| AVS 55th International Symposium & Exhibition | |
| Vacuum Technology | Tuesday Sessions |
| Session VT-TuA |
| Session: | Vacuum Gauging and Calibration |
| Presenter: | S.M. Thornberg, Sandia National Laboratories |
| Authors: | S.M. Thornberg, Sandia National Laboratories J.M. Hochrein, Sandia National Laboratories J.R. Brown, Sandia National Laboratories R.D. Boyd, Sandia National Laboratories |
| Correspondent: | Click to Email |
In order to reduce uncertainties in gas law calculations, one must address each of the major variables: pressure, temperature and volume. Very accurate temperature and pressure gauges are available and can be measured directly with commercial instruments. However, volume is typically the variable in the ideal gas law that consistently contributes greatly to the uncertainty when performing gas calculations. Reducing the volume uncertainty is particularly challenging because volume is not measured directly but is derived from other dimensional, pressure, volume, mass and/or temperature parameters. A delta-V/delta P method for accurately measuring volumes will be presented along with a discussion of ways used to reduce uncertainties and randomness. This method uses calibrated micrometers and precision pressure gauges in an “isothermal” (the goal is to reach a thermal stability where the temperature drifts less than 0.001°C during the 15 minute measurement duration) environment, all of which provides measurement repeatabilities within +/- 0.005 cc for a nominal 10 cc volume.