This International Standard specifies 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, the design of an apparatus that can perform vacuum gauge calibrations in an adequate manner can be deduced.

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 entire set is considered as the unit that has to be calibrated. Whereas, if only the gauge head (i.e. the 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/IEC17025, or an absolute measuring instrument (rare case), traceable to the SI units and to which a measurement uncertainty can be attributed.

This International Standard does not give guidance on how to treat special types of vacuum gauges, be they reference standards or units under calibration; it is intended that such guidance be given in other International Standards.

The pressure range for calibrations treated in this International Standard depends on the realized design of the calibration apparatus and on the type of reference gauge. The range varies in its limits from 10^-6 Pa to 110kPa.