Metric vs Imperial

[Searcaigh]

Having been brought up in imperial and gone through a metric monetary change in the UK, and now having lived most of my life outside of the UK in metric countries I only think metric. The UK still measures distance in miles and vehicles record speed in mph. Irrespective of metric, we still refer to distance as mileage and not kilometerage!

At least we don't use degrees Kelvin for temperature except in science, but in aviation all flight levels are recorded in feet except in Russia and perhaps a few other east European countries that use meters.

For diving though personally I am 100% metric, although when I did my original course in the UK back in 1985 the exam questions were in both imperial and metric, I used a calculator to convert all to metric, do the calculations and then convert back to imperial, made more sense to me at the time.

 

[Rhone Man]

UK is still very much imperial units, even thought it is in the EU and by law everything is required to be denominated in metric. Hence you buy milk in bottles marked "4.1 litres (1 imperial gallon)".

The imperial world is slowly inching (hah!) towards the metric system. When I started diving wetsuit thickness was measured in 16ths of an inch - now they are measured in mm.

Most postgraduate work in the sciences relies upon calculations in metric and published in that form.

 

[Lorenzoid]

I remember in elementary school in the '70s being prepared to switch to the metric system. I even owned a meter stick. But it turned out to be just a tease. Then, in high school and college science courses, we used metric. But outside in the everyday world we use Imperial. Uh, except for a few things, like medicine dosages that are always in milligrams, and bottled water always in liters. I don't care which system we use in America, but I wish we would pick one and use it in every situation. Yes, metric would be a bit easier for diving. I would be happy to switch.

 

[Kevrumbo]

Easy Imperial US/Metric Conversions for depth & pressure, that you can do in your head:

Depth in Meters multiplied by 10/3 gives Depth in Feet;
Feet multiplied by 3/10 gives Meters.
Example: 18m(10/3) = 60' ; 60'(3/10) = 18m

Pressure Bar multiplied by 3/2, and multiplied again by 10 gives Pressure PSI;
Pressure PSI multiplied by 2/3, and divided by 10 gives Pressure Bar.
Ex): 200bar(3/2)(10) = 3000psi ; 3000psi(2/3)/10 = 200bar.

___
Your common counting numbers, or Reference Cardinal Numbers, for depth in Scuba are:

Imperial US (feet) by 10's:
Ex): 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110 etc

Metric System goes by 3's:
Ex): 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33 etc

Practice the depth conversion factors above between the two number sequences. . .

 

[Rhone Man]

Easy Imperial US/Metric Conversions for depth & pressure, that you can do in your head:

It is easy for mathematically literate people, but hopefully one day it should also be unnecessary.

I always say that the organisation who could change it at a stroke is the NFL: change football fields to being measured in metres and the US would be metric in two years.

 

[GrumpyOldGuy]

.....and everything to do with construction (try buying a metric 2"x4")

I've been watching Canada trying to convert to metric for several decades. Until the USA switches, the imperial system ain't going away in a hurry.

Its rather ironic that a 2 x 4 is not 2 inches by 4 inches. The size refers to the rough cut size, not the finished size. Now days, its then sanded down to something close to 1.5 x 3.5 inches.
When you work on an antique home like my 200 year old baby in NH, the framing is done with actual size rough cut wood and you have to pick some up from a mill, not Home Depot to match.

 

[Mr. Willoughby]

I'd love to see your house. Being in a relatively newly settled part of Canada there aren't that many 200 year plus homes around that are still standing. Most of the Heritage status building in my city are made from the abundant sandstone deposits from the beaches of the ancient sea that used to form this region.


*hijack over*

 

[mala]

The most common & ubiquitous tank used at all destination dive-ops around the world IS the AL80/11L tank. That's the single tank & twinset I mostly use wherever I go --and 2 bar/min is not pointless and understood in my post above, to be relative to the AL80/11L tank. For any other metric tank ratings, simply do the math . . .

Does that clarify things better? Anyway, it's all easier using Metric System. . .

i agree but you guys make the maths so hard.

if you know the pressure and the size of tank you can do the amount of litres in it.
divide by your sac rate at that depth and there you go.

ali 80's are a bad example because ali 80's are not all the same volume and they only ever hold 80cu ft for 1 breath.

 

[Kevrumbo]

i agree but you guys make the maths so hard.

if you know the pressure and the size of tank you can do the amount of litres in it.
divide by your sac rate at that depth and there you go.

ali 80's are a bad example because ali 80's are not all the same volume and they only ever hold 80cu ft for 1 breath.

The maths aren't so hard once you objectively understand the units you are trying to derive. . .

Again my point is your SPG reads in pressure bar units --not in volumetric or even time units. Hence it is preferable (to me that is) to calculate a pressure SCR (pressure Surface Consumption Rate) that is based on your own volumetric SCR (also known as RMV) divided- by THE PARTICULAR METRIC TANK RATING OF THE CYLINDER IN USE!


All 11L/bar (AL80) tanks hold 11 litres at the surface pressure of 1bar, therefore simply multiply your fill pressure by 11L/bar, and you have the supplied amount of gas in litres for your dive. But again my point is whether you have a nominal or short fill -as long as you know your pressure SCR for the particular tank in use- you'll intuitively know how much breathing gas you have left for the dive at depth, even before checking & confirming with your SPG . . .and all easier done in practice with the Metric System than with the cumbersome Imperial US units.

 

[j2s]

Imperial-vs-Metric........Insanity-vs-logic.......There's a book that reminds me of this...It was made into a movie...Catch-22....Everyone should see/read it.........