Metric or Imperial

[Blackwood]

Since you will be predominantly diving in the US, stick with imperial units if for no other reason it's what most of your buddies will be using so it makes communication a lot easier. If you go to a dive spot where metric is the standard, it helps to have an SPG like the OMS units that read in both imperial and metric for easier communication and (more importantly, IMO) less stress underwater from doing a bunch of math in my head.

Why do any math in your head?

The gauge doesn't know or care whether the cylinder it's attached to is rated in L/BAR or CF/PSI.

If you're comfortable with one way of rating cylinders and someone hands you one rated differently, do the math beforehand.

A 12L cylinder holds 12L/BAR. If it's a 230BAR cylinder, it holds 2760L @ 230BAR.

2760L = 97.5CF, 230BAR = 3335PSI. So you can think of that cylinder like you think of a US HP100, more or less.

I agree that it's better to be fluent in both systems, but if you aren't, figure out the equivalency beforehand, not during. My $0.02

 

[fnfalman]

I use whatever my computer says to use. When it tells me to go up, I go up.

 

[DiveNav]

I write code in Metric, but, being based in SoCal, I dive Imperial

 

[JanK]

Out of curiosity: how are the pressures communicated in the imperial units. What I mean is that in metric you show the pressure in 10s of bars rounded to the nearest 10 bars, i.e,. 122 bar would be T (for 100bar) and 2 fingers (for 20 bars), or 78 would be a fist (50 bars) then 3 fingers (30 bars).

I suppose in imperial units you show 100s of PSIs, right?

 

[Walter]

I suppose in imperial units you show 100s of PSIs, right?

Right.

 

[drrich2]

I am pretty familiar with metric, having lived abroad quite a bit, but at the gut level I'm imperial, so that's what I use.

Above quoted from Vladimir's post.

My position is similar; I've not lived abroad, but via high school & college coursework, I've had to deal in metric a lot over a number of years. So for Chemistry of Physics problems, it's natural to think in metric.

But in the 'real world,' when thinking in terms of length, depth, volume and pressure, I think solidly in Imperial units. If you tell me how many kilometers it is to get to some place, I mentally figure a kilometer is about 0.6 miles, multiply & get it. If you tell me how many meters long a thing is, I times by 3 since a meter's almost (actually a bit over) a yard. A kilogram's about 2.2 lbs. Even temp.s, which I can't readily convert, I handle better in Imperial (I recall Chemistry labs are often kept at 20 or 25 degrees Celcius, which is a tad cool, and the lower 30's Celcius is rather hot; that's about it for me & Celcius).

Richard.

 

[Gerbs]

I think I posted xkcd: Converting to Metric before...

Gerbs

 

[rongoodman]

If you can get your head around metric it certainly makes planning dives much easier, in terms of relating pressure to depth. I spent some time with a young Polish woman on a liveaboard in the spring who never could figure out how much gas I had. If I see her again, I'll just swap out my SPG for one that reads in bars and switch the computer over to metric.

 

[boulderjohn]

It's pretty easy to do the conversion if you have to, for example, signal your air supply in bar instead of psi.

Well, for some people it is.

Last weekend I taught an AOW class to two people, and one of them had his air integrated computer set to metric because it is easier to deal with. I had some handouts that had information in imperial. I told him the simple math needed to convert, but he could not do it. I gave him the example of converting 50 bar to imperial, and even after I explained the process, he kept coming up with 550 PSI. (I suspect he has been unintentionally stiffing a lot of waitresses over the years.)

This man is a college educated professional.

I frequently run into students whose brains visibly turn off the minute you start talking about even the simplest arithmetic process.

 

[VictorP]

I have lived in Europe too long now I guess. Imperial just seems to be a completely different world, I find Metric easier. Though Metric is what is taught in schools in Canada so it's been easier for me to pick up.