On 10/01/2013 08:28, harry wrote:
On Jan 9, 9:36 pm, John Williamson
wrote:
Dave Liquorice wrote:
On Wed, 9 Jan 2013 19:27:02 +0000, tony sayer wrote:

He couldn't, nay did not, have any idea at all on how to convert bar
to PSI!..
TBH I'd have to go back to first principles and I'm not certain what a
"bar" actually is, 1 newton/square meter, naw that's way to small...
kilo newton/square meter? But even then I don't know the exact
conversion factor for kgf to pounds, it's about 2.2 but is that good
enough?

1 (Pound)/0.453592 (Kilogrammes) is 2.2046244201837774916665196917053.

How fussy are you and your applocation?

One bar is the same as 1000 mb or standard air pressure at sea level
the same as 14.50 PSI...

Except that the "Standard Atmosphere"(*) is 1013.25 mb or a tad under
14.7 psi... but that still doesn't tell me what a bar *is* in base units
of x newtons per square metre. My 14.5 times table isn't that good
either. B-)

Bar to Newtons per square metre conversion is easy. 1 bar is 100,000
N/m2, so you just need to move the decimal point. Fractionally over a
tonne weight per square meter on Earth.

1 bar is about 14.5 psi, or 0.987 standard atmospheres. So if you're
using a normal pressure gauge anywhere outside a lab, it's within the
"width of pointer" error limits to being 1 bar = 1 atmosphere. Failing
that, a more accurate short cut is to multiply pressure in bar by 15,
then knock two percent off and divide the total by 15 for "near enough"
atmospheres. That's quick mental arithmetic for me, and should be within
normal, natural, atmospheric pressure variations.

As for my 2.2, it's actually 2.204662 so, for this, 2.2 is "good enough".

(*) Except that there are quite a few "standard atmospheres" to choose
from. B-)

ISO standard temperature and pressure is 1 bar at 0 Celsius. Gauge
makers say that 1 bar is one atmosphere.
--
Tciao for Now!

John.

A bar was meant to atmospheric pressure but they got it wrong back
then.
A cubic metre of water was a metric tonne.
A metre was some fraction of the circumference of the earth (got that
wrong).
I think it was Napoleon's scientists. They even came up with a ten day
week.
http://en.wikipedia.org/wiki/Mesures_usuelles

The 10 day week was introduced earlier than that - 1793 if I have got it
right.

--
Rod