# US 5,781,306 A · Measuring apparatus for gas analysis > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,781,306 A - Document ID: US5781306A - Status: Granted - Kind: A - Application number: 08/565,396 - Filed: 1995-11-30 - Granted: 1998-07-14 - Earliest claimed: 1994-12-02 - Assignees: Erwin Sick GmbH Optik-Elektronik - Inventors: Wolfgang Hartig; Jurgen Kaufmann - Web page: https://patentgrep.com/patent/US5781306A ## CPC - G01N 21/31: Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry {(G01N21/72 takes precedence)} - G01N 21/8507: {Probe photometers, i.e. with optical measuring part dipped into fluid sample} - G01N 2021/8521: {with a combination mirror cell-cuvette} - G01N 2021/8578: {Gaseous flow} - 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 spectrometric gas measurement apparatus for the determination of the presence and/or concentration of gases in a spatial region has a spectrometric measurement head which transmits into the spatial region measurement radiation having the spectral ranges necessary for the determination of the gases. Furthermore, a reflector is provided at the spatial region which reflects the light which is passed through at least a part of the spatial region back to the measurement head where it is split up spectrally in an analyzer and then supplied to a photoreceiver arrangement. A measurement tube extending in the direction of light propagation is provided in the spatial region through which the measurement light passes. The measurement tube has a transverse throughflow opening, is closed at the end remote from the measurement head, accommodates the retro-reflector, and is also supplied at both ends of the transverse throughflow opening with flushing air which stands at a slight excess pressure relative to the spatial region. A reference tube with an audit cell is inserted in front of the measurement tube. ## Claims ### Claim 1 A spectrometric gas measuring apparatus for determining the presence of gases in a spatial region, the apparatus comprising: a spectrometric measurement head that is mountable at the spatial region including an irradiation source and an analyzer, the irradiation source transmitting measurement beams having spectral ranges required for the determination of the gases into the spatial region; a measurement reflector at the spatial region that reflects light that has passed through at least a portion of the spatial region back to the measurement head, the light being spectrally broken down in the analyzer; a photoreceiver arrangement that receives the spectrally broken down light from the analyzer and generates electrical signals that are respectively associated with a specific wavelength, the electrical signals being applied to an electronic evaluation circuit that determines the presence of the gases; and a measurement tube in the spatial region through which the measurement radiation passes, the measurement tube extending in a direction of light propagation and having a transverse throughflow opening communicating with the surrounding spatial region, the measurement tube being closed at an end remote from the measurement head and accommodating the measurement reflector, the measurement tube being supplied at both ends of the transverse throughflow opening with a spectrally neutral flushing gas relative to a spectral measurement range at a slightly higher pressure relative to the spatial region. ### Claim 2 (depends on 1) A gas measuring apparatus in accordance with claim 1 wherein the transverse throughflow opening extends in the direction of flow of the gas located in the spatial region. ### Claim 3 (depends on 1) A gas measuring apparatus in accordance with claim 1 wherein the flushing gas supply is provided into end regions of the measurement tube remote from the transverse throughflow opening. ### Claim 4 (depends on 1) A gas measuring apparatus in accordance with claim 1 wherein the transverse throughflow opening is formed as a transverse gap. ### Claim 5 (depends on 1) A gas measuring apparatus in accordance with claim 1 wherein the measurement tube is double-walled and the inner space of the double wall serves for the supply of flushing gas. ### Claim 6 (depends on 1) A gas measuring apparatus in accordance with claim 1 wherein a reference tube is inserted in front of the tube which is likewise traversed by the measurement radiation; wherein a reference cell, which can be filled in a defined manner with one or more reference gases, is provided in the reference tube and is closed off at least relative to the measurement tube; and wherein a zero-point reflector, which can be swung in and swung out, is provided at the end of the reference tube adjacent the measurement tube. ### Claim 7 (depends on 6) A gas measuring apparatus in accordance with claim 6 wherein the zero-point reflector is arranged in a space which is closed off at both ends by a window. ### Claim 8 (depends on 1) A gas measuring apparatus in accordance with claim 1 wherein space in front of the measurement reflector is closed off by a window. ### Claim 9 (depends on 6) A gas measuring apparatus in accordance with claim 6 wherein a further transverse throughflow opening is provided in the region of the reference cell. ### Claim 10 (depends on 9) A gas measuring apparatus in accordance with claim 9 wherein the further transverse throughflow opening extends in a direction of flow of gas located in the spatial region. ### Claim 11 (depends on 6) A gas measuring apparatus in accordance with claim 6 wherein the reference tube is of double-wall design, wherein an inner space of the double wall serves as a supply for flushing gas, and wherein measurement tube inner spaces and reference tube inner spaces are in flow communication. ### Claim 12 (depends on 6) A gas measuring apparatus in accordance with claim 6 wherein the reference cell is an audit cell. ### Claim 13 (depends on 6) A gas measuring apparatus in accordance with claim 6 wherein a flushing gas supply tube is inserted in front of the measurement tube. ### Claim 14 (depends on 6) A gas measuring apparatus in accordance with claim 6 wherein a flushing gas supply and extraction line is provided at an entrance to the reference tube. ### Claim 15 (depends on 6) A gas measuring apparatus in accordance with claim 6 wherein a thrust rod extends to the zero-point reflector in the reference tube. ### Claim 16 (depends on 6) A gas measuring apparatus in accordance with claim 6 wherein the measurement tube and the reference tube are formed as a one-piece tube structure. ### Claim 17 (depends on 1) A gas measuring apparatus in accordance with claim 1 wherein the measurement reflector comprises a retro-reflector. ### Claim 18 (depends on 1) A gas measuring apparatus in accordance with claim 1 wherein the photoreceiver arrangement generates electrical signals that are respectively associated with a specific range of wavelengths as opposed to a specific wavelength. ### Claim 19 (depends on 1) A gas measuring apparatus in accordance with claim 1 wherein the electronic evaluation circuit determines the concentration of gases. ### Claim 20 (depends on 1) A gas measuring apparatus in accordance with claim 1 wherein the neutral flushing gas comprises flushing air. ### Claim 21 (depends on 6) A gas measuring apparatus in accordance with claim 6 wherein the reference tube is closed off relative to the measurement head by a window. ### Claim 22 (depends on 13) A gas measuring apparatus in accordance with claim 13 wherein the flushing gas supply tube is inserted in front of the reference tube. ### Claim 23 (depends on 14) A gas measuring apparatus in accordance with claim 14 wherein the flushing gas supply and extraction line extends through the measurement head. ### Claim 24 (depends on 14) A gas measuring apparatus in accordance with claim 14 wherein the flushing gas supply and extraction line extends through the flushing gas supply tube. ### Claim 25 (depends on 15) A gas measuring apparatus in accordance with claim 15 wherein the thrust rod extends through the entrance to the reference tube. ### Claim 26 (depends on 25) A gas measuring apparatus in accordance with claim 25 wherein the thrust rod extends through the flushing gas supply tube. ### Claim 27 (depends on 25) A gas measuring apparatus in accordance with claim 25 wherein the thrust rod extends through the measurement head.