Spinning rotor gauge for operation at free spatial orientation

Abstract

A spinning rotor gauge (SRG) head with reinforced magnetic suspension and its metrological properties are presented. The new gauge can be operated at any orientation of the gauge head. Usually the gauge head stays with its axis vertical on the thimble (sensor tubing) which is fixed to the horizontal. Industrial applications sometimes require the thimble to be orientated in a non-horizontal position. This necessarily requires the gauge head axis, that is always perpendicular with respect to the thimble, to be tilted against the vertical. When the gauge head axis is vertical the magnetic drag on the rotating sensor is a minimum, effecting a residual pressure indication of the order of 10 −4 Pa, air equivalent. Maximum drag occurs with the gauge head axis horizontal. This is about 0.3 Pa equivalent, with a long-term stability of better than 10 −3 Pa. The rotor deceleration-versus-pressure characteristics were investigated for various inclination angles of the gauge head at pressures from atmospheric down to 10 −4 Pa.