Method and system for monitoring gas pressure for reference cavity of capacitance diaphragm gauge

摘要

A system and method detect the presence of an unacceptable quantity of gas molecules in the reference vacuum cavity of a capacitance diaphragm gauge (CDG). An independent pressure transducer has an active portion exposed to the reference vacuum cavity. The transducer includes a ring anode, a cylindrical inner wall surface that forms at least one cathode, and a magnet positioned with respect to the ring anode such that the magnetic flux of the magnet is generally aligned with the central axis of the ring anode. A high voltage source applies a voltage between the ring anode and the cathode. A current sensor senses a magnitude of any current flowing between the ring anode and the cathode via ionized gas molecules. A monitoring unit monitors the magnitude of the current sensed by the current sensor and activates an alarm when the magnitude of the current exceeds an acceptable magnitude.

主权项

1. A method for detecting the presence of an unacceptable quantity of gas molecules in the reference vacuum cavity of a capacitance diaphragm gauge (CDG), the method comprising:
inserting an independent pressure transducer into the reference vacuum cavity of the CDG, the independent pressure transducer comprising a ring anode, at least one cathode and a magnet, the magnet positioned to generate a magnetic flux along a central axis of the ring anode; applying a high voltage between the anode and the cathode to generate an electrical field to ionize gas molecules proximate to the anode and the at least one cathode; measuring a magnitude of a current flowing between the anode and the cathode via ionized gas molecules; and sensing when the magnitude of the current exceeds a predetermined acceptable current magnitude to thereby determine that the quantity of gas molecules in the reference vacuum cavity exceeds an acceptable quantity of gas molecules.