Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: havril on 29/03/2004 14:40:02

Title: vacuum measurements
Post by: havril on 29/03/2004 14:40:02

Somebody told me that the vacuum inside a certain container was 0.5 mbars. I did not have the opportunity to ask him to expand on how the mbar scale works. So I wonder if someone out there can help?

TIA
Harvey

Title: Re: vacuum measurements
Post by: roberth on 29/03/2004 23:59:11

I'm guessing that a mbar is a millibar or one thousandth of a bar. A bar is the atmospheric pressure at sea level and is equal to about 14 psi. When you see a weather map showing isobars (or areas of similar air pressure), the one's below 1000 represent low pressure areas and the ones above 1000 are high pressure areas. These measurements are in millibars.

Title: Re: vacuum measurements
Post by: qpan on 30/03/2004 11:29:53

The metric conversion is 1 bar = 10^5 Pa (Pascals = N/(m^2)), so one millibar = 10^2 Pa.

"I have great faith in fools; self-confidence my friends call it."
-Edgar Allan Poe

Title: Re: vacuum measurements
Post by: gsmollin on 30/03/2004 12:06:08

I'm going on memory here, so don't pillory me if I'm wrong... The definition of a bar = 1 million dynes / square centimeter. It converts to about 14.5 psi.