WO1999060384A1 - Device for detecting gas concentrations - Google Patents

Device for detecting gas concentrations Download PDF

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Publication number
WO1999060384A1
WO1999060384A1 PCT/EP1999/003299 EP9903299W WO9960384A1 WO 1999060384 A1 WO1999060384 A1 WO 1999060384A1 EP 9903299 W EP9903299 W EP 9903299W WO 9960384 A1 WO9960384 A1 WO 9960384A1
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WO
WIPO (PCT)
Prior art keywords
measuring
measuring station
telephone
light
station
Prior art date
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PCT/EP1999/003299
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German (de)
French (fr)
Inventor
Gerhard Müller
Original Assignee
Laser- Und Medizin-Technologie Ggmbh, Berlin
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Publication of WO1999060384A1 publication Critical patent/WO1999060384A1/en

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Classifications

    • 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
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/02—Details
    • 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
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/02—Details
    • G01J3/0264—Electrical interface; User interface
    • 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
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/28—Investigating the spectrum
    • G01J3/44—Raman spectrometry; Scattering spectrometry ; Fluorescence spectrometry
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N35/00—Automatic analysis not limited to methods or materials provided for in any single one of groups G01N1/00 - G01N33/00; Handling materials therefor
    • G01N35/00584—Control arrangements for automatic analysers
    • G01N35/00722—Communications; Identification
    • G01N35/00871—Communications between instruments or with remote terminals
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/02—Devices for withdrawing samples
    • G01N1/22—Devices for withdrawing samples in the gaseous state
    • G01N1/2273—Atmospheric sampling
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N35/00—Automatic analysis not limited to methods or materials provided for in any single one of groups G01N1/00 - G01N33/00; Handling materials therefor
    • G01N35/00584—Control arrangements for automatic analysers
    • G01N35/00722—Communications; Identification
    • G01N35/00871—Communications between instruments or with remote terminals
    • G01N2035/00881—Communications between instruments or with remote terminals network configurations
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/0004—Gaseous mixtures, e.g. polluted air
    • G01N33/0006—Calibrating gas analysers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/0004—Gaseous mixtures, e.g. polluted air
    • G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
    • G01N33/0062—General constructional details of gas analysers, e.g. portable test equipment concerning the measuring method or the display, e.g. intermittent measurement or digital display

Definitions

  • the invention relates to a device for regional detection of the relative concentration of at least one gaseous substance in an ambient gas, in particular in air, with at least one detection center and at least one measuring station which can be remotely controlled and / or queried.
  • Such a device is used, for example, for the detection of pollutant concentrations in the air in metropolitan areas, in the vicinity of industrial plants or landfills.
  • a number of measuring stations distributed over an area are connected to an acquisition center via radio, in particular via trunked radio.
  • the measuring stations are equipped with sensors for the 'respectively to be monitored relative concentrations of pollutants.
  • different measuring methods are used to determine the concentration.
  • the concentration of sulfur dioxide is determined from the analysis of UV fluorescence, while the method of non-dispersive infrared absorption is used for carbon monoxide, a chemiluminescence method is used for nitrogen oxides and a UV absorption method is used for ozone.
  • parallel electrical (conductivity determination) and radiological measurement methods (beta absorption) are used.
  • the large number of methods used in a measuring station initially requires a great technical and financial outlay, since numerous different measuring devices and corresponding equipment for supplying the measuring apparatus with the electrical power required for operation must be provided.
  • the measuring stations are usually housed in air-conditioned containers with dimensions of approximately 2 * 2 * 2 m.
  • the maintenance of the various measuring devices of a measuring station, for example reagents have to be replaced, as well as the often complicated evaluation of the measurement results requires a great deal of work by qualified technical personnel. Therefore, maintaining a dense network of measuring stations is currently uneconomical. In addition, high demands must be placed on the locations of the measuring containers (existing power supply, sufficient space).
  • Raman spectroscopy can be used to determine the relative concentration of a gas in an ambient gas.
  • a corresponding device is described for example in the document DE 27 23 939 C2.
  • this is a system intended for clinical or laboratory use, in which the gases to be measured are examined under defined, constant boundary conditions.
  • the widespread use of such a device in environmental analysis is desirable, but has so far not been possible due to the high price of adequate, powerful and stable light sources and the relatively complex optical equipment to achieve an appropriate measurement sensitivity. bar.
  • the light source is at least one green or blue light-emitting diode laser or optically pumped microchip laser
  • the light detector or a second light detector is designed in such a way that it also converts the light intensity raman scattered in the measuring cell into a proportional
  • second electrical measurement signal converts that a temperature sensor for generating a third electrical measurement signal proportional to the temperature of the ambient gas and a pressure sensor for generating a fourth electrical measurement signal proportional to the pressure of the ambient gas are provided in the measuring station, and that the four measurement signals for evaluation by telephone to the Registration center are communicable.
  • the concentration of numerous pollutants in the air can be measured simultaneously.
  • gases and vapors of interest for environmental analysis nitrogen (N2), oxygen (02), carbon dioxide (C02), ozone (03), sulfur dioxide (S02), carbon monoxide (CO), benzene (C6H6), hydrogen sulfide (H2S) , Ammonia (NH3), hydrogen chloride (HCl), toluene and xylene.
  • the Raman scattering intensity of the pollutants to be investigated that of the nitrogen contained in the sample is also measured according to the invention.
  • the relative concentrations of the pollutants can be determined from this by forming a ratio.
  • the air pressure and temperature values for calibration and drift compensation, which are simultaneously determined according to the invention, are included in the evaluation.
  • the use according to the invention of a green or blue diode laser or optically pumped microchip laser enables the measurement method to be used inexpensively.
  • the Raman scattering cross-section of the gases of interest is particularly large when interacting with green and, in particular, blue light, without the disruptive luminescence of the gases significantly overlaying the signal.
  • the lasers mentioned can therefore be operated with powers in the order of magnitude of 100 mW. Such lasers with stable performance in this area can now be produced inexpensively.
  • the measured values can be transmitted to the data acquisition center in real time by telephone and are immediately available for evaluation and for making environmental forecasts.
  • a multipass cell into which the gas to be examined is introduced is preferably used to generate a high scattering intensity. In this way, a laser photon is passed through the gas sample several times, which increases the likelihood of it being scattered.
  • a preferred embodiment of the invention uses the connections present in a telephone booth for data transmission and for supplying the measuring station with electrical power.
  • This variant has the great advantage that no additional infrastructure has to be provided for the erection of the measuring station.
  • telephone booths in cities are numerous and set up at relatively even intervals, so that a close-meshed measuring network that was previously not considered possible can be set up inexpensively.
  • the measured values determined can be queried by anyone or by telephone or via the Internet. This is a great help, especially for ozone-sensitive people, to help them assess their performance.
  • Another embodiment of the invention has mobile measuring stations which are arranged on road, rail or aircraft and which transmit the measured values to the detection center via mobile radio. In this way, pollutant concentrations can also be detected over a large area in a simple manner.
  • the device according to the invention is particularly suitable for detecting the spread of pollutant clouds and thus enables an early prognosis for warning the population of regions at risk from the pollutant cloud.
  • FIG. 1 shows a schematic representation of the device according to the invention
  • FIG. 2 shows a partially sectioned side view of a multipass cell according to the invention
  • Figure 3 is a partially sectioned front view of the multipass cell of Figure 1 and
  • Figure 4 is a circuit diagram for the gas flow in the measuring station.
  • Figure 1 shows an embodiment of the invention in a block diagram of a device 2 for regional detection of gaseous environmental pollutants.
  • a measuring station 4 and an acquisition center 6 are shown.
  • the heart of the measuring station 4 is a Raman multi-gas sensor 8, which is described in more detail below with reference to the following figures.
  • the measuring station 4 is arranged on the roof of a telephone booth 10 and is connected to the corresponding supply devices 12 provided for the operation of the telephone booth 10 in order to supply electrical power.
  • a measurement controller 14 controls the operation of the Raman multi-gas sensor 8 and uses a memory controller 16 to store the measurement data generated by it in a memory 18.
  • a connection controller 20 With the aid of a connection controller 20, a telephone connection to the acquisition center 6 is established via a modem 22 and a network termination unit 24 provided in the telephone booth 10 in order to transmit the data stored in the memory to a central computer 26 installed there.
  • the detection center also has a network termination unit 25 which is connected to a modem 27.
  • the transmitted data are stored and evaluated in the central computer 26.
  • the respective time of transmission can be predetermined from the central computer 26 by remote-controlled programming of the connection controller 22. Basically, with the device shown, the current measured values can be queried from the central computer at any time.
  • the latter can in turn access and output the stored measured values and the evaluated data by remote inquiry by telephone or via the Internet.
  • the controls 14 to 16, the memory 18 and the modem 22 are accommodated in a compact computer unit 28 with processor and working memory (not shown) and can be hard-wired or stored in the form of executable program files in the memory 18.
  • the second variant has the advantage that updated control programs can be installed remotely on all measuring stations from the central computer.
  • the measuring station described is to be operated independently of a telephone booth, a radio telephone and a corresponding modem must be provided instead of being connected to the network termination unit of the telephone booth.
  • FIG. 2 shows, in a partially sectioned side view, the core of the Raman multi-gas sensor 8, a multipass cell 30. It forms an essentially hollow cylindrical housing 32 of approximately 10 cm in diameter and approximately 40 cm in length, which rests on a base plate 38 with two supports 34 and 36. At one longitudinal end, an adjustable laser holder 40 is attached, on which a laser 42 is arranged. In the middle of the diameter and the longitudinal extent of the housing 32 and at the same time approximately in the focal point of a multipass arrangement, which is formed by two concave mirrors 44 and 46 arranged near the longitudinal ends, there is a transparent measuring cell (not shown here) with a gas sample. For the measurement via the gas system of the measuring station described below with reference to FIG. 4, the measuring cell is either continuously flushed through by the medium to be examined or previously filled with a defined amount of gas.
  • a green or blue diode laser is used for the measurements.
  • diode-pumped solid-state lasers with internal frequency doubling for example an Nd: YAG laser (532 nm)
  • Nd: YAG laser 532 nm
  • the wavelength of the emitted light is essential. Raman scattering cross sections of the gases to be detected are particularly high in the green and blue spectral range. Furthermore, the emitted light output should be around 100mW.
  • the types mentioned are particularly preferred because of their compact design and high efficiency, which are essential for the invention. Since the development of semiconductor lasers in the green and blue spectral range is currently making great progress, it can be assumed that even smaller laser modules will be available in the future with a further reduced power consumption.
  • the laser 42 radiates into the housing 32 through a not shown Inlet optics 48, which is provided with a shutter mechanism for recording the dark count rate of detectors described below.
  • the laser beam symbolized by a dotted line 50, runs in the longitudinal direction of the housing 32 in a vertical central plane and intersects the axis in the middle of the longitudinal extent of the housing at an acute angle.
  • the non-scattered light strikes the rear radiation concave mirror 46 and is then reflected back and forth by the multipass arrangement between the mirrors 44 and 46.
  • the sample is irradiated with each pass, which is known to significantly increase the scattered light intensity compared to a simple arrangement without a multipass.
  • a detector device 52 is installed in the region of a central plane of the housing perpendicular to the axis. It consists of six photomultiplier brackets 54 arranged at the same distance from one another in the circumferential direction. Photomultiplier housings 56 and, in the lower, cut part of the figure, openings 58 provided with detection optics can be seen in FIG. 2 as components of the brackets 54.
  • FIG. 3 shows the arrangement of the photomultiplier brackets 54 in a partially sectioned front view.
  • Lens and filter combinations 60 are visible in the section of the drawing. Since each photomultiplier is provided for the detection of one gas, a specific filter combination is arranged in each holder 54.
  • the filter combinations are each designed as single or multi-band filters so that, depending on the gas, they are only permeable to the wavelengths of one or more characteristic Raman scattering lines.
  • the approximately cylindrical photomultiplier tube (not shown) is inserted through a circular opening 62 and irradiated in operation from the direction perpendicular to the axis (“side-on”). Devices for the high voltage supply of the detectors are not shown in detail.
  • the photomultipliers are operated in the single photon count mode. The intensity of the Raman signal is thus measured as the number of photons registered over a time interval.
  • the photomultiplier is followed by a photon counting chain integrated in the measuring control 14.
  • the single photon count has the advantage that the signal can be integrated over adjustable long periods of time and can thus be measured with very high accuracy if required.
  • the number of photons registered by each photomultiplier is recorded in the memory 18.
  • the dark pulse rate of each photomultiplier is determined at regular intervals and the Corrected measured value accordingly by subtraction. This can take place in the measuring station itself or after the counting rates and the dark pulse rates have been transmitted by the central computer 26 in the detection station 6.
  • the count rate measured for this gas is divided by the count rate measured simultaneously for nitrogen.
  • the evaluation is also based on the simultaneously determined absolute air pressure and the temperature at the measuring station. In accordance with the general state equation for gases, these determine the number of gas particles contained in a reference volume and thus also the scatter rates.
  • the gas system of the Raman multi-gas sensor 8 is explained below with reference to FIG. 4.
  • two alternative inputs 64 and 66 are provided, through which the gas to be examined can flow into the multi-gas sensor 8.
  • the second input 66 is provided for connecting gas bottles for calibration measurements, while the first input is used in regular measuring operation.
  • Particle filters 68 and 70 are connected downstream of both inputs, each of which has a coarse filter with 0.45 micrometers and a fine filter with 0.2 micrometer pores.
  • a two-way valve 72 which can optionally be set electromagnetically by hand or by the measurement controller 14, allows gas to flow from the first input 64 in the actuated state and gas from the second input 66 into the multipass cell 30 in the non-actuated state.
  • a pressure sensor 72 is connected in parallel to the multipass cell, which measures the absolute pressure and generates a corresponding electrical signal, the value of which is written into the memory 18.
  • the multipass cell 30 is followed by a second and a third two-way valve 76 and 78, of which the first (76) in the non-actuated state is permeable to the second (78) and is actuated only for calibration measurements with gases flowing in under excess pressure in order to carry out a relative pressure measurement perform a corresponding sensor 80.
  • the sensor 80 measures the difference between the pressure of the gas in the multipass cell and the environment.
  • Both pressure sensors 74 and 80 are connected on the outlet side to a first outlet 82 through which the gas escapes into the environment.
  • a sensor for measuring the relative air humidity and a sensor for measuring the ambient temperature are not shown. Both continuously provide measurement signals that digitized and stored in memory 18.
  • the third two-way valve 78 leads in the non-actuated state to a second outlet 84 and in the actuated state to the input of a pump 86. This is actuated for the suction of the gas samples through the inputs 64 and 66 (as long as no excess pressure is applied there) and is also on the output side connected to the second outlet 84.
  • the pump can be used to draw in defined amounts of gas as well as for continuous operation.
  • the structure described with reference to the figures can be easily installed in a frame approximately the size of a suitcase and thus forms an easily and inconspicuously installable measuring station.
  • a holographic grating can be used in connection with a CCD line for intensity measurement. The entire spectrum of the scattered light is recorded.
  • a notch filter is preferably arranged between the sample and the CCD line. The size of a measuring station with this equipment is reduced even further.
  • cooling is required, preferably in the form of a Peltier cooler. The disadvantage of this is the greater energy consumption of such a device.
  • An accumulator can of course also be used to power the measuring station, preferably supplemented by a solar system. Operation on an accumulator has the advantage that the measuring station can be used in a mobile manner.

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Abstract

The invention relates to a device for detecting the concentration of a gaseous substance in a nitrogen-containing ambient gas, especially in the air, comprising a central detection station and a measuring station, in which a light source, a measuring cell and a light detector are provided for measuring concentrations, said detector converting the light intensity that is emitted by the light source and subjected to Raman scattering by the gaseous substance in the measuring cell into a measuring signal. The light source is a diode laser emitting a green or blue light or an optically pumped microchip laser. If the light detector or a second light detector are configured in such a way as to also convert the nitrogen Raman-scattered light intensity contained in the measuring cell into a second measuring signal, a temperature sensor and a pressure sensor are then provided in the measuring station and the measuring signals can be transmitted by telephone to the central detection station.

Description

Vorrichtung zum Erfassen von GaskonzentrationenDevice for detecting gas concentrations
Die Erfindung betrifft eine Vorrichtung zur regionalen Erfassung der relativen Konzentration mindestens eines gasförmigen Stoffes in einem Umgebungsgas, insbesondere in Luft, mit mindestens einer Erfassungszentrale und mindestens einer von ihr fernsteuerbaren und/oder fernabfragbaren Meßstation.The invention relates to a device for regional detection of the relative concentration of at least one gaseous substance in an ambient gas, in particular in air, with at least one detection center and at least one measuring station which can be remotely controlled and / or queried.
Eine solche Vorrichtung wird beispielsweise zur Erfassung von Schadstoffkonzentrationen in der Luft in Ballungsräumen, in der Nähe von Industrieanlagen oder Deponien verwendet. In der Regel ist dabei eine Anzahl über ein Gebiet verteilter Meßstationen mit einer Erfassungszentrale über Funk, insbesondere über Bündelfunk verbunden. Die Meßstationen sind mit Sensoren für die' jeweils zu überwachenden relativen Schadstoffkonzentrationen ausgerüstet. Dabei werden, je nach Schadstoff, unterschiedliche Meßverfahren zur Konzentrationsbestimmung eingesetzt. Beispielsweise wird für Schwefeldioxid die Konzentration aus der Analyse der UV-Fluoreszenz bestimmt, während für Kohlenmonoxid die Methode der nicht dispersiven Infrarotabsorption, für Stickoxide ein Chemilumineszenzver- fahren und für Ozon eine UV-Absorptionsmethode verwendet wird. Parallel dazu sind elektrische (Leitfähigkeitsbestimmung) und radiologische Meßverfahren (Beta- Absorption) im Einsatz.Such a device is used, for example, for the detection of pollutant concentrations in the air in metropolitan areas, in the vicinity of industrial plants or landfills. As a rule, a number of measuring stations distributed over an area are connected to an acquisition center via radio, in particular via trunked radio. The measuring stations are equipped with sensors for the 'respectively to be monitored relative concentrations of pollutants. Depending on the pollutant, different measuring methods are used to determine the concentration. For example, the concentration of sulfur dioxide is determined from the analysis of UV fluorescence, while the method of non-dispersive infrared absorption is used for carbon monoxide, a chemiluminescence method is used for nitrogen oxides and a UV absorption method is used for ozone. In parallel electrical (conductivity determination) and radiological measurement methods (beta absorption) are used.
Die Vielzahl der eingesetzten Verfahren in einer Meßstation erfordert zunächst einen großen technischen und finanziellen Aufwand, da zahlreiche unterschiedliche Meßgeräte sowie eine entsprechende Ausstattung zur Versorgung der Meßapparaturen mit der zum Betrieb notwendigen elektrischen Leistung bereitgestellt werden müssen. Zumeist werden die Meßstationen in klimatisierten Containern mit Ausmaßen von etwa 2*2*2 m untergebracht. Die Wartung der verschiedenen Meßapparaturen einer Meßstation, wobei zum Beispiel Reagenzien ersetzt werden müssen, sowie die oft komplizierte Auswertung der Meßergebnisse erfordert einen großen Einsatz qualifizierten technischen Personals. Daher ist der Unterhalt eines dichten Netzes von Meßstationen derzeit unwirtschaftlich. Zudem sind an die Standorte der Meßcontainer hohe Ansprüche zu stellen (vorhandene Stromversorgung, ausreichend Platz).The large number of methods used in a measuring station initially requires a great technical and financial outlay, since numerous different measuring devices and corresponding equipment for supplying the measuring apparatus with the electrical power required for operation must be provided. The measuring stations are usually housed in air-conditioned containers with dimensions of approximately 2 * 2 * 2 m. The maintenance of the various measuring devices of a measuring station, for example reagents have to be replaced, as well as the often complicated evaluation of the measurement results requires a great deal of work by qualified technical personnel. Therefore, maintaining a dense network of measuring stations is currently uneconomical. In addition, high demands must be placed on the locations of the measuring containers (existing power supply, sufficient space).
Solche Container lassen sich jedoch insbesondere in Ballungsräumen nicht flächendeckend, das heißt, mit einem mittleren Abstand von einigen hundert Metern installieren. Zur genauen Erfassung von Schadstoffkonzentrationen und zur Prognose von zeitlichen Konzentrationsverläufen ist jedoch eine hohe Dichte von Meßstationen wünschenswert, insbesondere in den Ballungsräumen und in der Umgebung von Industrieanlagen. Nach Havarien beispielsweise müssen auf der Basis laufend aktualisierter Meßdaten gezielte Sofortmaßnahmen zum Schutz der durch Schadstoffemission bedrohten Bevölkerung getroffen werden. Die dafür erforderlichen Meßdaten stehen derzeit aber nicht in ausreichender Anzahl und Aktualität zur Verfügung. Üblich ist eine Aktualisierung lediglich im Halbstunden- takt.However, such containers cannot be installed nationwide, that is, with an average distance of a few hundred meters, especially in metropolitan areas. However, a high density of measuring stations is desirable for the precise detection of pollutant concentrations and for the prognosis of concentration courses over time, particularly in the metropolitan areas and in the vicinity of industrial plants. After accidents, for example, targeted immediate measures must be taken to protect the population threatened by pollutant emissions on the basis of continuously updated measurement data. The measurement data required for this are currently not available in sufficient numbers and timeliness. An update is only done every half hour.
Es ist bekannt, daß die Ramanspektroskopie zur Bestimmung der relativen Konzentration eines Gases in einem Umgebungsgas verwendet werden kann. Eine entsprechende Vorrichtung ist beispielsweise in der Druckschrift DE 27 23 939 C2 beschrieben. Dabei handelt es sich jedoch um ein für den klinischen bzw. den Laborbetrieb vorgesehenes System, bei dem die zu messenden Gase unter definierten, konstant gehaltenen Randbedingungen untersucht werden. Der flächendeckende Einsatz einer solchen Vorrichtung in der Umweltanalytik ist wünschenswert, jedoch bislang aufgrund des hohen Preises adäquater, leistungsstarker und leistungsstabiler Lichtquellen sowie der relativ aufwendigen optischen Ausstattung zur Erzielung einer angemessenen Meßempfindlichkeit nicht realisier- bar.It is known that Raman spectroscopy can be used to determine the relative concentration of a gas in an ambient gas. A corresponding device is described for example in the document DE 27 23 939 C2. However, this is a system intended for clinical or laboratory use, in which the gases to be measured are examined under defined, constant boundary conditions. The widespread use of such a device in environmental analysis is desirable, but has so far not been possible due to the high price of adequate, powerful and stable light sources and the relatively complex optical equipment to achieve an appropriate measurement sensitivity. bar.
Aufgabe der Erfindung ist es daher, eine Vorrichtung der eingangs genannten Art anzugeben, deren Meßstation laufend aktualisierte Konzentrationswerte liefert, geringen Raum- und Energiebedarf hat und weitgehend wartungsfrei und preiswert arbeitet.It is therefore an object of the invention to provide a device of the type mentioned at the outset, the measuring station of which provides continuously updated concentration values, requires little space and energy and operates largely maintenance-free and inexpensively.
Die Aufgabe wird erfindungsgemäß dadurch gelöst, daß die Lichtquelle mindestens ein grünes oder blaues Licht emittierender Diodenlaser oder optisch gepumpter Mikrochiplaser ist, daß der Lichtdetektor oder ein zweiter Lichtdetektor derart gestaltet ist, daß er auch die vom in der Meßzelle enthaltenen Stickstoff ramangestreute Lichtintensität in ein proportionales, zweites elektrisches Meßsignal wandelt, daß in der Meßstation ein Temperatursensor zur Erzeugung eines der Temperatur des Umgebungsgases proportionalen dritten elektrischen Meßsignals und ein Drucksensor zur Erzeugung eines dem Druck des Umgebungsgases proportionalen vierten elektrischen Meßsignals vorgesehen sind, und daß die vier Meßsignale zur Auswertung telefonisch an die Erfassungszentrale übermittelbar sind.The object is achieved in that the light source is at least one green or blue light-emitting diode laser or optically pumped microchip laser, that the light detector or a second light detector is designed in such a way that it also converts the light intensity raman scattered in the measuring cell into a proportional , second electrical measurement signal converts that a temperature sensor for generating a third electrical measurement signal proportional to the temperature of the ambient gas and a pressure sensor for generating a fourth electrical measurement signal proportional to the pressure of the ambient gas are provided in the measuring station, and that the four measurement signals for evaluation by telephone to the Registration center are communicable.
Durch Verwendung eines Ramanspektroskopischen Meßverfahrens kann die Konzentration zahlreicher Schadstoffe in der Luft gleichzeitig gemessen werden kann. Dazu zählen insbesondere die für die Umweltanalytik interessierenden Gase und Dämpfe Stickstoff (N2), Sauerstoff (02), Kohlendioxid (C02), Ozon (03), Schwefeldioxid (S02), Kohlenmonoxid (CO), Benzol (C6H6), Schwefelwasserstoff (H2S), Ammoniak (NH3), Chlorwasserstoff (HCI), Toluol und Xylol.By using a Raman spectroscopic measuring method, the concentration of numerous pollutants in the air can be measured simultaneously. These include in particular the gases and vapors of interest for environmental analysis: nitrogen (N2), oxygen (02), carbon dioxide (C02), ozone (03), sulfur dioxide (S02), carbon monoxide (CO), benzene (C6H6), hydrogen sulfide (H2S) , Ammonia (NH3), hydrogen chloride (HCl), toluene and xylene.
Neben der Raman-Streuintensität zu untersuchender Schadstoffe wird erfindungsgemäß auch die des in der Probe enthaltenen Stickstoffs gemessen. Durch Verhältnisbildung lassen sich daraus die relativen Konzentrationen der Schadstoffe bestimmen. Dabei werden die erfindungsgemäß gleichzeitig bestimmten Luftdruck- und Temperaturwerte zur Kalibrierung und Driftkompensation in die Auswertung mit einbezogen.In addition to the Raman scattering intensity of the pollutants to be investigated, that of the nitrogen contained in the sample is also measured according to the invention. The relative concentrations of the pollutants can be determined from this by forming a ratio. The air pressure and temperature values for calibration and drift compensation, which are simultaneously determined according to the invention, are included in the evaluation.
Die erfindungsgemäße Verwendung eines grünen oder blauen Diodenlasers oder optisch gepumpten Mikrochiplasers ermöglicht den kostengünstigen Einsatz des Meßverfahrens. Der Raman-Streuquerschnitt der interessierenden Gase ist bei Wechselwirkung mit grünem und insbesondere blauem Licht besonders groß, ohne daß störende Lumineszenzen der Gase das Signal wesentlich überlagern. Die genannten Laser sind können daher mit Leistungen in der Größenordnung von 100mW betrieben werden. Derartige Laser mit stabiler Leistung in diesem Bereich sind inzwischen preiswert herstellbar. Durch telefonische Übermittlung können die Meßwerte in Echtzeit an die Erfassungszentrale übertragen werden und stehen sofort zur Auswertung und zur Erstellung von Umweltprognosen zur Verfügung.The use according to the invention of a green or blue diode laser or optically pumped microchip laser enables the measurement method to be used inexpensively. The Raman scattering cross-section of the gases of interest is particularly large when interacting with green and, in particular, blue light, without the disruptive luminescence of the gases significantly overlaying the signal. The The lasers mentioned can therefore be operated with powers in the order of magnitude of 100 mW. Such lasers with stable performance in this area can now be produced inexpensively. The measured values can be transmitted to the data acquisition center in real time by telephone and are immediately available for evaluation and for making environmental forecasts.
Erst die Gesamtheit der im Anspruch 1 genannten Merkmale machen eine Raman- spektroskopisches Meßvorrichtung für den wirtschaftlichen und flächendeckenden Einsatz in der Umweltanalytik einsetzbar. Dabei werden durch eine solche Vorrichtung Nachweisempfindlichkeiten bis zu 60 ppb erreicht.Only the entirety of the features mentioned in claim 1 make a Raman spectroscopic measuring device usable for economical and area-wide use in environmental analysis. Detection sensitivities of up to 60 ppb are achieved with such a device.
Vorzugsweise wird zur Erzeugung einer hohen Streuintensiät eine Multipasszelle verwendet, in die das zu untersuchende Gas eingeleitet wird. Auf diese Weise wird ein Laserphoton mehrfach durch die Gasprobe geleitet, wodurch die Wahrscheinlichkeit, daß es gestreut wird, erhöht wird.A multipass cell into which the gas to be examined is introduced is preferably used to generate a high scattering intensity. In this way, a laser photon is passed through the gas sample several times, which increases the likelihood of it being scattered.
Eine bevorzugte Ausführungsform der Erfindung nutzt die in einer Telefonzelle vorhanden Anschlüsse zur Datenübermittlung und zur Versorgung der Meßstation mit elektrischer Leistung. Diese Variante hat den großen Vorteil, daß keinerlei zusätzliche Infrastruktur für die Errichtung Meßstation bereitzustellen ist. Zudem sind Telefonzellen in Städten zahlreich und mit relativ gleichmäßigen Abständen aufgestellt, so daß preiswert ein bisher nicht für möglich gehaltenes, engmaschiges Meßnetz aufgebaut werden kann. Die ermittelten Meßwerte können telefonisch oder über das Internet von jedermann abgefragt werden. Dies ist insbesondere für ozonempfindliche Personen zur Voreinschätzung ihrer Leistungsfähigkeit eine große Unterstützung.A preferred embodiment of the invention uses the connections present in a telephone booth for data transmission and for supplying the measuring station with electrical power. This variant has the great advantage that no additional infrastructure has to be provided for the erection of the measuring station. In addition, telephone booths in cities are numerous and set up at relatively even intervals, so that a close-meshed measuring network that was previously not considered possible can be set up inexpensively. The measured values determined can be queried by anyone or by telephone or via the Internet. This is a great help, especially for ozone-sensitive people, to help them assess their performance.
Eine andere Ausführungs der Erfindung hat mobile Meßstationen, die an Straßen-, Schienen- oder Luftfahrzeugen angeordnet sind und die die Meßwerte über Mobilfunk an die Erfassungszentrale übermitteln. Auf diese Weise können in einfacher Weise Schadstoffkonzentrationen auch großräumig erfaßt werden.Another embodiment of the invention has mobile measuring stations which are arranged on road, rail or aircraft and which transmit the measured values to the detection center via mobile radio. In this way, pollutant concentrations can also be detected over a large area in a simple manner.
Im Havariefall eignet sich die erfindungsgemäße Vorrichtung besonders zur Erfassung der Ausbreitung von Schadstoffwolken und ermöglichen so eine frühzeitige Prognose zur Warnung der Bevölkerung durch die Schadstoffwolke gefährdeter Regionen.In the event of an accident, the device according to the invention is particularly suitable for detecting the spread of pollutant clouds and thus enables an early prognosis for warning the population of regions at risk from the pollutant cloud.
Weitere Vorteile und Merkmale der Erfindung werden bei der folgenden Be- Schreibung eines Ausführungsbeispieis anhand der Zeichnung deutlich. Darin zeigtFurther advantages and features of the invention are described in the following Spelling of an example of execution clearly from the drawing. In it shows
Figur 1 eine schematische Darstellung der erfindungsgemäßen Vorrichtung,FIG. 1 shows a schematic representation of the device according to the invention,
Figur 2 eine teilweise geschnittene Seitenansicht einer erfindungsgemäßen Multipasszelle,FIG. 2 shows a partially sectioned side view of a multipass cell according to the invention,
Figur 3 eine teilweise geschnittene Vorderansicht der Multipasszelle aus Figur 1 undFigure 3 is a partially sectioned front view of the multipass cell of Figure 1 and
Figur 4 einen Schaltplan für den Gasfluß in der Meßstation.Figure 4 is a circuit diagram for the gas flow in the measuring station.
Figur 1 zeigt als Ausführungsbeispiel der Erfindung in einem Blockschaltbild eine Vorrichtung 2 zur regionalen Erfassung von gasförmigen Umweltschadstoffen. Dargestellt ist eine Meßstation 4 sowie eine Erfassungszentrale 6.Figure 1 shows an embodiment of the invention in a block diagram of a device 2 for regional detection of gaseous environmental pollutants. A measuring station 4 and an acquisition center 6 are shown.
Kernstück der Meßstation 4 ist ein Raman-Multigassensor 8, der anhand der folgenden Figuren weiter unten näher beschrieben wird. Die Meßstation 4 ist auf dem Dach einer Telefonzelle 10 angeordnet und ist zur Versorgung mit elektrischer Leistung an die entsprechenden, für den Betrieb der Telefonzelle 10 vorgesehenen Versorgungseinrichtungen 12 angeschlossen.The heart of the measuring station 4 is a Raman multi-gas sensor 8, which is described in more detail below with reference to the following figures. The measuring station 4 is arranged on the roof of a telephone booth 10 and is connected to the corresponding supply devices 12 provided for the operation of the telephone booth 10 in order to supply electrical power.
Eine Meßsteuerung 14 steuert den Betrieb des Raman-Multigassensors 8 und sorgt mit Hilfe einer Speichersteuerung 16 für die Abspeicherung der von ihm erzeugten Meßdaten in einem Speicher 18 . Mit Hilfe einer Verbindungssteuerung 20 wird über ein Modem 22 und eine in der Telefonzelle 10 vorgesehene Netzabschlußeinheit 24 eine Telefonverbindung zur Erfassungszentrale 6 hergestellt, um die im Speicher festgehaltenen Daten an einen dort installierten Zentralrechner 26 zu übermitteln. Die Erfassungszentrale weist dazu ebenfalls ein Netzabschlußeinheit 25 auf, die mit einem Modem 27 verbunden ist. Die übermittelten Daten werden in dem Zentralrechner 26 gespeichert und ausgewertet. Der jeweilige Zeitpunkt der Übermittlung kann vom Zentralrechner 26 aus durch ferngesteuerte Programmierung der Verbindungssteuerung 22 vorbestimmt werden. Grundsätzlich ist mit der dargestellten Vorrichtung jedoch jederzeit eine Abfrage der aktuellen Meßwerte vom Zentralrechner aus möglich. Dieser kann wiederum auf eine Fernabfrage per Telefon oder über das Internet hin auf die gespeicherten Meßwerte und die ausgewerteten Daten zugreifen und ausgeben. Die Steuerungen 14 bis 16, der Speicher 18 und das Modem 22 sind in einer kompakten Rechnereinheit 28 mit Prozessor und Arbeitsspeicher (nicht dargestellt) untergebracht und können fest verdrahtet oder in Form ausführbarer Programmdateien im Speicher 18 abgelegt sein. Die zweite Variante hat den Vorteil, daß aktualisierte Steuerprogramme vom Zentralrechner aus auf allen Meßstationen ferninstalliert werden können.A measurement controller 14 controls the operation of the Raman multi-gas sensor 8 and uses a memory controller 16 to store the measurement data generated by it in a memory 18. With the aid of a connection controller 20, a telephone connection to the acquisition center 6 is established via a modem 22 and a network termination unit 24 provided in the telephone booth 10 in order to transmit the data stored in the memory to a central computer 26 installed there. For this purpose, the detection center also has a network termination unit 25 which is connected to a modem 27. The transmitted data are stored and evaluated in the central computer 26. The respective time of transmission can be predetermined from the central computer 26 by remote-controlled programming of the connection controller 22. Basically, with the device shown, the current measured values can be queried from the central computer at any time. The latter can in turn access and output the stored measured values and the evaluated data by remote inquiry by telephone or via the Internet. The controls 14 to 16, the memory 18 and the modem 22 are accommodated in a compact computer unit 28 with processor and working memory (not shown) and can be hard-wired or stored in the form of executable program files in the memory 18. The second variant has the advantage that updated control programs can be installed remotely on all measuring stations from the central computer.
Soll die beschriebene Meßstation unabhängig von einer Telefonzelle betrieben werden, so ist anstelle ihres Anschlusses an die Netzabschlußeinheit der Telefonzelle ein Funktelefon und ein entsprechendes Modem vorzusehen.If the measuring station described is to be operated independently of a telephone booth, a radio telephone and a corresponding modem must be provided instead of being connected to the network termination unit of the telephone booth.
Figur 2 zeigt in einer teilgeschnittenen Seitenansicht das Kernstück des Raman- Multigassensors 8, eine Multipasszelle 30. Sie bildet ein im wesentlichen hohlzylindrisches Gehäuse 32 von etwa 10cm Durchmesser und ca. 40cm Länge, das mit zwei Stützen 34 und 36 auf einer Bodenplatte 38 ruht. An einem Längsende ist eine justierbare Laserhalterung 40 befestigt, auf der ein Laser 42 angeordnet ist. In der Mitte des Durchmessers und der Längserstreckung des Gehäuses 32 und gleichzeitig etwa im Brennpunkt einer Multipassanordnung, die durch zwei nahe den längsseitigen Enden angeordnete Konkavspiegel 44 und 46 gebildet wird befindet sich eine hier nicht dargestellte, transparente Meßzelle mit einer Gasprobe. Die Meßzelle wird für die Messung über das unten anhand von Figur 4 beschriebene Gassystem der Meßstation entweder vom zu untersuchenden Medium kontinuierlich durchspült oderzuvor miteinerdefinierten Gasmenge gefüllt.FIG. 2 shows, in a partially sectioned side view, the core of the Raman multi-gas sensor 8, a multipass cell 30. It forms an essentially hollow cylindrical housing 32 of approximately 10 cm in diameter and approximately 40 cm in length, which rests on a base plate 38 with two supports 34 and 36. At one longitudinal end, an adjustable laser holder 40 is attached, on which a laser 42 is arranged. In the middle of the diameter and the longitudinal extent of the housing 32 and at the same time approximately in the focal point of a multipass arrangement, which is formed by two concave mirrors 44 and 46 arranged near the longitudinal ends, there is a transparent measuring cell (not shown here) with a gas sample. For the measurement via the gas system of the measuring station described below with reference to FIG. 4, the measuring cell is either continuously flushed through by the medium to be examined or previously filled with a defined amount of gas.
Für die Messungen wird ein grüner oder blauer Diodenlaser verwendet. Alternativ können auch diodengepumpte Festkörperlaser mit interner Frequenzverdopplung, also beispielsweise ein Nd:YAG Laser (532 nm) verwendet werden. Wesentlich ist zum einen die Wellenlänge des ausgestrahlten Lichts. Raman-Streuquerschnitte der zu nachzuweisenden Gase sind im grünen und blauen Spektralbereich besonders hoch. Weiterhin sollte die abgestrahlte Lichtleistung konstant etwa in der Größenordnung von 100mW liegen. Die genannten Bauarten werden insbesodere wegen ihrer kompakten Bauart und hohen Effizienz bevorzugt, die für die Erfindung wesentliche Bedeutung haben. Da die Entwicklung von Halbleiterlasern im grünen und blauen Spektralbereich derzeit große Fortschritte macht, ist anzunehmen, daß in Zukunft noch kleinere Lasermodule mit weiter verringerter Leistungsaufnahme zur Verfügung stehen.A green or blue diode laser is used for the measurements. Alternatively, diode-pumped solid-state lasers with internal frequency doubling, for example an Nd: YAG laser (532 nm), can also be used. The wavelength of the emitted light is essential. Raman scattering cross sections of the gases to be detected are particularly high in the green and blue spectral range. Furthermore, the emitted light output should be around 100mW. The types mentioned are particularly preferred because of their compact design and high efficiency, which are essential for the invention. Since the development of semiconductor lasers in the green and blue spectral range is currently making great progress, it can be assumed that even smaller laser modules will be available in the future with a further reduced power consumption.
Der Laser 42 strahlt in das Gehäuse 32 durch eine nicht näher dargestellte Einlaßoptik 48 ein, die mit einem Verschlußmechanismus für die Aufnahme der Dunkelzählrate unten beschriebener Detektoren versehen ist. Der Laserstrahl, symbolisiert durch eine gepunktete Linie 50, verläuft in Längsrichtung des Gehäuses 32 in einer vertikalen Mittelebene und schneidet die Achse in der Mitte der Längserstreckung des Gehäuses unter spitzem Winkel. Nach erstmaliger Durchstahlung der Probe trifft das nicht gestreute Licht auf den rückwärtigen Durchstrahlung Konkavspiegel 46 und wird anschließend durch die Multipassanord- nung zwischen den Spiegeln 44 und 46 hin- und hereflektiert. Bei jedem Durchlauf wird die Probe durchstrahlt, wodurch bekanntermaßen die gestreute Lichtintensität gegenüber einer einfachen Anordnung ohne Multipass wesentlich erhöht wird.The laser 42 radiates into the housing 32 through a not shown Inlet optics 48, which is provided with a shutter mechanism for recording the dark count rate of detectors described below. The laser beam, symbolized by a dotted line 50, runs in the longitudinal direction of the housing 32 in a vertical central plane and intersects the axis in the middle of the longitudinal extent of the housing at an acute angle. After penetration of the sample for the first time, the non-scattered light strikes the rear radiation concave mirror 46 and is then reflected back and forth by the multipass arrangement between the mirrors 44 and 46. The sample is irradiated with each pass, which is known to significantly increase the scattered light intensity compared to a simple arrangement without a multipass.
Zur Messung der Intensität des gestreuten Licht ist im Bereich einer zur Achse senkrechten Mittelebene des Gehäuses eine Detektorvorrichtung 52 eingebaut. Sie besteht aus sechs in Umfangsrichtung mit gleichem Abstand voneinander angeordneten Photomultiplierhaltungen 54. Zu erkennen sind in Figur 2 als Bestandteile der Halterungen 54 Photomultipliergehäuse 56 und, im unteren, geschnittenen Teil der Figur, mit Nachweisoptik versehene Öffnungen 58.To measure the intensity of the scattered light, a detector device 52 is installed in the region of a central plane of the housing perpendicular to the axis. It consists of six photomultiplier brackets 54 arranged at the same distance from one another in the circumferential direction. Photomultiplier housings 56 and, in the lower, cut part of the figure, openings 58 provided with detection optics can be seen in FIG. 2 as components of the brackets 54.
Figur 3 zeigt in einer teilweise geschnittenen Vorderansicht die Anordnung der Photomultiplierhalterungen 54. Im geschnittenen Teil der Zeichnung sind Linsen- und Filterkombinationenen 60 sichtbar. Da jeder Photomultiplier zum Nachweis je eines Gases vorgesehen ist, ist in jeder Halterung 54 eine spezifische Filterkombination angeordnet. Die Filterkombinationen sind jeweils als Einzel- oder Mehrbandfilter ausgebildet, um je nach Gas nur für die Wellenlängen einer oder mehrerer charakteristischer Ramanstreulinien durchlässig zu sein.FIG. 3 shows the arrangement of the photomultiplier brackets 54 in a partially sectioned front view. Lens and filter combinations 60 are visible in the section of the drawing. Since each photomultiplier is provided for the detection of one gas, a specific filter combination is arranged in each holder 54. The filter combinations are each designed as single or multi-band filters so that, depending on the gas, they are only permeable to the wavelengths of one or more characteristic Raman scattering lines.
Die (nicht dargestellte) etwa zylindrische Photomultiplierröhre wird durch eine kreisförmige Öffnung 62 eingeführt und im Betrieb aus zur Achse senkrechter Richtung bestrahlt ("side-on"). Vorrichtungen zur Hochspannungsversorgung der Detektoren sind nicht näher dargestellt. Die Photomultiplier werden im Modus der Einzelphotonenzählung betrieben. Die Intensität des Ramansignals wird also als Anzahl von über ein Zeitintervall registrierter Photonen gemessen. Dem Photomultiplier ist hierfür eine in die Meßsteuerung 14 integrierte Photonenzählkette nachgeschaltet. Die Einzelphotonenzählung hat den Vorteil, daß das Signal über einstellbar lange Zeitspannen integriert werden kann und so bei Bedarf mit sehr hoher Genauigkeit gemessen werden kann. Die Anzahl der von jedem Photomultiplier registrieren Photonen wird im Speicher 18 festgehalten. In regelmäßigen Abständen wird die Dunkelpulsrate jedes Photomultipliers bestimmt und der Meßwert durch Subtraktion entsprechend korrigiert. Dies kann in der Meßstation selbst oder nach Übermittlung der Zählraten und der Dunkelpulsraten durch den Zentralrechner 26 in der Erfassungsstation 6 erfolgen.The approximately cylindrical photomultiplier tube (not shown) is inserted through a circular opening 62 and irradiated in operation from the direction perpendicular to the axis (“side-on”). Devices for the high voltage supply of the detectors are not shown in detail. The photomultipliers are operated in the single photon count mode. The intensity of the Raman signal is thus measured as the number of photons registered over a time interval. For this purpose, the photomultiplier is followed by a photon counting chain integrated in the measuring control 14. The single photon count has the advantage that the signal can be integrated over adjustable long periods of time and can thus be measured with very high accuracy if required. The number of photons registered by each photomultiplier is recorded in the memory 18. The dark pulse rate of each photomultiplier is determined at regular intervals and the Corrected measured value accordingly by subtraction. This can take place in the measuring station itself or after the counting rates and the dark pulse rates have been transmitted by the central computer 26 in the detection station 6.
Um die relative Konzentration eines Schadstoffgases in Luft zu bestimmen, wird die für dieses Gas gemessene Zählrate durch die gleichzeitig für Stickstoff gemessene Zählrate dividiert. Der Auswertung wird neben den gemessenen Zähl- und Dunkelpulsraten auch der gleichzeitig bestimmte absolute Luftdruck sowie die Temperatur an der Meßstation zugrundegelegt. Diese bestimmen entsprechend der allgemeinen Zustandsgieichung für Gase die Zahl der in einem Bezugsvolumen enthaltenen Gasteilchen und somit auch die Streuraten.In order to determine the relative concentration of a pollutant gas in air, the count rate measured for this gas is divided by the count rate measured simultaneously for nitrogen. In addition to the measured count and dark pulse rates, the evaluation is also based on the simultaneously determined absolute air pressure and the temperature at the measuring station. In accordance with the general state equation for gases, these determine the number of gas particles contained in a reference volume and thus also the scatter rates.
Anhand von Figur 4 wird im folgenden das Gassystem des Raman-Multigassensors 8 erläutert. Bei dem vorliegenden Ausführungsbeispiel sind zwei alternative Eingänge 64 und 66 vorgesehen, durch die das zu untersuchende Gas in den Multigassensor 8 einströmen kann. Dabei ist der zweite Eingang 66 zum Anschluß von Gasflaschen für Kalibrierungsmessungen vorgesehen, während der erste Eingang im regulären Meßbetrieb verwendet wird. Beiden Eingängen sind Teilchenfilter 68 bzw. 70 nachgeschaltet, die jeweils einen Grobfilter mit 0,45 Mikrometer und einen Feinfilter mit 0,2 Mikrometer großen Poren aufweisen. Ein wahlweise per Hand oder von der Meßsteuerung 14 elektromagnetisch stellbares Zweiwegeventil 72 läßt im betätigten Zustand Gas aus dem ersten Eingang 64 und im nicht betätigten Zustand Gas aus dem zweiten Eingang 66 in die Multipasszelle 30 einströmen. Parallel zur Multipasszelle ist ein Drucksensor 72 geschaltet, der den absoluten Druck mißt und ein entsprechendes elektrisches Signal erzeugt, dessen Wert in den Speicher 18 geschrieben wird.The gas system of the Raman multi-gas sensor 8 is explained below with reference to FIG. 4. In the present exemplary embodiment, two alternative inputs 64 and 66 are provided, through which the gas to be examined can flow into the multi-gas sensor 8. The second input 66 is provided for connecting gas bottles for calibration measurements, while the first input is used in regular measuring operation. Particle filters 68 and 70 are connected downstream of both inputs, each of which has a coarse filter with 0.45 micrometers and a fine filter with 0.2 micrometer pores. A two-way valve 72, which can optionally be set electromagnetically by hand or by the measurement controller 14, allows gas to flow from the first input 64 in the actuated state and gas from the second input 66 into the multipass cell 30 in the non-actuated state. A pressure sensor 72 is connected in parallel to the multipass cell, which measures the absolute pressure and generates a corresponding electrical signal, the value of which is written into the memory 18.
Der Multipasszelle 30 sind ein zweites und ein drittes Zweiwegeventil 76 und 78 nachgeschaltet, von denen das erste (76) im nicht betätigten Zustand zum zweiten (78) hin durchlässig ist und nur für Kalibrierungsmessungen mit unter Überdruck einströmenden Gasen betätigt wird, um eine Relativdruckmessung mit einem entsprechenden Sensor 80 durchzuführen. Der Sensor 80 mißt die Differenz zwischen dem Druck des Gases in der Multipasszelle und der Umgebung.The multipass cell 30 is followed by a second and a third two-way valve 76 and 78, of which the first (76) in the non-actuated state is permeable to the second (78) and is actuated only for calibration measurements with gases flowing in under excess pressure in order to carry out a relative pressure measurement perform a corresponding sensor 80. The sensor 80 measures the difference between the pressure of the gas in the multipass cell and the environment.
Beide Drucksensoren 74 und 80 sind ausgangsseitig mit einem ersten Auslaß 82 verbunden, durch den das Gas in die Umgebung entweicht. Nicht dargestellt sind ein Sensor zur Messung der relativen Luftfeuchtigkeit sowie ein Sensor zur Messung der Umgebungstemperatur. Beide liefern kontinuierlich Meßsignale, die digitalisiert und im Speicher 18 festgehalten werden.Both pressure sensors 74 and 80 are connected on the outlet side to a first outlet 82 through which the gas escapes into the environment. A sensor for measuring the relative air humidity and a sensor for measuring the ambient temperature are not shown. Both continuously provide measurement signals that digitized and stored in memory 18.
Das dritte Zweiwegeventil 78 führt im nicht betätigten Zustand zu einem zweiten Auslaß 84 und im betätigten Zustand zum Eingang einer Pumpe 86. Diese wird zum Ansaugen der Gasproben durch die Eingänge 64 bzw. 66 (soweit dort kein Überdruck angelegt wird) betätigt und ist ausgangsseitig ebenfalls mit dem zweiten Auslaß 84 verbunden. Die Pumpe kann sowohl zum Ansaugen definierter Gasmengen als auch für den kontinuierlichen Betrieb verwendet werden.The third two-way valve 78 leads in the non-actuated state to a second outlet 84 and in the actuated state to the input of a pump 86. This is actuated for the suction of the gas samples through the inputs 64 and 66 (as long as no excess pressure is applied there) and is also on the output side connected to the second outlet 84. The pump can be used to draw in defined amounts of gas as well as for continuous operation.
Der anhand der Figuren beschriebene Aufbau läßt sich bequem in einen etwa handkoffergroßen Rahmen einbauen und bildet so eine leicht und unauffällig installierbare Meßstation.The structure described with reference to the figures can be easily installed in a frame approximately the size of a suitcase and thus forms an easily and inconspicuously installable measuring station.
In einer alternativen Ausführung kann auch anstelle einer Anzahl von Photomultiplie- rn mit vorgeschalteten Filtern zur spektralen Selektion des gestreuten Lichts ein holographisches Gitter in Verbindung mit einer CCD-Zeile zur Intensitätsmessung verwendet werden. Dabei wird das gesamte Spektrum des gestreuten Lichts aufgenommen. Um das intensive, Rayleigh-gestreute Licht auszublenden, wird vorzugsweise ein Notchfilter zwischen Probe und CCD-Zeile angeordnet. Die Baugröße einer Meßstation mit dieser Ausstattung wird noch weiter verringert. Jedoch ist zur Erhöhung der derzeit noch vergleichsweise geringen Nachweisempfindlichkeit der CCD-Elemente eine Kühlung erforderlich, vorzugsweise in Form eines Peltier-Kühlers. Als Nachteil tritt dabei der größere Energieverbrauch einer solchen Vorrichtung in Erscheinung.In an alternative embodiment, instead of a number of photomultipliers with upstream filters for spectral selection of the scattered light, a holographic grating can be used in connection with a CCD line for intensity measurement. The entire spectrum of the scattered light is recorded. In order to block out the intense, Rayleigh-scattered light, a notch filter is preferably arranged between the sample and the CCD line. The size of a measuring station with this equipment is reduced even further. However, in order to increase the currently relatively low detection sensitivity of the CCD elements, cooling is required, preferably in the form of a Peltier cooler. The disadvantage of this is the greater energy consumption of such a device.
Zur Stromversorgung der Meßstation kann selbstverständlich auch ein Akkumulator verwendet werden, vorzugsweise ergänzt durch eine Solaranlage. Der Betrieb an einem Akkumulator hat den Vorteil, daß die Meßstation mobil einsetzbar ist. An accumulator can of course also be used to power the measuring station, preferably supplemented by a solar system. Operation on an accumulator has the advantage that the measuring station can be used in a mobile manner.

Claims

Patentansprüche claims
1 . Vorrichtung zur regionalen Erfassung der relativen Konzentration mindestens eines gasförmigen Stoffes in einem stickstoffhaltigen Umgebungsgas, insbesondere in Luft, mit mindestens einer Erfassungszentrale und mindestens einer von ihr fernsteuerbaren und/oder fernabf ragbaren Meßstation, in der zur Konzentrationsmessung jeweils mindestens eine Lichtquelle, eine Meßzelle und ein Lichtdetektor vorgesehen ist, der die von der Lichtquelle ausgesandte und von dem gasförmigen Stoff in der Meßzelle ramangestreute Lichtintensität in ein proportionales, erstes elektrisches Meßignal wandelt, dadurch gekennzeichnet, daß die Lichtquelle mindestens ein grünes oder blaues Licht emittierender Diodenlaser oder optisch gepumpter Mikrochiplaser ist, daß der Lichtdetektor oder ein zweiter Lichtdetektor derart gestaltet ist, daß er auch die vom in der Meßzelle enthaltenen Stickstoff ramangestreute Lichtintensität in ein proportionales, zweites elektrisches Meßsignal wandelt, daß in der Meßstation ein Temperatursensor zur Erzeugung eines der Temperatur des Umgebungsgases proportionalen dritten elektrischen Meßsignals und ein Drucksensor zur Erzeugung eines dem Druck des Umgebungsgases proportionalen vierten elektrischen Meßsignals vorgesehen sind, und daß die vier Meßsignale telefonisch an die Erfassungszentrale übermittelbar sind.1 . Device for the regional detection of the relative concentration of at least one gaseous substance in a nitrogen-containing ambient gas, in particular in air, with at least one detection center and at least one measuring station which can be remotely controlled and / or remotely queried, in which at least one light source, one measuring cell and one for measuring the concentration Light detector is provided which converts the light intensity emitted by the light source and raman scattered by the gaseous substance in the measuring cell into a proportional, first electrical measurement signal, characterized in that the light source is at least one green or blue light emitting diode laser or optically pumped microchip laser, that the light detector or a second light detector is designed in such a way that it also converts the light intensity, which is scattered by the nitrogen contained in the measuring cell, into a proportional, second electrical measuring signal that in the measuring A temperature sensor for generating a third electrical measurement signal proportional to the temperature of the ambient gas and a pressure sensor for generating a fourth electrical measurement signal proportional to the pressure of the ambient gas are provided, and that the four measurement signals can be transmitted by telephone to the detection center.
2. Vorrichtung nach Anspruch 1 , dadurch gekennzeichnet, daß die Meßstation für die Fernsteuerung und Fernabfrage mit einem Funktelefon ausgestattet ist.2. Device according to claim 1, characterized in that the measuring station for remote control and remote inquiry is equipped with a radio telephone.
3. Vorrichtung nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß die Fernsteuerung und Fernabfrage ausschließlich bzw. alternativ über eine Festnetzverbindung erfolgt und die Meßstation hierfür an einen Telefonanschluß einer Telefonzelle angeschlossen ist.3. Apparatus according to claim 1 or 2, characterized in that the remote control and remote inquiry takes place exclusively or alternatively via a landline connection and the measuring station for this is connected to a telephone connection of a telephone booth.
4. Vorrichtung nach Anspruch 3, dadurch gekennzeichnet, daß die Meßstation Mittel zur Versorgung mit elektrischer Leistung aufweist, die an die für die elektrische Versorgung der Telefonzelle vorgesehenen Einrichtungen anschließbar sind.4. The device according to claim 3, characterized in that the measuring station has means for supplying electrical power which can be connected to the devices provided for the electrical supply of the telephone booth.
5. Vorrichtung nach einem der vorhergehenden Ansprüche, dadurch gekenn- zeichnet, daß die Meßstation auf dem Dach der Telefonzelle angeordnet ist.5. Device according to one of the preceding claims, characterized records that the measuring station is arranged on the roof of the telephone booth.
6. Vorrichtung nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß die Meßstation an einem Straßen-, Schienen- oder Luftfahrzeug angeordnet ist.6. The device according to claim 1 or 2, characterized in that the measuring station is arranged on a road, rail or aircraft.
7. Vorrichtung nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß zur Versorgung der Meßstation mit elektrischer Leistung von Akkumulatoren vorgesehen sind, die zumindest teilweise von Solarzellen gespeist werden.7. Device according to one of the preceding claims, characterized in that are provided to supply the measuring station with electrical power from batteries, which are at least partially fed by solar cells.
8. Vorrichtung nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die Meßstation von der Erfassungszentrale zur kontinuierlichen Konzentrationsmessung über eine Zeitspanne und zur sofortigen, kontinuierlichen Übermittlung der dabei ermittelten Meßdaten ansteuerbar ist.8. Device according to one of the preceding claims, characterized in that the measuring station can be controlled by the detection center for continuous concentration measurement over a period of time and for the immediate, continuous transmission of the measurement data determined thereby.
9. Vorrichtung nach einem der vorhergehenden Ansprüche, gekennzeichnet durch mindestens einen telefonisch und/oder über das Internet femsteuer- und fernabf ragbaren Schreib/Lesespeicher in der Erfassungszentrale zur Ausgabe der ermittelten Konzentrationswerte.9. Device according to one of the preceding claims, characterized by at least one read / write memory that can be remotely controlled by telephone and / or via the Internet and can be accessed remotely in the detection center for outputting the determined concentration values.
10. Vorrichtung nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß der Lichtdetektor ein Photomultiplier im Modus der Einzelphotonenzählung in Verbindung mit einer Photonenzählkette ist.10. Device according to one of the preceding claims, characterized in that the light detector is a photomultiplier in the mode of single photon counting in connection with a photon counting chain.
1 1 . Vorrichtung nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die Meßzelle in einer Multipassanordnung angeordnet ist. 1 1. Device according to one of the preceding claims, characterized in that the measuring cell is arranged in a multipass arrangement.
PCT/EP1999/003299 1998-05-16 1999-05-12 Device for detecting gas concentrations WO1999060384A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE1998122161 DE19822161A1 (en) 1998-05-16 1998-05-16 Automatic local and regional measurement of damaging emission profile for use around large chemical plants and rubbish tips
DE19822161.4 1998-05-16

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EP0242926A1 (en) * 1986-04-19 1987-10-28 N.V. Nederlandse Gasunie Method of determining a physical property of a medium
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DE102014202595B4 (en) 2014-02-13 2023-06-07 Robert Bosch Gmbh Method and device for determining oxygen in a closed container
US10429367B2 (en) 2014-05-07 2019-10-01 Qatar University Multi-parametric environmental diagnostics and monitoring sensor node

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