US4740086A
Expired / Lapsed
US
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Apparatus for the photoacoustic detection of gases
Assignee: Individual
•
Filing: 1985-01-30
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Granted: 1988-04-26
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Expires: 2005-01-30
Abstract
Abstract The apparatus for detecting gases comprises a photoacoustic gas detector 35, in which the intensity-modulated absorbed test light beam 32' is converted into noise and detected by means of microphone 36. The photoacoustic gas detector 35 is acoustically decoupled from the gas collecting point 54 by a gas-permeable diaphragm 52 or a rigid, porous material 52'. The gas chamber 35' of photoacoustic detector 35 can be scavenged by means of supply lines 38, 38' and valves 56, 56'. It is advantageous to use a thermal source 32 intensity-modulated by phase lag. The signal is processed at microphone 36 by means of a N-path filter comprising cyclic switch 63 and R-elements 62, 65, 65'. The apparatus can be used for detecting CO 2 and CO.
Inventors
- 👤 Oskar Oehler
- 👤 Klaus Mosbach
- 👤 Martin Seifert
- 👤 Heinrich Kunz
- 👤 Niels Kuster
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 11:56
CPC Classifications
G; G01; G01N; G01N21/00; G01N21/17; G01N21/1702; G01N2021/1704
Claims Analysis
Total Claims: 47
Claim 1
Independent Claim
135 words
An optical detection apparatus for selectively detecting gases including vapors, comprising: a light source located within optical collecting means defining an optical path; a gas collecting cell in said optical path, said gas collecting cell including photoacoustic gas detector means for generating signals representative of gases detected in said gas collecting cell; a monochromator in said optical path between said light source and said gas collecting cell; gas exchange means for supplying gases to and discharging gases from said gas collecting cell, said gas exchange means including an acoustically attenuating element at a gas collection point, said acoustically attenuating element being continuously permeable to gases and being exposed to a medium to be measured at the gas collecting point; and signal processing means, coupled to said detector means, for analyzing signals of said detector means.
Claim 2
Dependent Claim
135 words
An optical detection apparatus for selectively detecting gases including vapors, comprising: a light source located within optical collecting means defining an optical path; a gas collecting cell in said optical path, said gas collecting cell including photoacoustic gas detector means for generating signals representative of gases detected in said gas collecting cell; a monochromator in said optical path between said light source and said gas collecting cell; gas exchange means for supplying gases to and discharging gases from said gas collecting cell, said gas exchange means including an acoustically attenuating element at a gas collection point, said acoustically attenuating element being continuously permeable to gases and being exposed to a medium to be measured at the gas collecting point; and signal processing means, coupled to said detector means, for analyzing signals of said detector means.
Claim 3
Dependent Claim
22 words
An optical detection apparatus according to claim 1 wherein the medium to be measured at said gas collecting point is solid material.
Claim 4
Dependent Claim
23 words
An optical detection apparatus according to claim 1 wherein the medium to be measured at the gas collecting point is a liquid material.
Claim 5
Dependent Claim
19 words
An optical detection apparatus according to claim 1 wherein said acoustically attenuating element comprises rigid, porous and sintered material.
Claim 6
Dependent Claim
18 words
An optical detection apparatus according to claim 1 wherein said acoustic attenuating element comprises a gas permeable diaphragm.
Claim 7
Dependent Claim
23 words
An optical detection apparatus according to claim 5 wherein said permeable diaphragm is an enveloping boundary layer of the medium to be measured.
Claim 8
Dependent Claim
41 words
An optical detection apparatus according to claim 1 wherein said optical collecting means is arranged relative to said acoustically attenuating element such that said acoustically attenuating element is not significantly affected by a test light beam emitted by said light source.
Claim 9
Dependent Claim
53 words
An optical detection apparatus according to claim 7 wherein the test light beam is conveyed through a conical light pipe into said photoacoustic gas detector means such that a highly divergent light beam is formed that does not significantly irradiate said acoustically attenuating element positioned facing an opening in said conical light pipe.
Claim 10
Dependent Claim
37 words
An optical detection apparatus according to claim 8 wherein said photoacoustic gas detector means comprises a concave mirror for reflecting the test light beam passing out of the light pipe opening back to said conical light pipe.
Claim 11
Dependent Claim
23 words
An optical detection apparatus according to claim 1 wherein a passage extends between said photoacoustic gas detector means and the gas exchange means.
Claim 12
Dependent Claim
20 words
An optical detection apparatus according to claim 1 wherein said gas collecting point is connected to a gas producing means.
Claim 13
Dependent Claim
17 words
An optical detection apparatus according to claim 11 wherein said gas producing means is a chemical reactor.
Claim 14
Dependent Claim
19 words
An optical detection apparatus according to claim 12 wherein said chemical reactor is positioned at said gas collecting point.
Claim 15
Dependent Claim
21 words
An optical detection apparatus according to claim 13 wherein said chemical reactor comprises a reactor chamber containing a biologically active medium.
Claim 16
Dependent Claim
18 words
An optical detection apparatus according to claim 14 wherein said biologically active medium is immobilized on a support.
Claim 17
Dependent Claim
34 words
An optical detection apparatus according to claim 14 wherein said acoustically attenuating element separates said gas collecting point from a gas chamber of said photoacoustic gas detector means and supports said biologically active medium.
Claim 18
Dependent Claim
33 words
An optical detection apparatus according to claim 1 wherein said light source is thermal and is coupled to thermally modulated means for varying intensity by a phase lag of a periodic electric signal.
Claim 19
Dependent Claim
23 words
An optical detection apparatus according to claim 17 wherein the phase lag is carried out with a frequency of an integral frequency divider.
Claim 20
Dependent Claim
26 words
An optical detection apparatus according to claim 17 wherein the phase lag is carried out with an integral partial frequency of an alternating electric power source.
Claim 21
Dependent Claim
22 words
An optical detection apparatus according to claim 19 wherein the modulated intensity of said source is checked by a phase lag length.
Claim 22
Dependent Claim
26 words
An optical detection apparatus according to claim 20 wherein an additional light detector checks the modulated intensity of said source by measuring the phase lag length.
Claim 23
Dependent Claim
53 words
An optical detection apparatus according to claim 1 wherein said signal processing means comprises a selective amplifier and a signal analysis means, said signal analysis means subdividing a period of useful signals supplied by a microphone into at least two time slots and signal averaging in at least one of said time slots.
Claim 24
Dependent Claim
37 words
An optical detection apparatus according to claim 22 wherein said signal analysis means comprises a cyclic switch for subdividing the period of useful signals into time slots and a resistance element and capacitance elements for signal averaging.
Claim 25
Dependent Claim
41 words
An optical detection apparatus according to claim 23 wherein said cyclic switch is connected to at least two resistance capacitance elements, so that the phase between a modulating signal at said source and a signal at said microphone can be measured.
Claim 26
Dependent Claim
69 words
An optical detection apparatus according to claim 1 wherein said light source emits a test light beam producing photoacoustic signals; said optical collecting means comprises a semi-ellipsoidal concave mirror having an inner focal point provided with an optically partially transparent thermal source forming said light source, as well as a plane mirror-like counter-reflector having a central light exit opening positioned at a centrally bisecting plane of said semi-ellipsoidal mirror.
Claim 27
Dependent Claim
128 words
An optical detection apparatus for selectively detecting gases including vapors, comprising: a thermal light source located within optical collecting means defining an optical path, said light source being coupled to thermally modulated means for varying intensity by a phase lag of a periodic electric signal; a gas collecting cell in said optical path, said gas collecting gas including photoacoustic gas detector means for generating signals representative of gases detected in said gas collecting cell; a monochromator in said optical path between said light source and said gas collecting cell; gas exchange means for supplying gas to and discharging gases from said gas collecting cell, said gas exchange means including alternately closable valves; and signal processing means, coupled to said detector means, for analyzing signals of said detector means.
Claim 28
Dependent Claim
128 words
An optical detection apparatus for selectively detecting gases including vapors, comprising: a thermal light source located within optical collecting means defining an optical path, said light source being coupled to thermally modulated means for varying intensity by a phase lag of a periodic electric signal; a gas collecting cell in said optical path, said gas collecting gas including photoacoustic gas detector means for generating signals representative of gases detected in said gas collecting cell; a monochromator in said optical path between said light source and said gas collecting cell; gas exchange means for supplying gas to and discharging gases from said gas collecting cell, said gas exchange means including alternately closable valves; and signal processing means, coupled to said detector means, for analyzing signals of said detector means.
Claim 29
Dependent Claim
23 words
An optical detection apparatus according to claim 26 wherein the phase lag is carried out with a frequency of an integral frequency divider.
Claim 30
Dependent Claim
26 words
An optical detection apparatus according to claim 26 wherein the phase lag is carried out with an integral partial frequency of an alternating electric power source.
Claim 31
Dependent Claim
22 words
An optical detection apparatus according to claim 28 wherein the modulated intensity of said source is checked by a phase lag length.
Claim 32
Dependent Claim
26 words
An optical detection apparatus according to claim 29 wherein an additional light detector checks the modulated intensity of said source by measuring the phase lag length.
Claim 33
Dependent Claim
149 words
An optical detection apparatus for selectively detecting gases including vapors, comprising: a light source located within optical collecting means defining an optical path; a gas collecting cell in said optical path, said collecting cell including photoacoustic gas detector means for generating signals representative of gases detected in said gas collecting cell; a monochromator in said optical path between said light source and said gas collecting cell; gas exchange means for supplying gases to and discharging gases from said gas collecting cell, said gas exchange means including alternately closable valves; and signal processing means coupled to said detector means, for analyzing signals of said detector means, said signal processing means including a selective amplifier and a signal analysis means, said signal analysis means subdividing a period of useful signals supplied by a microphone into at least two time slots and signal averaging in at least one of said time slots.
Claim 34
Dependent Claim
149 words
An optical detection apparatus for selectively detecting gases including vapors, comprising: a light source located within optical collecting means defining an optical path; a gas collecting cell in said optical path, said collecting cell including photoacoustic gas detector means for generating signals representative of gases detected in said gas collecting cell; a monochromator in said optical path between said light source and said gas collecting cell; gas exchange means for supplying gases to and discharging gases from said gas collecting cell, said gas exchange means including alternately closable valves; and signal processing means coupled to said detector means, for analyzing signals of said detector means, said signal processing means including a selective amplifier and a signal analysis means, said signal analysis means subdividing a period of useful signals supplied by a microphone into at least two time slots and signal averaging in at least one of said time slots.
Claim 35
Dependent Claim
37 words
An optical detection apparatus according to claim 31 wherein said signal analysis means comprises a cyclic switch for subdividing the period of useful signals into time slots and a resistance element and capacitance elements for signal averaging.
Claim 36
Dependent Claim
41 words
An optical detection apparatus according to claim 32 wherein said cyclic switch is connected to at least two resistance capacitance elements, so that the phase between a modulating signal at said source and a signal at said microphone can be measured.
Claim 37
Independent Claim
105 words
A method of selectively detecting gases, including vapors, comprising the steps of: emitting light from a light source located within an optical collecting means into a gas collecting cell in an optical path of the light source; generating signals representative of gases detected in the gas collecting cell by photoacoustic gas detector means; opening the photoacoustic gas detector means to surrounding gases through an acoustically attenuating element which is continuously permeable to gases so that the surrounding gases penetrate the photoacoustic gas detector means; and analyzing signals generated by the photoacoustic gas detector means with signal processing means coupled to the photoacoustic gas detector means.
Claim 38
Independent Claim
105 words
A method of selectively detecting gases, including vapors, comprising the steps of: emitting light from a light source located within an optical collecting means into a gas collecting cell in an optical path of the light source; generating signals representative of gases detected in the gas collecting cell by photoacoustic gas detector means; opening the photoacoustic gas detector means to surrounding gases through an acoustically attenuating element which is continuously permeable to gases so that the surrounding gases penetrate the photoacoustic gas detector means; and analyzing signals generated by the photoacoustic gas detector means with signal processing means coupled to the photoacoustic gas detector means.
Claim 39
Dependent Claim
58 words
A method according to claim 34 wherein the gases to be measured are contained in a material having a boundary layer permeable to gases, the gases to be measured pass at least partially between the material and the photoacoustic gas detector means through a gas passage of the photoacoustic gas detector means and the gas permeable boundary layer.
Claim 40
Dependent Claim
36 words
A method according to claim 34 wherein the gases to be measured are dissolved in a liquid and are collected at a gas collecting point supplied with a liquid medium containing at least one dissolved gas.
Claim 41
Dependent Claim
30 words
A method according to claim 34 wherein a fluid medium is fed into and biologically reacted in a reactor containing at least one substrate such that dissolved gases are formed.
Claim 42
Dependent Claim
51 words
A method according to claim 34 wherein a medium is fed into a reactor containing dissolved substances which are biologically reacted in a reactor to form gases in dissolved form and to contain the dissolved substances in the medium; an additive is supplied to reversibly or irreversibly block the biological reaction.
Claim 43
Dependent Claim
34 words
A method according to claim 34 wherein several suspended biologically active substances are supplied to a reaction chamber to react substrates supplied in a sequence of steps up to at least one gaseous product.
Claim 44
Dependent Claim
41 words
A method according to claim 34 wherein a plant organism, photosynthesized under action of light radiation is measured; and at least partial direct gas exchange is conducted between the plant organism and the photoacoustic gas detector means through a gas passage.
Claim 45
Dependent Claim
17 words
A method according to claim 34 wherein at least one of CO 2 and CO are measured.
Claim 46
Dependent Claim
33 words
A method according to claim 41 wherein a phase position between signals at a light radiator and a microphone control the light source, the optical collecting means, the microphone and acoustic decoupling devices.
Claim 47
Dependent Claim
19 words
A method according to claim 34 wherein gas permeability and acoustic resistance of an acoustic decoupling device are measured.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-04-26 | 1991-10-26 | 1992-04-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-04-26 | 1995-10-26 | 1996-04-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-04-26 | 1999-10-26 | 2000-04-26 | $7700.00 | Window Closed / Lapsed |