Wüest M. 51 Wykes M. 82 Yamaguchi M. 17 Ybarra G. 129 Yubero F ...

JUNE 26 MONDAY AFTERNOON
WS-18-MoA. OR.4 LONG TERM SHIFT IN CAPACITANCE GAUGES: CONTRIBUTION
TO THE TOTAL UNCERTAINTY. J. M. Hidalgo * and J. L. de Segovia** Telstar Industrial S.L.
José Tapiolas 120, O8226 Terrassa Spain. ** Instituto de Ciencia de Materiales,CSIC,Cantoblanco,28240Madrid,Spain
e-mail:jldesegovia@icmm.csic.es/j.mhidalgo@telstar.es
One of the contributions to total uncertainty in capacitance gauges is the shift of long-term stability.
This contribution can be only determined by recalibrations usually with a periodicity of one year. In
the present work, we present a study of the “shift” of four capacitance manometers ranging from 1000
mbar to 10 -3 mbar. Recalibration of the reference standard took place at two National Laboratories
with one-year periodicity and for a total time up to six years depending of the gauge. This is an
enough extended period to obtain some conclusions about the long-term stability in this kind of
gauges. Based on their principle of working the higher contribution to the “shift” is expected from the
fatigue of the material of the membrane. The deviation i.e., the difference between the readings of
working standard of the National Laboratory and the calibrating gauge, are also discussed. The several
contributions to the total uncertainty are presented and compared with the uncertainty due to the shift.
As consecutive recalibrations are not performed at the same calibrating points in the primary standard
of the National Laboratory, it is necessary to perform interpolations to obtain the differences of the
readings at the same calibrating points, uncertainty considered in the final expanded uncertainties
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