Identification of unknown gases using infrared absorption spectroscopy
AssigneeThe Foxboro Company
InventorsStephen Day, Kailash Swarna
Life of this patent
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Abstract
A method and apparatus for identifying an unknown gas by generating an infrared spectrum of the unknown gas using an infrared spectrophotometer that includes a circular variable interference filter, compressing the infrared spectrum of the unknown gas, and comparing the compressed infrared spectrum of the unknown gas to a library of compressed infrared spectra of reference compounds. After comparison, the compressed spectra that most closely match the unknown gas are decompressed and displayed. Because frequency characteristics of circular variable interference filters vary from filter to filter, information designating these frequency characteristics for the particular filter employed are used in generating the infrared spectrum of the unknown gas.
Claims17
A method of identifying an unknown gas, comprising:
- generating a set of infrared spectra of reference compounds to produce a library of infrared spectra of reference compounds,
- capturing a sample of said unknown gas,
- directing infrared energy through the captured sample of said unknown gas,
- producing a set of data corresponding to infrared characteristics of said unknown gas using an infrared spectrophotometer including a circular variable interference filter configured to receive the infrared energy directed through the captured sample of said unknown gas, said variable interference filter being comprised of a plurality of segments, each of said segments transmitting infrared energy across a frequency band from a starting frequency at a first end of said segment to an ending frequency at a second end of said segment, and
- identifying said unknown gas by generating an infrared spectrum of said unknown gas using said set of data and information designating said starting and ending frequencies of each of said segments of said variable interference filter.
An apparatus for identifying an unknown gas, comprising:
- an infrared spectrophotometer including a gas cell configured to capture a sample of said unknown gas, a source of infrared energy configured to direct infrared energy through said unknown gas in said gas cell, and a circular variable interference filter configured to receive the infrared energy directed through said unknown gas in said gas cell for producing an infrared spectrum of said unknown gas, said variable interference filter being comprised of a plurality of segments, each of said segments transmitting infrared energy across a frequency band from a starting frequency at a first end of said segment to an ending frequency at a second end of said segment,
- a library of infrared spectra of reference compounds, and
- circuitry for comparing said infrared spectrum of said unknown gas to said infrared spectra from said library, said circuitry using information about the starting and ending frequencies of each of said segments in making said comparison.
Dependencies are inferred from the claim text.