Metric measurements?

[TMHeimer]

Since moving to Canada in 1977 I have long ago become fluent with kilometres & Celsius (no doing the "formulas" to figure it out). That's because of hearing weather forcasts and driving. But don't ask me to do weights (grams/kilos, etc.). I have read that 300 PSI = 200 Bar. That would seem pretty simple to pick up quickly. Interesting that we use PSI in Canada for tank pressure and feet for depth, but Celsius for water temp. I am pretty good with metres though.

 

[Storker]

I have read that 300 PSI = 200 Bar

Not quite. 3000 psi = 200 bar. Roughly.

 

[Chavodel8en]

Im an ignorant American.

I can roughly calculate a meter as equivalent to 3 feet in my head. All other metric measurements - cm, g, kg, deg C, bar -- are a mystery to me.

Im sure that if I was exposed to bar, I would get used to it quickly. As it is I would probably just roughly think of it as 1/10 of psi.

Whats funny is that I absolutely recognize that metric is a far superior system. But its tough to break your habits.

 

[Ana]

The pressure in a submarine is kept at about one atmosphere. The highest I've seen is two atmospheres for a leak test, and the lowest at nearly 8000' on the altimeter in engineering.


The ease in using metric or imperial is dependant upon how much you use the system. So it isn't so much that you get it, it is whether you use it. Living where imperial is the convention, there is no reason for me to use metric, say for gas planning, especially when all my dive buddies would be using imperial. It would be the same issue if the OP started using imperial with his buddies.

When in Rome...
Bob

I would agree if you are referring to visualizing a particular unit or system of units once you use it frequently, even if it is a combination from both systems. I learned to deal with psi and feet for diving.

Now when it comes to just pure calculations the Imperial system just blows, and I'm not even going to mention the blessed fraction of inches ... s o n o f a b ***** t c h. No wonder land surveyors use decimal feet.

You may not have a good idea of how big or small are 47 cm... but there is no need for a calculator to know they are 0.47m or 470mm. Boling water 100C, frozen 0C. 1 liter of pure cold water weights 1 kg.
Makes it easy to teach little kids with their 10 fingers.

Seriously the Imperial system is actually un-American. I wish they kicked out during the Revolutionary war. The dollar is divided in 100 pennies. We don't talk about 11/32nds of a dollar. Fraction speak only belongs when talking about pizza or pie and even with that, no one eats 9/16ths of pizza. ijs

 

[taimen]

It is tough to break your habits. Even after living for many years in the US, I was never able to buy meat or produce without doing the full conversions to grams in my head.
Same in scuba. I can't really adapt. I talk about 80cf bailouts but do all the calculations in metric.

 

[MargaritaMike]

The pressure in a submarine is kept at about one atmosphere. The highest I've seen is two atmospheres for a leak test, and the lowest at nearly 8000' on the altimeter in engineering.

Bob, when I first read the post that used submarine pressure I, too, was thinking that big boat that goes under the water, and it didn't make sense to me. Then I reread it thinking submarine = underwater and it made more sense to me.
I don't know for sure which way it was intended, but I could move on to the next post not totally befuddled. The operative word is totally.

Cheers -

 

[BRT]

Ever go shopping for car tires? Tire width is metric, rim diameter is imperial inches.

Those 80's Michelin TRX metric tires never caught on.

And to find the height of the tires in inches you have to multiply the width by the aspect ratio, change it to inches and add it to the rim diameter.

 

[Storker]

It is a measurement of volume, just like the liter. It is just under the US scuba labeling scheme we label them by effective capacity.

So you know that a HP100 contains about the same amount of gas as a LP100. Where as under the European labeling they would be labeled as 12L and 15L (IIRC) respectively to find out their effective capacity you would need to find the working pressure and multiple that out.

If my gas consumption rate is 15 L/min and I'm carrying a 15L tank , that's 1 bar/min at the surface, 3 bar/min at 20m and 4 bar/min at 30m. If I'm breathing 20 L/min and carrying a 10L, that's 2 bar/min at the surface, 6 bar/min at 20m and 8 bar/min at 30m. I can do that in my head and need only the actual tank numbers to do the math.

Now if your gas consumption rate is 0.4 cuF/min, how many psi/min is that at the surface, at 60ft and at 100ft? For an LP100 and an HP100?

 

[Lorenzoid]

I am American and never used metric except as a machinist. I know the conversion factors by heart. . . .

I still can't think in metric. I can't visualize 39 cm. . . .

I'm part of the small slice of the American public who are relatively fluent in metric length measurement because we were forced to play around with a "meter stick" in grade school in the '70s when the US was getting serious about switching over. I was at that age where one absorbs knowledge like a sponge, and I feel fortunate that I can still visualize that meter stick and X centimeters on it pretty easily. Granted, it's so close to a "yard stick" that it's not a major achievement, but what I'm saying is that I actually visualize that wooden stick with its printed centimeter divisions whenever I need to visualize centimeters.

 

[Storker]

I'm part of the small slice of the American public who are relatively fluent in metric length measurement because we were forced to play around with a "meter stick" in grade school in the '70s when the US was getting serious about switching over. I was at that age where one absorbs knowledge like a sponge, and I feel fortunate that I can still visualize that meter stick and X centimeters on it pretty easily. Granted, it's so close to a "yard stick" that it's not a major achievement, but what I'm saying is that I actually visualize that wooden stick with its printed centimeter divisions whenever I need to visualize centimeters.

I use these approximate visualizations:

1 mm: the length of the clipped off piece of my fingernail (yes, I prefer to keep my nails short)
1 cm: the width of my forefinger
1": the length of the outer joint of my thumb
10 cm: the width of my hand, plus a little
1': a little more than the length of my foot
1 m: the distance from my waist to the floor, or the length of one very long step
1 km: about 15 minutes' walk along the road, or about a 1 hour long hike in the terrain off track
1 statute mile: a little more than one and a half km
1 nautical mile: almost two km