Recommended practices for the use of spinning rotor gauges in inter-laboratory comparisons

• The spinning rotor gauge is a common transfer standard in high-vacuum comparisons.
• Factors affecting gauge stability are discussed.
• The stability of SRGs in various key comparisons is summarized.
• A set of recommended practices for using spinning rotor gauges is given.

The spinning rotor gauge (SRG) is a common transfer standard in key comparisons (KCs) and other intercomparisons for pressures in the range of 1.0 × 10−4 Pa to 1.0 Pa. To make absolute pressure measurements using a SRG, a calibration factor, known as the accommodation coefficient, must be determined. Comparisons which utilize SRGs require each participant to determine the accommodation coefficient. The accommodation coefficient of an SRG is known to have excellent long-term stability (⩽0.1% over 1 year; k = 1) in a laboratory environment where the rotor remains undisturbed and attached to a vacuum standard, but the long-term stability of SRGs used in comparisons is often worse than what is observed in the participants own laboratory. Recently, the Bureau International des Poids et Mesures Consultative Committee for Mass and Related Quantities Working Group on Low Pressures held a workshop to discuss the stability of the accommodation coefficient in inter-laboratory comparisons. Here we summarize the data presented during the workshop and the ensuing discussions and give a list of recommended practices derived from the workshop.