval and put it in your table. Calculate a new set of maximum times and write them down. If you don't remember the times you can take up your wetnotes and look at them during the dive. Or write them on a wristslate if you like that kind of stuff.

And then you carry on like that. What you will see in your table is that you are pretty much clear from nitrogen after a couple of hours. So you'll start over from the beginning again.

Also after you've been diving like this for a while you will notice that you often end up with the same numbers. Mostly because you're diving the same size tanks, profiles etc. Also remember that a minute here or there doesn't matter. Just check the variation on different brands of computers and how much time they say you have left :-)

What does matter however is how you dive, how you feel and your activites during and after the dive. I think Dr Deco wrote some good stuff about that.

And that's the big advantage of using tables. Besides making you more aware of your profiles you can also adjust them according to workload, cold, fitness level and whatever you can think of. As you learn more you can incorporate that into your profile. Maybe throw in a couple of deep stops on the way up, ascend ultra slow the last 20 feets and things like that.

Gasplanning is also a breeze because you already know what you are allowed to do (depth/time) before you actually do it.

The downside is that this is not for everybody, just like cave diving or tec diving.

The upside is that all you ever need is a $99 bottomtimer and if you start with technical diving, you already have a lot of good skills and habits that you are going to need.

Best,
Peter Steinhoff

[Norm]

IMO: Primarily most folks using bottom timers today use them for technical diving when they have precut trimix tables otherwise, most (sport) divers stick with dive computers. Bottom timers do however make an excellent (limited info) backup for computers or analog gages.
Norm

[tyrell]

Hey

Its a little difficult to understand from the question what kind of dive u plan on the weekend so its hard to recommend u to use computer or table.

Can u b more specific? What types of dives, how many a day, what depth, trimix, nitrox, air, diving conditions?

Whn comparing a plan made with the dive computer and a table there r basically the same. The difference is when this plan was made.

The major difference between the computer and the table is that when using the table u plan the entire dive including air consumption in advance.
When using a computer u r not planning the dive in advance but letting the computer plan the dive according to the profile. (now , if u plan the dive with a table and dive according to the computer then its not truly a computer dive because the dive was planed before u went down.) This situation might b dangerous because if u r not a very experienced diver u cant tell how much air u will need to complete the dive safely including all the deco stops. As far as I know there r no dive computers who can calculate the air u got in more then one tank.

Remember if u make a mistake planning with table , u can recalculate. Whn having a mistake with the computer it’s a little complicated.

Also when using computers in tech dive they give u very little safety. Of course in some computers u can set how conservative the computer will b, but it will effect all the dive profile and not only the more dangerous points during the dive. These points can b controlled when planning a dive with a table.

When comparing the dive profile made with a table and a same profile dive with a computer u will find them pretty much the same. Computers use the same tables with the same calculations. The difference between tables and computers that when using a table u know before entering the water what u r doing trough the dive. When relaying on the computer u don’t know what the profile will be ten minutes from now, in what depth u gonna be and how many deco stops u will need and if u have enough air.


mark

[DIR Tec Diver]

Biggest problem I have seen with the UWATEC bottom timer is reading it in low light, however the new one out this year will have back lighting so it will be much better.

Having a computer but putting it into gauge mode has a lot of advantages. You have the backlighting and the ability to download the dive data to your computer. This gives you a lot of valuable data as you learn about decompression, your profiles at your favorite sites etc. and will give you a big advantage for dive planning.

Don't get tricked into relying on a computer to do the calculations for you. Good dive planning and then having a computer in gauge mode or using a standard bottom timer will give you all the data and info you need.

have fun

[BigJetDriver]

DIR Tec Diver once bubbled...
Good dive planning and then having a computer in gauge mode or using a standard bottom timer will give you all the data and info you need.

have fun

Good dive planning, and then having a computer, (At least one that you haven't crippled!), running RGBM and reading constant PPO2 is even better. Of course, a bottom timer and back-up tables in your pocket are truly a wise back-up!;)

I really don't understand what it is with these folks from "The Amish Diving Society"! They want to use horses and buggies to get to the dive site, trash them there dangerous new-fangled computer thingies, and use stone tablets to write their wet-notes on!

If we did that in my profession, we'd still be flying open cockpit bi-planes! I realize we are celebrating the 100 year anniversary of the invention of the airplane, and building flying models of the Wright Flyer, but no one seriously wants to go back to flying like that!

I guess it truly is a George Irvine, religious cult sort of thing, kind of like the "Snake Handlers" we have back in the hills of W.Va.:confused:

Perhaps it's a form of Luddite-ism. "Break the machine! The machine is evil! The machine is the tool of the Devil! The old ways were the best ways!"....or some such twisted philosophy!:wacko:

[IzzyTahil]

I dont use a computer and still use a analog timepiece with bezel AND a bottom timer used as a primary/redundant timer. I still plan all dives using tables and usually know exactly how long my ABT will be (as margin, I usually plan 10 ft deeper then the max bottom of the depth.)

A good computer in gauge mode will be great for the actual dive profile an info on how you dive.

plan the dive. dive the plan.

[norcaldiver]

BigJetDriver69 once bubbled...


I really don't understand what it is with these folks from "The Amish Diving Society"! They want to use horses and buggies to get to the dive site, trash them there dangerous new-fangled computer thingies, and use stone tablets to write their wet-notes on!

Hilarious! Amish divers...I gotta remember that.
But I totally agree. I carry 2 computers-same maker, dif models....and I have an anolog SPG in the bag just in case.

[BigJetDriver]

IzzyTahil once bubbled...
I dont use a computer and still use a analog timepiece with bezel AND a bottom timer used as a primary/redundant timer. A good computer in gauge mode will be great for the actual dive profile an info on how you dive.



"Break the machine! The machine is EVIL! The machine is the tool of the DEVIL! The old ways were the best ways!!!!"

Okay! I give up! When you walk down the jetway to go somewhere, you'll have to walk out on the grass. I'll have the Waco biplane ready to go. Forget about any baggage, however, and it's going to take a l-o-o-o-o-o-n-g time to get across this country! That is, if the weather will let us! =-)

[Cave Diver]

BigJetDriver69 once bubbled...
I really don't understand what it is with these folks from "The Amish Diving Society"! They want to use horses and buggies to get to the dive site, trash them there dangerous new-fangled computer thingies, and use stone tablets to write their wet-notes on!

If we did that in my profession, we'd still be flying open cockpit bi-planes! I realize we are celebrating the 100 year anniversary of the invention of the airplane, and building flying models of the Wright Flyer, but no one seriously wants to go back to flying like that!

I guess it truly is a George Irvine, religious cult sort of thing, kind of like the "Snake Handlers" we have back in the hills of W.Va.:confused:


It all depends on what you are wanting to do. I've planned several dives that *most* computers won't let me do. I've "bent" my computer on a couple of occassions. However since it was just along for the ride to provide profile download capability, it was of no real consequence.

And the use of depth gauge and bottom timers is hardly archaic, as a lot of those people still use computers. They use them to generate profiles before the dive, they dont just take them u/w with them.

There are a few dive computers with capabilities for handling more advanced dives, but most of them are $$$ and I can't justify the price vs. any percieved advantage. I've spent a lot of time running profiles using dive software on my PC and I've gotten a fair understanding of how they generate and I can anticipate a lot of outcomes when I make changes.

I think that is an important factor, because if something goes sideways when I'm in the water, I have a clue on how to deal with it instead of blindly relying on a computer to save my bacon.

In regard to G.I. I've personally never met the man and most of the comments I've seen him make are very abrasive. But it's very hard to argue with his methods when you see the end results.

[BigJetDriver]

Cave Diver once bubbled...
[B]

It all depends on what you are wanting to do. I've planned several dives that *most* computers won't let me do. I've "bent" my computer on a couple of occassions. However since it was just along for the ride to provide profile download capability, it was of no real consequence.

NOTE: IT IS A RULE OF THUMB AMONG THE HYPERBARIC MEDICINE FOLKS (AND SINCE I DO HOLD A DMT TICKET, I CAN SAY THIS WITH CERTAINTY) THAT COMPUTERS NEVER GET BENT, DIVERS DO!

And the use of depth gauge and bottom timers is hardly archaic, as a lot of those people still use computers. They use them to generate profiles before the dive, they dont just take them u/w with them.

NOTE: AS I HAVE SAID BEFORE, AND WILL SAY AGAIN, BACK-UP CAPABILITY (I.E. DEPTH GAUGE, SOME KIND OF BOTTOM TIMER, AND TABLES IN YOUR POCKET) IS A MUST! REDUNDANCY IS LIFE!

There are a few dive computers with capabilities for handling more advanced dives, but most of them are $$$ and I can't justify the price vs. any percieved advantage. I've spent a lot of time running profiles using dive software on my PC and I've gotten a fair understanding of how they generate and I can anticipate a lot of outcomes when I make changes.

NOTE: NO HUMAN BEING CAN EQUAL THE COMPUTATIONAL SPEED AND ACCURACY OF A GOOD DECO METER, ESPECIALLY ONE READING REAL-TIME PO2 AND RECOMPUTING EVERY FEW SECONDS. IF THERE IS SUCH A PERSON, PROFESSOR XAVIER WANTS TO MEET HIM (OR HER)!

I think that is an important factor, because if something goes sideways when I'm in the water, I have a clue on how to deal with it instead of blindly relying on a computer to save my bacon.

NOTE: NO ONE CAN BREATHE FOR YOU, SWIM FOR YOU, OR THINK FOR YOU! ALWAYS STOP, BREATHE, THINK, THEN ACT! (TOM MOUNT, IANTD)

In regard to G.I. I've personally never met the man and most of the comments I've seen him make are very abrasive. But it's very hard to argue with his methods when you see the end results.

NOTE: THANK GOD FOR GEORGE AND HIS FELLOW CRASH TEST DUMMIES! THEY ARE DOING SOME GREAT EXPERIMENTS ON THEIR OWN BODIES. GEORGE IS QUITE PLEASANT IN PERSON. NOW, IF SOMEONE COULD JUST STOP HIM FROM EXPOSING THE SOCIOPATHIC SIDE OF HIS PERSONALITY ON THE INTERNET, HE WOULD HAVE A MUCH BETTER REPUTATION THAN HE DOES AT PRESENT!

/B]

Although this may sound like strange advice, coming from someone who does what I do for a living: "DON'T WING IT! PLAN THE DIVE, AND DIVE THE PLAN!"

Just remember, have a good computer, and use it to its maximum advantage! Just don't use it to replace your brain!

As Mr. Natural used to say: "Get the right tool for the job, kids!"=-)

[Cave Diver]

BigJetDriver69 once bubbled...


Although this may sound like strange advice, coming from someone who does what I do for a living: "DON'T WING IT! PLAN THE DIVE, AND DIVE THE PLAN!"


Sounds like we funamentally agree on our diving styles, we just use slightly different methods of accomplishing it.

[BigJetDriver]

Cave Diver once bubbled...


Sounds like we fundamentally agree on our diving styles, we just use slightly different methods of accomplishing it.

I believe you're right, but hey, as my diving guru, Frans Vandermolen (IANTD International Advisory Board) says: "Analyze it, test it rigorously, and if it works reliably and well for you, use it!" Or again, as one of our other "Cavers" says when quoting the great explorer Sheck Exley: "What works, works!" (...as quoted by Caveseeker7).

Actually, I remember both Frans and John Orlowski laughing like hyenas at me while I ripped stuff off my rig one time after a run through the caves. After all, they HAD kept saying: "Simplify! Simplify!"...and I had said: "Hey, this has worked well so far (as a deep trimix rig)!" But, as they say, that's another story!

As Tom Mount often says: "If we ever stop learning, we die!" To which I can only say: "Amen!";)

[Cave Diver]

BigJetDriver69 once bubbled...
As Tom Mount often says: "If we ever stop learning, we die!" To which I can only say: "Amen!";)

Yet another thing we agree on.

I see you're in the Houston area. Do you ever dive with any of the swampers out at Twin Lakes?

[BigJetDriver]

Cave Diver,

My current rig (when not teaching basic scuba) is an Extended Range Inspiration with seven liter tanks, a Widolf commercial FFM, and OTS military through-water comm gear. Running mixed gas as I generally do, it is not very suitable for the depth regime found at Twin Lakes.

I usually go over to Florida, or down to Belize (Protech on Ambergris Caye) for my personal diving. If you want some great deep open water stuff, give Peter Jones or Roni Lieberman a try at <www.protechbelize.com>! Cheers, mate! :)

[BigJetDriver]

peter_steinhoff once bubbled...

...Write down the maximum allowed bottom time for all depths in your wetnotes and try to remember them if possible. (Try to remember them if possible??????...Ed.)

Make your first dive and during the dive check your time and depth now and then and try to memorize them. If you (sic) diving a square profile it's easy. If not you're probably starting deep and moving up shallower in which case you can use your average depth. It doesn't have to be super accurate - deco theory is a blunt tool.

(SO, IF DECO THEORY IS SUCH A BLUNT TOOL, THEN TEN OR FIFTEEN MINUTES DIFFERENCE AT SAY TWENTY METERS, OR SIXTY METERS FOR THAT MATTER, SHOULDN'T MATTER! AFTER ALL, AS STATED ABOVE..."it doesn't have to be super accurate..."!!)

Anyway, for the second dive you take the depth from the first dive, the bottomtime and the surface interval and put it in your table. Calculate a new set of maximum times and write them down. If you don't remember the times you can take up your wetnotes and look at them during the dive. Or write them on a wristslate if you like that kind of stuff.

And then you carry on like that. What you will see in your table is that you are pretty much clear from nitrogen after a couple of hours. So you'll start over from the beginning again.

Also after you've been diving like this for a while you will notice that you often end up with the same numbers. Mostly because you're diving the same size tanks, profiles etc. Also remember that a minute here or there doesn't matter. Just check the variation on different brands of computers and how much time they say you have left :-)

What does matter however is how you dive, how you feel and your activites during and after the dive. I think Dr Deco wrote some good stuff about that.

And that's the big advantage of using tables. Besides making you more aware of your profiles you can also adjust them according to workload, cold, fitness level and whatever you can think of. As you learn more you can incorporate that into your profile. Maybe throw in a couple of deep stops on the way up, ascend ultra slow the last 20 feets and things like that.

(SINCE YOU ARE ALREADY IN THE EXPERIMENTAL MODE, WHY NOT THROW IN SOME REALLY BIZARRE STUFF LIKE REVERSE SAW-TOOTH PROFILES AND FAST ASCENTS?? AS A DMT, I AM ALWAYS INTERESTED IN UNUSUAL CASES WHEN WE PLAN TREATMENT IN THE CHAMBER.)

Gasplanning is also a breeze because you already know what you are allowed to do (depth/time) before you actually do it.

The downside is that this is not for everybody, just like cave diving or tec diving.

(AS ONE OF OUR OTHER WRITERS HAS POINTED OUT, THIS IS DEFINITELY NOT FOR EVERYBODY. THIS IS TRULY WAVE-OF-THE-HAND JEDI MIND-TRICK STUFF AS PRACTICED BY THE DEVOUT OF THE "AMISH DIVING SOCIETY"! DON'T TRY THIS OUTSIDE THE CHURCH, KIDS!)

The upside is that all you ever need is a $99 bottomtimer and if you start with technical diving, you already have a lot of good skills and habits that you are going to need.

Best,
Peter Steinhoff [/B]

LVX,

If my interjected comments seem a bit sarcastic, I apologize! I am simply trying to debunk some mysticism here!

Let me see if I can make these points more formally:

(1) A diving computer is NOT truly a computer, as we think of it in terms of desktops or laptops. It is a single-purpose miro-processor with a specific program or algorithm built into it. Its job is to do the computations that you have been taught to do when using the tables. The benefit is that it can, and does, sample real-world parameters (depth and time, at a minimum) and constantly re-calculate your totals, usually at an interval of one to three seconds. (If you can calculate faster than it can, Professor Xavier has a place for you in his school!) REMEMBER, HOWEVER, THAT A GOOD DECO METER IS JUST A TOOL. IT IS A GOOD TOOL, BUT STILL JUST A TOOL!

(2) The computer is a piece of mechanical equipment, like your regulators, or lights, etc. It can fail, and if it does, the question is: "What are ya gonna do now, soldier?" It then follows that you should have an understanding of your tables, how they work, and what they do for you. This is where you take out your back-up tables, and refer to your back-up bottom timer and depth gauge! As Tom Mount of IANTD says: "Stop, breathe, think, then act!"

To sum up: "Is a good dive computer an excellent diving tool? Mais certainement! Absolutely! But should you blindly utilize one without understanding the basics? Not only no, but Hell no! That makes about as much sense as blindly following the rantings of the Great God Trey in the "Amish Diving Society"!

As Mr. Natural used to say: "Get the right tool for the job, kids!"=-)

[Cave Diver]

BigJetDriver69 once bubbled...
Cave Diver,

My current rig (when not teaching basic scuba) is an Extended Range Inspiration with seven liter tanks, a Widolf commercial FFM, and OTS military through-water comm gear.

Wow! Say that three times fast! lol Well I guess I wont see you at that mud puddle. Maybe I'll catch you in Florida some time.