Multi-channel infrared gas sensor with compensation for mechanical disturbance

Abstract

The present invention relates to a multi-channel infrared gas sensor, comprising: a beam splitter device, which splits an infrared beam incident on the beam splitter device along a predetermined incident axis into four infrared sub-beams; four bandpass filters and four infrared sensors, wherein the first and second infrared effective signal sensors are arranged so that their corresponding effective signal sensor detection surfaces are symmetrically oriented with respect to an effective signal sensor symmetry plane located between the effective signal sensor detection surfaces, and wherein the first and second infrared reference signal sensors are arranged so that their corresponding reference signal sensor detection surfaces are symmetrically oriented with respect to a reference signal sensor symmetry plane located between the reference signal sensor detection surfaces, wherein no effective signal sensor detection surface is oriented orthogonally to the effective signal sensor symmetry plane, and wherein no reference signal sensor detection surface is oriented orthogonally to the reference signal sensor symmetry plane.

Description

Technical Field

[0001] The present invention relates to a multi-channel infrared gas sensor, which comprises:

[0002] - a beam splitter device, which is designed to split an infrared beam incident on the beam splitter device along a predetermined incidence axis into a plurality of infrared sub-beams,

[0003] a first bandpass filter arranged in a first beam path of the first infrared sub-beam, said first bandpass filter having a predetermined first bandwidth and a transmission maximum at a predetermined first useful signal wavelength,

[0004] a first infrared-signal-effective sensor arranged in the first beam path of the first infrared sub-beam downstream of the first bandpass filter,

[0005] a second bandpass filter arranged in a second beam path of a second infrared sub-beam different from the first infrared sub-beam, wherein the second bandpass filter has a predetermined second bandwidth and a transmission maximum at a predetermined first reference signal wavelength, wherein the first reference signal wavelength is different from the first effective signal wavelength,

[0006] - a first infrared-reference signal sensor located in a second beam path of the second infrared sub-beam downstream of the second bandpass filter.

[0007] The invention also relates to a breathing apparatus having such a multi-channel infrared gas sensor. Background Art

[0008] The term "infrared" is also abbreviated as IR in the present application. Likewise, the multi-channel-infrared gas sensor is also referred to as "multi-channel-IR gas sensor" or simply as "gas sensor" hereinafter.

[0009] A gas sensor of the type mentioned at the outset is known from US 2007 / 0241280 A1. It is also known from this document to use such a gas sensor to measure gas proportions, in particular CO 2 , in the breathing gas of a living patient.

[0010] In the case of artificial respiration of living patients, whether it is now artificial respiration of completely sedated or comatose patients who are therefore unable to breathe on their own, or only for assisting the breathing of patients who breathe spontaneously at least for a period of time, knowing the gas composition of the breathing gas is helpful and important for monitoring the patient's vital functions and / or monitoring the correct operation of the breathing device. This is well known in the relevant professional field. Thus, for example, it is possible to determine how oxygen metabolism works in the patient by detecting the CO2 content in the inhaled breathing gas and the exhaled breathing gas. However, this is only one of many possible examples.

[0011] The gas sensor known from US 2007 / 0241280 A1 uses a reflecting and transmitting beam splitter to split the infrared beam incident on the beam splitter into two infrared sub-beams. The first infrared sub-beam is deflected to the first sensor via a first bandpass filter. The first bandpass filter has a transmission maximum at the infrared absorption wavelength of CO2 as the useful signal wavelength and has a small first bandwidth, thereby changing the sensor signal as strongly as possible depending on the corresponding CO2 content of the measurement gas passed by the infrared beam incident on the gas sensor. The first sensor is therefore an infrared useful signal sensor.

[0012] After passing through the second bandpass filter and additionally through the bandstop filter, the second infrared sub-beam is deflected onto the second sensor. The second bandpass filter has a transmission maximum at the infrared absorption wavelength of CO2 as the reference signal wavelength and has a larger bandwidth than the first bandpass filter. The bandstop filter also has an extinction maximum or a transmission minimum at the infrared absorption wavelength of CO2. The result is that the signal of the second sensor does not change with changes in the CO2 content of the measured gas, or only changes in a negligible range. Therefore, the second sensor is an infrared reference signal sensor.

[0013] An IR reference signal sensor is required in order to be able to evaluate the absorption of infrared light by CO2 in the measurement gas and thus the proportion of CO2 in the measurement gas by comparing the signal of the IR useful signal sensor with the signal of the IR reference signal sensor. This also applies to the present invention.

[0014] It is helpful here to derive the useful signal of the IR useful signal sensor and the reference signal of the IR reference signal sensor from the same incident infrared beam, in order to ensure that the useful signal and the reference signal are subjected to essentially the same interference factors both qualitatively and quantitatively, so that a quantitative change in the useful signal caused only by interference factors will also cause a corresponding change in the reference signal. It is thus possible to prevent the erroneous conclusion from the change in the useful signal that a change in the gas fraction identified by the wavelength of the useful signal has occurred. This also applies to the present invention.

[0015] The IR-useful signal sensor and the IR-reference signal sensor are arranged on the known gas sensor so that their respective sensor detection surfaces are tilted relative to each other around a virtual tilt axis. In the schematic diagram shown in US2007 / 0241280A1, the respective flat sensor detection surfaces are oriented at a 90° tilt relative to each other. The known gas sensor is assumed to have sensor detection surfaces extended on all sides intersecting in their common virtual tilt axis. The sensor detection surface of the IR-useful signal sensor and the sensor detection surface of the IR-reference signal sensor are arranged mirror-symmetrically with respect to a symmetry plane containing the virtual tilt axis.

[0016] US 2007 / 0241280 A1 does not mention a specific IR sensor used in the known gas sensor. However, there are IR sensors that are sensitive not only to the incidence of infrared light, but also to mechanical loads such as vibrations. Such mechanically sensitive IR sensors are also direction-dependent, that is, mechanical loads of the same magnitude act differently on the same IR sensor depending on the direction in which the mechanical load acts on the IR sensor.

[0017] The gas sensor known from US 2007 / 0241280 A1 therefore has the disadvantage that mechanical loads acting uniformly on the gas sensor as a whole act differently on the IR useful signal sensor and the IR reference signal sensor, which can lead to undesirable inaccuracies in the determination of the gas fraction of interest in the measurement gas. Summary of the invention

[0018] Therefore, the purpose of the present invention is to improve the gas sensor mentioned at the beginning with respect to the mechanical sensitivity of the gas sensor so that it provides higher accuracy under the same mechanical load as the gas sensor of the prior art, or its detection results are not so strongly affected by the mechanical load compared with the detection results of the gas sensor of the prior art.

[0019] According to the invention, this object is achieved by a gas sensor of the type mentioned at the outset, wherein the beam splitter device is designed to split the incident infrared beam into at least four infrared sub-beams, wherein the multi-channel infrared gas sensor further comprises:

[0020] a third bandpass filter arranged in a third beam path of the third infrared subbeam, wherein the third bandpass filter has a predetermined third bandwidth and a transmission maximum for a predetermined second effective signal wavelength,

[0021] a second infrared-signal-effective sensor located in a third beam path of a third infrared sub-beam downstream of the third band-pass filter,

[0022] a fourth bandpass filter arranged in a fourth beam path of the fourth infrared subbeam, wherein the fourth bandpass filter has a predetermined fourth bandwidth and a transmission maximum for a predetermined second reference signal wavelength,

[0023] a second infrared-reference signal sensor located in a fourth beam path of a fourth infrared subbeam downstream of the fourth bandpass filter,

[0024] wherein the extension directions of the first, second, third and fourth beam paths or infrared sub-beams are different from each other in pairs, wherein each of the first and second reference signal wavelengths is different from each of the first and second effective signal wavelengths, wherein the first and second infrared-effective signal sensors are arranged so that their corresponding effective signal-sensor detection surfaces are symmetrically oriented with respect to an effective signal-sensor symmetry plane located between the effective signal-sensor detection surfaces, and wherein the first and second infrared-reference signal sensors are arranged so that their corresponding reference signal-sensor detection surfaces are symmetrically oriented with respect to a reference signal-sensor symmetry plane located between the reference signal-sensor detection surfaces, wherein no effective signal-sensor detection surface is oriented orthogonally to the effective signal-sensor symmetry plane, and wherein no reference signal-sensor detection surface is oriented orthogonally to the reference signal-sensor symmetry plane.

[0025] If the present application generally refers to an IR sensor in conjunction with the present invention, this also refers to an IR useful signal sensor and an IR reference signal sensor. If only the two IR useful signal sensors or only the two IR reference signal sensors are referred to, respectively, and it is not important to determine the corresponding IR sensor pair as a useful signal sensor or a reference signal sensor, then in the present application, IR sensors of the same specification are referred to.

[0026] By dividing the infrared beam incident into the beam splitter device into at least four infrared sub-beams, at least two infrared sensors can be used as IR-effective signal sensors and at least two infrared sensors can be used as IR-reference signal sensors. According to the present invention, at least two infrared sensors of the same specifications are oriented symmetrically relative to each other. Therefore, the mechanical load effect orthogonal to the symmetry plane of the two infrared sensors of the same specifications, that is, on the one hand, orthogonal to the effective signal-sensor symmetry plane of the IR-effective signal sensor and on the other hand, orthogonal to the reference signal-sensor symmetry plane of the IR-reference signal sensor, can act on the two symmetrically oriented IR sensors with the same or similar action magnitude but in opposite action directions. By appropriately switching or / and evaluating the sensor signals of the two symmetrically oriented IR sensors, the undesirable effects of mechanical loads such as impacts with the same magnitude or similar magnitude but directed in opposite directions can be used to cancel or reduce each other. Although each individual IR sensor provides a sensor signal that is undesirably changed due to the mechanical load, the undesirable effect of the mechanical load on the two IR sensors of the same specifications can be reduced or even eliminated in a simple manner based only on the signal itself. This can be achieved, for example, by forming a geometric or arithmetic mean from the individual signals of sensors of the same specification. This applies to the IR useful signal sensors among one another and to the IR reference signal sensors among one another. Thus, the compensation of the gas sensor according to the invention with respect to mechanical interference influences from at least one spatial direction is possible without additional filters, solely from the signal itself, due to the described orientation and arrangement of the IR sensor.

[0027] “Different in pairs” means that two arbitrarily selected infrared sub-beams have different directions of extension in the beam path. This can relate to sections of the beam path, but preferably to the entire beam path of at least four infrared sub-beams after reaching the beam splitter device.

[0028] By aligning the sensor detection surface of IR sensors of the same size non-orthogonally to their associated symmetry plane, a relatively large sensor detection surface and thus a high gas sensor sensitivity can be achieved without the result being a gas sensor with a large base area orthogonal to the axis of incidence. This makes it possible to obtain a spatially compact gas sensor that is advantageous, particularly for the respiratory devices discussed below.

[0029] In the course of this application it will be explained how mechanical interference influences also from other spatial directions can be at least partially compensated by further advantageous measures, so that in an improved version of the above-mentioned gas sensor according to the invention a gas sensor which is increasingly insensitive to mechanical interference influences can be obtained with the aid of simple mechanisms.

[0030] Although the gas sensor can use more than four infrared sub-beams, the beam splitter arrangement preferably splits the incident infrared beam into exactly four infrared sub-beams which impinge on the IR sensor after passing through the bandpass filter.

[0031] It should be noted that the invention does not require a symmetrical arrangement of IR sensors of the same size about their axis of symmetry, but does not exclude such a symmetrical arrangement, but only requires a symmetrical orientation of the sensor detection surfaces of IR sensors of the same size about their plane of symmetry. Since only the direction of action of the mechanical load is important for the effect of the mechanical load on the gas sensor, the above-mentioned symmetrical orientation of the sensor detection surfaces of the respective IR sensors of the same size about the sensor symmetry plane associated therewith is not to be understood as strictly symmetrical in the sense that one IR sensor must be opposite to an IR sensor of the same size in the sensor symmetry plane associated therewith of the two IR sensors. The orientation symmetry required here is sufficient if the sensor detection surfaces of the IR sensors of the same size are oriented symmetrically non-orthogonally to the symmetry plane associated therewith, i.e. if the sensor detection surfaces of the two IR sensors of the same size are either arranged parallel to their plane of symmetry or are arranged inclined at the same angle, but in different directions of inclination, to a common virtual inclination axis located in the associated plane of symmetry on different sides of the plane of symmetry. Symmetrically oriented sensor detection surfaces can be arranged offset relative to one another along an axis located in the respective associated plane of symmetry.

[0032] However, preferably, due to the resulting simplification of the beam guidance of the infrared sub-beams after reaching the beam splitter device, IR sensors of identical specifications are not only oriented symmetrically with respect to their associated symmetry planes via their respective sensor detection surfaces, but are also arranged symmetrically with respect to their symmetry planes and are preferably situated opposite each other on the respective symmetry planes.

[0033] The symmetry of the orientation of the IR sensors of identical dimensions is preferably mirror-symmetrical due to the resulting simplification of the beam guidance of the at least four infrared sub-beams. The useful signal sensor symmetry plane and the reference signal sensor symmetry plane are therefore preferably each a mirror-symmetrical plane.

[0034] Preferably, the first and second IR-effective signal sensors and the first and second IR-reference signal sensors are pyroelectric infrared sensors, respectively. Pyroelectric infrared sensors usually have a coated sensor detection surface, and the coating is heated by the incidence of infrared light. Most pyroelectric infrared sensors also have piezoelectric properties and are sensitive to mechanical loads. Because the piezoelectric effect at a pyroelectric infrared sensor usually only occurs for mechanical load components acting orthogonally to the sensor detection surface, but not for mechanical load components parallel to the sensor detection surface, the preferred pyroelectric infrared sensor as the IR sensor of the gas sensor of the present invention is directionally anisotropically mechanically sensitive.

[0035] Preferably, the IR useful signal sensor and the IR reference signal sensor are respectively sensors of identical construction, preferably identical. Therefore, the determination of the IR sensor used as an IR useful signal sensor or an IR reference signal sensor depends on the bandpass filter that interacts with the respective IR sensor. The wavelength of the transmission maximum of the respective bandpass filter first determines whether the IR sensor arranged downstream of the respective bandpass filter is an IR useful signal sensor or an IR reference signal sensor. The second and fourth reference signal wavelengths are selected such that they do not coincide as far as possible with the absorption wavelengths of the gas components of the measurement gas to be measured by means of the gas sensor. The signal obtained from the IR reference signal sensor is then essentially independent of the composition of the measurement gas in the desired manner.

[0036] In contrast, at least one of the first and second useful signal wavelengths is preferably selected such that it coincides with an absorption wavelength of a gas component of the measurement gas to be detected by the gas sensor, or is at least close to this absorption wavelength, so that a change in the proportion of the gas component to be detected in the measurement gas leads to a significant change in the useful signal of the IR useful signal sensor. The multi-channel IR gas sensor presented here is preferably a non-dispersive CO2 sensor or a non-dispersive NOx sensor. x Sensors, especially non-dispersive NO2 sensors.

[0037] More fundamentally, the useful signal sensor symmetry plane and the reference signal sensor symmetry plane can coincide in the same symmetry plane. In this case, one IR useful signal sensor and one IR reference signal sensor are located on each side of the symmetry plane. Here, as already mentioned, IR sensors of identical specifications do not have to be directly opposite each other in the symmetry plane, although this is usually done due to the simplicity of the beam guidance of the infrared sub-beams resulting therefrom. If the reference signal sensor symmetry plane is different from the useful signal sensor symmetry plane, an advantageously spatially compact gas sensor can be obtained. The orthogonal arrangement of the useful signal sensor symmetry plane and the reference signal sensor symmetry plane is particularly advantageous due to the spatial compactness of the gas sensor obtained thereby while a relatively large structural space is available for arranging the individual IR sensors.

[0038] As already described above, the sensor detection surfaces of IR sensors of the same specification can be oriented parallel to the symmetry plane associated therewith. However, this complicates the beam guidance of the four infrared sub-beams onto the corresponding sensor detection surfaces. It is therefore advantageous if the first and second infrared-effective signal sensors are arranged such that their corresponding sensor detection surfaces are mutually tilted about a virtual effective signal tilt axis, and the first and second infrared-reference signal sensors are arranged such that their corresponding sensor detection surfaces are mutually tilted about a virtual reference signal tilt axis that is different from the effective signal tilt axis.

[0039] In the described mutually tilted arrangement, a further equalization effect can be used in the piezoelectric properties of the IR sensors which occur most frequently orthogonally to their sensor detection surface: As already described above, the component of the mechanical load orthogonal to the symmetry plane of a pair of identical IR sensors can be equalized in each identical IR sensor by mutual cancellation or at least reduction due to their signal contributions which are equal in magnitude or similar in magnitude but directed in opposite directions. The other component of the mechanical load in the symmetry plane and orthogonal to the virtual tilt axis causes a signal contribution of the mechanical load of the same magnitude and direction in the two identical IR sensors. If the IR useful signal sensor and the IR reference signal sensor are tilted in the same way about the useful signal tilt axis or the reference signal tilt axis, respectively, and the two different tilt axes are either in a common plane or in planes parallel to one another, then for all IR sensors the components of the signal contribution of the mechanical load in the respective symmetry plane and orthogonal to the respective tilt axis are of the same magnitude, directed in the same direction and occur synchronously. Therefore, although each signal of each IR sensor is changed by the mechanical load, each signal of each IR sensor is changed in the same way, by the same value and simultaneously, so that when taking into account the reference signal and the effective signal to determine the proportion of the gas component in the measured gas, this influence of the mechanical load can be significantly reduced or even completely balanced.

[0040] Also advantageously, in order to minimize the structural space requirement of the gas sensor, the beam splitter device can be a reflector-beam splitter device. This means that at least four infrared sub-beams are formed by reflection of the incident infrared beam from the reflector-beam splitter device along different directions. By using such a reflector-beam splitter device, the four infrared sub-beams formed by reflection can be very simply deflected to the sensor detection surfaces described above of the IR-effective signal sensor and the IR-reference signal sensor, and the sensor detection surfaces are tilted to each other around the corresponding tilt axis. When using the reflector-beam splitter device, all infrared-effective signal sensors and all infrared-reference signal sensors can be located on the same side of the reflector-beam splitter device, for example, on the incident side of the beam splitter device, on which the incident infrared beam is incident on the beam splitter device. Therefore, substantially all optical devices and sensor devices of the multi-channel-infrared gas sensor can be arranged between the incident opening or the incident window and the carrier of the reflector-beam splitter device, wherein the infrared beam passes through the incident opening or the incident window and is incident on the beam splitter device.

[0041] The beam splitter device can include a plurality of sub-devices, each of which splits the infrared beam incident thereon into less than four infrared sub-beams, but the sub-devices provide a total of four infrared sub-beams for the initially incident infrared beam. However, the above-mentioned preferred reflector-beam splitter device can have a plurality of reflector bodies in a simple manner, each of which has a large number of differently oriented reflector surfaces, more precisely, preferably has one reflector surface for each desired infrared sub-beam. That is, the reflector body can be a multi-faceted body that tapers along a tapering axis, whose side surfaces are reflector surfaces for the incident infrared beam. For example, if exactly four infrared sub-beams are desired, a pyramidal reflector body can be used, wherein preferably, due to the resulting symmetrical structure of the gas sensor, the tapering axes of the pyramidal reflector bodies are oriented parallel to the incident axis.

[0042] If the overall installation space requirement is small but there is still enough space to arrange a relatively large sensor detection area, the infrared useful signal sensors and the infrared reference signal sensors can be arranged alternately in a circumferential direction around a virtual arrangement axis.

[0043] The simple construction of the tapered multi-faceted reflector body described above makes it possible to achieve a space-saving arrangement in which the first and second infrared useful signal sensors are diagonally opposite each other with respect to a virtual arrangement axis and / or in which the first and second infrared reference signal sensors are diagonally opposite each other with respect to a virtual arrangement axis.

[0044] If the virtual setting axis is the incident axis, the gas sensor can be adapted to uniquely deflect each of the at least four infrared sub-beams relative to the incident infrared beam. Therefore, the infrared beam as an information carrier is only affected to a very small extent by the beam splitting, which enables accurate detection results of the gas sensor.

[0045] Insofar as the infrared sub-beams impinge on each sensor detection surface of the at least four IR sensors with substantially the same intensity, an irradiation of the IR sensors and their sensor detection surfaces that is as uniform as possible can be achieved with the infrared sub-beams in such a way that the effective signal-sensor symmetry plane and / or the reference signal-sensor symmetry plane contain the setting axis or extend parallel to the setting axis. Preferably, the setting axis is the intersection straight line of the effective signal-sensor symmetry plane and the reference signal-sensor symmetry plane.

[0046] Preferably, IR sensors of the same specification, which are respectively oriented symmetrically with respect to the sensor symmetry plane, are oriented relative to their sensor symmetry plane in such a way that their respective sensor detection surfaces form an angle with a magnitude of 45° with the sensor symmetry plane. Thus, mechanical loads orthogonal to the sensor symmetry plane can be eliminated or significantly reduced directly by additive or subtractive signal processing of IR sensors of the same specification. For example, the signals of IR sensors of the same specification can be processed into a common signal information by averaging. A geometric mean or an arithmetic mean can be formed as the average value. If the sensor symmetry plane contains a setting axis, this applies to IR sensors of the same specification that are oriented symmetrically with respect to the sensor symmetry plane for each mechanical load orthogonal to the setting axis. Therefore, preferably, the effective signal-sensor symmetry plane and the reference signal-sensor symmetry plane contain the setting axis.

[0047] In order to achieve that the two identical IR sensors are subjected in the same way to mechanical loads having a component orthogonal to the respective tilting axes of the pair of identical IR sensors, the useful signal tilting axis or the reference signal tilting axis can extend orthogonally to the setting axis. Preferably, the useful signal tilting axis and the reference signal tilting axis extend orthogonally to the setting axis, whereby the component of the mechanical load extending parallel to the setting axis acts synchronously on all four IR sensors in the same amount and in the same orientation. It can thus be ensured that the reference signal provided by the two IR-reference signal sensors and the useful signal provided by the two IR-useful signal sensors are changed in the same way and simultaneously by the component of the mechanical load extending along the setting axis.

[0048] Mechanical load components parallel to the tilting axis or orthogonally to the setting axis and parallel to the associated symmetry plane of a pair of IR sensors of equal size generally have no effect on the signal provided by the IR sensor pair. The gas sensor can thus be made almost completely insensitive to mechanical loads, i.e., independently of the direction of action of the mechanical loads acting on it.

[0049] In order to achieve the smallest possible number of deflections of the incident infrared beam or the infrared sub-beams generated therefrom, it is advantageous if the sensor detection surface of each infrared useful signal sensor and the sensor detection surface of each infrared reference signal sensor are tilted toward the beam splitter device.

[0050] In principle, it is conceivable that each reference signal wavelength is greater than each useful signal wavelength or less than each useful signal wavelength. In principle, the two reference signal wavelengths can also be identical. However, if the two reference signal wavelengths differ in magnitude, a particularly high-quality reference signal can be obtained, since random interferences caused by the temporarily unexpectedly present gas components, i.e., the measurement gas, then act only on one of the two IR reference signal sensors. In order to provide a reference signal that is as robust as possible, the first or second useful signal wavelength lies in magnitude between the first and second reference signal wavelength. It is particularly preferred that the two useful signal wavelengths lie between the first and second reference signal wavelength.

[0051] The effective signal wavelength defines the gas component in the measurement gas that can be detected by the gas sensor. In principle, it is conceivable that the effective signal wavelengths differ in magnitude, although they are intended to detect the same gas component. In order to ensure that the IR effective signal sensor can optimally evaluate the absorption information transmitted by the infrared sub-beam incident on it, it is advantageous if the first and second effective signal wavelengths do not differ in magnitude by more than one third of the smaller bandwidth of the first and second bandwidths. Preferably, the first and second effective signal wavelengths are equal in magnitude. A preferred application of the gas sensor described herein is the detection of CO2 in the respiratory gas of inspiration and / or expiration during the patient's instrumented breathing. For CO2 detection, the first and second effective signal wavelengths are preferably in the range between 4.25 μm and 4.28 μm. The first reference signal wavelength can be in the range of 3.90 μm to 4.0 μm, particularly preferably 3.95 μm, and the second reference signal wavelength can be in the range of 4.40 μm to 4.5 μm, particularly preferably 4.45 μm.

[0052] In order to ensure that the signal of the IR-useful signal sensor reacts sensitively to changes in the proportion of the gas component defined by the useful signal wavelength, while the signal of the IR-reference signal sensor should remain as constant as possible, it is advantageous that each of the second and fourth bandwidths is smaller in magnitude than each of the first and third bandwidths. Therefore, the second and fourth bandpass filters can each have a bandwidth in the two-digit nanometer range, while the first and third bandpass filters can each have a bandwidth in the three-digit nanometer range. In the second and fourth bandpass filters and the first and third bandpass filters, the bandpass filter with a smaller transmission maximum wavelength can have a larger bandwidth. The bandwidth of the second and fourth bandpass filters is preferably in the range of 50 to 99 nm, in particular in the range of 60 to 90 nm. The bandwidth of the first and third bandpass filters is preferably in the range of 150 to 200 nm, in particular in the range of 170 to 180 nm.

[0053] Due to the advantageous orientation and arrangement of the IR useful signal sensor and the IR reference signal sensor, the above-described gas sensor provides the following basic possibility: the gas sensor is designed to be insensitive to mechanical external loads. The actual signal equalization of the signals used in the gas sensor can be obtained in the following way: the gas sensor includes an evaluation device, which determines reference information from the signals of the first and second infrared reference signal sensors, the evaluation device determines useful information from the signals of the first and second infrared useful signal sensors, and the evaluation device outputs the following information from the comparison of the reference information and the useful information, which is information about the proportion of the gas identified by the first and / or second useful signal wavelength in the measurement gas irradiated by the infrared beam entering the gas sensor. The evaluation device can be implemented by an integrated circuit or a microchip in the sensor housing of the gas sensor. However, the evaluation device can also be an external evaluation device, which is arranged outside the sensor housing of the gas sensor and is connected to the IR sensor of the gas sensor in a signal transmission conductive manner.

[0054] Precisely during artificial respiration, the pipe components through which the breathing gas flows are contaminated during the breathing operation. This applies in particular to the side of the pipe for exhalation, where the patient's body fluids reach. Therefore, it is advantageous to frequently replace the measuring vessel, which may also be contaminated by moisture, saliva, etc. In order to be able to use a gas sensor with expensive measuring technology provided with a replaceable measuring vessel, the gas sensor can have a sensor housing, which has: a first compartment, in which a beam splitter device, an infrared-effective signal sensor and an infrared-reference signal sensor are provided; and a second compartment spatially away from the first compartment, in which an infrared radiation source is provided, wherein a receiving structure for accommodating the measuring vessel between the first compartment and the second compartment is provided. The receiving structure can include a receiving gap between the two compartments, in which a section of the measuring vessel that can be viewed from the second compartment toward the first compartment can be accommodated.

[0055] Due to the particularly advantageous use of the presently described gas sensor, the invention also relates to a respiratory device for at least assisted artificial respiration of a living patient, the respiratory device comprising:

[0056] - a source of breathing gas,

[0057] a breathing circuit device for conducting inspired breathing gas from a breathing gas source to a proximal breathing gas outlet on the patient side and for conducting exhaled breathing gas away from a proximal breathing gas inlet,

[0058] a pressure changing device for changing the pressure of the breathing gas in the breathing circuit arrangement,

[0059] a control device for operating a breathing gas source and / or a pressure changing device, and a multi-channel infrared gas sensor, as described above and improved, for detecting at least one gas component in the inhaled and / or exhaled breathing gas.

[0060] The breathing gas source can be a breathing gas reservoir, such as a gas cylinder, or a coupling structure for fluid-mechanical coupling to the premises of the clinic, which provides the breathing gas in a pipeline network. The breathing gas source can also be a fan, which extracts the breathing gas from the breathing gas reservoir and conveys it in the breathing line device. In this case, the breathing gas reservoir can be the surroundings of the breathing device, from which the breathing gas source extracts the ambient air.

[0061] The pressure changing device can include a valve, for example, for reducing the pressure of the breathing gas decompressed from the breathing gas source. The pressure changing device can be or include the above-mentioned fan. That is, depending on the design of the breathing gas source, the breathing gas source and the pressure changing device can also be formed by consistent device components of the two devices, or can also be formed by the same device. The measuring vessel can guide the breathing gas, which is irradiated or transmitted with infrared light from the gas sensor to detect the presence of at least one gas component and its share of the measured gas. The measuring vessel can be a shunt measuring vessel, in which the breathing gas that has been separated from the breathing tube device flows.

[0062] Advantageously, the breathing tube device comprises a measuring vessel through which the breathing gas can flow, which forms an unbranched part of the breathing tube device and can be coupled to a multi-channel infrared gas sensor for infrared transmission of the breathing gas. The measuring vessel is then a mainstream measuring vessel, which conducts the inspiratory breathing gas supplied directly to the patient and / or the exhaled breathing gas directed away from the patient. Advantageously, the measuring vessel is arranged in the breathing tube device in a detachable and replaceable manner so that it can be replaced simply, quickly and hygienically with a new, functional measuring vessel in the event of corresponding contamination.

[0063] The above-described evaluation device of the gas sensor can be part of a control device of the respiratory device.

[0064] Advantageously, the control device is designed to change one or more operating parameters of the breathing gas source and / or one or more operating parameters of the pressure changing device based on the detection results of the multi-channel infrared gas sensor, for example if the breathing gas source is a fan.

[0065] The breathing gas outlet and the breathing gas inlet can be the same opening, for example at the proximal end of an endotracheal tube. However, they can also be two different openings. The respiratory device can have any patient interface, for example the above-mentioned endotracheal tube or a laryngeal mask or other interface suitable for artificial respiration. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] The present invention will be described in detail below with reference to the accompanying drawings. The accompanying drawings show:

[0067] Figure 1 shows a schematic exploded view of a breathing apparatus according to the present invention;

[0068] Figure 2 The longitudinal section shows the Figure 1 The measuring vessel and the Figure 1 A roughly schematic cross-sectional view of a multi-channel infrared gas sensor according to the present invention;

[0069] Figure 3 Show Figure 2 The beam splitter device, four infrared sensors and four bandpass filters partially covered by the infrared sensors are arranged along the Figure 2 A top view when observing the incident axis starting from section III-III;

[0070] Figure 4 A rough schematic illustration showing the effect of equalization of an arrangement of infrared sensors in a multi-channel-infrared gas sensor; and

[0071] Figure 5 Exemplary graphs showing different signal levels with an IR-active signal sensor during absorption, non-absorption and reabsorption phases of CO2 (upper graph) and signal levels with an IR-reference signal sensor during the same phases. DETAILED DESCRIPTION

[0072] exist Figure 1 In the figure, an embodiment of a breathing apparatus according to the invention is generally indicated by 10. The breathing apparatus 10 comprises a breathing gas source 12 in the form of a fan and a control device 14 for setting operating parameters of the breathing gas source 12. The breathing gas source 12 and the control device 14 are accommodated in the same housing 16. Valves known per se, such as an inhalation valve and an exhalation valve, are also located in the housing. However, they are not Figure 1 Not specifically shown.

[0073] The control device 14 of the respiratory device 10 has an input / output device 18, which includes a plurality of switches, such as pushbutton switches and rotary switches, so that data can be input into the control device 14 if necessary. The delivery power of the fan of the respiratory gas source 12 can be changed by the control device in order to change the amount of respiratory gas delivered from the respiratory gas source per time unit. Therefore, in the present embodiment, the respiratory gas source 12 is also the pressure changing device 13 of the respiratory device.

[0074] A breathing circuit arrangement 20, which in this example comprises five flexible hoses, is connected to the breathing gas source 12. A first inhalation breathing hose 22 extends from a filter 24 arranged between the breathing gas source 12 and the first inhalation breathing hose itself to a regulating device 26, where the breathing gas provided by the breathing gas source 12 is humidified to a preset humidity and, if necessary, provided with an aerosol medicament. The filter 24 filters and cleans the ambient air provided by the fan as the breathing gas source 12.

[0075] The second inspiratory breathing hose 28 leads from the regulating device 26 to the inspiratory manifold 30. The third inspiratory breathing hose 32 leads from the manifold 30 to a Y-connector 34, which connects the distal inspiratory circuit 36 ​​and the distal expiratory circuit to form a combined proximal inspiratory-expiratory breathing circuit 40.

[0076] From the Y-connector 34 back toward the housing 16 , a first exhalation breathing hose 42 extends to an exhalation water collector 44 , and from there a second exhalation breathing hose 46 extends to the housing 16 , where the exhaled breathing gas is discharged into the surroundings via an exhalation valve (not shown).

[0077] On the combined inspiratory-expiratory side of the Y-connector 34 that is close to the patient, a flow sensor 48, here a differential pressure flow sensor 48, is located following the Y-connector 34, which detects the inspiratory flow of breathing gas toward the patient and the expiratory flow away from the patient. A line device 50 transmits the gas pressure that is present on both sides of the flow obstruction in the flow sensor 48 to the control device 14, which calculates the amount of inspiratory and expiratory breathing gas flowing per time unit from the transmitted gas pressure and in particular from the difference in the gas pressure.

[0078] In the direction away from the Y-connector 34 and toward the patient, following the flow sensor 48 is a measuring vessel 52 for non-dispersive infrared detection of a predetermined gas fraction in the respiratory gas. In the present example, this gas fraction is the CO2 fraction in the respiratory gas. Here, the CO2 fraction in both the inhaled respiratory gas and the exhaled respiratory gas is of interest, since the change in the CO2 fraction between inhalation and exhalation is a measure of the metabolic capacity of the patient's lungs. Figure 1 One of the side windows 53 can be seen in FIG. 1 , through which infrared light can enter into the measuring cell 52 or can be emitted therefrom, depending on the orientation of a multi-channel infrared gas sensor 54 detachably coupled to the measuring cell.

[0079] The infrared gas sensor 54 can be coupled to the measuring vessel 52 so that the infrared gas sensor 54 can penetrate the measuring vessel 52 with infrared light. From the intensity of the infrared light, more precisely from its spectral intensity, the amount or proportion of a predetermined gas in the measurement gas flowing through the measuring vessel 52 can be inferred in a manner known per se. The predetermined gas, here CO2, absorbs infrared light of a defined wavelength. The intensity of the infrared light in this wavelength is essentially related to the absorption of infrared light of this wavelength by the predetermined gas after passing through. The comparison of the intensity of the infrared light of a defined wavelength with the wavelength of the absorption spectrum of the infrared light that does not belong to the expected gas proportion in the measurement gas provides information about the proportion of the predetermined gas in the measurement gas. The IR gas sensor 54 is therefore connected to the control device 14 of the respiratory device 10 via the data line 56 and transmits the described intensity information to the control device 14 via the data line 56.

[0080] Following the measuring vessel 52 in the direction toward the patient is a further hose piece 58 on which an endotracheal tube 60 is arranged as a breathing interface to the patient. The proximal opening 62 of the endotracheal tube 60 is both a breathing gas outlet, through which the inspired breathing gas is introduced into the patient through the endotracheal tube 60, and a breathing gas inlet, through which the exhaled breathing gas is guided back from the patient into the endotracheal tube 60.

[0081] exist Figure 2 , a cross section through a measuring cell 52 is roughly schematically shown, and a longitudinal section through a multi-channel IR gas sensor 54 coupled thereto is roughly schematically shown. Figure 2 The measuring vessel 52 in the Figure 2 The drawing plane in FIG. 1 is traversed by the breathing gas. The infrared beam 64 of the gas sensor 54 is parallel to Figure 2 The drawing plane in Figure 2 Stretch in the drawing plane.

[0082] The gas sensor 54 comprises a sensor housing 66, in whose first compartment 68 a sensor device 70, which will be explained in detail below, is arranged, and the sensor housing comprises a second compartment 72, in which an infrared radiation source 74 is arranged. Merely by way of example, an onboard sensor control device 76 is arranged in the second compartment 72, which communicates with the infrared radiation source 74 and the sensor device 70 via lines 75 and 77 in the form of signal transmission, and which communicates with the control device 14 via the data line 56 in the form of signal transmission. In the present example, the control device 14 of the respiratory device 10 can act as a superior control device of the IR gas sensor 54 and request the detection value of the sensor control device 76, which then controls the infrared radiation source 74 accordingly for operation and sends the detection signal detected by the sensor device 70 to the control device 14 for evaluation by the control device. The control device 14 is therefore an evaluation device of the IR gas sensor 54.

[0083] The two compartments 68 and 72 are bridged by a housing bridge 67. The housing bridge 67 and the side walls 68a and 72a of the two compartments 68 and 72 connected to the housing bridge form a clamping receptacle 79, into which the measuring vessel 52 can be introduced and anchored in a releasably clamped manner. The measuring vessel 52 and the housing 66 of the gas sensor 54 can be separated from each other again by overcoming the clamping force only by hand. Additionally or alternatively, a locking mechanism can be provided for locking the gas sensor and the measuring vessel 52 to each other.

[0084] Each of the compartments 68 and 72 has a respective infrared-transmissive window 78, through which the infrared beam 64 emitted by the infrared radiation source 74 passes. Since the infrared beam 64 must completely pass through the measuring vessel 52, the measuring vessel 52 has a respective window 53 on both sides of the flow channel determined by it, which is transmissive to infrared light and is also passed through by the infrared beam. In the section accommodated in the IR gas sensor 54, the measuring vessel 52 is preferably designed to be mirror-symmetrical with respect to a mirror-symmetry plane orthogonal to the infrared beam 64, since the direction in which the infrared beam 64 passes through the measuring vessel 52 is not important. Therefore, the IR gas sensor 54 can also be connected to the measuring vessel 52. Figure 2 The views are different around orthogonal to Figure 2 The drawing plane and the axis of the infrared beam 64 are coupled to the measuring vessel 52 in a manner rotated by 180°.

[0085] The sensor device 70 has its own sensor device housing 80 . The sensor device housing 80 comprises a window 82 , through which the infrared radiation beam 64 along an axis of incidence E can be incident on the sensor device housing 80 .

[0086] After passing through the window 82, the incident infrared beam 64 strikes a beam splitter device 84 which has a plurality of pyramidal reflector bodies (not shown) and which splits the components of the infrared beam 64 incident thereon into four infrared sub-beams at angles of equal magnitude with respect to the axis of incidence E. Of the four infrared sub-beams, two infrared sub-beams with opposite sub-beam extension components are located in the same sub-beam plane, wherein the two sub-beam planes are orthogonal to one another and contain the axis of incidence E as a common intersection axis in the example shown.

[0087] The second infrared beam 86 and the fourth infrared beam 88 are parallel to Figure 2 The second infrared beam and the fourth infrared beam extend in the drawing plane. Figure 3 The second infrared beam and the fourth infrared beam each form an angle with the incident axis E having a magnitude of about 45°.

[0088] The first infrared radiation beam 85 also moves away from the incident axis E at an angle of about 45°. Figure 2 The observer of the infrared sub-beam 87 extends toward the first band pass filter 90 and the first infrared-effective signal sensor 92 located downstream of the first band pass filter. That is, the first infrared sub-beam 85 reaches the first infrared-effective signal sensor 92 only after passing through the first band pass filter 90. The fourth infrared sub-beam 87 does not Figure 2 is shown in the figure because it is completely located in Figure 2 The fourth infrared beam is in front of the drawing plane. Figure 3 Shown in.

[0089] Second bandpass filter 94 is located upstream of first infrared-reference signal sensor 96 in the beam path of second infrared sub-beam 86 .

[0090] exist Figure 2 Not shown in the figure, because it is located in Figure 2 The third bandpass filter 98 before the drawing plane is located upstream of the second infrared-effective signal sensor 100 in the beam path of the third infrared beam 87 (see Figure 3 ).

[0091] Finally, a fourth bandpass filter 102 is located upstream of a second infrared-reference signal sensor 104 in the beam path of fourth infrared subbeam 88 .

[0092] exist Figure 3 The arrows in denoted the pairwise different directions of extension 85v, 86v, 87v and 88v of the first to fourth infrared radiation beams 85, 86, 87 and 88 or their beam paths.

[0093] The first and third bandpass filters 90 and 98 have a transmission maximum in the absorption wavelength range of CO 2 , for example in the range between 4.25 μm and 4.28 μm. Their bandwidth is in the range from 170 nm to 180 nm.

[0094] The second and fourth bandpass filters 94 and 102 have transmission maxima in a range outside the absorption wavelength of CO 2 , for example in the range of 3.90 μm to 4.0 μm and / or in the range of 4.40 μm to 4.5 μm. Their bandwidth is in the range of 60 nm to 90 nm.

[0095] The IR sensors 92, 96, 100 and 104 are preferably identical in structure. They are pyroelectric IR sensors which are orthogonal to their respective sensor detection faces 92a, 96a and 104a and are piezoelectrically sensitive. This also applies to the second IR-signal sensor 98, however, its sensor detection face 100a is only Figure 3 The sensor detection surfaces 92a, 96a, 100a and 104a of the IR sensors 92, 96, 100 and 104 are flat.

[0096] The sensor detection surfaces 96a and 104a of the first and second IR-reference signal sensors 96 and 104 are arranged around the sensor detection surfaces 96a and 104a which are perpendicular to the Figure 2 The tilt axes N of the drawing plane of FIG. 1 are tilted 90° to each other. Therefore, the sensor detection surfaces 96a and 104a are oriented toward each other and toward the beam splitter device 84. The first and second IR-reference signal sensors 96 or 104 are oriented about a plane orthogonal to Figure 2 The reference signal sensor symmetry plane V of the drawing plane containing the incident axis E and the tilt axis N is oriented mirror-symmetrically. The same applies to the first and second IR useful signal sensors 92 and 98, but their useful signal sensor symmetry plane W is parallel to Figure 2 However, it also contains the incident axis E. The sensor detection surface 92a of the first IR-effective signal sensor and the sensor detection surface of the second IR effective signal sensor 100 are mutually inclined by approximately 90° about the tilt axis M, which is located in a common plane orthogonal to the incident axis E with the tilt axis N and forms a right angle with the tilt axis N.

[0097] In other words, in an embodiment, the tilt axis N and the incident axis E extend a symmetry plane V, while the tilt axis M and the incident axis E extend a symmetry plane W, as in Figure 3 As seen in.

[0098] The IR resonant signal sensors 96 and 104 oriented symmetrically with respect to the symmetry plane V and their associated bandpass filters 94 and 102 are designed to be mirror-symmetrical with respect to the symmetry plane W. The same applies to the IR useful signal sensors 92 and 100 oriented symmetrically with respect to the symmetry plane W and their associated bandpass filters 90 or 98 being arranged mirror-symmetrically with respect to the symmetry plane V.

[0099] As in Figure 3 As shown in FIG. , IR sensors 92, 96, 100 and 104 are arranged alternately at equal angular intervals of 90° about an arrangement axis A coinciding with the incident axis E. In the direction of rotation about the arrangement axis A, an IR active signal sensor is followed by an IR reference signal sensor, and vice versa. Figure 3 Draw in Figure 2 The sensor detection surface 100a is not visible in the figure.

[0100] The small squares in the beam splitter arrangement 84 symbolize pyramidal reflector bodies 84 a arranged in rows and columns, whose pyramid axes are parallel to one another and to the axis of incidence E.

[0101] exist Figure 4 How mechanical loads act on the sensor device 70 is described in FIG. 7 . Assume that there is a mechanical impact load L parallel to Figure 1 and Figure 2 The drawing plane of the symmetry plane W acts parallel to the incident axis E and perpendicular to the setting axis A. The mechanical impact load L acts parallel to the symmetry plane W and perpendicular to the incident axis E and perpendicular to the setting axis A. Figure 2 As shown in Figure 4 Due to the symmetrical orientation of the IR-signal sensors 92 and 100, the contents described with respect to the IR-signal sensor 92 apply accordingly to the IR-signal sensors 92, 96 and 104. Figure 2 and Figure 4 IR-signal sensor 100 not shown.

[0102] The pyroelectric IR sensors 92, 96, 100 and 104 have a piezoelectric sensitivity orthogonal to their sensor detection surfaces 92a, 96a, 100a and 104a, that is, a mechanical load having a component orthogonal to the sensor detection surface triggers an electrical signal in the IR sensor concerned, and the polarity of the electrical signal is related to the direction of action of the mechanical load orthogonal to the sensor detection surface.

[0103] The IR-signal sensors 92 and 100 are oriented with their sensor detection surfaces 92a and 100a parallel to the mechanical impact load L, so that the mechanical impact load L has no component orthogonal to the sensor detection surfaces 92a and 100a. The mechanical impact load L therefore does not interfere with the IR detection signals of the IR-signal sensors 92 and 100.

[0104] On the IR-reference signal sensors 96 and 104, the mechanical impact load L can be decomposed into mutually orthogonal components L1 and L2, wherein the component L1 is oriented orthogonally to the sensor detection surface 96a of the first IR-reference signal sensor 96, and wherein the component L2 is oriented orthogonally to the sensor detection surface 104a of the second IR-reference signal sensor 104. Due to the angular orientations of the sensor detection surfaces 96a and 104a with respect to the setting axis A and the incident axis E that are the same in magnitude but oppositely directed, the magnitudes of the mutually orthogonal components L1 and L2 are the same, however, compared to the component L2 and its orientation with respect to the sensor detection surface 104a, the component L1 is oppositely directed with respect to the sensor detection surface 96a. Therefore, the mechanical impact load L interferes with the original infrared induced detection signal in each of the IR-reference signal sensors 96 and 104, and superimposes the interference signal induced by the mechanical impact load L on the infrared induced detection signal. However, the two interference signals of the IR-reference signal sensors 96 and 104 are synchronous and directed in opposite directions, so that they can be cancelled out by corresponding signal processing, for example by signal addition of the detection signals of the IR-reference signal sensors 96 and 104. The two signals of the reference signal sensors 96 and 104 are then also interference-free with the signals of the useful signal sensors 92 and 100.

[0105] Because the reference signal-sensor symmetry plane V and the effective signal-sensor symmetry plane W intersect in the setting axis A and therefore both planes V and W contain the setting axis A, the following applies to each mechanical load orthogonal to the setting axis A: its effect on the signals in IR sensors 92 and 100 and 96 and 104 of the same specifications can be offset or significantly reduced by corresponding signal processing of sensors of the same specifications.

[0106] Therefore, the mechanical load or load component extending along the setting axis A cannot be eliminated or significantly reduced in infrared sensors of the same specifications. However, in the embodiment in which all IR sensors 92, 96, 100 and 104 are oriented at the same angle relative to the setting axis A, the same disturbing influence of the load on all IR sensors is caused, so that the influence of the mechanical load on the correctness of the detection result obtained from the signal of the gas sensor 54 regarding the proportion of CO2 in the measured gas can be significantly reduced, because the mechanical load acting along the setting axis A affects the useful signal obtained from the signals of the IR useful signal sensors 92 and 100 and the reference signal obtained from the signals of the IR reference signal sensors 96 and 104 essentially synchronously, in the same amount and in the same direction. The difference between the signal level of the IR useful signal sensors 92 and 100 and the signal level of the IR reference signal sensors 96 and 104, which is actually important for determining the absorption of infrared light, does not change or changes only to a negligible extent.

[0107] Since each mechanical load can be subdivided into a component parallel to the arrangement axis A and a component orthogonal thereto, the sensor device 70 presented here allows the interfering effects of the mechanical loads acting on the sensor device 70 to be largely eliminated.

[0108] exist Figure 5 , the signals of the IR sensors 92 , 96 , 100 and 104 are plotted along the abscissa as the time axis. Figure 5 The vertical axis represents the level of the corresponding signal.

[0109] Signal 112 originates from first IR-active signal sensor 92 , signal 116 originates from first IR-reference signal sensor 96 , signal 120 originates from second IR-active signal sensor 100 , and signal 124 originates from second IR-reference signal sensor 104 .

[0110] The effective signal 132 is obtained, for example, by averaging, from the signals 112 and 120. The reference signal 136 is obtained from the signals 116 and 124, for example likewise by averaging.

[0111] Although the two signals 116 and 124 of the IR reference signal sensors 96 and 104 are respectively disturbed by mechanical loads, which can be seen in the periodic oscillations of the corresponding signal levels, the resulting reference signal 136 is hardly influenced by the mechanical loads. The same applies to the signals 112 and 120 of the IR useful signal sensors 92 and 100 and the useful signal 132 obtained therefrom and proportional thereto.

[0112] exist Figure 5, the signals 112 and 120 originating from the IR useful signal sensors 92 and 100 and the useful signal 132 formed therefrom initially have a low level, which is attributed to the absorption of the infrared light of the infrared beam 64 by the CO2 content in the measured gas in the measuring vessel 52. This is followed by a signal with a higher level, in which less CO2 is present in the measured gas in the measuring vessel 52 and thus less infrared light is absorbed in the wavelength range of the bandpass filters 90 and 98. This phase with a higher level is followed in turn by a phase with a lower level of the signals 112 and 120 and therefore also of the useful signal 132. Figure 5 The signal does not come from real breathing conditions, but is obtained through experimental design in the laboratory.

[0113] Likewise, the mechanical loads of the IR sensors 92 , 96 , 100 and 104 that cause the respective vibration signals 112 , 116 , 120 and 124 are also induced by the vibration table, which do not correspond to the arbitrary-random mechanical loads of the actual medical use of the gas sensor 54 .

Claims

1. A multi-channel infrared gas sensor (54), comprising: - a beam splitter device (84) configured to split an infrared beam (64) incident on the beam splitter device (84) along a predetermined incidence axis (E) into a plurality of infrared sub-beams (85, 86, 87, 88), a first bandpass filter (90) arranged in a first beam path of the first infrared sub-beam (85), the first bandpass filter having a predetermined first bandwidth and a transmission maximum for a predetermined first useful signal wavelength, a first infrared-signal-effective sensor (92) arranged downstream of the first bandpass filter (90) in a first beam path of the first infrared sub-beam (85), a second band pass filter (94) arranged in a second beam path of a second infrared sub-beam (86) different from the first infrared sub-beam (85), wherein the second band pass filter (94) has a predetermined second bandwidth and a transmission maximum for a predetermined first reference signal wavelength, wherein the first reference signal wavelength is different from the first effective signal wavelength, a first infrared-reference signal sensor (96) located downstream of the second bandpass filter (94) in a second beam path of the second infrared sub-beam (86), The beam splitter device (84) is configured to split an incident infrared beam (64) into at least four infrared sub-beams (85, 86, 87, 88), wherein the multi-channel infrared gas sensor (54) further comprises: a third bandpass filter (98) arranged in a third beam path of the third infrared sub-beam (87), wherein the third bandpass filter (98) has a predetermined third bandwidth and a transmission maximum for a predetermined second effective signal wavelength, a second infrared-signal sensor (100) located downstream of the third bandpass filter (98) in a third beam path of the third infrared beam (87), a fourth bandpass filter (102) arranged in a fourth beam path of the fourth infrared beam (88), wherein the fourth bandpass filter (102) has a predetermined fourth bandwidth and a transmission maximum for a predetermined second reference signal wavelength, a second infrared-reference signal sensor (104) located downstream of the fourth bandpass filter (102) in a fourth beam path of the fourth infrared beam (88), wherein the extension directions (85v, 86v, 87v, 88v) of the first beam path, the second beam path, the third beam path and the fourth beam path are different from each other in pairs, wherein each of the first reference signal wavelength and the second reference signal wavelength is different from each of the first effective signal wavelength and the second effective signal wavelength, wherein the first infrared-effective signal sensor (92) and the second infrared-effective signal sensor (100) are arranged so that their corresponding effective signal-sensor detection surfaces (92a, 100a) are symmetrical with respect to the effective signal-sensor symmetry plane located between the effective signal-sensor detection surfaces (92a, 100a); The invention relates to a first infrared-reference signal sensor (96) and a second infrared-reference signal sensor (104) arranged so that their respective reference signal-sensor detection surfaces (96a, 104a) are symmetrically oriented with respect to a reference signal-sensor symmetry plane (V) located between the reference signal-sensor detection surfaces (96a, 104a), wherein no effective signal-sensor detection surface (92a, 100a) is oriented orthogonally to the effective signal-sensor symmetry plane (W), and wherein no reference signal-sensor detection surface (96a, 104a) is oriented orthogonally to the reference signal-sensor symmetry plane (V), It is characterized in that the first infrared-effective signal sensor (92) and the second infrared-effective signal sensor (100) are arranged so that the corresponding effective signal-sensor detection surfaces (92a, 100a) are tilted 90° to each other around a virtual effective signal-tilt axis (M), and the first infrared-reference signal sensor (96) and the second infrared-reference signal sensor (104) are arranged so that the corresponding reference signal-sensor detection surfaces (96a, 104a) are tilted 90° to each other around a virtual reference signal-tilt axis (N).

2. The multi-channel infrared gas sensor (54) according to claim 1, It is characterized in that The useful signal-sensor symmetry plane (W) and the reference signal-sensor symmetry plane (V) are different from each other.

3. The multi-channel infrared gas sensor (54) according to claim 1 or 2, It is characterized in that The beam splitter device (84) is a reflector-beam splitter device, and all infrared-effective signal sensors (92, 100) and all infrared-reference signal sensors (96, 104) are located on the incident side of the beam splitter device (84), on which the infrared beam (64) entering the multi-channel-infrared gas sensor (54) is incident on the beam splitter device (84).

4. The multi-channel-infrared gas sensor (54) according to claim 3, It is characterized in that The infrared effective signal sensors (92, 100) and the infrared reference signal sensors (96, 104) are alternately arranged along a circumferential direction around a virtual arrangement axis (A).

5. The multi-channel-infrared gas sensor (54) according to claim 4, It is characterized in that The first infrared-effective signal sensor (92) and the second infrared-effective signal sensor (100) are diagonally opposed to each other with respect to the virtual setting axis (A), and / or the first infrared-reference signal sensor (96) and the second infrared-reference signal sensor (104) are diagonally opposed to each other with respect to the virtual setting axis (A).

6. The multi-channel-infrared gas sensor (54) according to claim 4, It is characterized in that The virtual setup axis (A) is the incidence axis (E).

7. The multi-channel-infrared gas sensor (54) according to claim 4, It is characterized in that The useful signal sensor symmetry plane (W) and / or the reference signal sensor symmetry plane (V) contain the arrangement axis (A) or extend parallel to the arrangement axis (A).

8. The multi-channel infrared gas sensor (54) according to claim 1 or 2, It is characterized in that The sensor detection surface (92a, 100a) of each infrared-effective signal sensor (92, 100) and the sensor detection surface (96a, 104a) of each infrared-reference signal sensor (96, 104) are inclined toward the beam splitter device (84).

9. The multi-channel infrared gas sensor (54) according to claim 1 or 2, It is characterized in that The first effective signal wavelength and / or the second effective signal wavelength is located between the first reference signal wavelength and the second reference signal wavelength in magnitude.

10. The multi-channel infrared gas sensor (54) according to claim 1 or 2, It is characterized in that The first effective signal wavelength and the second effective signal wavelength differ in magnitude by no more than one-third of the smaller of the first and second bandwidths.

11. The multi-channel infrared gas sensor (54) according to claim 1 or 2, It is characterized in that Each of the second and fourth bandwidths is smaller in magnitude than each of the first and third bandwidths.

12. The multi-channel infrared gas sensor (54) according to claim 1 or 2, It is characterized in that The multi-channel infrared gas sensor (54) comprises an evaluation device, which obtains reference information (136) from the signals of the first infrared reference signal sensor (96) and the second infrared reference signal sensor (104), the evaluation device obtains effective information (132) from the signals of the first infrared effective signal sensor (92) and the second infrared effective signal sensor (100), and the evaluation device outputs information about the proportion of the gas identified by the first effective signal wavelength and / or the second effective signal wavelength in the measurement gas irradiated by the incident infrared beam (64) from the comparison of the reference information (136) and the effective information (132).

13. The multi-channel infrared gas sensor (54) according to claim 1 or 2, It is characterized in that The multi-channel infrared gas sensor (54) has a sensor housing (66), which has: a first compartment (68), in which the beam splitter device (84), the infrared effective signal sensor (92, 100) and the infrared reference signal sensor (96) are arranged; and a second compartment (72) spatially away from the first compartment (68), in which an infrared radiation source (74) is arranged, wherein a receiving structure (79) for accommodating a measuring vessel (52) between the first compartment (68) and the second compartment (72) is arranged between the first compartment (68) and the second compartment (72).

14. A respiratory device (10) for at least assisted artificial respiration of a living patient, the respiratory device comprising: - a source of breathing gas (12), a breathing circuit device (20) for conducting inspired breathing gas from the breathing gas source (12) to a proximal breathing gas outlet on the patient side and for conducting exhaled breathing gas out of a proximal breathing gas inlet, a pressure changing device (13) for changing the pressure of the breathing gas in the breathing circuit arrangement (20), a control device (14) for operating the breathing gas source (12) and / or the pressure changing device (13), and - A multi-channel infrared gas sensor (54) according to any one of claims 1 to 13, which is used to detect at least one gas component in inhaled and / or exhaled respiratory gas.

15. The breathing apparatus (10) according to claim 14, It is characterized in that The multi-channel-infrared gas sensor (54) is a multi-channel-infrared gas sensor (54) according to claim 11, wherein the multi-channel-infrared gas sensor (54) comprises an evaluation device defined in claim 12, which is part of a control device (14) of the breathing device (10).

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