US divers using metric?

[Redshift]

Scuba seems to be rather unique using bar. Pascals (kPa) seems to relate closer to PSI than bar, at least for me.

1 pascal =
0.000145037738 pounds per square inch

What?! How does it relate closer to PSI? 1 bar = 10^5 Pa.

 

[Storker]

Pascals (kPa) seems to relate closer to PSI than bar, at least for me.

Huh? You DO know that 1 bar = 100 kPa, don't you?

BTW, bar isn't an SI unit, but it's very useful because it's so close to one standard atmosphere. The difference is just 1.3%


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[Aquavelvet]

Yes, which is why it would be much easier to convert "every day life" to metric. You'd save a lot of time in school learning stuff that are completely pointless and unnecessary exercises in a metric world.

You know, you're really just concocting a straw man argument. All we really need to know for daily life is how many quarts or pints to a gallon and how many inches per foot. The rest don't come into play much, and for the rare cases they do, we've got these new-fangled handheld computers.


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[dmoore19]

What?

You do know that bar is related to atmospheric pressure, I am glad. Other than units for Scuba, what value is in a real world application? kPa is far more useful and relates to PSI better. IMO

Huh? You DO know that 1 bar = 100 kPa, don't you?

BTW, bar isn't an SI unit, but it's very useful because it's so close to one standard atmosphere. The difference is just 1.3%


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Typos are a feature, not a bug

 

[dfx]

You know, you're really just concocting a straw man argument. All we really need to know for daily life is how many quarts or pints to a gallon and how many inches per foot. The rest don't come into play much, and for the rare cases they do, we've got these new-fangled handheld computers.

I'm not arguing that and it certainly isn't a straw man. I'm well aware that for the simplest things in daily life, it doesn't matter either way. There's no advantage in using metric and there's no advantage in using imperial. The difference arises when you look at the not-as-simple cases and look outside of daily life. Then there's a clear advantage in using metric over imperial, which is why all the scientific circles use metric only. So now there's the question of whether using metric everywhere has an advantage over using metric only in some cases and using an obsolete and cumbersome system in other cases. Yes, of course there is.

But hey, at least you guys are in good company

 

[dfx]

You do know that bar is related to atmospheric pressure, I am glad. Other than units for Scuba, what value is in a real world application? kPa is far more useful and relates to PSI better. IMO

I don't get it, how does it relate to PSI better? They're all measures of pressure.

 

[dfx]

On the usefulness of handheld computers to convert things, since another thread was just talking about a depth of 42 meters, I was wondering how much that was in feet, so I put it into my handy conversion app and this is what it told me

 

[Kevrumbo]

C'mon y'all . . .is this thread turning into my own personal Blog on how to OBJECTIVELY/PRACTICALLY utilize the Metric System for Scuba both here in the US and abroad???

Sad to say, but the irony is most American hard core "GUE Practitioner Divers" are totally ignorant even when you try to explain the advantages of metric units in gas planning versus US Imperial units (I bet founder Jarrod Jablonski and even old timer "Red Neck" GUE Instructor David Rhea use a bar SPG on their fun & mission oriented dives!).

And yet some more examples & explanations on the advantages:

Discovered an interesting one-to-one correspondence between depth and gas consumption rate in bar/min, while diving with double AL80's (and why I now prefer using the Metric System even here in the States). An example:

18m depth, same as 2.8 ATA -->translates directly to 2.8 bar/min
21m depth, same as 3.1 ATA -->translates directly to 3.1 bar/min
24m depth, same as 3.4 ATA -->translates directly to 3.4 bar/min
27m depth, same as 3.7 ATA -->translates directly to 3.7 bar/min
30m depth, same as 4.0 ATA -->translates directly to 4.0 bar/min

So for an arbitrary & convenient time period of say, for example 10 minutes, at a particular depth above, you would expect to consume:

2.8 bar/min(10min) = 28 bar
3.1 bar/min(10min) = 31 bar
3.4 bar/min(10min) = 34 bar
3.7 bar/min(10min) = 37 bar
4.0 bar/min(10min) = 40 bar

Essentially then, all you need to know is your depth in ATA and your time at that depth, and you'll know instantly how much gas you've consumed --even before looking at your SPG!

Parameters:
Surface Consumption Rate (SCR): 22 litres/min*ATA
Twin 11 litre tanks (double AL80's): 22 litres/bar total tank rating.

Now divide SCR by total tank rating (22 divided by 22). You get: 1 bar/min*ATA (and there's the secret math trick discovered --the unity conversion ratio of 1 bar/min*ATA which lets you transform directly from depth to a delta bar per minute rate, and subsequent SPG bar consumed).

So ideally, the motivation is to electively use a tank cylinder (or twinset doubles cylinders) to match your own volume Surface Consumption Rate for a convenient 1 bar/min pressure Surface Consumption Rate. For example, if you have a 15 litre/min volume SCR (same as 0.50 cubic ft/min US Imperial units), get a 15 litre/bar rated cylinder --a Steel LP95 or HP119 Tank-- to give you a 1 bar/min SCR. Of course your consumption at depth, (DCR or Depth Consumption Rate) depends on your ATA depth as a multiplier factor (Atmospheres Absolute ATA multiplier factor is simply your depth in meters divided-by-ten and add one: So 30 meters equals 4 ATA; 28 meters equals 3.8 ATA; and so on). . . Therefore your DCR at 30 meters depth will be 1 bar/min multiplied by 4 ATA equals 4 bar/min, and you know after 10 minutes of nominal breathing that 40 bar of gas will be consumed (4 bar/min multiplied by 10 minutes equals 40 bar).

Don't any of y'all US Divers see the elegant power & ease of smartly calculating in your head, vital gas usage -both pre-dive & real-time on-the-fly- all by using the Metric System?

 

[dmoore19]

It may well relate perfectly to Scuba. I think it does. but for real life purposes Bar is pretty useless.

I don't get it, how does it relate to PSI better? They're all measures of pressure.

 

[dfx]

It may well relate perfectly to Scuba. I think it does. but for real life purposes Bar is pretty useless.

And which real life purposes would that be? Like pressure in bicycle or car tires, which often is given in bar? Or you mean things like atmospheric pressure, which is usually given in hPa (1000 hPa = 1 bar), but where you guys don't use PSI but rather inches of mercury (which equals a convenient 0.491098 PSI for conversion purposes)?