GB2035552A - Radiation detection of gas compositions - Google Patents
Radiation detection of gas compositions Download PDFInfo
- Publication number
- GB2035552A GB2035552A GB7940508A GB7940508A GB2035552A GB 2035552 A GB2035552 A GB 2035552A GB 7940508 A GB7940508 A GB 7940508A GB 7940508 A GB7940508 A GB 7940508A GB 2035552 A GB2035552 A GB 2035552A
- Authority
- GB
- United Kingdom
- Prior art keywords
- detector
- radiation
- gas
- equipment
- source
- 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 54
- 238000001514 detection method Methods 0.000 title description 2
- 239000000203 mixture Substances 0.000 title description 2
- 239000007789 gas Substances 0.000 claims description 53
- 238000012806 monitoring device Methods 0.000 claims description 9
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims description 8
- 238000004458 analytical method Methods 0.000 claims description 7
- 239000003546 flue gas Substances 0.000 claims description 7
- 238000012544 monitoring process Methods 0.000 claims description 7
- 238000011065 in-situ storage Methods 0.000 claims description 6
- WSMQKESQZFQMFW-UHFFFAOYSA-N 5-methyl-pyrazole-3-carboxylic acid Chemical group CC1=CC(C(O)=O)=NN1 WSMQKESQZFQMFW-UHFFFAOYSA-N 0.000 claims description 4
- 238000003780 insertion Methods 0.000 claims description 2
- 230000037431 insertion Effects 0.000 claims description 2
- 230000001360 synchronised effect Effects 0.000 claims description 2
- 230000004913 activation Effects 0.000 claims 1
- 230000000007 visual effect Effects 0.000 abstract description 3
- 239000000523 sample Substances 0.000 description 8
- 238000005070 sampling Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 239000003517 fume Substances 0.000 description 2
- 238000012423 maintenance Methods 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 1
- 229910002091 carbon monoxide Inorganic materials 0.000 description 1
- 238000004587 chromatography analysis Methods 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 230000008030 elimination Effects 0.000 description 1
- 238000003379 elimination reaction Methods 0.000 description 1
- 229910052732 germanium Inorganic materials 0.000 description 1
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000005375 photometry Methods 0.000 description 1
- 231100000614 poison Toxicity 0.000 description 1
- 230000007096 poisonous effect Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 230000011664 signaling Effects 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000004611 spectroscopical analysis Methods 0.000 description 1
- 239000002912 waste gas Substances 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
- B01J23/24—Chromium, molybdenum or tungsten
- B01J23/28—Molybdenum
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23M—CASINGS, LININGS, WALLS OR DOORS SPECIALLY ADAPTED FOR COMBUSTION CHAMBERS, e.g. FIREBRIDGES; DEVICES FOR DEFLECTING AIR, FLAMES OR COMBUSTION PRODUCTS IN COMBUSTION CHAMBERS; SAFETY ARRANGEMENTS SPECIALLY ADAPTED FOR COMBUSTION APPARATUS; DETAILS OF COMBUSTION CHAMBERS, NOT OTHERWISE PROVIDED FOR
- F23M11/00—Safety arrangements
- F23M11/04—Means for supervising combustion, e.g. windows
- F23M11/047—Means for supervising combustion, e.g. windows by observing the flue gas
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N5/00—Systems for controlling combustion
- F23N5/003—Systems for controlling combustion using detectors sensitive to combustion gas properties
-
- 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
- G01N21/3504—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing gases, e.g. multi-gas analysis
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N2231/00—Fail safe
- F23N2231/20—Warning devices
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T50/00—Aeronautics or air transport
- Y02T50/60—Efficient propulsion technologies, e.g. for aircraft
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Physics & Mathematics (AREA)
- General Engineering & Computer Science (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Organic Chemistry (AREA)
- Materials Engineering (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth 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
The invention provides an infra red source 8 to one side of, e.g., a gas flue; a detector 4 spaced from the infra red source across the gas flow; and a band-pass filter and a filter cell 6, filled with a gas component of interest, both positioned in a radiation path between the detector 4 and the source 8; the detector 4 being connected in a circuit capable of measuring 14-18 radiation both direct from the source 8 and passing through the gas component filter 6, determining 19 the difference between the two levels of radiation, and dividing 20 that difference by either the measured direct radiation or the measured radiation passing through the filter cell 6, to provide 21 an output from the circuit representing the amount of monitored gas present in the gas flow. The output can be used to activate audible or visual signal means, or as a control signal to modify the conditions, e.g., at the burner of a boiler. <IMAGE>
Description
SPECIFICATION
Radiation detection of gas compositions
This invention relates to the monitoring of gas and is particularly concerned with the selective determination of particular constituents of the gas.
There are many applications where gas must be analysed, e.g., in a flue gas there can be a carbon monoxide content, the quantity of which can give an accurate assessment as to whether or not a burner is operating at, above, or below optimum efficiency. There are also other applications where gases are known to contain an obnoxious or poisonous content and which must be closely controlled.
Equipment that is currently commercially availalbe, e.g., for CO monitoring of boiler or furnace waste gas, generally falls into two categories, those in which the gas is first sampled and the sample analysed, and those which monitor the gas in-situ.
Most conventional equipment falls into the category where sampling is first effected, the gas being sampled through a filter probe to remove solid particles, then dried to remove any condensates, and finally passed to the analyser itself. The analyser would normally embody any one of many known techniques for analysis such as photometry, spectroscopy, filter reduction and chromatography. The major disadvantage of such techniques lies in the gas sampling itself, the analysers themselves usually being very adequate. Sampling systems generally require a considerable amount of maintenance and are known to be unreliable.
So far as in-situ monitoring is concerned, equipment is availalbe but which in the main operates on a spectrometer principle for the simultaneous analysis of a number of gases usually CO, SO2, NOx, and CO2. Although the actual analysis of the gas can be effected with reasonable accuracy, a problem inherent in spectrometers is that they tend to be very sensitive instruments which need extensive protection against vibration. For this reason such instruments when used in-situ tend to be of great bulk and the spectrometer itself must be mounted on a very substantial base. Optical alignment is critical requiring difficult and sensitive setting up and maintenance. Such equipment also tends to be expensive, automatically providing more information than is strictly required.
According to the present invention, equipment for the monitoring of gas in-situ comprises an infra-red source adapted to be located in ducting or the like through which the gas to be analysed passes, a detector spaced from the infra red source, a band-pass filter between the detector and the source to restrict incoming radiation to a predetermined wavelength range, and a filter cell adapted to be positioned in the radiation path between the detector and the source, filled with the gas component requiring analysis, the detector being connected in a circuit capable of measuring radiation direct from the source and passing through the gas component filter cell, determining the difference between the two levels of radiation dividing the difference by either of the levels of radiation received by the detector, to provide an output from the said circuit that is a function of the amount of monitored gas present in the gas flow.
Preferably, and to ensure that the signals received by the detector is not distorted by absorption of radiation by the filter cell windows or indeed by dirt contamination of the windows, a second reference cell is provided filled with a gas component which does not absorb radiation over the wave-lengths selected by the band-pass filter.
The gas component filter cell and the reference cell when provided may each be permanently located in the radiation path, and when two radiation paths would be required one for each cell, with two detectors, again one for each cell. The two radiation paths can be provided by two separate sources or by employing a beam splitter in the radiation from a single source. Alternatively with a single source of radiation each gas component filter cell can be mounted for selective introduction into the radiation path alternately with the other.
Preferably the infra red source is an electrically heated plate, which can be protected by an infra red transmissive window, e.g., germanium and can be mounted in an opening to one side of the ducting. The detector is preferably a pyroelectric detector such as lithium tantalate, a form of detector offering high sensitivity and stability with low noise. With certain types of detector such as a lithium tantalate detector which is an a.c. detector and does not function with direct energy, a chopper blade must be provided between the detector and the source to chop incoming radiation to a predetermined frequency, and the chopper blade can also form part of the self-contained unit.The detector, chopper blade (when provided), and band-pass filter along with the electronic circuits may be formed as a self-contained unit for mounting at the opposite side of the boiler ducting to the infra red source, or the necessary electronic circuits may form a separate self contained unit adapted to be located in any convenient position with the audible or visual signalling means similarly mounted whereever convenient. Alternatively, the radiation source and the detector can be formed as a single unit of generally tube-like character with the radiation source at one end and the detector at the other, and with the tube pervious to gas. This allows the tube to be inserted into a flue gas when testing is required.It is still further possible within the spirit of the invention to provide both the infra red source and the or each detector to one side of a flue, and for infra red radiation to be transmitted across the flue gas to a reflector and back to the detector. Within the possibility, the reflector can be mounted on the flue gas wall to one side and the source and detector mounted on the flue gas wall to the opposite side. It would be equally possible to mount the source and the detector at one end of the tube and the reflector at the opposite end of the tube with the tube again being pervious to gas and capable of insertion into the flue gas.
When the two filter cells are mounted in line, it is preferred that they are secured to a solenoid, the reciprocal movement of which repeatedly introduces first one and then the other filter cell into the radiation path. By switching the gas component filter cell in and out of the radiation path alternatively with the inert gas filter cell, the difference in signals from the detector is a function of the concentration of the particular gas in the flue. By dividing the difference in signal by one or other of the signals themselves, the final output from the circuits is again a function of the concentration of the gas, and there is the substantial reduction, if not elimination, of problems of drift of calibration and temperature co-efficient, and the avoidance of major problems caused by dirt coatings on necessary lenses utilised to focus the radiation on to the detector.
The invention therefore provides analysing equipment that is, compact, rugged and relatively inexpensive.
As a further possibility within the invention, in a form of construction where two detectors are provided, each can be provided with a pair of in-line gas cells for selective introduction into the radiation path but with the movement of the cells synchronized in antiphase. This allows the possibility of the provision of substantially continuous readings of gas under analysis, and has the additional advantage that any stray fume passing up the stack and which could disturb the readings in a single detector system results in readings by the two detectors which are self-cancelling to a large extent so that accurate readings for the gas under analysis can be maintained despite the presence of fume.
It is obviously advantageous to periodically check the calibration of the monitoring device of the invention. It is therefore preferred to provide reference means comprising a second infra red source which has a fixed concentration of gas or no gas at all enclosed in a sight path which sight path can be directed into the monitoring device of the invention at predetermined intervals to allow the monitoring device to give readings for a predetermined gas concentration and which can then be utilised to determine the accuracy of the equipment and allow such calibration as is required.
The monitoring devices as discussed above all involve the use of a separate source of infra red radiation. It will however be understood that it will be possible in certain circumstances to allow the radiation emitted by hot gas itself to be used as the source directed at the detector.
One embodiment of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a front elevation of the monitoring device of the invention; and
Figure 2 is a block diagram of the circuitry of the monitoring device of Fig. 1.
In Fig. 1 a monitoring device for the monitoring of gas in-situ has an infra red source 1 adapted to be located in ducting or the like (not shown) through which the gas to be analysed passes and a detector/signal processor unit 2 adapted to be located in spaced relationship from the infra red source. The unit 2 has a sight tube 3 adapted to focus incoming radiation from the infra red source on a lithium tantalate detector head 4. A rotary push-pull solenoid 5 supports and locates a filter cell 6 filled with the gas component to be analysed and a further dummy filter cell (not shown) alternately in the radiation path from the radiation source to the detector head. The unit further includes a chopper blade and band-pass filter between the detector of the detector head 4 and the infra red source.Printed circuit boards 7 containing the circuitry to provide control over the operation of the solenoid 5 and the processing of the signals received from the detector head are also provided in the units.
To provide for auto-calibration, the signal processor unit 2 can also include a further infra red source 8, which through mirrors 9 and 10 can direct infra red radiation at the detector head. The mirror 9 is fixed and the mirror 10 mounted on a rotary solenoid 11 to keep the mirror 10 in an inoperative position during normal use of the unit.
Fig. 2 shows the circuitry of the unit 2 in block diagram form. Thus, the solenoid 5 is driven by a drive and timing circuit 1 2 to bring the filter cell 6 and the dummy cell 1 3 in the radiation path. The signals received by the detector head 4 are fed to a pre-amplifier 14, the output from which is fed either to a first sample and hold circuit 1 5 or a second output sample and hold circuit 16. The drive and timing circuit 1 2 also controls two switches 1 7, 18 such that when the dummy cell 1 3 is in the radiation path the signal is fed to the sample and hold circuit 1 6 and when the filter cell 6 is in the radiation path the signal is fed to the sample and hold circuit 1 5. The output from each sample and hold circuit is fed to a differencer circuit 1 9 where the two signal values are subtracted, one from the other, the output from the differencer being fed to a divider circuit 20 to which is also fed the output from the sample and hold circuit 1 5. The output from the divider circuit 20 is fed to a lineariser 21, the output from which can be utilised to provide an audible or visual signal showing the extent of the monitored gas in the gas flow under test and/or used as a control signal for adjustment of the operating conditions at the burner.
Claims (14)
1. Equipment for the monitoring of gas insitu comprising an infra red source adapted to be located in ducting or the like through which the gas to be analysed passes, a detector spaced from the infra red source, a bandpass filter between the detector and the source to restrict incoming radiation to a predetermined wavelength range, and a filter cell adapted to be positioned in the radiation path between the detector and the source, filled with the gas component requiring analysis, the detector being connected in a circuit capable of measuring radiation direct from the source and passing through the gas component filter cell, determining the difference bdtween the two levels of radiation dividing the difference by either of the levels of radiation received by the detector, to provide an output from the said circuit that is a function of the amount of monitored gas present in the gas flow.
2. Equipment as in Claim 1, wherein a second reference cell is provided filled with a gas component which does not absorb radiation over the wave-lengths selected by the band-pass filter.
3. Equipment as in Claim 1, wherein the gas component filter cell and the reference cell when provided are permanently located in the radiation path, and when two radiation paths would be required one for each cell, with two detectors, again one for each cell.
4. Equipment as in Claim 3, wherein the two radiation paths are provided by two separate sources or by employing a beam splitter in the radiation from a single source.
5. Equipment as in Claim 1 or Claim 2, wherein a single source of radiation is provided, each gas component being mounted for selective introduction into the radiation path alternately with the other.
6. Equipment as in any of Claims 1 to 5, wherein the infra red source is an electrically heated plate.
7. Equipment as in any of Claims 1 to 6, wherein the detector is a pyroelectric detector.
8. Equipment as in Claim 7, wherein the detector is a lithium tantalate detector.
9. Equipment as in Claim 8, wherein a chopper blade is provided between the detector and the source to chop incoming radiation to a predetermined frequency.
10. Equipment as in any of Claims 1 to 9, wherein the detector, chopper blade (when provided), and band-pass filter along with the electronic circuits are formed as a self-contained unit for mounting at the opposite side of the boiler ducting to the infra red source.
11. Equipment as in any of Claims 1 to 9, wherein the radiation source and the detector are formed as a single unit of generally tubelike character with the radiation source at one end and the detector at the other, and with the tube pervious to gas.
12. Equipment as in any of Claims 1 to 9, wherein both the infra red source and the or each detector are provided to one side of a flue, a reflector being provided at the opposite side of the flue.
1 3. Equipment as in Claim 12, wherein the infra red source and the detector are mounted at one end of a tube and the reflector at the opposite end of the tube with the tube being pervious to gas and capable of insertion into the flue gas.
14. Equipment as in Claim 5, wherein the two filter cells are secured to a solenoid, the activation of which repeatedly introduces first one and then the other filter cell into the radiation path.
1 5. Equipment as in Claim 3, wherein each detector is provided with a pair of in-line gas cells for selective introduction into the radiation path but with the movement of the cells synchronized in antiphase.
1 6. Equipment as in any of Claims 1 to 15, wherein calibration is provided for by including means comprising a second infra red source which has a fixed concentration of gas or no gas at all enclosed in a sight path which sight path can be directed into the monitoring device of the invention at predetermined intervals to allow the monitoring device to give readings for a predetermined gas concentration and which can then be utilised to determine the accuracy of the equipment and allow such calibration as is required.
1 7. Equipment for the monitoring of gas in-situ substantially as hereinbefore described with reference to the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB7940508A GB2035552B (en) | 1978-11-29 | 1979-11-23 | Radiation detection of gas compositions |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB7846533 | 1978-11-29 | ||
| GB7940508A GB2035552B (en) | 1978-11-29 | 1979-11-23 | Radiation detection of gas compositions |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2035552A true GB2035552A (en) | 1980-06-18 |
| GB2035552B GB2035552B (en) | 1983-07-06 |
Family
ID=26269787
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB7940508A Expired GB2035552B (en) | 1978-11-29 | 1979-11-23 | Radiation detection of gas compositions |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2035552B (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2493475A1 (en) * | 1980-11-03 | 1982-05-07 | Econics Corp | METHOD AND APPARATUS FOR CONTROLLING THE AIR AND FUEL SUPPLY OF A COMBUSTION PROCESS, BASED ON THE RATE OF CARBON MONOXIDE OR UNBURNED HYDROCARBONS OR THE OPACITY OF EXHAUST GASES |
| EP0261452A2 (en) * | 1986-09-20 | 1988-03-30 | Horiba, Ltd. | Gas analyzer |
| GB2226401A (en) * | 1988-12-13 | 1990-06-27 | Robin John Hutchinson | Gas analysis apparatus |
| US5599179A (en) * | 1994-08-01 | 1997-02-04 | Mississippi State University | Real-time combustion controller |
| CN111886448A (en) * | 2017-11-06 | 2020-11-03 | 帕埃拉斯阿尔塔精密有限公司 | Food cooking unit |
-
1979
- 1979-11-23 GB GB7940508A patent/GB2035552B/en not_active Expired
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2493475A1 (en) * | 1980-11-03 | 1982-05-07 | Econics Corp | METHOD AND APPARATUS FOR CONTROLLING THE AIR AND FUEL SUPPLY OF A COMBUSTION PROCESS, BASED ON THE RATE OF CARBON MONOXIDE OR UNBURNED HYDROCARBONS OR THE OPACITY OF EXHAUST GASES |
| EP0261452A2 (en) * | 1986-09-20 | 1988-03-30 | Horiba, Ltd. | Gas analyzer |
| EP0261452A3 (en) * | 1986-09-20 | 1990-01-31 | Horiba, Ltd. | Gas analyzer |
| GB2226401A (en) * | 1988-12-13 | 1990-06-27 | Robin John Hutchinson | Gas analysis apparatus |
| GB2226401B (en) * | 1988-12-13 | 1992-11-25 | Robin John Hutchinson | Gas analysis |
| US5599179A (en) * | 1994-08-01 | 1997-02-04 | Mississippi State University | Real-time combustion controller |
| CN111886448A (en) * | 2017-11-06 | 2020-11-03 | 帕埃拉斯阿尔塔精密有限公司 | Food cooking unit |
| CN111886448B (en) * | 2017-11-06 | 2023-06-20 | 帕埃拉斯阿尔塔精密有限公司 | Food cooking unit |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2035552B (en) | 1983-07-06 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| 732 | Registration of transactions, instruments or events in the register (sect. 32/1977) | ||
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19941123 |