DE1598780A1 - Process and device for infrared absorption analysis of flowable media - Google Patents

Description

HÖGER - LEGAL RIGHTS - GRIESSBACH - HAECKER PATENT LAWYERS IN STUTTGART

159878Q

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Dr. Expl.

Mine Safety Appliances Company Pittsburgh, Pa. 15208, U.S.A.

Process and equipment via infrared · »Absorption analysis of flowable media

The invention relates to the infrared Abaorptions ~ analyae flowable mixtures in which ^r 4ie "component to be measured a defined infra-red Abeorptionsbande has overlapping with the Abaorptionsbande a second component of the mixture, wherein

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however, the second component also has considerable infrared absorption within a defined wavelength range outside, but not necessarily adjacent to the absorption band of the component to be measured. In particular, deals the invention with the determination of the carbon dioxide concentration in gas mixtures that also contain water vapor, -which is the infrared absorption of carbon dioxide is measured in a narrow spectral range that is completely covered by the much broader absorption band of water vapor.

Although the application of the measuring method according to the invention is not limited to this, an important application is the measurement of the carbon dioxide concentration in the exhaled gas represents a person whose physiological reactions are being studied, for example to determine the filter effectiveness of a respiratory protective device if it is used continuously over a longer period of time Times and under very different conditions, for example under conditions that the Dispersion of toxic war chemicals in the start Simulate atmosphere, i'all such a facility significantly advance technology in this area

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willρ bo Ble must be able to indicate fluctuations in the COp concentration within a very short time, ie within a time span that can be less than 1.5 milliseconds _9, which corresponds to a response frequency of the device of at least 100 Hz. A detector with a response time of the order of magnitude of 500 microseconds is suitable. Furthermore, such a device must not obstruct the breathing flow through its "sample" chamber, but must allow an essentially momentary flow through, so that the device must be required to be small enough to fit inside the face mask of a respirator to be tested to be worn to avoid delays in delivery to the "sample". Because of these requirements, and because few facilities with sufficient sensitivity and response time are available, it is desirable that a practical measuring instrument utilize the meaningful and well-defined infrared absorption band of carbon dioxide, which has a center wavelength of approximately 2.72 microns Absorption band is compared to other absorption bands, for example those whose center wavelength is approximately 4.2 micro »

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is preferred, although carbon dioxide is also there Has considerable infrared absorption .-- An obvious one Obstacle to using the COg absorption band With shorter wavelengths, however, is the fact that they go completely through the very much broader absorption band is covered by water vapor, which has a center wavelength of approximately 2.67 microns * Since water vapor rises in varying proportions up to is normally in the breath for full saturation, when measuring the CQg absorption in a wavy line area in which the water vapor absorbs the problem such as the absorption caused by the overlap of the water vapor absorption band should be compensated * The solution of this problem now serves the invention <.

Further, advantageous developments of the invention Features are contained in the claims and / or in the following description, which the Explanation of an embodiment shown in the drawing serves the invention; show it

1 shows a diagram of two representative absorption bands of carbon dioxide and water vapor in the Wavelength range between 2.55 and 3.05 microns;

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o2 an idealized diagram of essential parts

the absorption bands of Flg.1; 3 shows a schematic representation of an invention gemäsaen device with a bridge circuit

for measuring infrared absorption; Figure 4 is a plan view of the assembled optical

, Parts of the facility? Figure 5 is a Explosionszeiehnung _e, partly in section ,, · the device shown in Fig * 4, however

in greater measure than this; Fig.6 is a side view of the shown in Fig.4

Infrared radiation source; 7 is a diagram showing the Durohlass curves of a suitable sentence from an input * «one

Analyzer «- and a reference filter shows}

Fig.8a

and BTd a thematic representation of the effect of the Rotate the neutral attenuator shown in Fig. 5 is shown, and

Flg.9a

and FIG. 9b shows a schematic illustration of the effect the rotation of the analyzer and reference filter, which are shown in Fig.5.

The infrared frequencies absorbed by a compound are a function of the type and arrangement

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of the atoms that make up the molecules of the compound " Every molecule can ala a complex oscillation system It can be understood which characteristic resonance frequencies have. Most connections fall some of these frequencies in the infrared range dea electromagnetic spectrum «Jedoeti absorb homoatomic Oases like nitrogen, oxygen and hydrogen do not have infrared radiation, which is why their absorption range does not overlap with that of other connections. On the other hand, molecules' Jaeteroatomic Gases such as carbon dioxide and water vapor when irradiated with a broad spectrum of infrared radiation has resonance frequencies that are in the infrared spectrum « and their absorption is proportional to the number of molecules with resonance frequencies in the absorbed region. As a result, the percentage of energy absorbed is a measure for the gas concentration.

You inventive device contains a broadband infrared radiator, which is in front of an inlet window or filter is mounted. This filter filters the large part the undesired wavelengths of the radiation source and undesired ambient radiation. On the

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On the other hand, the filter is permeable for certain wavelengths, namely for a first wavelength range, which at least partially comprises the overlapping cables of the absorption bands of the connection to be measured and the connection with its absorption bands superimposed, and the filter also allows a second wavelength range through the at least partially comprises the non-overlapping part of the absorption band of the overlapping connection alone. Parts of the radiation - in the following occasionally as analysis-beam are referred to - are passed through the input filter therethrough, pass through an analyzer window or filter hinduroh to INEM analyzer detector _t and another part of the radiation - the in The following is now and then referred to as a reference beam - runs through a reference window or filter to a "reference detector" The analyzer filter is permeable to an analyzer wavelength range that partially allows the first-mentioned wavelength range, but no radiation of the second wavelength range (The wavelength ranges were defined above), whereby the radiation of both wavelength ranges first had to pass through the input filter, on the other side

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the reference filter for a reference wavelength range is permeable, which at least partially the second wavelength range, but not radiation of the first Wellenlängenbereiohs comprises "Both the Analyaatorals also Beaugs detector responsive to changes in the intensity of the infrared radiation of the Analysatorbzsw _e of the reference * beam at if the su parsing?

in

Mixture of infrared radiation aem. wiröL exposed beeohxäefcenen optical path For example, the mixture may be in a sample chamber containing Ain _r which is arranged between the radiation source and the EingangBfilter β In a preferred embodiment of the invention, the detectors are connected in a bridge circuit so that the output of the analyzer Detektora from that of the Besuga detectors is subtracted o The Auagangasignal of the bridge maintenance is a difference signal and proportional to the amount of the energy absorbed in the analyzer wavelength range by the COg contained in the sample chamber. 2PaIIs water vapor is contained in the sample chamber, ao the infrared absorption both in the analyzer wavelength range ale as well as in the reference wavelength range is essentially the same »ao that this influence on the difference formation

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is eliminated.

As shown in FIG. 1, the substantial part of the GOg absorption band lies in the range between 2.65 and 2 ^ 82 microns and around a central wavelength which is "about 2.72 microns". This COg absorption band completely overlaps the broader one Absorption band of water vapor, the essential part of which is approximately between 2.51 and 2 _- 87 microns and around a central wavelength of approximately 2.67 microns. A key feature of these two absorption bands is first of all because of their overlapping essential parts, which are crossed by the cross ear Area A in the idealized absorption spectrum of FIG. 2 have approximately the same width as the non-overlapping essential part of the water vapor absorption band alone, which is shown in FIG. 2 by the single hatched area B, and secondly that the absorption caused by the water vapor essentially Bowohl in the overlapping as well as in the non-overlapping part of the absorption ande about the same iat.

In its ' simplest form, shown in Fig. is shown somewhat echematically, has the device according to the invention

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an infrared radiator 1, a sample chamber 2, an input filter 3 ₉ an analyzer filter 4 »a suction filter 59 an analyzer detector β and a reference detector 7 the input filter arranged next to each other, as well as ea with the analyzer and beaug detector behind these two puters of the 3? all XBt. The detectors are connected in a üfceatst © ne bridge, which is denoted by 10 and has a suitable measuring device M for displaying differences in the output signals of the detectors.

The infrared radiation from the infrared radiator 1 passes through the mixture in the sample chamber 2 and then passes through the input filter 3 ″ which filters out most of the unwanted radiation of the infrared spectrum and the ambient radiation. The analyzer filter 4 and the reference filter 5 each have approximately half the area of the input filter 3, so that approximately equal parts of the radiation pass through the two filters 4 and 5. A filter is selected as the analyzer filter 4, which is

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is längenhereich permeable, which at least partially covers the of the absorption band of the Kohiendioxyds and that of the water vapor common wavelength region (region A in Figure 2), and as a reference filter 5, a filter ₉ is selected which is permeable in a Wellenlängenbereioh, the! at least partially the adjacent Part of the absorption band of the water vapor alone (zone B in Iig, 2},> The analyzer detector 6 measures the radiation of an analyzer beam 11, which successively passes through the sample chamber, the input filter and the analyzer filter - the reference detector 7 measures the radiation of a reference beam 12, which passes the sample channels, the input filter and the Beaugsfilter in close proximity. The infrared radiator 1 and the two filters 5 and 6 are chosen and arranged in such a way that "if the mixture in the sample chamber only contains a homoatomic gas or a misalignment of homoatomic gases, which do not absorb in the infrared * range, approximately the same beam treatment powers impinge on the detectors 6 and 7, so that there is a difference in the output signals of the two actuators. If the sample chamber also contains water vapor, it will absorb part of the

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infrared radiation, however, it absorbs the same amounts ia the wavelength ranges _s for which the two filters 4 and 5 are permeable, so that there is no difference signal in this Pail either. However, when the sample chamber also contains carbon dioxide, so absorbs this infrared radiation in that WEI 'but not lenlängenbereichj for the Analyaatorfliter eats transmissive in the wavelength range, for d.en the Besaigsf ilter is permeable _y si ο that less radiation power at the detector 6 as aa. Detector Y is measured. As a result, the Wheatstone bridge 10 is unchecked and the differential signal is proportional to the concentration of the 00 in the sample chamber.

In Figures 4 to 6, the inventive device is shown in more detail The infrared radiator 1 is an electrically heated filament 20 of a conventional glass bulb 21 'which has a lens 22 at its front ends _β Obv? OHL the e.mitierten from the filament wave

tr

lengths occupy a wide range of wavelengths «so the longer-wave radiation is about 3c5 micron wavelength essentially from the glass of the Glass bulb absorbed. The glass bulb 21 is screwed into a lamp holder 23, which is adjustable on a Base 24 is fastened with the aid of three screws 26,

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with respect to the axis of the optisohen erfindungsgemäseen means ermögliohen a slight tilting of the lamp holder in each direction, _a In this manner, the infrared radiator can be adjusted so that in Abvgeseiaheit of carbon dioxide in the sample chamber same detector "output signals are generated. The infrared radiator unit is attached to one end of a tube 27 by means of screws 28 which engage in an annular groove 29 surrounding the base 24. The tube 27, which serves as a housing, is mounted on a carrier 31 which can be fastened in a breathing mask (not shown) in front of the mouth of the person wearing this mask. The carrier 31 has a connection plug 32 for making various electrical connections outside the mask, so that, for example, electrical connections are made between the filament and a power source (not shown) and between the detectors 6 and 7 and other switching elements of the bracket held outside the mask can"

At the other end of the tube 27 is a detector cells * device 33 attached so that between this

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direction and the infrared radiator a distance of about 1 inch is created _β The space in between represents the sample chamber 2; As shown in Figure 4, the tube forming the housing of the sample chamber has openings 34 around this space which allow breath to pass quickly through the sample chamber when the device is worn in a breathing mask , which is preferably made of a material with low thermal conductivity, for example made of plastic. A cell carrier 37 fits into the housing and is fastened to it with screws 38. The following components are held in place within the cell housing by a retaining ring 39 provided with a thread, which are shown in FIG 5, another spacer 42, which carries the rotatable filters 4 and 5, the two detectors 6 and 7, an aluminum absorber 4.3 »on which the detectors are attached, a heating element 44 and a spacer washer 45. When the mentioned components are combined in the cell device are, then there is one

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very compact and essentially dense structural unit with an anxiety less than 1 inch. Electrical leads 46 and 47 extend from the detectors and the heating element away through the end of the cell housing through.

The detectors 6 and 7 are lead sulfide ^ oto resistors, those on the market in various sizes and geometrical shapes Dimensions are available and have excellent sensitivity as well as good frequency response and kurae Response times. Each detector has the 3? Orm a thin layer of lead sulfide and both layers are arranged next to each other on a common carrier, the expansion coefficient of which is approximately the same that of the aluminum absorber 43. The impedance the detectors is sufficiently small that they are at some distance from other switching elements of the Wheatstone bridge 10 can be arranged, aolamge one adequate shielding is provided. Because the sensitivity the detectors depends significantly on the temperature, this temperature must be within narrow limits being held. The easiest way to do this is to have both detectors at the same temperature keeps that slightly higher than the highest ambient temperature

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to which they are exposed in use 5 the temperature so it only has to be slightly above body temperature. To maintain an even temperature, Both detectors are attached to the aluminum absorber 43, which is against the heating element 44 is applied * The heating element can usually be an electrical resistor 48, which is on a ceramic Support 49 is attached, and preferably on the side of the aluminum absorber remote from the heating element.

In the case of slight fluctuations in temperature, a Thermistor 51 in a slot 52 on the other side of the heating element arranged. A suitable thermistor for this purpose is the type Veco 35 A 5? the one at room temperature a resistance of approximately 5 kg ohms and a sensitivity of approximately 500 ohms per degree Celsius Has. When the resistor 48 of the heating element is connected to a Power source, not shown, connected via a conventional control circuit, also not shown containing the thermistor 51, the temperature of the detectors can be kept within narrow limits. It must be mentioned that the Detelttorelemente against · * - via convection currents from the environment through other components of the detector roller device are shielded, and that in the heat element as a result of the

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Control of temperature peaks generated by the thermistor largely attenuated by the Alurainium absorber and thus have no undesirable influence on the detectors themselves via temperature fluctuations. In addition, the aluminum baorber holds the temperature gradient between the two detectors on one minimum value.

The input filter 5 and the analyzer and reference filters 4 and 5, respectively, are bandpass interference filters which for the desired purpose. Such filters are known and contain a carrier which is permeable to infrared radiation and which is provided with layers Materials with different refractive indices is coated, so that only the desired wavelength is transmitted, whereas all other wavelengths are transmitted by interference and reflection be held. For practical reasons, the information about interference filters is the one you want Properties based on the macroscopic character of the absorption band in question, not 3edooh to the actual, detailed characteristic. However, it is essential that the wavelength range of a.

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Each filter is large enough that the differences in the fine lines of the absorption curve between the two areas of the water vapor absorption band, ie the two areas that pass through the analyzer and the reference filter. . mediate each other. On the other hand, the bandwidth of the bandpass must not be so large that superfluous radiation is allowed to pass in the edge area, since otherwise the sensitivity of the device according to the invention would be reduced. In addition, the two wavelength ranges that are allowed through by the analyzer and the reference filter should overlap as _little as possible. have curves as shown in FIG. 7 as a function of the wavelength and denoted by 60, 61 and 62. The transmission of the input filter (curve 60) is not shown beyond 2.89 microns as the upper slope of the curve is relatively insignificant in view of the fact that lead sulfide detectors do not have remarkable sensitivity for wavelengths above 3 microns. To ensure"

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that the radiation let through by the analyzer or reference filter is correctly registered with respect to the corresponding water vapor or carbon dioxide absorption band (see Fig. 2), the average wavelength for the analyzer filter is usually 2.760 microns and for the reference filter a Wavelength of 2.579 microns was chosen, and each of these S ¹ U- * ter has a transmission bandwidth of approximately $ 0.12 · microns $ 30

The Wheatstone bridge, in which the detectors 6 and 7 form two bridge members, also has two precision resistors R1 and R2 in the other two bridge members. Pie circuit is powered by a battery V or other direct current source. A fixed resistor R3 ₉ in series with the battery limits the detector current to a safe value. The original tuning of the bridge is carried out by means of a potentiometer R4, which is designed as an adjustable resistor and is located between the two fixed precision resistors R1 and H2. This circuit subtracts the output signal of the analyzer system 6 from that of the reference detector 7

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If water vapor is present, both the analyzer beam and the reference beam, i.e. also the output signals of the two detectors, should be the same becomes, in such a way that the output of the Wheatstons bridge delivers almost the value zero? The bridge is then finally adjusted by adjusting the potentiometer R4.

Another alternative to the comparison is «, das8 the rotatable neutral attenuator 40, which is in front of the input filter (Pig. 5) is set * This attenuator has the shape of a thin Ring 66, over the lower part of which a grid 67 », for example a wire mesh, extends. The attenuator normally takes the position shown in Fig. 8a, in which the grating of the from the infrared radiator 1 to the detectors 6 and 7 radiation is not absorbed. However, through Rotate the ring 66, for example with the help of key slots 68 (FIG. 8b), the position of the grid can be set so that it more or less weakens the radiation directed at the detectors.

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Such a decrease sets the output signals of the detectors, causing the Wheatstone Broke can be matched in whole or in part. Such a Abstimraittel is particularly advantageous when the outputs of the two detectors 6 and 7 are not matched to within about 10 $, as aie ea should actually be. Through the attenuator d, h. adjustment effect caused by the grid changes with the transparency of the sitter, so that a more wide-meshed one (jitter weakens less and consequently allows a more precise adjustment than a narrow one maaohiges grid; however, leaves itself an impermeable ülement a rough vote instead of the grid Normally, such an adjustment is used when assembling and testing the device according to the invention, However, there is an adjustment after the final assembly not necessary anymore. However, if this wakes up, it can it is easy to make provision that the attenuator is also adjustable in use, for example by making the ring 66 look radially close through a slot in the cell « Gehäuee 36 hindu extending arm provides.

As already mentioned, the two filters 4 and 5

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be rotatably arranged in the spacer 42. Normally, the two filters are arranged immediately behind them with respect to the detectors, as shown in FIG However, if these two filters are rotated - for example with the aid of a suitable tool which allows flattened areas 69 to be stretched out, the two filters are also rotated with respect to the detectors, as shown in FIG. 9b, and it is thereby possible Modify the incidence of the radiation so that part of the radiation transmitted by the analyzer or reference filter falls on the reference detector or the analyzer detector “Such adjustment is generally only made prior to final assembly of the facility However, it is also possible to make such an adjustment in use by means similar to those discussed above in connection with the attenuator 40-o r- ^

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If the gas in the sample chamber 2 has a carbon dioxide concentration of 10 $, it is found with a sample chamber length of about 1 inch that about 6 $ of the infrared radiation from the analyzer is absorbed by the carbon dioxide. If the output signals of both detectors are absent of carbon dioxide and water vapor are equal, at a carbon dioxide concentration of $ 10 in the absence of water vapor the output signal of the analyzer _{detector drops to Q 9} 94, and the difference between the output signals of the two detectors is 1-0.94 or 0.06. If the same grain mixture is additionally saturated with water vapor (which corresponds to an amount of approximately 6.2 $ water at 98 _S 6 ° F), the radiation in both the analyzer and the reference beam is equally attenuated by approximately 5.6 $ ₉ so that the output signal of both detectors is reduced to 0.964 by the water vapor, but the output signal of the analyzer »detectora is further reduced by the absorption caused by the carbon dioxide to O“ 964 - the product of 0.06 χ 0.964, equivalent to 0 _t 9062 ; the difference between the two output signals from the detectors is then 0.964 * 0.9062 or 0.0578. In other words, that of the maximum concentration

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Absorption caused by water vapor in the breath only reduces the output signal by 3.6 $. This error is a percentage error of the measured value and not of the total measuring range , so that the absolute value of the errorB decreases with the carbon dioxide concentration. For example, in the absence of carbon dioxide, the sensitivity of the device to water vapor is zero

The device according to the invention is particularly suitable for constant monitoring of the COg content in the breath of a Person wearing breathing apparatus. The device is sufficiently small, both in size as well as in weight, ao that it can be built into a breathing apparatus of the type M-17, for example »

The device accommodated in the tube 27 according to Figure 4 has a length of ungelähr 2.69 inches and a diameter of about 81 inches O _3; it weighs about 4 »5 ounces. The Wheatstone bridge and the heating circuit as well as a power source can either be worn by the person wearing this device or placed on another carrier outside the breathing apparatus. The fixed detectors have essentially none

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Microphone effect, and if you connect it to the other switching elements with cables that have a low level of noise, the noise is extremely minimal not be damaged. The display of the device is independent of the flow of breath through the sample chamber, the response time of the device is only limited by the fundamental detector time constant of normally 500 microseconds. The maximum respiratory rate is well above this value, so that the response time of the facility is well below the required value.

Of course, the input filter 3 can be omitted if the infrared radiator 1 only emits radiation with a narrow bandwidth, and this radiation is the same as that let through by the input filter, or if analyzer and reference filters 5 and 5 are used, which are also used for incident radiation work satisfactorily with a large bandwidth.

The measurement could also be carried out in such a way that

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make a comparison of the output signals of the two detectors 6 and 7, these signals are compared in another way by forming the difference, for example by determining their relationship or by adjusting a parameter of the bridge circuit, whereby the bridge is balanced »Ee but other measuring methods are also possible *

In the described device, the output signals of two detectors are compared, the _t isolated but subjected to an analyzer and a reference beam simultaneously. However, it is also possible to make such a comparison by using the successive output signals of a single detector which is successively exposed to an analyzer and a reference beam. In the exemplary embodiment described, the output signals of the two detectors are separated; but delivered at the same time? In the last-described case, the two output signals are emitted by one and the same detector, but in succession. A device corresponding to the example described last can easily be obtained by daao in the loading

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only one analyzer 'Petektor 6 is used, which is alternately exposed to the analyzer' and the reference beam in that the analyzer and the reference 'filter are moved so that they successively and alternately a single beam from the infrared emitter to the detector 6 interrupt. Each difference in the successive output signals of the detector results in an output signal which varies as a function of time, which amplified _p can be measured and compared with a reference value using conventional means. Such a device can have a very short response time if the alternating frequency between the analyzer and reference beam, the

one
both fall on a single detector is increased.,

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Claims (1)

A 34 842 b b - 93 Feb 15, 1966 Patent claims: 1. A method for the quantitative Infrarotabaorptionsanalyse a flowable mixture comprising a au determining first and sweite Heto? Oatomare component contains _P soft latter one a particular infrared "absorption band of the first ■ component overlapping infrared" absorption band and at least one d outside the absorption band? R first Component has effective infrared _{absorption band s} characterized in that the mixture is penetrated by a first infrared ray with a spectrum limited to the overlapping area of the absorption band and by a second infrared _{ray B} whose spectrum does not include the absorption band of the second component _r which is effective outside the absorption band of the first component includes the absorption band of the first component, and that the radiation energies of both infrared rays behind the mixture are measured and compared « 2 "Method according to claim 1 _e, characterized in that the intensities and bandwidths of the two infrared rays are set ao that the difference between the measured radiation energies is independent of the concentration BATH 009882/1725 A 34 842 b 2 Q b - 93 ^C 7 Feb 15, 1966 the second component is " 3- procedure according to. Claim 2 »characterized in that both infrared rays radiate through the sample on the same side and their radiation energies are measured on the same side., 4c Method according to one or more of the preceding claims for determining the COG-content of a gas mixture which contains water vapor * characterized in ₀ that the infrared absorption band of the Kohlendiobcyds that with the center wavelength of about 2.72 microns, and the only infrared absorption band of water vapor that with the Center wavelength of approximately 2.67 microns is chosen » 5. Device for carrying out the method according to one or more of the preceding claims with a device for blasting the mixture and a measuring device for measuring the radiant energy, characterized by an infrared radiator, the spectrum of which is at least partially the overlapping part of the absorption bands both components as the first spectral range, as well as at least part of the outside of the absorption « . BAD OFW3IW 30 - ' 009 882/17 25, Λ 34 842 b b - 93 IO 15 »Feb 1966 band of the first component effective absorption band of the second component as a wide spectral range includes »furthermore by an analyzer filter with a pass _{band which at least partially covers the first" but no essential part of the second spectral range 9} as well as by a reference filter with at least partially the second, but none essential rope of the first spectral range encompassing transmission range * 6 "Device according to claim 5" characterized by a Input filter with a narrow pass range, however comprises the first and the second spectral range. 7. Device according to claim 5 or 6, characterized in that that in the optical path behind the analyzer filter a first Detector and a second detector behind the reference filter it is intended to measure the radiation energies » 8. Device according to one or more of claims 5 to 7, characterized in that the analytical filter a Durohlass bandwidth with a center wavelength between 2e67 and 2.85 microns. 9 * Device according to one or more of claims 5 to 8, characterized in that the reference filter is a Pass-through bandwidth with a mean wavelength between 2.49 and 2.67 microns. 8AD 009882/1725 A 34 842 1) 3 A b - 93 Feb 15, 1966 10. Device according to claim 8, characterized in that that the half-wave length is approximately 2ο76 microns * 11. The device of claim 9, characterized in that the center wavelength is approximately 2.58 microns. 12o device according to one or more of claims 7 "to 11» characterized »that the detectors are arranged on a metallic heat absorber ₉ which is coupled to a heating element and kept at a" constant temperature » 13σ device according to one or more of claims 7 12 _9, characterized in that the betectors are lead sulfide films arranged on a carrier « 14. Device according to _t one or more of claims 7 to 13 »characterized in that the analyzer and the Besugs · symmetrical filter sur optical axis of the device are adjacent to each other are preferably arranged in a plane perpendicular to the optical axis"" 15 »Device according to claim 14» characterized in that the two udders can be rotated around the optical axis. BAD ORIGINA 0 0 S 8 8 2/1 7 2 5 A 34 842 b _ ^ b - 93 3 Z 15. * ebr. 1966 Device according to claim 14 or 15 »characterized» that the two detectors are symmetrical to the optical axis next to each other »preferably in one to the optical Axis * are arranged in a vertical plane 17. Device according to one or more of claims 7 to 13 »characterized« .that between the infrared radiator and one of the detectors is an adjustable infrared absorbing one Absohwächer is arranged. 18. Device according to Anepruch 17, characterized in that the attenuator is a rotatable about the optical axis and in the beam path between the radiator and one of the Detectors is swiveling mesh, 19 * Device according to one or more of claims 5 to 18, characterized in that all filters and detectors are mounted in one cell » 20. Device according to one or more of claims 5 to 19 «characterized in that a chamber for receiving the to be irradiated mixture is provided, which has passage openings for the mixture. 0 0 9 8 8 2/1725 Blank page