This Technical Specification lays down the physical, technical and metrological conditions to be fulfilled when calibrations of vacuum gauges are performed by direct comparison with a reference gauge. From the conditions described can be deduced how to design an apparatus that can perform vacuum gauge calibrations in an adequate manner.
The vacuum gauges to be calibrated can be of any kind. Many types of gauges consist of several parts. Typically, these are gauge head, cable, operational device and signal read out. This whole set is considered as the unit that has to be calibrated. Whereas, if only the gauge head (i.e. that part of the vacuum gauge directly exposed to the vacuum) is calibrated, all set-ups and conditions would have to be recorded such that the user of the calibrated gauge head would be able to perform the measurements in the same manner as during the calibration.
The reference gauge is either a calibrated gauge traceable to a vacuum primary or national standard (normal case), with a calibration certificate according to ISO/IEC 17025, or an absolutely measuring instrument (rare case), traceable to the SI units and to which a measurement uncertainty can be attributed.
This Technical Specification does not give guidance on how to treat special types of vacuum gauges, be they reference standards or units under calibration, and it is intended that such guidance be given in other technical specifications.
The pressure range for calibrations treated in this Technical Specification depends on the realised design of the calibration apparatus and on the type of reference gauge. The range varies in its limits from 10 Pa to 110 kPa.