Need suggestions about budget dive computer

[boulderjohn]

BT and tables or software. Gue is about planning and backup planning. When you plan a dive to say 50 meters or 150 ft for 40 minutes, there is a way to adjust deco if the actual average depth is more (or less) than planned. Or if you overstay your time at depth.

It is not about the way you plan your dive (of course there are different ways!) but about the fact that if you have planned your dive, why would you need a computer with you underwater?
But lets agree to disagree because it seems we are
I wish you plenty of good dives with or without computer

It is not really a matter of not liking computers. It's more a question of needing (or that lack of that) one. As said, we plan our dives and have a method of adjusting that plan if the average depth or the bottom time changes.

Having this method eliminates problems like differing algorithms producing different outcomes. That may not sound like a big deal but at depths of 60 m or 180 feet plus a minute more bottom time makes for a lot more deco. Having a set plan and a bottom timer eliminates discrepancies and misunderstandings during the dive.

For 30 m or 100 ft dives that is not a big deal. But Gue trains with the end in mind so even at rec levels you are trained as if your end goal is tech 2 or cave 2.
It just makes no sense to train students in using computers and then telling them they don't need them when they progress to tech 1 or cave 1.

I was thoroughly trained in and even required to use the methods being described for several years. Everyone in our dive group used these methods. The thinking was that a computer can make a mistake, so it is better to use "the computer between your ears." I did all of this using a simple Uwatec bottom timer. In my experience, though, if you choose to go this route, there is an advantage to using a computer in gauge mode instead. Here is an example of why this is true.

Two friends of mine were doing a decompression dive to only 150 feet using their computers in gauge mode and ratio deco to guide their ascents. As trained, they planned the dive carefully, including maximum depth and the ascent profile, and they did their best to follow that plan. Both were certified at the Tech 2 level, so they had lots of experience doing this. They estimated their maximum depths, began their ascents on time, and followed their plan. They were not dummies--one was just completing his Ph.D in software design. The simple math required for this was well within their skill sets.

So why was it an advantage that they were using computers in gauge mode?

After they both got DCS, they were able to download the actual dive profile to see what mistakes they made. It turns out they had dipped below their planned maximum depth enough times in the dive that their average depth for that portion of the dive was about 8 feet deeper than they thought. When they ascended to their first decompression stop, an ascent that should have taken about 30 seconds actually took nearly 3 minutes, and they had not realized that. This means they should have added about two minutes to their bottom time. Finally, they saw that they had miscounted their stop times, shaving 3 minutes off an ascent plan that they actually should have extended by more than a few minutes.

So, because they were using the computers in gauge mode and could check out the details of the dive in the dive log, we all were able to see what mistakes the computers between their ears had made. In all the other cases in which people in our group got DCS while using these dive planning methods, the divers were using simple bottom times and we thus had no way of doing such an analysis.

 

[KenGordon]

I was thoroughly trained in and even required to use the methods being described for several years. Everyone in our dive group used these methods. The thinking was that a computer can make a mistake, so it is better to use "the computer between your ears." I did all of this using a simple Uwatec bottom timer. In my experience, though, if you choose to go this route, there is an advantage to using a computer in gauge mode instead. Here is an example of why this is true.

Two friends of mine were doing a decompression dive to only 150 feet using their computers in gauge mode and ratio deco to guide their ascents. As trained, they planned the dive carefully, including maximum depth and the ascent profile, and they did their best to follow that plan. Both were certified at the Tech 2 level, so they had lots of experience doing this. They estimated their maximum depths, began their ascents on time, and followed their plan. They were not dummies--one was just completing his Ph.D in software design. The simple math required for this was well within their skill sets.

So why was it an advantage that they were using computers in gauge mode?

After they both got DCS, they were able to download the actual dive profile to see what mistakes they made. It turns out they had dipped below their planned maximum depth enough times in the dive that their average depth for that portion of the dive was about 8 feet deeper than they thought. When they ascended to their first decompression stop, an ascent that should have taken about 30 seconds actually took nearly 3 minutes, and they had not realized that. This means they should have added about two minutes to their bottom time. Finally, they saw that they had miscounted their stop times, shaving 3 minutes off an ascent plan that they actually should have extended by more than a few minutes.

So, because they were using the computers in gauge mode and could check out the details of the dive in the dive log, we all were able to see what mistakes the computers between their ears had made. In all the other cases in which people in our group got DCS while using these dive planning methods, the divers were using simple bottom times and we thus had no way of doing such an analysis.

Or they could have used a computer in computer mode, had it complain, and thought twice about their mental maths and saved getting bent. Just because it is doing the calcs doesn't stop you following a plan on a slate. Typically the computer will be more liberal, but when it isn't take note and have a think.

 

[boulderjohn]

One last attempt...

It is not about the way you plan your dive (of course there are different ways!) but about the fact that if you have planned your dive, why would you need a computer with you underwater?

As I said in the post before that....

As I said earlier, you only seem to think one kind of dive planning is dive planning. There are many ways to plan a dive, and some of them involve using a computer.

It seems to me that if you have chosen a dive planning method that involves using a computer under water, then it would be a good idea to have a computer under water when you execute that plan. That may seem silly, but that is how I see it, at least.

 

[jale]

One last attempt...

As I said in the post before that....


It seems to me that if you have chosen a dive planning method that involves using a computer under water, then it would be a good idea to have a computer under water when you execute that plan. That may seem silly, but that is how I see it, at least.

Luckily it is your last

 

[Centrals]

It just makes no sense to train students in using computers and then telling them they don't need them when they progress to tech 1 or cave 1.

I was trained on table in 1996 for my OW course.
When I ventured to tec dive in 1998/99 I was also trained by table and then gradually to soft wear + slate. Interestingly most tec divers that I had met over the yrs are also using soft ware + slate and only a few of them using tec computer as back up.
Yes it is rather strange to see rec divers mainly using computer while tec divers use BT + pre-planned profile!

 

[doctormike]

Yes it is rather strange to see rec divers mainly using computer while tec divers use BT + pre-planned profile!

My instructor had me plan the dive and write it on my wrist slate (with a backup in my wet notes, along with contingency plans for over depth / time, lost gas). I also would dive with my Petrel, but do the deco on the slate. Usually, the Petrel will clear deco before the slate does (since I tend to plan for maximum depth but spend some time above that). As my instructor pointed out, it's a good feeling to see your computer clear but still have the gas to finish a more conservative deco schedule, knowing that in the worst case scenario if you had to get out of the water after that you would likely be safe.

But this setup could work the other way - if boulderjohns friends had been diving computers, they would have had an alert that they had inadvertently broken their schedules by going over on depth, by the slow ascent, and by the miscounted stop time. Presumably, they would have had enough gas to complete their actual required deco...

 

[boulderjohn]

When I ventured to tec dive in 1998/99 I was also trained by table and then gradually to soft wear + slate. Interestingly most tec divers that I had met over the yrs are also using soft ware + slate and only a few of them using tec computer as back up.
Yes it is rather strange to see rec divers mainly using computer while tec divers use BT + pre-planned profile!

I have seen and dived with people doing tec dives in a lot of different ways. I have done pure ratio deco, with nothing but a bottom timer. I have done preplanned schedules with nothing but preplanned contingency schedules for backup. I have done preplanned schedules with computers for backup. I have done computers as the primary, with a preplanned schedule as the backup.

There was a thread debating these different methods a few years ago, and one of the participants, one of the most well known tec divers in the world, said he follows a computer for deco, with another computer as a primary backup and preplanned schedules as a second back up. He said that he never expects to get to that second back up, because his buddy is also diving with two computers. having four computers fail would certainly be an unusual experience. His main reasoning was that he does a lot of wreck exploration, and he really doesn't know for sure where he is going to go and how long he is going to stay there. (You may have watched some of those dives on TV.) You can only use preplanned schedules with true confidence if you are diving well known sites. A lot of tec diving is like that, but a lot of it is not.

 

[Centrals]

There was a thread debating these different methods a few years ago, and one of the participants, one of the most well known tec divers in the world, said he follows a computer for deco, with another computer as a primary backup and preplanned schedules as a second back up. He said that he never expects to get to that second back up, because his buddy is also diving with two computers. having four computers fail would certainly be an unusual experience. His main reasoning was that he does a lot of wreck exploration, and he really doesn't know for sure where he is going to go and how long he is going to stay there. (You may have watched some of those dives on TV.) You can only use preplanned schedules with true confidence if you are diving well known sites. A lot of tec diving is like that, but a lot of it is not.

Did he has unlimited supply of breathing/deco gases?
I believe most deep wreck divers are turning to CCR for one obvious reason.

As for me: Plan the dive and dive the plan.

 

[boulderjohn]

Did he has unlimited supply of breathing/deco gases?
I believe most deep wreck divers are turning to CCR for one obvious reason.

As for me: Plan the dive and dive the plan.

I love the way you leap to an absurd extreme to refute someone.

There are many ways to plan a dive. One way is to go to a very well known location and decide ahead of time exactly how long you will stay at a planned depth or depths. That works beautifully in those well known locations. Of course, that means that someone who used a different method of planning went there first so that those who follow will know what to expect.

In my experience, many or even most of the people who say "Plan the dive and dive the plan" only know one method of planning a dive, and when they encounter a dive planned a different way, they think it is unplanned because the plan does not look like the only one they know.

 

[Centrals]

There are many ways to plan a dive but the limiting factor is the availability of the gas.
If you believe computer is the way to go then it is your own choice. There are plenty divers who would not agree and that are their choices as well.
The boatman would know when and where to expect a smb pop up. If there is any substantial delay then he will start looking or notify the authority. A proper dive plan covers more than just the profile. There is no point having a plan if you do not use it.