Designation:D4023–82a(Reapproved1996)AnAmericanNationalStandardStandardTerminologyRelatingtoHumidityMeasurements1ThisstandardisissuedunderthefixeddesignationD4023;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(e)indicatesaneditorialchangesincethelastrevisionorreapproval.absolutehumidity,vaporconcentration,vapordensity,dv—theratioofthemassofwatervapormvtothetotalvolumeofthemoistairv:dv5mvv(1)dewcell,dewprobe—aninstrumentthatmeasuresthetem-peratureatwhichasaturatedsaltsolution(usuallyoflithiumchloride)isinequilibriumwiththewatervaporinmoistair.dew-/frost-pointhygrometer—aninstrumentthatmeasuresthesurfacetemperatureatwhichambientwatervaporcondenses.dry-bulbtemperature,t—thetemperatureoftheambientair,forexample,thetemperaturethatismeasuredbythedrybulbthermometerofapsychrometer.electrichygrometer—aninstrumentthatdeterminesthewatervaporcontentofanatmospherebymeasuringthechangeinresistanceorcapacitanceofhygroscopicmaterial.enhancementfactor—thecorrectionforthedepartureofthemixtureofairandwatervaporfromidealgaslaws.ice-bulbtemperature,ti—thetemperaturethatathermometerindicateswhenitsbulbissurroundedbyathinfilmofice(orafrozenmoistenedcovering),andallowedtocoolbysublimationoftheiceintothesurroundingair.mechanicalhygrometer—aninstrumentfordeterminingthewatervaporcontentofanatmospherebymeasuringthedimensionalchangeproducedinanhygroscopicmaterial.mixingratio,r—theratioofthemassofwatervapormvtothemassofdryairmapresentinthemoistair;r5mvma(2)molefractionofwatervapor,xv—theratioofthenumberofmolesofwatervapornvtothetotalnumberofmolesofwateranddryair;xv5nvnv1na(3)where:nv5mvMv(4)na5maMa(5)andwhereMvandMaarethemolecularweightsofwatervaporandair,respectively.psychrometer,aspirated—anhygrometercomprisingwet-anddry-bulbthermometersthataremountedinahousingtowhichisattachedamotordrivenfanorblowerthatdrawsairoverthethermometerbulbs...
