Uncertainties in calibration using capacitance diaphragm gauges as reference standard

A study of the uncertainties in calibration using capacitance diaphragm gauges as reference standard in the range from 1000 mbar to 10⁻³ mbar is presented. The contributions to the expanded uncertainty are: (i) Uncertainty from the calibration certify of the reference standard; (ii) Long-term stability or shift; (iii) Uncertainties inherent to the reference standard; (iv) Uncertainties derived from the calibration chamber; and (v) Uncertainties derived from the calibration procedure. These contributions have been determined for four reference standard capacitance diaphragm gauges of 1.3 mbar, 13 mbar, 130 mbar and 1300 mbar full scale used in routine calibration. Long-term stability or shift jointly with the uncertainty displayed in the calibration certifies issued by a National Metrological Laboratory are the main contributions to the expanded uncertainty. Values of the shift for each of the reference standard for a period of several years are presented and discussed. Best-expanded uncertainties obtained from calibration of a gauge of similar characteristics to the reference standards are:

10−3-1 mbar	4-0.2% of the reading
1-13 mbar	0.2% of the reading
13-130 mbar	0.2-0.08% of the reading
130-1300 mbar	0.2-0.06% of the reading

Full-size table