Method and apparatus for detecting gas concentration with infrared absorption characteristics
First Claim
1. A method for detecting gas concentration with infrared absorption characteristics, comprising the following steps:
- a. feeding gas containing a certain amount of gas to be detected into a detecting chamber in a detecting light path;
b. transmitting an infrared light containing a specific wavelength λ
through the detecting chamber, so as to generate an infrared light signal reflecting concentration information of the gas to be detected, wherein the gas to be detected has maximum absorption to the infrared light at the specific wavelength λ
;
c. processing the infrared light signal which passed through the detecting chamber, so as to obtain a measured value C0 of the concentration of the gas to be detected; and
d. computing a calibrated value C of the concentration of the gas to be detected according to a formula C=C0*β
, wherein β
is a calibration factor;
wherein the calibration factor β
is obtained by a calibration step of;
switching a reference chamber filled with a reference gas having a known concentration value C1 into the detecting light path to replace the detecting chamber, then repeating the step b and the step c to obtain a measured value C2 of the concentration of the reference gas in the reference chamber, and thus determining the calibration factor β
by a formula of β
=C1/C2 according to the measured value C2 and the known concentration value C1 of the reference gas.
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Abstract
A method and an apparatus for detecting gas concentration with infrared absorption characteristics have the function of automatic calibration. The function of automatic calibration is accomplished in such a manner that a reference chamber filled with CO2 gas of a known concentration is added in the apparatus; by switching the reference chamber in real-time or periodically into the detecting light path, the measured value of the concentration of CO2 gas in the reference chamber can be obtained; then by comparing the measured value with the standard value of known concentration of CO2 gas, the calibration factor is obtained; once finishing the calibration process, a detecting chamber is switched into the detecting light path so that a concentration of a gas can be detected accurately. In the apparatus of the present invention, the same detecting light path (e.g. the infrared light source, and the light filter, etc.), the same infrared light signal processing unit (e.g. the infrared sensor, the amplification circuit and the single-chip microcomputer system, etc.) are used for both the calibration process and the detection process. Therefore, the negative effect caused by difference of the characteristics of temperature drift of circuit components between different light paths in prior art can be eliminated, and the errors in the detected results by using the apparatus in the present invention is greatly reduced. In addition, the structure of the apparatus in the present invention is relatively simple, resulting in the lower production cost and no necessity for the manual maintenance.
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Citations
19 Claims
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1. A method for detecting gas concentration with infrared absorption characteristics, comprising the following steps:
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a. feeding gas containing a certain amount of gas to be detected into a detecting chamber in a detecting light path; b. transmitting an infrared light containing a specific wavelength λ
through the detecting chamber, so as to generate an infrared light signal reflecting concentration information of the gas to be detected, wherein the gas to be detected has maximum absorption to the infrared light at the specific wavelength λ
;c. processing the infrared light signal which passed through the detecting chamber, so as to obtain a measured value C0 of the concentration of the gas to be detected; and d. computing a calibrated value C of the concentration of the gas to be detected according to a formula C=C0*β
, wherein β
is a calibration factor;wherein the calibration factor β
is obtained by a calibration step of;switching a reference chamber filled with a reference gas having a known concentration value C1 into the detecting light path to replace the detecting chamber, then repeating the step b and the step c to obtain a measured value C2 of the concentration of the reference gas in the reference chamber, and thus determining the calibration factor β
by a formula of β
=C1/C2 according to the measured value C2 and the known concentration value C1 of the reference gas. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An apparatus for detecting gas concentration with infrared absorption characteristics, in which a gas to be detected having maximum absorption to an infrared light of a specific wavelength λ
- , the apparatus comprising;
a detecting light path unit which includes;
an infrared light source for emitting the infrared light containing the specific wavelength λ
; and
a detecting chamber being located in the detecting light path and containing the gas to be detected, wherein the infrared light passes through the detecting chamber, and thereby forms an infrared light signal reflecting concentration information of the gas to be detected;a gas path unit for feeding gas containing a certain amount of the gas to be detected into the detecting chamber; and a processing unit for processing the infrared light signal to obtain the calibrated concentration of the gas to be detected; wherein the detecting light path unit further includes a reference chamber for a calibration process in which a reference gas having a known concentration C1 is filled hermetically; and the apparatus further comprises a chamber switching device, which is used for switching the reference chamber into the detecting light path of the detecting light path unit during the calibration process and for switching the detecting chamber into the detecting light path of the detecting light path unit during the detection process. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19)
- , the apparatus comprising;
Specification