Abstract A calibration device is provided for a gas analyzer which measures the amounts of a plurality of gases in a gas sample. A source of radiation is applied through a gas sample, and selectively applied to an infrared detector by a filter wheel which alternately applies radiation from an absorption region of the gas to be measured and from a transparent or reference wavelength. Filters for different absorption regions are used with the reference filter to detect the presence of different gases in the sample. A calibration device is inserted between the source and the infrared detector which attenuates radiation in the desired absorption regions while passing radiation in the reference region. The calibration device is comprised of a suitable infrared transmissive substrate, such as germanium, with different anti-reflective coatings on each side of the element to achieve the necessary attenuation for the measured wavelengths while passing radiation in the reference wavelength.
A calibration device for a gas analyzer comprising a. a sample cell containing a sample of the gases to be analyzed, b. an infrared detector, c. a source of radiation directed through said sample cell and onto said infrared detector, d. means for selectively applying radiation passed from said source through said sample cell onto said infrared detector for at least two absorption regions for gases to be measured and at least one reference region whereby signals are generated by said detector in accordance with the amount of radiation applied thereto in said regions, e. circuit means for processing said signals to measure the amounts of at least two gas constituents in said sample cell, and f. a single calibration element for insertion between said source and said infrared detector having anti-reflection coatings on each side thereof for attenuating radiation in at least two absorption regions while transmitting radiation in said reference region.
Claim 2
Dependent Claim
153 words
A calibration device for a gas analyzer comprising a. a sample cell containing a sample of the gases to be analyzed, b. an infrared detector, c. a source of radiation directed through said sample cell and onto said infrared detector, d. means for selectively applying radiation passed from said source through said sample cell onto said infrared detector for at least two absorption regions for gases to be measured and at least one reference region whereby signals are generated by said detector in accordance with the amount of radiation applied thereto in said regions, e. circuit means for processing said signals to measure the amounts of at least two gas constituents in said sample cell, and f. a single calibration element for insertion between said source and said infrared detector having anti-reflection coatings on each side thereof for attenuating radiation in at least two absorption regions while transmitting radiation in said reference region.
Claim 3
Dependent Claim
27 words
The calibration device set forth in claim 1 wherein said single calibration element comprises an element of infrared transmissive material having anti-reflection coatings on each side thereof.
Claim 4
Dependent Claim
34 words
The calibration device set forth in claim 2 wherein said two absorption regions are 3.4 and 4.6 microns and said anti-reflection coatings are quarter-wavelength thick at 4 microns and quarter-wavelength thick at 20 microns.