Multiple channel photo-ionization detector for simultaneous and selective measurement of volatile organic compound
AssigneeRAE Systems, Inc.
InventorsHong T. Sun, Peter C. Hsi
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Abstract
A multiple-channel photo-ionization detector (PID) determines the concentrations of specific gases or classes of gases. The PID includes a UV lamp, an optical window which is divided into multiple zones with each zone producing a UV light beam having a distinctive maximum photon energy. The ionization chamber of the PID includes multiple ion detectors. The PID measures ionization currents and concentrations of gases ionizable by each UV light beam. A method of determining the concentrations and/or identifications of the individual component gases uses differences and/or ratios of measured concentrations or currents.
Claims20
A photo-ionization detector comprising:
- a UV light source;
- an optical window having a plurality of window zones, one of the window zones transmitting UV light having a first energy spectrum, which is different from a second energy spectrum of UV light transmitted from another one of the window zones;
- an ionization chamber adjacent to the optical window;
- and
- a plurality of ion detectors in the ionization chamber, each of the ion detectors measuring ionization that UV light from a corresponding one of the window zones causes.
A method for determining a concentration of selected gas compounds in a gas, comprising:
- producing a plurality of UV light beams, wherein a first energy spectrum of one of the UV light beams differs from a second energy spectrum of another one of the UV light beams;
- passing the UV light beams through the gas;
- measuring a plurality of current signals caused by the UV light beams ionizing gas molecules;
- and
- determining the concentration of the selected gas compounds from a difference in measurements.
A method for identifying a gas in a sample, comprising:
- producing a plurality of UV light beams, wherein a first energy spectrum of one of the UV light beams differs from a second energy spectrum of another one of the UV light beams;
- passing the UV light beams through the sample;
- measuring current signals caused by ionization of the sample associated with respective UV light beams;
- and
- comparing a ratio derived from the current signals to a ratio associated with the gas.
Dependencies are inferred from the claim text.