Why I am getting a backup pressure gauge for my hoseless air integrated wrist dive computer.

[tbone1004]

Best first regulator, DIY service

read why it shouldn't be necessary with proper dive planning. Most people don't properly plan their dives for whatever reasons, and they end up thinking that a backup SPG is necessary when it really isn't.

The odds of an analog SPG failing aren't very high, however the spool o-rings do fairly regularly, as do HP hoses, so if I were diving WAI, I wouldn't bother with it and define my contingent dive time based on WAI failure and have that written on my slate

 

[joe10540]

There are two types of divers (probably many many more but for the sake of this thread we will stick to two) that you see regularly.

Diver one knows how much breathing gas they have at the start of the dive and a dive profile in mind before splashing. taking those numbers he/she is able to figure a rough estimate of how long said gas will last and they will undoubtedly be back on the boat with plenty of available gas even if they aren't the last ones up.

Diver two has really no idea how much gas is in their tank, sees 2600psi or 3000psi and says ok I'm good. Jumps over the side with no real plan or idea how long they can stay down with the gas on their back and follows the SPG like a fuel gauge only coming back to the boat when they have run down to 500psi or whatever arbitrary number they have picked or been told to be back on the boat with.

Diver one could probably complete the entire dive with nothing more than a depth gauge and timer where as diver two would surlely end up OOA if they didn't have their SPG. So if you are like diver one you would probably see a redundant analog SPG as a waste of space and added drag or an additional failure point or whatever diver two sees it as life insurance and can justify the space drag expense or whatever.

To each his/her own. Safe diving!

 

[barth]

Best first regulator, DIY service

read why it shouldn't be necessary with proper dive planning. Most people don't properly plan their dives for whatever reasons, and they end up thinking that a backup SPG is necessary when it really isn't.

The odds of an analog SPG failing aren't very high, however the spool o-rings do fairly regularly, as do HP hoses, so if I were diving WAI, I wouldn't bother with it and define my contingent dive time based on WAI failure and have that written on my slate

If you plan your dive you don't need an backup spg and you don't need an air integrated computer. An spg and a boltsnap would be enough. You can check it a couple of times during the dive and check it before the dive starts and when the dive has been started.

Time and depth I will check more during the dive, it is nice to have them on my wrist.

If you do not plan dives and have no idea how much gas you use. Then it would be nice to have an air integrated dive computer. It would also be nice to have a backup spg to continue the dive when your computer is not telling your pressure anymore.

 

[Colliam7]

Good thread. Three points come out of it, for me at least.

1. Equipment, be it a brass-and-glass SPG, or a wireless AI configuration, can and will fail. For both, the probability of failure on any given dive is actually quite low, and it is hard to say that one approach is absolutely better than the other.

2. Proper dive planning should be the first step in gas management, after which actual monitoring of gas supply, with either equipment approach, becomes a good form of redundancy.

3. Each diver makes a choice of their approach to gas monitoring based on a number of factors, many of which are somewhat subjective, and reflect the diver's experience, and knowledge. I know that I 'trust' my brass-and-glass SPG more than my WAI. I can't say that trust is objective. But, it is what it is. That means I always have the B&G SPG, whether I have a WAI transmitter with me or not.

I have had plenty of WAI computer sync failures during a dive. Usually the sync failure problem is transient, sometimes it is not. Because I plan my dive times according to gas supply (and I know my gas consumption, and check my SAC a couple of times each dive season, under 'relaxed' finning conditions and under conditions of exertion), and always carry a B&G SPG, computer sync failures are an annoyance not a dive ending event. I have never had a B&G failure. But, all that is just MY experience, and others have had different experiences. I have had situations where my SPG swivel was bubbling during a dive, and I have gone ahead with the dive (or several dives), and changed out the O-rings later.

Whatever a diver chooses is up to them. I do what I do because it works for me. But, I tell students that gas planning is always the first step, after which there are several options for gas monitoring.

 

[idocsteve]

But, what if your dive buddy needed some of your air? Since you had neither a dive computer or a SPG you could only guess how much air you had left, which is not a good way to handle potential air issues. Actually, that does not sound like very good dive planning. What dive op allowed you to dive with no means to determine your air supply? And yes, I know diving is possible without a computer or SPG (did it myself on every dive in the 60s), but that was a different time before the era of SPGs, much less dive computers.

That's why I'm installing a backup SPG!

To those divers who say that with proper planning, a diver should have a pretty good idea of how much gas they have at any point during the dive without looking, I won't pretend to be that good.

I guess some people can drive their cars and stay under the limit without glancing at the speedometer too.

The technology is there, I'm going to use it as necessary.

A point that seems to be getting lost on this thread as well as some older ones that I read that prompted me to write this one is that if my air integrated dive computer fails, I won't necessarily abort the dive, especially if it's a good one that I've traveled a long way and spent a lot of money on.

Obviously if you're going to abort the dive you don't need all that redundancy.

 

[Joneill]

Good thread. Three points come out of it, for me at least.

1. Equipment, be it a brass-and-glass SPG, or a wireless AI configuration, can and will fail. For both, the probability of failure on any given dive is actually quite low, and it is hard to say that one approach is absolutely better than the other.

2. Proper dive planning should be the first step in gas management, after which actual monitoring of gas supply, with either equipment approach, becomes a good form of redundancy.

3. Each diver makes a choice of their approach to gas monitoring based on a number of factors, many of which are somewhat subjective, and reflect the diver's experience, and knowledge. I know that I 'trust' my brass-and-glass SPG more than my WAI. I can't say that trust is objective. But, it is what it is. That means I always have the B&G SPG, whether I have a WAI transmitter with me or not.

I have had plenty of WAI computer sync failures during a dive. Usually the sync failure problem is transient, sometimes it is not. Because I plan my dive times according to gas supply (and I know my gas consumption, and check my SAC a couple of times each dive season, under 'relaxed' finning conditions and under conditions of exertion), and always carry a B&G SPG, computer sync failures are an annoyance not a dive ending event. I have never had a B&G failure. But, all that is just MY experience, and others have had different experiences. I have had situations where my SPG swivel was bubbling during a dive, and I have gone ahead with the dive (or several dives), and changed out the O-rings later.

Whatever a diver chooses is up to them. I do what I do because it works for me. But, I tell students that gas planning is always the first step, after which there are several options for gas monitoring.

You guys realize that many of us are tropical divers where you don't know the actual dive site until a few minutes before you drop off the boat. You have a fixed supply of gas in an AL80 or AL100 and you have a general idea of max depth and contours. However, there is no true gas planning beyond agreeing on turn and ascent pressures (your gas supply is fixed/predetermined).

Therefore, the "plan" evolves as the dive progresses and, ultimately, is to be back on the boat in 60 minutes and/or ascend when you or your buddies hit a predetermined reserve (usually 700-800 psi depending on depth).

So, once you descend, it is really more about monitoring your gas consumption and remaining gas as that can be affected by many factors on a given day/dive (the actual profile you end up following, time at max depth, current, fitness, how relaxed you are, etc.). Over time, you get more comfortable with estimating your gas consumption and don't need to check as often.

However, for me (and I suspect many others), having a redundant air supply check is helpful and provides a sense of security (1 less issue to worry about or have to abort a dive for). In addition, a 2" SPG on a miflex hose clipped off to a D-ring is not really adding any noticeable drag (I'm not to win a speed race when I dive).

For tech divers, it's a different story!

 

[Colliam7]

You guys realize that many of us are tropical divers where you don't know the actual dive site until a few minutes before you drop off the boat. You have a fixed supply of gas in an AL80 or AL100 and you have a general idea of max depth and contours. However, there is no true gas planning beyond agreeing on turn and ascent pressures (your gas supply is fixed/predetermined).

I will disagree with this, although I think your view is a common (mis)conception among divers, so you are not alone.

To begin, I would suggest that you actually ARE engaging in gas planning - agreeing on turn pressures and ascent pressures is an important part of gas planning. So, give yourself some credit here! But, I would suggest you can do even more. While it is a good practice to agree on turn pressures, it would be even better to agree on turn times as well, because each diver has a rough idea of how long they can stay down, with whatever cylinder they happen to be diving. Then, they may periodically monitor their SPG, but as a form of redundancy to confirm what they already planned.

I go on coastal boats dives to sites where I have not dove before, but I still plan my dives. The planning starts before I ever get on the boat - by checking my SAC. If you do not know what your personal gas consumption is, measure it on your next dive. All you need is a timing device and your SPG (be it B&G or WAI). Swim at a constant depth and finning rate for 10 minutes (I personally think 20 is better, but even 5 is better than nothing), checking your cylinder pressure before you start and when you stop finning. Then calculate your air consumption after the dive, it is simple algebra. While I recommend doing it in open water, at the very least get in a pool and check it. That is absurdly easy to do. No, it won't be a two decimal point level of precision measurement - no SAC measurement ever is. But, you will have a basis for determining how long you can stay at whatever depth is reported for whatever site you end up diving. And, you can easily do a 'relaxed' swim in a pool, and an full exertion swim in a pool and come up with some data. In fact, in this day and time there is little excuse for a diver not knowing approximately what their individual gas consumption is.

For me, the planning continues with asking about the site conditions - depth, current, temperature - even if that is only 5 minutes before I splash. I will ask about the site plans before the boat leaves the dock. But, it is not uncommon to get to the planned site, and find there is strong current, or 3 other boats tied in, so we go to an alternate site. There should be a site brief before the first diver (besides the DM who may splash early to tie in) hits the water. If for some inexplicable reason, there isn't a brief, ask! I am not going to jump off a boat without knowing something about the depth and terrain, simply because some DM says 'follow me'.

This issue has NOTHING to do with technical diving. It is simply good recreational diving practice. And, it is not hard at all. Yes, thousands of dives are conducted each year with divers 'riding' their SPG (or their computer). And, at the extreme of that practice, I see divers swimming along, continuously holding their console in front of them. It is almost painful to watch, because they are so focused on the SPG that they hardly see anything else during what might be a wonderful dive. But, just because thousands of dives are done that way doesn't mean the situation cannot, or should not, be improved upon.

I admit, I started out that way - 'riding' my SPG - because way back when, I didn't have an OW (or AOW) instructor who said anything to me about dive planning, other than, 'You need to start your ascent when you reach 500 psi'. In hindsight, that was completely inadequate. But, just because that is the way I was originally trained did not mean that it was beyond my ability to improve upon my gas planning.

If a diver wants to 'ride' their SPG as their primary approach to gas management, that is their decision. But, it is not necessary, it is not the only thing a recreational diver can do, and frankly, it compromises the fun of diving. But, just as with the choice of monitoring equipment, it is the choice of the diver to do things the way they want to do them.

 

[Joneill]

I did not say I do not plan my dive - I said I did not plan my gas (beyond agreed turn/ascent psi). The fact is that I can't - I have what I have - they won't give me more.

OK, just so we are all on the same page: 'what' don't you have before you splash? And, 'who' won't give you more? I simply disagree that 'the fact is I can't'. Even if a dive plan changes under water, there should be a plan to be changed, developed in advance.

For example, do you approximately know your SAC / RMV? That is a straightforward matter to calculate, before you arrive at whatever unknown site you may be diving, before you even sign up for the boat trip.

Therefore, once I'm under, in addition to monitoring max depth and NDL to avoid tox/deco, the most important thing I need to monitor is my gas = fact.

And, I am not disagreeing with monitoring your gas, nor that gas = fact. But, I am saying that this monitoring should be a form of redundancy, used to confirm whatever plan (time) you had before the dive.

 

[Joneill]

I will disagree with this, although I think your view is a common (mis)conception among divers, so you are not alone.

To begin, I would suggest that you actually ARE engaging in gas planning - agreeing on turn pressures and ascent pressures is an important part of gas planning. So, give yourself some credit here! But, I would suggest you can do even more. While it is a good practice to agree on turn pressures, it would be even better to agree on turn times as well, because each diver has a rough idea of how long they can stay down, with whatever cylinder they happen to be diving.

I go on coastal boats dives, to sites where I have not dove before, but I still plan my dives. The planning starts before I ever get on the boat - by checking my SAC. If you do not know what your personal gas consumption is, get in a pool and check it. That is easy to do. No, it won't be a two decimal point level of precision measurement. But, you will have a basis for determining how long you can stay at whatever depth is reported for whatever site you end up diving. And, you can easily do a 'relaxed' swim in a pool, and an full exertion swim in a pool and come up with some data. In fact, in this day and time there is little excuse for a diver not knowing approximately what their individual gas consumption is.

For me, the planning continues with asking about the site conditions - depth, current, temperature - even if that is only 5 minutes before I splash. I will ask about the site plans before the boat leaves the dock. But, it is not uncommon to get to the planned site, and find there is strong current, or 3 other boats tied in, so we go to an alternate site.

This issue has NOTHING to do with technical diving. It is simply good recreational diving practice. And, it is not hard. Yes, thousands of dives are conducted each year with divers 'riding' their SPG (or their computer). And, at the extreme of that practice, I see divers swimming along, continuously holding their console in front of them. It is almost painful to watch, because they are so focused on the SPG that they hardly see anything else during what might be a wonderful dive. But, just because thousands of dives are done that way doesn't mean the situation cannot, or should not, be improved upon.

I admit, I started out that way - 'riding' my SPG - because way back when, I didn't have an OW (or AOW) instructor who said anything to me about dive planning, other than, 'You need to start your ascent when you reach 500 psi'. In hindsight, that was completely inadequate. But, just because that is the way I was originally trained did not mean that it was beyond my ability to improve upon my gas planning.

If a diver wants to 'ride' their SPG as their primary approach to gas management, that is their decision. But, it is not necessary, it is not the only thing a recreational diver can do, and frankly, it compromises the fun of diving. But, just as with the choice of monitoring equipment, it is the choice of the diver.

I don't agree with you at all. Sure, it is good to understand what your RMV/SAC is as it helps you estimate how long your gas will last. At 50 dives in, I'm getting a pretty good understanding of that. However, estimate versus reality can be quite different as I've said. A plan is just a best guess estimate. Why agree to turn times that might end up being too short or too long? Ultimately, using pre-agreed times instead of pressure and ignoring your gas could be quite dangerous.

It's also not about riding an SPG - it's about using technology to maximize my dive time and my situational awareness. It's about starting with a rough plan but managing the dive and adapting to the conditions that unfold in real time. Why would one not want to do that? It's 2017 - not 1963.

 

[BoltSnap]

I dive with two AI computers, one is in a console (hose AI) and one is a hoseless AI wrist computer.