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US 6,969,857 B2Granted
Compensated infrared absorption sensor for carbon dioxide and other infrared absorbing gases
AssigneesSouthwest Research Institute, Gas Research Institute
InventorThomas E. Owen
Life of this patent
Estimating the term…
Abstract
A gas sensor, whose chamber uses filters and choppers in either a semicircular geometry or annular geometry, and incorporates separate infrared radiation filters and optical choppers. This configuration facilitates the use of a single infrared radiation source and a single detector for infrared measurements at two wavelengths, such that measurement errors may be compensated.
Claims21
A sensor for detecting an infrared absorbing subject gas in a gas mixture, comprising:
- a sensor chamber being generally in the shape of a hollow tube;
- an infrared radiation source at a first end of the sensor chamber, operable to generate a beam of infrared radiation along the length of the chamber;
- a first filter operable to receive a portion of the beam of infrared radiation and passing a wavelength of radiation known to be attenuated by transmission through the subject gas;
- a second filter operable to receive a second portion of the beam of infrared radiation and passing a wavelength of radiation known to be not significantly attenuated by transmission through the subject gas;
- wherein the filters are arranged immediately adjacent each other to form a cross-sectional closed-shaped geometry having an inner filter and an outer filter;
- a chopper operable to selectively and in succession block and pass radiation from the first filter and the second filter, the chopper comprising a stationary array of light modulating elements that are controllable in two sections to alternately block and pass the radiation;
- wherein the sections of the array have the same geometry as the inner and outer filter;
- and
- an infrared detector for detecting radiation passed through the chopper.
6 more elements
A method of detecting an infrared absorbing subject gas in a gas mixture, comprising:
- generating a beam of infrared radiation with a light source;
- filtering a first portion of the beam of infrared radiation, using a first filter, which passes a wavelength of radiation known to be attenuated by transmission through the subject gas;
- filtering a second portion of the beam of infrared radiation, using a second filter, which passes a wavelength of radiation known to not be significantly attenuated by transmission through the subject gas;
- wherein the filters are arranged immediately adjacent each other to form a cross-sectional polygon-shaped geometry having an inner filter and an outer filter;
- wherein the filters are equidistant from the light source;
- using a chopper to selectively and in succession block and pass radiation from the first and second filters, the chopper comprising a stationary array of light modulating elements that are controllable in two sections to alternately block and pass the radiation;
- wherein the sections of the array have the same geometry as the inner and outer filter;
- and
- detecting radiation passed through the chopper.
6 more elements
Dependencies are inferred from the claim text.