IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Vacuum Science & Technology Thursday Sessions
       Session VST-ThM

Paper VST-ThM3
Using Capacitance Diaphragm Gauges at Different Temperatures

Thursday, November 1, 2001, 9:00 am, Room 125

Session: Pressure & Flow Measurement Instruments & Their Calibration
Presenter: J.C. Greenwood, National Physical Laboratory, U.K.
Authors: J.C. Greenwood, National Physical Laboratory, U.K.
U.M.E. Christmas, University of Surrey, UK
Correspondent: Click to Email
Capacitance diaphragm gauges are used in many industrial applications for absolute pressure measurements. The gauges are heated to improve stability but this procedure introduces thermal transpiration effects due to the temperature difference between the gauge head and the vacuum system. Calibration incorporates these effects although the calibration data are only valid when the gauge is operated at the same temperature as that during calibration. In practice, different temperatures are used and systematic errors are introduced. The calibration data can be represented using a thermal transpiration model but it is not clear whether such a model provides an adequate method of predicting performance at different temperatures. Two capacitance diaphragm gauges have been calibrated over the pressure range 0.02 Pa to 133 Pa at three different ambient temperatures and the calibration data at temperatures of 291K and 301K have been compared with the data predicted by applying a thermal transpiration model to data collected at 293K. The uncertainty associated with making such a prediction is evaluated.