The QMS system can continuously sample gas at flow rates of several milliliters per minute. The inlet can be equipped to sample at pressures from 1 bar to 10 mbar. Data is acquired continuously, as opposed to batch sampling which is employed by gas chromatographs. The QMS has a fast response time of less than 0.5 seconds. Complete spectra can be recorded in seconds, and individual masses can be measured at rates up to 25 points per second.
The QMS uses a two stage pressure reducing inlet to sample gases at high pressure. This allows the use of a residual gas analyzer (which operates at high vacuum) as the detector. Different capillaries permit the system to sample at higher or lower pressures. A large flow is drawn through the capillary which drops the pressure three decades. A hybrid turbomolecular/drag pump draws a small amount of gas through an aperture, which reduces the pressure to about 10-6 Torr, while most of the flow is bypassed directly to a diaphragm pump. Solenoid valves control the gas flow.
The entire system is controlled by a microprocessor which ensures correct operation of the pumps and valves. The software manages the spectrometer and acquires data in a choice of six different modes. An optional high-vacuum 2.75" CF port provides direct access to the RGA.