The high pressure sensitivity extension of thermal conductivity gauges

The various methods which have been proposed for extending thermal conductivity gauges beyond their normal sensitive range in the direction of atmospheric pressure are reviewed. An important development has been the application of thermal convection effects and various suggestions to employ both forced and natural convection have been used to extend the pressure sensitive range into the region of small Knudsen numbers, where the thermal conductivity of the gas is virtually independent of pressure. Some recent results are given which were obtained with a constant temperature hot wire gauge employing only the natural convection effect.