>OK folks this might be the dummest question but... >Is a vacuum gauge going from 30" of vacuum down to 0" the same as a >manifold pressure gauge going from 0" of pressure up to 30". If so, and >it's just a dial face change, why are the latter so much more expensive. >See, for example, in the Aircraft Spruce catalog (mine is old at >1998-1999):
No, the two gauges are not the same. A vacuum gauge is measured in inches of mercury and uses an internal bourdon tube which flexes and contracts with pressure changes and is what a standard pressure gauge uses to measure pressure. A manifold pressure gauge measures inches of water which is a very low pressure and incorporates a diaphragm to make the measurement and is calibrated accordingly. Now, if you really want to save money, my company sells every type of pressure gauge you can think of and we have 63mm (2 1/2") 0-30" hg gauges for $25 each. These are all stainless steel case, panel mount held in place by a U-clamp. Mark Jones (N886MJ Wales, WI
