Enclosure sealing testing system - uses measurement of partial pressure of helium in air extracted from evacuated enclosure

摘要

Natural helium in the air is used to check sealing of an enclosure. A vacuum is created in the enclosure which is surrounded by air and periodic samples are taken from the enclosure. Sealing is checked by measuring partial pressure of helium in the sample. A pump (14) with valve (15) is used to create a vacuum in an enclosure (10) which is surrounded by air (12). A measuring chamber (16) is evacuated through valves (26, 40) by a pump (32). An open valve (20) allows measuring chamber pressure to stabilise then the valve is closed. An outlet valve (26) is opened to allow a measuring system (30) to sense partial pressure of helium. Calibration is performed using known quantity of helium from a source (42).