# US 8,785,857 B2 · Infrared sensor with multiple sources for gas measurement > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,785,857 B2 - Document ID: US8785857B2 - Status: Granted - Kind: B2 - Application number: 13/242,677 - Filed: 2011-09-23 - Published: 2013-03-28 - Granted: 2014-07-22 - Earliest claimed: 2011-09-23 - Assignees: MSA Technology, LLC - Applicants: Christopher D. Starta; Robert E. Uber; Thomas Trautzsch; Frederick J. Schuler - Inventors: Christopher D. Starta; Robert E. Uber; Thomas Trautzsch; Frederick J. Schuler - Web page: https://patentgrep.com/patent/US8785857B2 ## CPC - G01N 21/59: Transmissivity (G01N21/25 takes precedence) - G01N 21/3504: for analysing gases, e.g. multi-gas analysis - G01N 21/3151: {using two sources of radiation of different wavelengths (G01N21/33 - G01N21/39 take precedence)} - G01N 2201/023: Controlling conditions in casing - G01N 2201/0636: Reflectors - G01N 2201/0662: Comparing measurements on two or more paths in one sample - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) ## Abstract A closed path infrared sensor includes an enclosure, a first energy source within the enclosure, at least a second energy source within the enclosure, at least one detector system within the enclosure and a mirror system external to the enclosure and spaced from the enclosure. The mirror system reflects energy from the first energy source to the at least one detector system via a first analytical path and reflects energy from the second energy source to the at least one detector system via a second analytical path. Each of the first analytical path and the second analytical path are less than two feet in length. ## Claims ### Claim 1 A closed path infrared sensor, comprising: an enclosure, a first energy source within the enclosure, at least a second energy source with the enclosure, at least one detector system within the enclosure, and a mirror system external to the enclosure and spaced from the enclosure, the mirror system reflecting energy from the first energy source to the at least one detector system via a first analytical path and reflecting energy from the second energy source to the at least one detector system via a second analytical path, each of the first analytical path and the second analytical path being less than two feet in length, a length of the first analytical path within the enclosure being less than 10% of a total length of the first analytical path, and a length of the second analytical path within the enclosure being less than 10% of a total length of the second analytical path. ### Claim 2 (depends on 1) The sensor of claim 1 wherein each of the first analytical path and the second analytical path is less than one foot in length. ### Claim 3 (depends on 1) The sensor of claim 1 wherein each of the first analytical path and the second analytical path is less than six inches in length. ### Claim 4 (depends on 1) The sensor of claim 1 wherein the mirror system comprises a first mirror section having a concave shape over at least a portion of a surface thereof and a second mirror section having a concave shape over at least a portion of a surface thereof. ### Claim 5 (depends on 4) The sensor of claim 4 wherein the surface of the first mirror section and the surface of the second mirror section intersect. ### Claim 6 (depends on 5) The sensor of claim 5 wherein the first analytical path and the second analytical paths are of approximately the same length. ### Claim 7 (depends on 6) The sensor of claim 6 wherein the enclosure comprises a window transmissive of infrared energy positioned between each of the first energy source, the second energy source, and the at least one detector system and the mirror system. ### Claim 8 (depends on 6) The sensor of claim 6 wherein the length of the first analytical path within the enclosure is less than 5% of the total length of the first analytical path, and the length of the second analytical path within the enclosure is less than 5% of the total length of the second analytical path. ### Claim 9 (depends on 5) The sensor of claim 5 wherein the first mirror section and the second mirror section are formed on a monolithic base. ### Claim 10 (depends on 7) The sensor of claim 7 wherein the monolithic base is formed from a polymeric material upon which a reflective surface is supported. ### Claim 11 (depends on 7) The sensor of claim 7 wherein the mirror system is supported upon a mirror support that is spaced from the enclosure by at least one extending member in operative connection with the enclosure. ### Claim 12 (depends on 1) The sensor of claim 1 wherein the enclosure comprises a window transmissive of infrared energy positioned between each of the first energy source, the second energy source, and the at least one detector system and the mirror system. ### Claim 13 (depends on 1) The sensor of claim 1 wherein the at least one detector system is a multi-channel detector system including a housing and a beam splitter within housing. ### Claim 14 (depends on 13) The sensor of claim 13 wherein the beam splitter is adapted to split incident infrared light energy into two beams, wherein one beam is directed to a reference channel and another beam is directed to an analytical channel. ### Claim 15 (depends on 1) The sensor of claim 1 wherein the first energy source is modulated at a first frequency and the second energy source is modulated at a second frequency different from the first frequency. ### Claim 16 (depends on 1) The sensor of claim 1 wherein the mirror system comprises a first mirror defining the first analytical path and a second mirror defining the second analytical path, wherein the first mirror is located at a first position and the second mirror is located at a second position different from the first position so that a length of the first analytical path is different from a length of the second analytical path. ### Claim 17 (depends on 16) The sensor of claim 16 wherein each of the first analytical path and the second analytical path is less than one foot in length. ### Claim 18 (depends on 16) The sensor of claim 16 wherein each of the first analytical path and the second analytical path is less than six inches in length. ### Claim 19 (depends on 18) The sensor of claim 18 wherein the enclosure comprises a window transmissive of infrared energy positioned between each of the first energy source, the second energy source, and the at least one detector system and the mirror system. ### Claim 20 A method of detecting a gas, comprising: exciting a first energy source positioned within an enclosure such that energy from the first energy source impinges upon a mirror system positioned external to the enclosure and spaced from the enclosure, the mirror system reflecting energy from the first energy source to at least one detector system positioned within the enclosure via a first analytical path, exciting at least a second energy source positioned within an enclosure such that energy from the second energy source impinges upon the mirror system, the mirror system reflecting energy from the second energy source to the at least one detector system via a second analytical path, which is different from the first analytical path, each of the first analytical path and the second analytical path being less than two feet in length, a length of the first analytical path within the enclosure being less than 10% of a total length of the first analytical path, and a length of the second analytical path within the enclosure being less than 10% of a total length of the second analytical path; and determining a concentration of the gas based upon an analytical signal output from the detector system corresponding to the first analytical path and an analytical signal output from the detector system corresponding to the second analytical path.