Without going back to the picture, differential pressure gauge are common in industry - 0 Pa indicates that the pressure on both sides are equal, a negative pressure indicates that the pressure on the left hand side (whatever is meant by that) is greater and a positive pressure indicates that the pressure on the right-hand side is greater.
Of course, if you are measuring the pressure against a vacuum, you will always have a positive pressure. _____ From: [email protected] [mailto:[email protected]] On Behalf Of Michael Payne Sent: 09 July 2009 20:54 To: U.S. Metric Association Subject: [USMA:45330] Vacuum display I was under the impression SI pressure in Pascal's was always positive. Earth pressure near 100 kPa, Mars pressure near 20 kPa, outer space near 0 Pa. Is this correct. I see the gauge from Yellow Jacket has an area listing a minus side. Mike Payne
