GB2024417A - Non-dispersive infrared gas analyser - Google Patents
Non-dispersive infrared gas analyser Download PDFInfo
- Publication number
- GB2024417A GB2024417A GB7921315A GB7921315A GB2024417A GB 2024417 A GB2024417 A GB 2024417A GB 7921315 A GB7921315 A GB 7921315A GB 7921315 A GB7921315 A GB 7921315A GB 2024417 A GB2024417 A GB 2024417A
- Authority
- GB
- United Kingdom
- Prior art keywords
- gas
- radiation
- measured
- cuvette
- absorption
- 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.)
- Withdrawn
Links
- 230000005855 radiation Effects 0.000 claims abstract description 52
- 238000010521 absorption reaction Methods 0.000 claims abstract description 24
- 230000002452 interceptive effect Effects 0.000 claims abstract description 6
- 238000005259 measurement Methods 0.000 claims description 6
- 239000007789 gas Substances 0.000 abstract description 41
- 230000000694 effects Effects 0.000 abstract description 3
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 6
- 239000000203 mixture Substances 0.000 description 2
- 230000035699 permeability Effects 0.000 description 2
- 239000003990 capacitor Substances 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 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
- G01N21/17—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
- G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
- G01N21/37—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light using pneumatic detection
Landscapes
- Physics & Mathematics (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Health & Medical Sciences (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
A non-dispersive infrared gas analyser is provided with means to reduce the effect of interfering gases whose absorption bands overlap the absorption bands of the gas component to be measured, and comprises a radiation source (1), a measuring path including a cuvette (4) containing the gas to be measured and an interference filter (11), having an absorption edge in the overlapping region of the interfering gases and being transmissive in the remaining absorption region of the gas component to be measured, and a comparison path including a cuvette (5) containing the gas to be measured and of a shorter length than the cuvette (4), modulating means (3) in both radiation paths and a radiation receiver (7-10). <IMAGE>
Description
SPECIFICATION
A non-dispersive infra-red gas analyser
The invention relates to a non-dispersive infra- red gas analyser comprising a radiation source, a measuring radiation path in which a test cuvette charged with the sample gas is located, a comparison radiation path, a modulating device for the radiation in both paths and a radiation receiving device having the absorption properties of the gas component to be measured and such that the difference in the signal amplitudes of the radiation-receiving device, which corresponds to the two radiation beams is a measure of the concentration of the gas component to be measured. Such an analyser is described, for example, in German Patent Specification No.
730478.
If gas components which overlap the absorption bands of the gas component to be measured are located in the sample gas mixture to be analysed, then considerable errors of measurement may occurr particularly in the case of very small concentrations of gas to be measured. Therefore, numerous proposals have already been put forward with the aim of overcoming as far as possible this characteristic of the analyser, designated as cross sensitivity. Thus in German Offenlegungsschnft No. 25 52 165 on
Page 6, second paragraph ifjs mentioned that interference filter plates can be used to this end. In practice all the radiation in the overlapping region must be kept away from the radiation-receiving device by the filter in order to achieveFa good result.However, much of the radiation energy provided for the measuring process is lost.
Moreover it has become apparent that in practice it is not possible to provide or find an appropriate filter in each case which will ensure an optimum result.
Furthermore, photometric dual-path gas analysers (US Patent Specification No.
27 61 067) the cross-sensitivity can be reduced by using radiation beams of different wavelengths in conjunction with cuvettes of different lengths arranged in the two radiation paths and charged with sample gas (US Patent Specification No.
2761067).
The invention seeks to devise a non-dispersive infra-red gas analyser of the type to which the invention relates which has a particularly low cross-sensitivity or whose cross-sensitivity can be cancelled out almost to zero.
According to the invention there is provided a non-dispersive infra-red gas analyser comprising a radiation source a measuring radiation path in which a test cuvette charge with a sample gas is located, a comparison radiation path, a modulating device for the radiation in both paths and a radiation receiving device having the absorption properties of the gas component to be measured and such that the difference in the signal amplitudes of the radiation-receiving device, which corresponds to the two radiation beams is a measure of the concentration of the gas component to be measured, wherein in order to suppress the interference of interfering gas components the absorption bands of which overlap the absorption band of the gas component to be measured, a curvette charged with the sample gas and of a smaller length than the test cuvette is arranged in the comparison radiation path and wherein an interference filter is located in the measurement radiation path, the filter having an absorption edge in the overlapping region and being permeable in the remaining absorption region of the gas component to be measured. Thus, among other things, the property of interference filters is utilised so that the spectral permeability changes with the angular position in relation to the direction of the beams.
The invention will now be described, in greater detail, by way of example with reference to the drawing, the single figure of which shows diagrammmatically one embodiment of the invention.
The analyser has an infra-red radiation source 1, the radiation of which is supplied through a conducting device 2 to a measurement radiation path 1, and a comparison radiation path 11. The two radiation beams are alternatively interrupted by a rotating diaphragm plate 3. The gas mixture to be analysed flows through cuvettes 4 and 5 located in the radiation paths and which are of different length the longer cuvette being located in measurement radiation path. A further cuvette 6 is located in the comparison radiation path, and is filled with a gas which does not absorb infra-red radiation. It merely serves to produce the same path lengths through the cuvettes in both radiation paths.
The periodically interrupted radiation beams passing out of the cuvettes pass into absorption chambers 7 and 8 of a differential pressure measuring device 9 which is filled with the gas component whose presence in the sample gas is to be measured. The resultant pressure differences, ascertained with the aid of a membrane capacitor 10, between the absorption chambers are a measure of the proportion of the gas component 'to be measured present in the sample gas.
An interference filter 11 is arranged between the cuvette 4 in the measurement radiation path and the absorption chamber 7 of the differential pressure measuring device. This filter 11 can be displaced and/or tilted in relation to the crosssection of the radiation beam as indicated by arrows. A diaphragm 12 in the comparison radiation path makes exact zero equalisation possible for the case where the sample gas does not contain the gas component to be measured.
The bandwidth of the interference filter is selected so that it has an absorption edge lying in the region of the overlap between the absorption band of the gas component to be measured and the absorption band of the interfering gas component or components complete permeability being provided in the remaining absorption region of the gas component. The effect of the interfering accompanying gases on the test result is thus reduced considerably. A further and particularly large suppression of interference is brought about by the radiation absorption of the sample gas in the cuvette 5, the most suitable length of which is to be ascertained emperically.
Finally, it may prove to be advisable, for the purpose of achieving an optimum effect, to introduce the interference filter 11 over only part of the entire cross-section of the radiation beam and also to tilt in relation to its associated radiation path.
For example, when measuring hexane in automobile gas with the analyser in accordance with the invention with a measuring range of 300 ppm and with a proportion of 15% CO2, there was only a variation in indication corresponding to 1 ppm of hexane. The indication remained practicaily unaffected with a proportion of 10% of
CO and a water vapour concentration corresponding to saturation at 20 OC. The length of the cuvette 4 was 190 mm and that of the cuvette 5 was 0.2 mm.
Claims (6)
1. A non-dispersive infra-red gas analyser comprising a radiation source, a measuring radiation path in which a test cuvette charged with the sample gas is located, a comparison radiation path, a modulating device for the radiation in both paths and a radiation receiving device having the absorption properties of the gas component to be measured and such that the difference in the signal ampitudes of the radiation receiving device, which corresponds to the two radiation beams is a measure of the concentration of the gas component to be measured wherein in order to suppress the interference of interfering gas components the absorption bands which overlap the absorption band of the gas component to be measured, a cuvette charged with the sample gas and of a smaller length than the test cuvette is arranged in the comparison radiation path and wherein an interference filter is located in the measurement radiation path, the interference filter having an absorption edge in the overlapping region and being permeable in the remaining absorption region of the gas component to be measured.
2. A gas analyser according to Claim 1, wherein the interference filter is arranged so that it only affects a part of its associated radiation beam.
3. A gas analyser according to Claim 1 or 2, wherein the interference filter is tilted with respect to the radiation path.
4. A gas analyser according to any one of
Claims 1 to 3, wherein the ratio of the lengths of the cuvettes carrying the sample gas is between 1/5 and 1/1000.
5. A gas analyser according to any one of
Claim 1 to 3, wherein a further cuvette is located in the comparison radiation path and is filled with gas which is inert to infra-red radiation, the cuvette 6 being of such a length that both cuvettes in the radiation path take up the same length as the test cuvette.
6. A non-dispersive infra-red gas analyser substantially as described herein with reference to the drawing.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19782827345 DE2827345A1 (en) | 1978-06-22 | 1978-06-22 | NON-DISPERSIVE INFRARED GAS ANALYZER |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2024417A true GB2024417A (en) | 1980-01-09 |
Family
ID=6042421
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB7921315A Withdrawn GB2024417A (en) | 1978-06-22 | 1979-06-19 | Non-dispersive infrared gas analyser |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS552998A (en) |
| DE (1) | DE2827345A1 (en) |
| FR (1) | FR2434385A1 (en) |
| GB (1) | GB2024417A (en) |
| NL (1) | NL7904593A (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4432939A (en) * | 1980-04-14 | 1984-02-21 | Fuji Electric Co., Ltd. | Ammonia gas analyzer |
| JPS5784099A (en) * | 1980-11-13 | 1982-05-26 | Mitsubishi Heavy Ind Ltd | Dry cleaning machine |
| JPS573698A (en) * | 1980-06-09 | 1982-01-09 | Mitsubishi Heavy Ind Ltd | Dry cleaning machine |
| JPS5784100A (en) * | 1980-11-13 | 1982-05-26 | Mitsubishi Heavy Ind Ltd | Dry cleaning machine |
| JPS5892843A (en) * | 1981-11-26 | 1983-06-02 | Horiba Ltd | Nondispersion type infrared analyzer for measurement of two components |
| JPH0696069B2 (en) * | 1989-03-28 | 1994-11-30 | 三洋電機株式会社 | Washing machine |
| AU632439B2 (en) * | 1989-10-05 | 1992-12-24 | Sanyo Electric Co., Ltd. | Drum-type washing machine |
| JP2007154593A (en) * | 2005-12-08 | 2007-06-21 | Asahi Kasei Construction Materials Co Ltd | Joint structure of external facing panel |
-
1978
- 1978-06-22 DE DE19782827345 patent/DE2827345A1/en not_active Withdrawn
-
1979
- 1979-03-30 FR FR7908000A patent/FR2434385A1/en not_active Withdrawn
- 1979-06-12 NL NL7904593A patent/NL7904593A/en not_active Application Discontinuation
- 1979-06-19 GB GB7921315A patent/GB2024417A/en not_active Withdrawn
- 1979-06-22 JP JP7823479A patent/JPS552998A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| DE2827345A1 (en) | 1980-01-10 |
| NL7904593A (en) | 1979-12-28 |
| JPS552998A (en) | 1980-01-10 |
| FR2434385A1 (en) | 1980-03-21 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |