Sidestream infrared gas analyzer requiring small sample volumes
First Claim
1. An infrared gas analyzer for detecting the concentration of a gaseous component of a substantially gaseous flow stream provided via an airway, comprising:
- a source of infrared radiation having a first aperture;
an infrared energy detector disposed in an optical path of said infrared radiation so as to receive incident radiation from said infrared radiation source and to produce electrical signals representative of the received incident radiation, said infrared energy detector having a second aperture;
a sample cell disposed in a plane substantially perpendicular to said optical path said sample cell directing at least a portion of said substantially gaseous flow stream, in a direction substantially perpendicular to said optical path, between said infrared radiation source and said detector via a detection volume in said optical path, said sample cell comprising a gas passage for said substantially gaseous flow stream said sample cell having a cross-section which smoothly changes from a cross-section of said airway to a first aperture of said detection volume in a plane substantially parallel to said optical path so as to prevent turbulence in said substantially gaseous flow stream as it passes through said gas passage and said detection volume;
a first optical funnel in said optical path between said infrared radiation source and said detection volume which reduces a cross-section of said first aperture of said infrared radiation source to a cross section of a second aperture of said detection volume in a plane substantially perpendicular to said optical path without a measurable reduction in signal strength of said infrared radiation from said infrared radiation source as it passes through said first optical funnel and said detection volume;
a second optical funnel in said optical path between said detection volume and said infrared energy detector which increases a cross-section of said second aperture of said detection volume to a cross-section of said second aperture of said infrared energy detector without a measurable reduction in signal strength of said infrared radiation from said infrared radiation source as it passes through said second optical funnel and said second aperture of said infrared energy detector for detection by said infrared radiation detector; and
processing means for processing said electrical signals representative of the received incident radiation so as to produce an indication of the concentration of said gaseous component in said substantially gaseous flow stream.
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Accused Products
Abstract
An infrared gas analyzer implementing an optically stabilized detector in a sidestream configuration. In order to reduce the pneumatic sampling volume, an "optical funnel" or collimator is used to resize the optical aperture of a multi-channel optically stabilized detector without compromising signal strength. The smaller pneumatic volume is desirable in order to minimize the time required for a gas wavefront from the sample cell to traverse the optical aperture, thereby minimizing pneumatic response time. The geometry of the sample cell of the invention is also streamlined so that sharp corners or transitions which might induce turbulent gas flow are eliminated. The sample cell of the invention thus promotes smooth, laminar flow of aspirated respiratory gases through the optical aperture so as to preserve the temporal relationship of gas concentration wavefronts within the gas stream and to thereby allow the analyzer to exhibit a faster pneumatic response.
147 Citations
7 Claims
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1. An infrared gas analyzer for detecting the concentration of a gaseous component of a substantially gaseous flow stream provided via an airway, comprising:
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a source of infrared radiation having a first aperture; an infrared energy detector disposed in an optical path of said infrared radiation so as to receive incident radiation from said infrared radiation source and to produce electrical signals representative of the received incident radiation, said infrared energy detector having a second aperture; a sample cell disposed in a plane substantially perpendicular to said optical path said sample cell directing at least a portion of said substantially gaseous flow stream, in a direction substantially perpendicular to said optical path, between said infrared radiation source and said detector via a detection volume in said optical path, said sample cell comprising a gas passage for said substantially gaseous flow stream said sample cell having a cross-section which smoothly changes from a cross-section of said airway to a first aperture of said detection volume in a plane substantially parallel to said optical path so as to prevent turbulence in said substantially gaseous flow stream as it passes through said gas passage and said detection volume; a first optical funnel in said optical path between said infrared radiation source and said detection volume which reduces a cross-section of said first aperture of said infrared radiation source to a cross section of a second aperture of said detection volume in a plane substantially perpendicular to said optical path without a measurable reduction in signal strength of said infrared radiation from said infrared radiation source as it passes through said first optical funnel and said detection volume; a second optical funnel in said optical path between said detection volume and said infrared energy detector which increases a cross-section of said second aperture of said detection volume to a cross-section of said second aperture of said infrared energy detector without a measurable reduction in signal strength of said infrared radiation from said infrared radiation source as it passes through said second optical funnel and said second aperture of said infrared energy detector for detection by said infrared radiation detector; and processing means for processing said electrical signals representative of the received incident radiation so as to produce an indication of the concentration of said gaseous component in said substantially gaseous flow stream. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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Specification