Gas analyzer
First Claim
1. A gas analyzer comprising:
- an infrared energy source for repetitively directing along an optical path and toward a sample cell first infrared energy having a first wave length generally different from the wave lengths absorbed by a gas sample, second infrared energy having a second wave length, at least some of which will be absorbed by a gas sample, and substantially no infrared energy;
a sample cell disposed in said optical path, said sample cell having substantially infrared transparent windows to allow infrared radiation to pass therethrough;
detector means sensitive to infrared radiation in said optical path passing through said sample cell, said detector means comprising a photodetector coupled to a controllable power source;
synchronizing means for providing signals indicative of the state of radiation being emitted from said infrared energy source;
electronic means coupled to said synchronizing means and said detector means for providing a first signal of a first predetermined level when said infrared energy source is directing said first infrared energy along said optical path, for providing a second signal of a second predetermined level when said infrared energy source is directing substantially no infrared energy along said optical path, and for providing a third signal of a level substantially equal to said first signal level when said infrared energy source is directing said second infrared energy along said optical path and said sample cell is substantially free of the gas to be detected;
said electronic means including automatic gain control means coupled to said power source to maintain the difference in said first and second signal levels at a predetermined level, whereby the difference in said third and first signal levels is indicative of the gas to be detected in the sample cell.
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Accused Products
Abstract
An improved gas analyzer for measuring the presence of one or more gaseous compounds in a gas sample. The gas analyzer has an infrared source stabilized against temperature variations by a radiation loading scheme in combination with a selected source environmental temperature sensitivity to provide a stable source temperature without a conventional temperature controller. A rotating interference filter assembly is disposed in the optical path. This assembly alternately totally blocks radiation, passes radiation in a wave length band which will not be absorbed by a random gas sample, and sequentially passes radiation in one or more additional bands which will be absorbed by one or more gases in the sample cell. The sample cell features a unique enclosed cell with infrared transparent windows which are substantially free of impingement of contaminants of the gas sample thereon. A unique detector provides protection against deterioration from moisture while allowing easy and inexpensive assembly. The system electronics eliminates sensitivities to background radiation, contamination of windows, etc., and provides a self test capability.
59 Citations
27 Claims
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1. A gas analyzer comprising:
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an infrared energy source for repetitively directing along an optical path and toward a sample cell first infrared energy having a first wave length generally different from the wave lengths absorbed by a gas sample, second infrared energy having a second wave length, at least some of which will be absorbed by a gas sample, and substantially no infrared energy; a sample cell disposed in said optical path, said sample cell having substantially infrared transparent windows to allow infrared radiation to pass therethrough; detector means sensitive to infrared radiation in said optical path passing through said sample cell, said detector means comprising a photodetector coupled to a controllable power source; synchronizing means for providing signals indicative of the state of radiation being emitted from said infrared energy source; electronic means coupled to said synchronizing means and said detector means for providing a first signal of a first predetermined level when said infrared energy source is directing said first infrared energy along said optical path, for providing a second signal of a second predetermined level when said infrared energy source is directing substantially no infrared energy along said optical path, and for providing a third signal of a level substantially equal to said first signal level when said infrared energy source is directing said second infrared energy along said optical path and said sample cell is substantially free of the gas to be detected; said electronic means including automatic gain control means coupled to said power source to maintain the difference in said first and second signal levels at a predetermined level, whereby the difference in said third and first signal levels is indicative of the gas to be detected in the sample cell. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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- 26. A gas analyzer for detecting the amount of a specific gaseous compound in a gas sample, comprising, means for directing radiation through the gas sample, such radiation including radiation at a first wave length which is substantially different from wave lengths absorbed by the gas sample and radiation at a second wave length which is substantially absorbed by the specific gaseous compound, means for periodically interrupting the radiation from said directing means, detector means for detecting the radiation of the first and second wave lengths after such radiation has passed through the gas sample and for detecting background radiation in the absence of radiation from said directing means, said detector means providing first and second electrical output signals representative, respectively, of the amounts of radiation at the first and second wave lengths passing through the gas sample, said detector means further providing a background electrical output signal representative of background radiation, gain control means for holding the first and second electrical output signals to a predetermined reference level amplitude in the absence of the specific gaseous compound in the gas sample, said gain control means being responsive to deviation of the first electrical output signal from the predetermined reference level, said gain control means including a servo loop responsive to the background electrical output signal to stabilize said gain control means for variations in background radiation, and sensing means for sensing the difference between the amplitude of the second electrical output signal and the reference level amplitude in the presence of the specific gaseous compound, whereby the signal provided by said sensing means is representative of the amount of the specific gaseous compound in the gas sample compensated for the effect of background radiation.
Specification