Abstract: Spinning rotor gauge has excellent metrological characteristics in high vacuum. However, condensable gas, such as water vapor, is more likely to absorb or occur phase transition on the chamber or rotor surface. It would lead to the deviation of the measurand, what is more, the nonlinear change of the tangential momentum accommodation coefficient. Pointing at this problem, a balanced and stable pre-stage pressure of water vapor was generated by pumping and sublimating solid ice, and then the standard pressure was obtained by adiabatic expansion. The adsorption and desorption curves of water vapor molecules on the chamber surface were tested at room temperature (23 ℃) and high temperature (150 ℃), respectively. The corresponding adsorption and desorption amounts under the same pressure were calculated. Finally, the deviation between the measured value and the revised standard pressure was analyzed. The determination results show that it is challenging to obtain the accurate standard pressure at 23 ℃. Only the adsorption amount of water vapor molecules on the walls of chamber and its associated pipelines can be calculated after closing the valve. At 150 ℃, some water vapor molecules may adsorb on the walls of adjacent pipelines with temperature lower than 150 ℃, resulting in the measured pressure slightly lower than the standard pressure.

Key words: spinning rotor gauge, static expansion method, water vapor, adsorption