AVS 51st International Symposium
    Vacuum Technology Tuesday Sessions
       Session VT-TuP

Paper VT-TuP5
New Approach to the Calibration of 10 torr Precise Vacuum Gauges

Tuesday, November 16, 2004, 4:00 pm, Room Exhibit Hall B

Session: Poster Session
Presenter: S.Y. Woo, Korea Research Institute of Standards and Science, Korea
Authors: S.Y. Woo, Korea Research Institute of Standards and Science, Korea
I.M. Choi, Korea Research Institute of Standards and Science, Korea
B.S. Kim, Korea Research Institute of Standards and Science, Korea
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Capacitance diaphragm gauges (CDG) are electromechanical pressure sensors in which the displacement of a stretched thin metal diaphragm is detected by a capacitance measurement. These are very accurate gauges and frequently used as transfer gauges. In order to calibrate such accurate vacuum gauges, precise mercury manometers have been used. However, complexity, harmfulness of mercury vapor, and cost of mercury manometers made it difficult to use in many calibration laboratories. As a substitute, a gas-operated piston gauges can be used for calibration of such vacuum gauges. But it is difficult to use them for low pressure measurements, because the pressure must be balanced against the weight of the piston, which generally corresponds to a pressure of several kilopascals. To reduce this minimum operating pressure, we adopted a variable bell-jar pressure method. We also developed a new home-made automatic mass loading apparatus which makes it possible to add or remove weights easily without breaking the vacuum during the calibration. Our calibration system can be used to measure pressures from 100 Pa to 2 kPa in the absolute mode. In this paper, practical calibration results are given for two different CDGs in the range of 10 torr full scale.