US divers using metric?

[DiverGuam]

Since many tourist dives entail a group dive with a guide, and guides often ask for people's remaining gas pressure, do the metric folks ever run into confusion trying to signal their pressure?

For example, the guide asks my pressure & I've got 1500 on my gauge. Depending on house rules, I can show 5 fingers on one hand 3 times, or put 1 finger to my wrist (for 1,000 PSI) & then hold up 5. Either way, done.

What does the metric guy do?

I'm guessing metric comes up often enough that the guides will be familiar with it; I'd just like to know how they do it.

Richard.

Don't ask people for numbers, just percentages is the best way to do it. In fact, as an instructor doing lots of guiding, I figure it's my job to have fun divers leave as better divers than when they came, and enforcing some level of gas management, by stressing percentages and not numbers, is a pretty easy thing to teach, and an easy way to have a diver leave as a better diver.

In any international tourist location, both the rental gear and the customers are randomly assigned. Lots of divers who have never used PSI are given imperial dive sets, and vice versa. So percentages are really the only way one can go anyway.

I would like to point out also that many divers cannot tell the difference between their depth gauges and their pressure gauges once the units are swapped. I wish that were not the case, but it is.

 

[Storker]

Down here in the south its 15l 200bar thats the norm

That's just because you've got old gear :cool2: You won't find many new 15x200 tanks for sale even "down south", however 10L and 12L 300bar, and 12L and 15L 232bar singles are ubiquitous in the stores.

however lets face it - norway aint the episenter of scuba diving

Dang! Have I misunderstood for so long?

Although the 15l 200 bar ones will have a little bit more gas in them

Yep, about 10%. Noticable, but not dramatic. IME, your buddy's SAC rate is usually more significant for bottom time than whether he dives a 10x300 or a 15x200.

Besides, a 15x200 is nearly neutral when empty, while a 10x300 is some 4kg negative when empty. That's something to factor in if you're carrying a lot of weight (e.g. if you're diving dry with heavy undergarments).

I am less fond of their measuring gas in liters for some reason, probably because of the absurdly large numbers involved, but it does make more sense to work with the 1ATA volume of the cylinder and the pressure in ATA.

IME, that's the way we do it in the metric part of the world, at least on OC. We use the water volume of the tank, and tank pressure, never total surface volume of air in the tank.

The fist as a fifty bar sign is generally used to signal you are at your reserve

It's also a good general sign for 5 or 50 if you're wearing three-finger gloves (which I prefer when the water temp drops below 10C), since there's less risk of confusion. How do you distinguish 3 (30) or 4 (40) from 5 (50) when you only have three "fingers" showing? Also, it's hard to distinguish the raised hand with splayed fingers (5 or 50) with the raised palm ("stop").

Personally I prefer one handed signals. 1 - 5 is the number of fingers held vertically and 6 - 9 is the number of fingers held horizontally plus 5.

Nice if you're not wearing gloves, or thin 5-fingers, or drygloves. If the water's cold and you're wearing thick 3-finger wetgloves, it's kinda awkward to use.

A "T" like a timeout signal is 100 bar only because it is pretty well accepted as the signal for a half tank. Of course if you are using a 300 bar tank, that wouldn't be until 150 bar.

What I see is that the timeout "T" usually means 100 bar regardless of tank size and working pressure. I guess it's an example of how the meaning of words and signs drifts with time.

 

[bradells]

Since many tourist dives entail a group dive with a guide, and guides often ask for people's remaining gas pressure, do the metric folks ever run into confusion trying to signal their pressure?

For example, the guide asks my pressure & I've got 1500 on my gauge. Depending on house rules, I can show 5 fingers on one hand 3 times, or put 1 finger to my wrist (for 1,000 PSI) & then hold up 5. Either way, done.

What does the metric guy do?

I'm guessing metric comes up often enough that the guides will be familiar with it; I'd just like to know how they do it.

Richard.

This is all apart of the dive briefing (it's never a single sided discussion about the dive). If I have my gear, its usually all metric (Bar/Meter), and I let the in water DM know. Same thing with ascents, I take my time.

On occasion I forget or it just happens that too much stuff is going on the boat before people splash in for a quick reminder. It's funny to signal 150, and seeing the DM freak out as he's thinking we're at half a tank before we've headed back to the boat.

Also, its easy for myself to do conversions if it hurts the other divers heads ...


BRad

 

[alewar]

What I see is that the timeout "T" usually means 100 bar regardless of tank size and working pressure. I guess it's an example of how the meaning of words and signs drifts with time.

At least in Germany, the "T" means that you now have half of your gas, this is usually 100 bar. It's a kind of "turning pressure" for people that don't know better. The T-sign isn't followed by any other number and you are supposed to let your buddy know when you reach this pressure. If you want to communicate your pressure more precisely you use the finger numbers without any T. The fist means 50 bar. Both signs are independent of the size and number of tanks and only used in recreational dives.

 

[Tigerman]

When in doubt.. just show them the damn gauge...

Sent fra min GT-I9300 via Tapatalk

 

[gwklein]

Being in my late 50's and having grown up using U.S. Imperial my whole life, when I first started diving where everyone else was using metric, diving briefings only in metric left me at a loss and there was some confusion between and the other divers and me on the actually dive. I once tried showing underwater my Imperial integrated computer to the metric users but this resulted in even more confusion. So I switched my computer to metric for depth and bar for pressure. This caused me some internal confusion but worked better overall and I got use to it by the end of the week. Weird thing, though, was that all the weights for weight belts on the boat were in pounds and not kilos.

 

[drbill]

I used to use the metric system when I traveled since I didn't carry my own gear as a long-term backpacker (trips of 2-3 months through many countries). Of course being a scientist I was fairly used to using it for my research so it wasn't a big deal.

 

[JMBL]

Perhaps more to the point is you are safer diving the units you are familiar with... the units you think in. Any verbal input you get about a dive site can be converted before hitting the water — where distraction and narcosis might compromise your mental conversions.

I totally agree with that.

Some years ago, while diving in France, close to the Italien Riviera I met that guy : American, not speaking French, and not diving metrics. He had a hell of a time finding a buddy. To be honest, the owner of the dive center was a total jerk, it didn't help...

I ended up diving with him because nobody wanted as a buddy either. So, according to the description of the site, we double checked our diving profile : depth in meters/feet ; return pressure bar/psi. It just worked perfect.

 

[Tigerman]

Surprise, surprise.. most of the world don't speak french - despite the obvious belief in the french population that everyone should be...

 

[mathauck0814]

I use metric for gas planning, blending and rebreather diving. I still measure depth and distance in feet and use fahrenheit on my computer though.