GB2116316A - Infrared radiation gas analyzer - Google Patents
Infrared radiation gas analyzer Download PDFInfo
- Publication number
- GB2116316A GB2116316A GB08306203A GB8306203A GB2116316A GB 2116316 A GB2116316 A GB 2116316A GB 08306203 A GB08306203 A GB 08306203A GB 8306203 A GB8306203 A GB 8306203A GB 2116316 A GB2116316 A GB 2116316A
- Authority
- GB
- United Kingdom
- Prior art keywords
- infrared
- filter
- gas
- infrared rays
- sample
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 230000005855 radiation Effects 0.000 title claims abstract description 49
- 239000004615 ingredient Substances 0.000 claims abstract description 30
- 238000002485 combustion reaction Methods 0.000 claims abstract description 4
- 230000009977 dual effect Effects 0.000 claims description 3
- 230000000712 assembly Effects 0.000 claims 1
- 238000000429 assembly Methods 0.000 claims 1
- 239000007789 gas Substances 0.000 description 39
- 238000010276 construction Methods 0.000 description 13
- 238000010586 diagram Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 2
- 238000011109 contamination Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 230000000087 stabilizing effect Effects 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000002329 infrared spectrum Methods 0.000 description 1
- 239000011810 insulating material Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/71—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light thermally excited
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
- G01J5/60—Radiation pyrometry, e.g. infrared or optical thermometry using determination of colour temperature
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/314—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry with comparison of measurements at specific and non-specific wavelengths
Landscapes
- Health & Medical Sciences (AREA)
- Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
- Physics & Mathematics (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Investigating Or Analysing Materials By Optical Means (AREA)
Abstract
An infrared radiation gas analyzer comprises an infrared detector 11 upon which infrared rays emanating from a sample of gas at a raised temperature are incident, a filter 9 for transmitting rays in a waveband radiated by the ingredient to be determined and a filter 10 for transmitting rays in an adjacent waveband, the filters being alternately inserted in the ray path to the detector, the concentration being determined by computer 13 from the difference as the ratio of the amplified electrical signals from detector 11. Alternatively, two detectors may be used one with filter 9 and the other with filter 10. The gas chamber 1 may have a heater 4 to heat the sample or may for example be an internal combustion engine exhaust pipe with a cell window 1a in the wall. <IMAGE>
Description
SPECIFICATION
Infrared radiation gas analyzer
The present invention relates to a gas analyzer for determining the concentration of specific ingredients in a sample of gas.
The conventional determination of gas concentration has been carried out using a nondispersive infrared absorption analyzer applying Lambert-Beer's law. However, such an analyzer requires an infrared light source and a power source for stabilizing said light source. In addition, it is expensive owing to the complicated construction of the circuit. Furthermore, optical adjustment is required in order to adjust the amount of light incident upon a reference cell and the amount of light incident upon a sample cell because the reference cell must be installed in order to prevent generation of the drift owing to a light source and said sample cell.
In this invention, these disadvantages are virtually eliminated by the use of an infrared radiation gas analyzer for determining the concentration of specific ingredients present in a sample of gas, which analyzer is simple in construction and inexpensive, in which the infrared radiation of specified wavelength radiated by a gas molecule (excepting a monoatomic molecule) and characteristic of a gas when the gas molecule is heated to raised temperatures is measured without using either an infrared light source or a power source for stabilizing said light source both of which have been required in the conventional infrared gas analyzer.
It is thus an object of the present invention to provide an operationally useful infrared radiation gas analyzer, which can determine the presence and concentration of a gas with high accuracy.
The present invention provides an infrared radiation gas analyzer comprising a chamber for gas being tested and having a window provided with a covering of infrared radiation transmitting material, a rotatable chopper in spaced relation with said window and having its axis of rotation displaced relative to the central axis of said window, a pair of filters for transmitting radiation transmitted by said radiation transmitting material in two adjacent bands of the infrared spectrum, one filter transmitting in each band, one or two infrared detectors, said detector or each of said detectors being aligned with said filter or filters and producing an electric signal when infrared radiation is incident thereon and means for converting the electric signal or signals emitted by said detector or detectors to provide an indication of the presence of, or if desired, the proportion of a gaseous component present in a mixture of gases in said gas holder.
The invention will now be further described, by way of example, with reference to the accompanying drawings in which:
Fig. 1 is a schematic diagram illustrating one embodiment of an infrared radiation gas analyzer according to the present invention;
Fig. 2 is a front view of part of the device shown in Figure 1 showing a chopper provided with two filters;
Figs. 3a and 3b are graphs illustrating the relative radiation intensity;
Fig. 4 is a schematic diagram illustrating an alternative construction of the analyzer according to the present invention; and
Fig. 5 is a schematic diagram illustrating a third construction of an analyzer according to the present invention.
Referring now to Fig. 1 of the drawings a sample cell 1 is provided with an inlet 2 for a sample of gas an an outlet 3 for said sample gas.
The internal surface of the cell 1 is a mirror surface, and the cell 1 is provided, at the ends thereof, with cell windows 1 a and 1 b formed of infrared ray-transmitting material to minimise the infrared radiation dose from the background. A heater 4 is provided for heating a sample of gas within the cell 1, in which cell a sample of gas is heated to a temperature of at least 1 000C to radiate infrared rays, in order to increase the radiation from the sample of gas and reduce the radiation from the background. Numeral 5 designates an insulating material used in the construction of heater 4.A rotatable chopper 6 is provided with two filters; namely a first filter 9 for transmitting infrared rays having wavelengths within a specified band and emanating from an ingredient to be determined present in a sample of the gas (for example, the 4.3 ,um band having a high relative radiation intensity in the case of determination of CO2 concentration); and a second filter 10 for transmitting infrared rays having wavelengths, which are outside the above specified band but are near to it. The filters are symmetrically located in positions about the axis of rotation 8 of the body of rotary chopper, as shown in Fig. 2. A screen provided with a slit is located adjacent the chopper 6.
An infrared radiation detector 11 is provided for alternately receiving infrared rays transmitted through the first filter 9 and infrared rays transmitted through the second filter 10, thus producing an alternating current electric signal having an amplitude corresponding to the infrared radiation dosse being generated. Solid detectors such as pyroelectric detectors can be satisfactorily used as the detector 11.
An amplifier 12 is provided for amplifying an alternating current electric signal generated by the infrared detector 11, and the output of the amplifier feeds a comparison computer 1 3 for determining the difference or ratio between the amplified alternating current electric signals alternately fed in.
For example, in the case of the determination of CO2 concentration, the first filter 9 transmits infrared rays (A+B), which are the total of the infrared rays A radiated only by CO2 and having wavelengths within the specified band W as shown in Fig. 3a of the drawings and infrared rays
B having wavelengths within the specified band
W and radiated from the background (background infrared rays) as shown in Fig. 3b of the drawings, while the second filter 10 transmits the background infrared rays B' having wavelengths within the band W' adjoining the specified band
W. As shown in Fig. 3b the band of background infrared rays W' is almost as broad as W and B is nearly equal to B'.Accordingly, the infrared radiation A can be approximately detected by subtracting or dividing an infrared radiation dose
B' transmitted by the second filter 10 from the total infrared radiation dose (A+B) transmitted through the first filter 9. (A+B-B'A) or
AxB c.A B'
Furthermore, a device 14 for determining the intensity of the incident rays is provided in order to calculate and indicate the concentration of a gaseous ingredient being determined upon the basis of a signal emanating from the comparision computer 13.
In the above described construction, the total (A+B) of infrared rays A radiated by the ingredient to be determined and of infrared rays B radiated by the background and having wavelengths within the specified band W and infrared rays B' radiated from the background and having wavelengths within the band W' adjoining the specified band W are alternately incident upon the infrared detector 11 through the filters 9, 10 on chopper 6 and the concentration of the ingredient under test is determined by the indicating device 14 on the basis of the difference or ratio, of the infrared radiation doses (A+B-B') or
AxB
B'
Thus the accurate determination of concentration is possible by removing infrared rays radiated by the background.It follows that the accurate determination of concentration is possible by making use of the difference between the infrared radiation doses even when the cell 1 and the cell window 1 a are contaminated or the temperatures are changed, thus altering the amounts of infrared radiation received.
Furthermore, a construction may be produced in which the cell window 1 b is not present. This is illustrated in Figure 4. Although a construction in which a sample of gas is introduced into the cell
1, is described above, an exhaust-gas pipe for conveying hot exhaust gas from an internal combustion engine may be regarded as the cell and provided with the cell window 1 a and the chopper 6 carrying the filters, the screen having the slit 7 and the infrared detector device 11 may
be aligned upon one side of the window 1 a so that the concentration of the ingredient to be determined in an exhaust gas at raised temperatures can be determined.
In addition, although the construction, in which the chopper 6 is provided with a first filter 9 and a second filter 10, is shown in the drawings, the filters 9, 10 may be provided separately. Various kinds of known detector and filter can be used as the infrared detector 11 and the filters 9 and 10.
The concentrations of various different components can be detected by replacing the filters 9 and 10 by filters which transmit infrared rays of appropriate wavelength. Thus, the ingredient to be measured is not limited.
In the present invention, an infrared light source and a power source for providing a source of light, which are incidental to a conventional nondispersive infrared absorption analyzer, are not required. Furthermore, a reference cell and an optical adjusting mechanism for preventing the drift arising from a light source are not required.
Thus the concentration of the specified ingredient present in a sample of gas can be determined using a simple and inexpensive construction.
Particular attention is paid to the fact that an infrared radiation dose incident upon an infrared detector is changed by the radiation of infrared rays having the same wavelength as those radiated by the ingredient being determined from cells as a result of the high temperatures of the cells or the contamination of the cells and cellwindows or of a change in temperature, as a result of which the zero point is changed and this becomes an important source of error in the measurement in the determination of concentration. As a result a second filter is used in order to detect the background infrared rays by means of an infrared detector.Thus an infrared radiation dose emanating from the ingredient to be determined can be detected upon the basis of the difference in or ratio between an infrared radiation dose radiated from a sample of gas including background infrared rays, which are transmitted by the first filter, and a radiation dose of background infrared rays, which are transmitted by the second filter. That is to say, the concentration of the ingredient to be determined can be accurately detected by using improved gas analyzer in which infrared rays transmitted by a first filter, and infrared rays, transmitted by a second filter, are alternately incident upon a single infrared detector or upon a pair of infrared detectors from which a resultant signal is derived proportional to the difference between the two signals produced by the pair of detectors.
Fig. 5 illustrates a further embodiment of the invention in which a dual type infrared detector 1 7 has two detecting elements a and b which partially cancel out the two signals respectively generated by the elements a and b and emits a resultant signal representing the difference between the two. The first filter 1 8 transmits infrared rays radiated from the ingredient to be determined present in a sample of gas and having wavelengths within the specified band W (for example 4.3 ym band of high radiation coefficient when determining the concentration of CO2). The second filter 1 9 transmits infrared rays having wavelengths within the band W' which is adjacent to the specified band W.The filters 18 and 19 have substantially the same transmission factor and half width vaiue.
The first filter 18 and the second filter 19 are respectively disposed in front of the detecting elements a and b of the infrared detector 1 7, so that infrared rays (background infrared rays), radiated by the cell 1 and incident upon the elements a and b, partially cancel out each other.
The infrared detector 1 7 produces only a signal proportional to the infrared rays radiated by the ingredient as determined by the rays respectively transmitted through the first filter 1 8 and the second filter 1 9. The infrared detector 1 7 emits an alternating current electric signal proportional to the concentration of the ingredient to be determined.
An amplifier 20 amplifies the electric signals emitted by the infrared detector 1 7. Although not shown on the drawing, the signals amplified by the amplifier 20, are emitted in the form of signals proportional to the concentration of the ingredient to be determined.
According to the above described construction, infrared rays are radiated from a sample of gas introduced into the cell 1 and having a definite pressure and simultaneously background infrared rays are radiated from said cell 1 itself when said sample gas is heated to the desired temperature by means of said heater 4.
In this construction infrared rays (A+B) and infrared rays B' are respectively incident upon the detecting elements a and b, and the background infrared rays cancel each other out (A+B-B'#A).
Thus a radiation dose of A of infrared rays radiated by the ingredient to be determined can be measured by means of the infrared detector 1 7. Thus, the concentration of the ingredient desired can be accurately determined on the basis of the radiation dose A of infrared rays. It goes without saying that the concentration can be accurately determined in the same manner as described above even though the radiaiton dose of background infrared rays is changed because of the contamination of said cell 1 and said cellwindow 1 a and the like since said infrared detector 7 detects only the concentration of the
ingredient to be determined on the basis of absolute values.
In addition, although an embodiment in which said sample gas is heated to the desired temperature by means of said heater 4 was described above, said sample gas may be heated to the suitable temperature range and the temperature compensation may be carried out by
using a thermometer for measuring temperatures of gas, or gas which was preliminarily heated to a
raised temperature may be introduced into said
cell 1. Furthermore, exhaust gas pipes for
exhausting exhaust air from internal combustion
engines and factories may be regarded as said cell
1 as shown in Fig. 4 and the same construction as in the embodiment shown in Fig. 5 may be used, if desired.
Furthermore, the concentration of various kinds of ingredient can be detected by replacing said first filter 1 8 and said second filter 1 9 with filters which transmit infrared rays having various kinds of wavelength. That is to say, the ingredients to be determined are not limited.
In such an arrangement, attention is paid to the fact that the radiation dose of background infrared rays radiated from said cell and cell-window is several times or maybe several tens of times as large as the radiation dose of infrared rays radiated from a sample gas, whereby a slight change in temperature has an influence on the zero point, or the radiation dose of infrared rays incident upon said infrared detector is changed owing to the change of said cell, said cell-window and the like in radiation coefficient and the like, and as a result the zero point is changed and this becomes an important factor of errors of measurement in the detection of concentration.
As a result, the concentration of the specified gaseous ingredient can be accurately determined by removing the influence of background infrared rays. That is to say, only the radiation dose of infrared rays radiated from the ingredient to be determined can be detected by means of a dual type infrared detector by cancelling the total of a radiation dose A of infrared rays radiated from the ingredient to be determined and having wavelengths of the specified range W and a radiation dose B of background infrared rays having the same wavelengths as those of infrared rays radiated from the ingredient to be determined, which are transmitted through the first filter, and a radiation dose B' of background infrared rays nearly equal to the above described radiation dose B of background infrared rays, which are transmitted through the second filter, each other (A+B-B').
It is also possible to calculate the ratio of the measured values in the embodiment according to
Fig. 5.
Claims (7)
1. An infrared radiation gas analyzer comprising an infrared detector upon which infrared rays emanating from a sample of gas at a raised temperature are incident, a first filter for transmitting infrared rays having wavelengths in the specified band and radiated by the ingredient to be determined present in said sample of gas and a second filter for transmitting infrared rays having wavelengths adjacent the said specified band, said first filter and said second filter alternately traversing the path of infrared rays which are incident upon said infrared detector, and the concentration of the ingredient to be determined being determined on the basis of the difference or ratio between successive doses of infrared rays transmitted through said filters and incident upon said infrared detector.
2. An infrared radiation gas analyzer comprising a chopper and a dual type infrared detector provided with two detecting elements upon which infrared rays emanating from a sample of gas at a raised temperature are respectively incident after passage through said chopper, a first filter for transmitting infrared rays emanating from the ingredient to be determined present in said sample of gas and having wavelengths within the specified band being disposed in front of one of said elements while the second filter for transmitting infrared rays having wavelengths adjacent the specified band is arranged in front of the other of said elements so that the concentration of the ingredient to be determined can be ascertained on the basis of the difference between the doses of infrared rays transmitted through said filters and respectively incident upon the two detecting elements of said infrared detector.
3. An infrared radiation gas analyzer as claimed in claim 1 or 2, in which said gas sample is contained in a sample cell.
4. An infrared radiation gas analyzer as claimed in claim 1 or 2, in which said gas sample is contained in an exhaust gas conduit, e.g. from an internal combustion engine or a factory.
5. An infrared radiation gas analyzer as claimed in claim 1, in which said first and second filters are mounted in a rotatable chopper.
6. An infrared radiation gas analyzer as claimed in claim 2, in which said first filter is associated with one detecting element, said second filter is associated with the other detecting element and said chopper is disposed between said window and said filter and detecting element assemblies.
7. Infrared radiation gas analyzers substantially as hereinbefore described, with reference to
Figures 1 to 3 or Figure 4 or Figure 5 of the accompanying drawings.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1982033703U JPS58136757U (en) | 1982-03-09 | 1982-03-09 | Infrared radiation gas analyzer |
| JP1982033702U JPS58136756U (en) | 1982-03-09 | 1982-03-09 | Infrared radiation gas analyzer |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8306203D0 GB8306203D0 (en) | 1983-04-13 |
| GB2116316A true GB2116316A (en) | 1983-09-21 |
| GB2116316B GB2116316B (en) | 1985-11-06 |
Family
ID=26372446
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08306203A Expired GB2116316B (en) | 1982-03-09 | 1983-03-07 | Infrared radiation gas analyzer |
Country Status (2)
| Country | Link |
|---|---|
| DE (1) | DE3307133C2 (en) |
| GB (1) | GB2116316B (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1999026058A1 (en) * | 1997-11-14 | 1999-05-27 | American Iron And Steel Institute | Method and apparatus for off-gas composition sensing |
| WO1999050649A1 (en) * | 1998-03-27 | 1999-10-07 | The Secretary Of State For Defence | Flame photometer detector |
| EP1603172A1 (en) * | 2004-05-31 | 2005-12-07 | TDK Corporation | Carbon dioxide concentration measuring device, method of measuring carbon dioxide concentration and burning appliance therefor |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4971447A (en) * | 1988-03-17 | 1990-11-20 | Siemens Aktiengesellschaft | Method for measuring concentration of chemical substances |
| DE4124116A1 (en) * | 1991-07-17 | 1993-01-21 | Iris Gmbh Infrared & Intellige | SPECTRAL PYROELECTRIC INFRARED MOTOR SENSOR |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4110618A (en) * | 1965-06-08 | 1978-08-29 | American Standard Inc. | Adiabatic compression infrared emission vapor detector |
| US4100412A (en) * | 1976-10-29 | 1978-07-11 | Hausdorff Harry H | Selective multichannel optical time-shared detector for chromatography |
| JPS586996B2 (en) * | 1977-02-15 | 1983-02-07 | 国際技術開発株式会社 | Flame detection method |
-
1983
- 1983-03-01 DE DE19833307133 patent/DE3307133C2/en not_active Expired
- 1983-03-07 GB GB08306203A patent/GB2116316B/en not_active Expired
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1999026058A1 (en) * | 1997-11-14 | 1999-05-27 | American Iron And Steel Institute | Method and apparatus for off-gas composition sensing |
| US5984998A (en) * | 1997-11-14 | 1999-11-16 | American Iron And Steel Institute | Method and apparatus for off-gas composition sensing |
| WO1999050649A1 (en) * | 1998-03-27 | 1999-10-07 | The Secretary Of State For Defence | Flame photometer detector |
| GB2352034A (en) * | 1998-03-27 | 2001-01-17 | Secr Defence | Flame photometer detector |
| GB2352034B (en) * | 1998-03-27 | 2002-09-25 | Secr Defence | Flame photometer detector |
| EP1603172A1 (en) * | 2004-05-31 | 2005-12-07 | TDK Corporation | Carbon dioxide concentration measuring device, method of measuring carbon dioxide concentration and burning appliance therefor |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8306203D0 (en) | 1983-04-13 |
| DE3307133A1 (en) | 1983-09-29 |
| DE3307133C2 (en) | 1986-04-24 |
| GB2116316B (en) | 1985-11-06 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19940307 |