Method of Measuring Low Pressures Using Thermistors and Determining Orifice Effects in Rarefied Gas Flow . Methode de Mesure de Basses Pressions Par Thermistances et Determination des Effets Dorifice Dans des Ecoulements de Gaz Rarefie

摘要

Details concerning the use of thermistors as vacuum gages are given for the pressure range between 1 and 500 microns of mercury. The thermistor device is based upon the principle that the dissipation constant of the thermistor depends on the thermal conductivity of the gas in which it is immersed. Sensitive elements are miniaturized so that they can be easily mounted, as on a wind tunnel model, for example. Orifice effects on wall pressure and impact pressure measurements were studied as a function of several flow conditions involving a wide range of Mach numbers and Reynolds numbers. The results indicate that it is possible to choose an appropriate pitot tube diameter according to actual flow conditions, in order to avoid a significant orifice effect. (Author)