

| Subject: | Re: Gauges |
| From: | Keith Hughes |
| Date: | Sat, 11 Oct 2008 12:47:52 -0700 |
Mike wrote: > As I said; 14.7 psi is a standard that is equal to atmopheric pressure > when measured at sea level................... Well, no you stated that 1 Bar = 1 ATM = 14.7 psi, which is clearly incorrect. Use the converter link *you* provided - it's quite simple. 1 Barg = 14.5 psig, 1 Bara = 14.5 psia. > > http://www.ilpi.com/msds/ref/pressureunits.html > > http://www.unitconversion.org/pressure/bar-conversion.html > > http://wiki.xtronics.com/index.php/Pressure_Conversion_Table > > > P.S.I. (bara or absolute bar) is not the same as P.S.I.G. (barg or > guage bar). The sea level standard has everything to do with guages; Absolute is referenced to vacuum, "gauge" is referenced to ambient pressure. Neither has *any* relevance to the unit conversion. 1 bar does not equal 14.7 psia. And sea level has nothing to do with pressure gauges - altimeters yes, that's why when you get the barometer reading from the airport weather station, it is Not the actual atmospheric pressure, it's the equivalent sea level pressure, corrected for local conditions of altitude and air density. Absolute pressure gauges/transducers are referenced to vacuum (i.e. read 0 at full vacuum), and gauge pressure gauges/transducers have to be calibrated to read zero at station pressure (i.e. ambient atmospheric pressure). At all elevations and atmospheric pressures, ambient pressure is 0 psig. Absolute pressure gauges/transducers, in ambient conditions, will read the atmospheric pressure. Here in Phoenix, ambient pressure is 0 psig, 14.15 � psia. Keith Hughes '86 Westy Tiico (Marvin)
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