There is no way to solve that problem with a pressure gauge alone, but the difference should be small enough not to matter seriously if you are driving. Unless it's a hurricane or some other extreme weather system. Peter -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads