Atmospheric Sampling and Gas Analysis

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The Stanford Research Systems QMS series gas analyzers offer an efficient, cost-effective solution for a wide range of applications.  These mass spectrometers simplify the task of on-line process monitoring, analysis of gas species, leak detection, and troubleshooting.

On-Line Monitoring

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.

• 100, 200 or 300 amu systems
• Pressures from 10 mbar to 1 bar
• Better than 1 amu resolution
• <0.5 second response time 
• Compact, transportable design
• 6 decades of dynamic range 
• RGA Windows software
• RS-232 interface

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.

 QMS Schematic
QMS schematic