公开(公告)号：US3612990A

公开(公告)日：1971-10-12

申请号：US3612990D

申请日：1969-10-24

Applicant: BECKMAN INSTRUMENTS INC

Inventor： DUCA ANTHONY DEL

IPC: G01N27/74 ,  G01R33/12 ,  G01R29/22

CPC classification number: G01N27/74

Abstract: Apparatus for determining the partial pressure of a paramagnetic gas in a gas mixture wherein a pivotally mounted test body, in the form of two hollow spheres in a dumbbell configuration, is supported in an inhomogeneous magnetic field, the test body being deflected from a null position when the paramagnetic gas is present and being restored to the null position by an electrostatic force, the magnitude of the restoring force being a function of the partial pressure of the paramagnetic gas, the improvement wherein mechanical constraints are provided to prevent excessive rotation or linear deflection of the test body. The mechanical constraint consists of at least two, and preferably four, electrostatic pole pieces positioned very close to the dumbbells on opposite sides thereof for limiting the deflection of the test body. In addition, the four pole pieces may be electrically cross-connected to form a capacitance bridge whereby deflection of the test body from its null position unbalances the bridge providing an output signal which may be fed back to the pole pieces to restore the test body to the null position.