>Posted on 15 Aug 1996 at 11:39:22 by JHEIMANN.US.ORACLE.COM > > >Analog depth gauges are just pressure meters, so a reading of 20 ffw >on an analog gauge means the same absolute pressure at altitude as >at sea level. So you are right, if I used an analog gauge, this is >a really dumb question. > Not all analog gauges are absolute pressure gauges: The capillary gauge is an analog gauge and it measures ambient pressure in units of the pressure at the surface. This is very convenient if you want to use sealevel tables in thin air. Now the pressure at altitude (in psi) is p(altitude) = 14.69 exp (- [altitude]/27500 feet) which means the corrective factors for the various quantities you might be interested in during the execution of such a dive can be extracted depending on what type of pressure gauges you have. Regards, John
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