Rae Systems, Inc.

Wenjun Yang

Peter C Hsi

A gas analysis system and method use foreground broadband gas monitoring and background selective gas analysis. The foreground broadband monitoring indicates concentrations of a class of chemicals or contaminants in a gas sample, provides real-time warnings of contaminants, and can activate the background selective analysis. Separate broadband detectors and gas analyzers can respectively perform broadband monitoring and selective analysis. To reduce system components, a broadband detector that performs broadband monitoring switches to measure concentrations of chemicals output from a separation device for the selective analysis.

Gas analyzer with real-time broadband monitoring and snapshot selective detection

A photo-ionization detector (PID) employs combinations of ion mobility spectrometry, ionization energy discrimination, and chemical filtering to identify the presence and quantity of specific gases. One such PID introduces a gas sample into an ionization chamber at an end of a drift tube. UV light from a PI source ionizes ionizable molecules contained in the gas sample. The PI source includes either multiple UV lamps, each having a specific energy level for discriminating between potential constituents of the gas sample or one multiple-energy level UV lamp with different light bandwidth window zones and a zone selector. A shutter grid separates the ionization chamber from the drift tube. When the shutter grid is open, an electric field in the drift tube attracts ions that travel against the flow of a drift gas until a collector electrode at the end of the drift tube captures the ions. A time required for the ions to travel the length of the drift tube is characteristic of the type of ion. Thin mesh electrodes in the drift tube sustain a uniform electric field so that groups of ions traveling down the drift tube to create well defined current pulses at the collector electrode.

Selective photo-ionization detector using ion mobility spectrometry

A discharge ionization detector (DID) includes a sensor that uses an alternating current (AC) discharge through a working gas as an ionization source. The sensor includes a discharge chamber, into which the working gas is introduced, and an ionization chamber, into which a sample gas is introduced. UV photons from the discharge chamber and metastable particles that enter the ionization chamber from the discharge chamber ionize molecules in the sample gas. The ions generated from the ionized sample gas are measured as a current indicating the quantity of ionizable molecules in the sample gas. For selective identification of molecules in the sample gas, one or more chemical filters can filter the sample gas to separate target gases from gases that interfere with detection of the target gases. Additionally, a supply for the working gas can change the working gas to change the maximum energy available for ionization of the sample gas. Thus, current measurements with different working gases indicate quantities of classes of molecules having different ionization potentials.

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San Jose, CA, United States of America

Wenjun Yang