Measurement system for a monitoring system

Abstract

Measuring system (100) for determining gas concentrations in a breathing gas mixture (15) for a monitoring system for monitoring a breathing gas supply of an aircraft or an underwater vehicle with a gas transport module (50), a measuring gas line (10), a measuring device (66) with a measuring element (681) in a measuring chamber (30), with a pressure sensor (591), a magnetic arrangement (683) comprising an electromagnet and a coil, a calculation and control unit (70) with an associated data storage (77) and a circuit arrangement (68), • wherein the module for gas transport (50) is designed to supply a quantity of a breathing gas mixture (15) to the measuring element (681) in the measuring chamber (30), • wherein the measuring device (66) is configured with the circuit arrangement (68) to operate a heating structure on a membrane of the measuring element (681) in order to transfer defined quantities of heat into the breathing gas mixture (15) or to subsets of the breathing gas mixture (15) in the measuring chamber (30), • wherein the measuring device (66) is configured with the pressure sensor (591) to determine a pressure measurement value (599) which indicates a pressure inside the measuring chamber (30), • wherein an acceleration sensor is arranged in or on the measuring system (100), which is configured to determine measurement data on accelerations, on a current spatial orientation of the measuring system (100) or changes in spatial orientation and to provide this data to the calculation and control unit (70), • wherein the measuring device (66) is designed with the electromagnet, the coil and the circuit arrangement (68) to generate a magnetic field acting on the measuring element (681), • wherein the circuit arrangement (68) is configured to measure the measured values ​​of the measuring element (681) with an alternating voltage signal component U X∼ and with a DC signal component U X =to provide to the calculation and control unit (70), • wherein the data storage (77) contains a first data record (78) with initial data and at least one second data record (79) with further data, • where the first data set (78) indicates a first situation in the breathing gas mixture (15) at a first pressure level, • where the second data set (79) indicates a second situation of gases or breathing gas mixture (15) at a second pressure level, • wherein the calculation and control unit (70) is based on the AC signal components and DC signal components ◯ including the pressure reading (599), which indicates a current pressure level inside the measuring chamber (30), ◯ including the first data set (78) and ◯ including the second data set (79) to determine a current oxygen concentration in the breathing gas mixture (15), • wherein the calculation and control unit (70) is designed to perform a predictive inclusion of the current pressure measurement value (599) and the first and second data set (78, 79) in the determination of the current oxygen concentration based on the measurement data of the accelerometer, • wherein the calculation and control unit (70) is configured to provide an output signal (908) indicating the current oxygen concentration in the breathing gas mixture (15).

Description

[0001] The present invention relates to a paramagnetic measuring system for determining gas concentrations for a monitoring system. In particular, the invention relates to a measuring system that is used as part of a monitoring system to monitor the supply of breathing gas with a sufficient concentration of oxygen to a person in an aircraft or underwater vehicle. According to the invention, the measuring system is capable of detecting the oxygen concentration in the breathing gas mixture during operation. Paramagnetic methods are frequently used to determine the oxygen concentration in gases. These methods are based on the fact that oxygen molecules are paramagnetic due to their permanent magnetic dipole moment, whereas most other gases have diamagnetic properties. It is generally known that the thermal conductivity of paramagnetic gases changes under the influence of magnetic fields.The cause of this behavior is apparently the fact that paramagnetic gases possess a permanent magnetic moment, which, however, does not normally manifest itself externally due to the thermal molecular motion of the gas molecules.

[0002] A sufficiently strong external magnetic field ensures that the magnetic dipole moments of the individual molecules are aligned. This causes, on the one hand, a change in susceptibility, which results in an increase in magnetic flux; on the other hand, a certain molecular arrangement is established in the gas, thereby restricting the degrees of freedom and thus the possibilities of transferring heat energy to neighboring molecules via collisions.

[0003] This slightly alters the thermal conductivity of the gas.

[0004] A basic principle for measuring oxygen in a measuring chamber using heat conduction changes associated with paramagnetism is described in US 6 430 987 B1.

[0005] US 2023 / 0114548A1 describes a method for determining the presence of an anesthetic gas in the breathing gas mixture in addition to measuring oxygen.

[0006] US Patent 2023 / 0114548A1 discloses a measuring system for determining gas concentrations in a gas mixture of a gas sample by utilizing thermal conductivity and paramagnetic effects of thermal conductivity in the gas mixture. A circuit arrangement delivers measured values ​​with an AC signal component and a DC signal component to a processing and control unit. By incorporating data sets, the oxygen concentration in the gas mixture is determined by normalizing AC signal components, and the concentration of another gas in the gas mixture is determined by normalizing DC signal components.

[0007] A monitoring system for monitoring pilots and / or co-pilots is known from US 2021 / 0 405 008 A1.

[0008] German patent DE 10 2023 121 409 A1 discloses a monitoring system for aircraft pilots. Such a system can ensure that pilots have a safe and breathable gas supply by measuring the concentrations of gases, particularly oxygen and carbon dioxide, in the breathing air and comparing them to limit values. It can detect potential contaminants in the breathing gas, which is crucial for maintaining the health and performance of pilots during flight. This increases safety in aviation, as real-time air quality data is available, which can help prevent dangerous situations during flight operations.

[0009] The monitoring system is preferably designed as part of the equipment as a self-sufficient and mobile, body-worn unit with its own independent power supply.

[0010] Typical applications of paramagnetic measurement systems are known from the field of medical technology for the analysis of oxygen concentrations in respiratory gas mixtures. These typical applications of the measurement systems take place within a typical ambient pressure range of 1000 hPa ± 150 hPa. In this pressure range, the effects of pressure on the thermal conductivity of a gas mixture do not yet have a significant impact on the measurement accuracy of the oxygen concentration. At larger deviations from standard pressure of 1013 mbar (corresponding to 1013 hPa) under normal conditions (sea level), the different molecular sizes of the various gas components present in the gas mixture can manifest as pressure-dependent effects.

[0011] One pressure-dependent effect is the collision probability of molecules depending on the total number of molecules per unit volume, which also depends on the pressure.

[0012] Jet aircraft operate at altitudes of up to 15,000 feet or more above the ground, which is approximately 4,500 meters. At these altitudes, pressure conditions, depending on the season, weather, latitude, and temperature, are around 575 hPa. Rapid maneuvers by jet aircraft can cause rapid changes in pressure levels. For example, a descent from above 4,000 meters to below 1,000 meters results in a pressure increase with a gradient of approximately +300 hPa, which can affect the measuring system. Therefore, there is a need for a measuring system capable of accurately determining the concentration of oxygen in a gas mixture under varying pressure conditions, even at high altitudes.

[0013] The present invention therefore aims to provide an improved measuring system for pressure ranges below normal conditions, for example, for the monitoring of breathing gas supply in aircraft. A further objective is to provide an improved measuring system for pressure ranges far above normal conditions, for example, for the monitoring of breathing gas supply in underwater vehicles or diving applications.

[0014] These and other tasks are solved by a measuring system with the features of claim 1.

[0015] Further features and details of the invention can be found in the dependent claims, the description and the drawings.

[0016] A measuring system according to the invention comprises at least the following components to solve the problems: a module for gas transport, a measuring gas line a measuring device ◯ with a measuring element in a measuring chamber, ◯ with a pressure sensor, ◯ with a magnetic arrangement with an electromagnet and with a coil, a calculation and control unit with an associated data storage system, a circuit arrangement.

[0017] The gas transport module is designed to draw defined quantities or partial quantities of breathing gas mixture from a measurement point, particularly from a person's breathing mask and / or from the cabin or cockpit, via the sample line and convey it to the monitoring system or the measurement chamber. For this purpose, the gas transport module is pneumatically and / or fluidically connected to the measurement point and the measurement chamber via the sample line. The measuring element is a planar semiconductor or silicon element (MEMS, semiconductor chip) with a membrane and features a heating element on the membrane and a heat conduction measuring unit at a measurement point. The heat conduction measuring unit is designed as a thermocouple or a thermopile. The heating element can, for example, be a resistive heating element.

[0018] The calculation and control unit is designed to record thermoelectric voltage signals provided by the measuring element of the measuring device.

[0019] The measuring device includes a pressure sensor arranged in or on the measuring chamber or measuring element to detect a pressure reading that indicates a pressure level inside the measuring chamber or a pressure level of a breathing gas mixture flowing into the interior of the measuring chamber. The measuring device is configured with the pressure sensor to determine a pressure reading that indicates a pressure level inside the measuring chamber.

[0020] The measuring device, together with the circuitry, is designed to heat the heating element on the diaphragm of the measuring element. The measuring element is positioned in the measuring chamber such that a sample of the breathing gas mixture can be supplied to the measuring element. The measuring element is heated to an operating temperature higher than the temperature of the breathing gas mixture present in the measuring chamber. The measuring device, together with the electromagnet, the coil, and the circuitry, is designed to generate a magnetic field acting on the measuring element. If a paramagnetic gas is present in the breathing gas mixture at the measuring element, the thermal conductivity changes proportionally to the proportion of the paramagnetic gas under the influence of the magnetic field. For example, if oxygen is present in the breathing gas mixture, a temperature increase occurs, which results in an increase in the thermoelectric voltage signals detectable at the heated measuring element.Configurations of the operation using the calculation and control unit and the circuit arrangement, in particular for controlling, controlling and regulating the temperature of the measuring element, can preferably and for example be: • as operation with a constant heating voltage, • as an operation with a constant heating current, • implemented in practice as an operation with a constant heating output.

[0021] The circuit arrangement is designed for signal processing of the thermoelectric voltage signals, providing measured values ​​with an AC signal component and a DC signal component to the calculation and control unit.

[0022] The signal processing is implemented using suitable circuits, such as lock-in systems and high-pass / low-pass filter circuits, to split the thermoelectric voltage signals into AC and DC signal components. Suitable variants for operating the measuring elements and processing the thermoelectric voltage signals can be found, for example, in US 2023 / 0114548A1. The circuit arrangement is designed to process measured values ​​from the measuring element with an AC signal component U. X~ and with a DC signal component U X= to provide to the costing and control unit.

[0023] The calculation and control unit is designed with the circuit arrangement to generate a modulated magnetic field acting on the measuring element by means of activating and deactivating the electromagnet with the coil arrangement.

[0024] The calculation and control unit is connected to the circuit arrangement for splitting the thermoelectric voltage signals into AC signal components U. X~ and DC signal components U X = formed. The alternating current signal components represent components of heat conduction that are modulated and influenced by the magnetic field. Such influence is due to the paramagnetic effect in heat conduction for the oxygen components in the breathing gas mixture. The direct current signal components represent components of heat conduction in the breathing gas mixture that are not influenced by the magnetic field.

[0025] The calculation and control unit is designed to determine the current oxygen concentration in the breathing gas mixture from the ratio of the modulated heat conduction components to the heat conduction components that are not modulated by the magnetic field. Ideally, this ratio represents the current oxygen concentration in cases where a binary gas mixture is present, i.e., for example, a gas mixture consisting of a significant proportion of oxygen and a predominant proportion of nitrogen with negligible amounts of carbon dioxide and noble gases, and with a low water content, such as dry ambient air, technical or medical compressed air.In reality, however, a breathing gas mixture is not a binary gas mixture, since during exhalation the concentrations of water vapor and carbon dioxide in particular are significantly higher compared to inhalation.

[0026] To account for gas mixtures, such as breathing gas mixtures with more than two relevant gas components, characteristic curves are required to correct the ratio of modulated heat conduction components to those not modulated by the magnetic field. The number and selection of the required characteristic curves are crucial, but also increase the complexity of systemic or individual calibration and measurement operation.

[0027] Preferably, coefficients for linear or higher derivatives of the influences are calculated from the characteristic curves.

[0028] For concentrations of oxygen (O2) in a breathing gas mixture, the following approach for setting up characteristic curves according to the following formula 1 is an example: CO2=K1*a1 / b1+K2*(a1 / b1)2+K3*a1+K4*a12+K5*b1+K6*b12+K7*c1+…, where K X The coefficients of the components present in the breathing gas are represented, and the quantities a1, b1, c1, ... each represent measured quantities of thermal conductivity, such as the thermal conductivities dependent on the magnetic field and the thermal conductivities independent of the magnetic field of the gases in the gas mixture. Furthermore, the quantities a1, b1, c1, ... can also include information on vapor pressures, dew points of the gases in the gas mixture, or their water content in the gas mixture. These coefficients are available to the measuring system for subsequent measurement operations.

[0029] The calculation and control unit is designed according to the invention to include an effect of the surrounding pressure in the determination of the current oxygen concentration in the breathing gas mixture.

[0030] During the design of the measuring system, characteristic curves are recorded, which reflect, for example, the influence of material properties of the measuring elements, effects and boundary conditions of inflow, flow and / or outflow of supplied quantities of breathing gas mixture into the measuring chamber, material properties and structural designs of the measuring chamber or through processes of semiconductor manufacturing of the measuring elements (MEMS), for example in the form of possible variations in the membrane thickness of the measuring elements.

[0031] To counteract or compensate for these influences, the thermoelectric voltage signals with AC and DC signal components and / or the ratios of AC to DC signal components for typical breathing gas mixtures containing oxygen can be measured as part of a functional test for various compositions of the breathing gas mixture with proportions of oxygen, carbon dioxide, nitrogen, moisture or water vapor. These measurements are recorded and stored in a data memory (RAM, ROM) as data sets, which then characterize this measuring system individually or systemically in the form of a characteristic curve, a family of characteristic curves or as a characteristic map.

[0032] The recording of the characteristic curves or the characteristic map is usually carried out under normal conditions of pressure and temperature or under typical defined ambient conditions of pressure and temperature, for example according to the approach described by formula 1.

[0033] During the measurement operation of the measuring system in use for determining gas concentrations when supplying people with the breathing gas mixture, the data sets from the data storage are then used to determine the current oxygen concentration in the breathing gas mixture with the highest possible accuracy from the AC voltage signal components and DC voltage signal components.If, as intended by the object of the present invention, the measuring system is to be used at higher altitudes with lower pressure levels compared to normal conditions, as well as under rapidly changing pressure situations during flight operations, it is necessary to maintain the measurement accuracy of the oxygen concentration by performing the characteristic curves, maps, and sets of characteristic curves not only at one typical pressure level, but at at least two pressure levels, in order to take into account the extended pressure range that can occur during flight operations in the measuring system and to include the pressure-dependent effect on the thermal conductivity of different gas components in the breathing gas mixture, even for pressure conditions differing from sea level and the Earth's surface, when evaluating the signal and determining a current oxygen concentration in the breathing gas mixture.It should also be possible to operate the system even with fluctuations in pressure levels inside the measuring chamber caused by flight operations and maneuvers.

[0034] During measurement operation, the pressure sensor plays an essential role in continuously determining the current pressure level inside the measuring chamber or the pressure level of the breathing gas mixture - as well as fluctuations in the pressure level - and providing this information to the calculation and control unit.

[0035] The incorporation of the pressure-dependent effect into the determination of the oxygen concentration according to the invention can be carried out in the manner described below. According to the invention, the thermoelectric voltage signals are recorded to generate characteristic curves or maps of the measuring elements at at least two defined and different pressure levels. This can be done, for example, as part of a test of the measuring system following assembly or configuration, or as part of a subsequent adjustment or calibration.The thermoelectric voltage signals with AC and DC signal components and / or the ratio of AC to DC signal component as a quotient are determined for different and typical compositions of moisture, oxygen, nitrogen, carbon dioxide in the breathing gas mixture as a first situation in the breathing gas mixture at a first pressure level and stored as a characteristic curve, a family of characteristic curves or a characteristic map as a first data set in the data memory.The thermoelectric voltage signals with AC and DC signal components and / or the ratio of AC to DC signal component as a quotient are determined for different and typical compositions of moisture, oxygen, nitrogen, carbon dioxide in the breathing gas mixture as a second situation in the breathing gas mixture at at least one further second pressure level and stored as a characteristic curve, a family of characteristic curves or a characteristic map as a second data set in the data memory.

[0036] The calculation and control unit is designed based on the AC and DC signal components. • including the pressure reading, which indicates a current pressure level inside the measuring chamber, • including the first data set and • to determine the current oxygen concentration in the breathing gas mixture, taking into account the second data set.

[0037] The calculation and control unit is thus designed to determine an output signal, indicating an oxygen concentration in the breathing gas mixture, based on the AC and DC signal components, the current pressure level inside the measuring chamber, and the first and second data sets. For this purpose, the calculation and control unit can, for example, apply corresponding characteristic curves for at least two pressure levels according to the approach previously described in Formula 1. The coefficients can then be used accordingly as coefficients P for at least two pressure levels. x , Q xThe measured variables a1, b1, c1 of the heat conduction are formed and the measured variables a1, b1, c1 for the at least two further pressure levels are formed as a2, b2, c2, or a3, b3, c3 and are accordingly stored in the first or second data set and kept ready for measurement operation.

[0038] Taking the first pressure level into account as the basis for the first data set is done, for example, using the approach according to the following formula 2: CO2=P1*a2 / b2+P2*(a2 / b2)2+P3*a2+P4*a22+P5*P1+P6*b22+P7*c2+… .

[0039] Consideration of the further or second pressure level as a basis for the second data set is done, for example, with the approach according to the following formula 3: CO2=Q1*a3 / b3+Q2*(a3 / b3)2+Q3*a3+Q4*a32+Q5*Q1+Q6*b32+Q7*c3+… .

[0040] The calculation and control unit is designed to provide the output signal that indicates the specific oxygen concentration.

[0041] The following is a summary description of the inventive design of the measuring system for determining gas concentrations during the administration of breathing gas mixtures to individuals. The measuring system comprises a gas transport module, a measuring gas line, and a measuring device. The measuring device includes a measuring element in a measuring chamber. The gas transport module is designed to supply a quantity of breathing gas mixture to the measuring element in the measuring chamber. The measuring device includes a calculation and control unit with an associated data storage device and a circuit arrangement. The measuring device also includes a magnetic arrangement with an electromagnet and a coil.

[0042] The measuring device is designed with the circuit arrangement for the operation of a heating structure on a membrane of the measuring element in order to transfer defined quantities of heat into the breathing gas mixture or to subsets of the breathing gas mixture in the measuring chamber.

[0043] The measuring device is equipped with a pressure sensor for determining a pressure measurement value that indicates a pressure level inside the measuring chamber. The measuring device is equipped with an electromagnet, a coil, and a circuit arrangement for generating a magnetic field acting on the measuring element. The circuit arrangement is configured to provide measured values ​​from the measuring element to the calculation and control unit with both an AC and a DC signal component.

[0044] The data storage contains a first data record with initial values ​​and at least one second data record with further values.

[0045] The first data set indicates a situation of gases or respiratory gas mixtures at a first pressure level.

[0046] The second data set indicates a situation of gases or respiratory gas mixtures at a second pressure level.

[0047] In special embodiments, at least one further or third data set with further values ​​for a third or further pressure levels can be stored in the data storage device, which indicate a third or further situation in the breathing gas mixture at a further pressure level.

[0048] In order to improve measurement operations for low pressure ranges below normal conditions, such as those that may occur in aircraft (jet aircraft, helicopters) or in flight applications (parachutists), as well as for high pressure ranges above normal conditions, such as those that may occur in underwater vehicles (submarines) or in diving applications (mine divers, maintenance divers, welding divers), the data storage can also contain data sets for the low or high pressure ranges commonly encountered in these applications.

[0049] In the following description of "low pressure levels in flight operations," a comparable technical implementation for "high pressure levels in diving operations" should also be evident. In both application scenarios (flight operations, diving operations), the calculation and control unit is designed and capable of performing an oxygen concentration determination with pressure compensation using the data sets from the data storage.

[0050] The calculation and control unit is designed to determine a current oxygen concentration in the breathing gas mixture based on the AC voltage signal components, DC voltage signal components, taking into account the pressure measurement value, which indicates a current pressure level inside the measuring chamber, and including the first and second data sets.

[0051] The calculation and control unit is designed to provide an output signal indicating the current oxygen concentration in the breathing gas mixture.

[0052] Embodiments show how the calculation and control unit can be designed to incorporate the current pressure measurement and the data sets stored in the data memory into the determination of the current oxygen concentration in the breathing gas mixture during measurement operation.

[0053] The following examples show variations for incorporating the first and second data sets into the determination of the current oxygen concentration for a current pressure level in the breathing gas supply of 703 hPa during flight operations, corresponding to an altitude of approximately 3000 meters. In this example, the first data set comprises a characteristic curve, a set of characteristic curves, or a map with an ambient pressure reference level of 650 hPa. The second data set comprises a characteristic curve, a set of characteristic curves, or a map with a reference level of 1050 hPa.

[0054] In a first variant for including the first and second data sets, one approach would be to use the second data set during measurement operation as long as the current pressure level in the breathing gas mixture is above 650 hPa, and then switch to the first data set as soon as the current pressure level of the breathing gas mixture is below 650 hPa.

[0055] In a corresponding preferred embodiment, the calculation and control unit is designed to include the current pressure measurement, the first data set and the second data set or the third or further data sets by means of switching between the data sets to determine the current oxygen concentration.

[0056] In a second variant according to a further preferred embodiment for including the first and second data sets, one approach would be to perform an interpolation during measurement operation based on the data of the first data set (assigned to 650 hPa) and the second data set (assigned to 1050 hPa) and to generate an interpolated data set during operation that is representative for the current pressure level of 703 hPa with regard to different and typical compositions of moisture, oxygen, nitrogen, and carbon dioxide in the breathing gas mixture.

[0057] Preferably, linear interpolation can be used when there are two data sets.

[0058] To illustrate a third variant according to a further preferred embodiment, let us assume – as in the two previous examples – that the first data set has a characteristic curve or map with a pressure level of 1050 hPa as its data basis, and the second data set has a characteristic curve or map with a pressure level of 650 hPa as its data basis. In this third example, the pressure level prevailing during measurement is even lower than the 703 hPa assumed in the previous examples, for example, 600 hPa, which would correspond to a further increase in the aircraft's flight altitude to approximately 4200 meters compared to the first and second examples.In this third variant, an approach would be to extrapolate the data of the first data set (assigned to 1050 hPa) and the second data set (assigned to 650 hPa) to the current pressure level of 600 hPa during measurement operation, and to generate an extrapolated data set during operation that is representative for the current pressure level of 600 hPa with regard to different and typical compositions of moisture, oxygen, nitrogen, carbon dioxide in the breathing gas mixture.

[0059] Preferably, linear extrapolation can be used when there are two data sets.

[0060] In further preferred embodiments, the thermoelectric voltage signals, their AC and DC signal components, and / or their ratio for different and typical compositions of oxygen, nitrogen, and carbon dioxide in the breathing gas mixture can be determined for additional pressure levels and stored as characteristic curves, a family of characteristic curves, or a characteristic map as further data sets in the data memory. This advantageously allows, for example, more precise switching between different characteristic curves based on the pressure measurement at the current measurement time during operation. Alternatively, this also advantageously allows interpolations and extrapolations based on the pressure measurement at the current measurement time during operation to be performed using a large number of data points on the characteristic curves, with improved approximation of the actual pressure-dependent effect.Furthermore, with more than three or five support points, nonlinear interpolations or extrapolations can also be used and form preferred embodiments.

[0061] In a preferred embodiment, the interpolation or extrapolation can be performed by the calculation and control unit as a linear interpolation or extrapolation, or as a piecewise linear interpolation or extrapolation. In a preferred embodiment, the interpolation or extrapolation can be performed by the calculation and control unit as a nonlinear interpolation or nonlinear extrapolation, in particular as a quadratic or cubic interpolation or extrapolation.

[0062] In further preferred embodiments, potential effects on the thermoelectric voltage signals can be predicted based on data or knowledge of the ratios and time delays of pressure increases or decreases between the ambient or cabin pressure and the pressure in the breathing mask effective for the pilot's respiration. These effects can then be predictively incorporated into the determination of the oxygen concentration by the calculation and control unit. Such effects include, for example, changes in the thermal conductivity of the gas mixture. According to this further preferred embodiment, an accelerometer can be arranged in or on the measuring system for this purpose. This accelerometer is configured to acquire measurement data on accelerations, the current spatial orientation of the measuring system, or changes in spatial orientation, and to provide this data to the calculation and control unit.The calculation and control unit can be configured to predictively incorporate the current pressure reading, as well as the first and second data sets, into the determination of the current oxygen concentration based on the measurement data from the accelerometer. Alternatively, the accelerometer can be arranged in or on the monitoring system and assigned to the measurement system.

[0063] With the help of an acceleration sensor - in particular a 3-axis acceleration sensor arranged on the measuring system - flight maneuvers can be identified and possible future pressure changes can be predicted or estimated by the calculation and control unit.

[0064] In this way, for example, a descent maneuver can be identified, and the pressure increase of 300 hPa, which results from a descent by a difference in altitude of 3000 m, for example from above 4000 meters to below 1000 meters, can thus be predicted.

[0065] This predetermination can enable the calculation and control unit to take into account various flight maneuvers (take-off, landing, descent, loop), the conditions and time delays of pressure increase or decrease between the ambient pressure or cabin pressure and the pressure effective for the pilot's breathing in the breathing mask as pressure-dependent effects when determining the current oxygen concentration in the breathing gas mixture.

[0066] According to the invention, the pressure-dependent effects can thus be taken into account in such a way that a change in the pressure level in the breathing gas mixture during a flight maneuver can be included in the determination of the current oxygen concentration, which predictably affects the measuring system and thus the gas mixture in the measuring chamber towards the end of a flight maneuver (descent, ascent).

[0067] In a further preferred embodiment, the calculation and control unit can be configured to incorporate into the determination of the oxygen concentration a measured value from a temperature sensor, which indicates a temperature level in the measuring chamber, and / or provided information regarding a temperature level in the breathing gas mixture. In a procedure comparable to the approaches described by formulas 1, 2, and 3 for different temperature levels as a basis for realizing characteristic curves, maps, or families of characteristic curves stored in data sets in the data memory, this preferred embodiment can provide further approaches by formulas 4 and 5 to incorporate at least two different temperature levels as data sets in the determination of the oxygen concentration, additionally through interpolations, extrapolations based on the data sets, or switching between the data sets.

[0068] For example, the coefficients R can be determined for two different temperature levels. x , S x The measured quantities a1, b1, c1 of heat conduction for the two temperature levels are formed and calculated as a2, b2, c2, and a3, b3, c3, respectively, and stored accordingly in further data sets and kept ready for measurement operation. Considering a temperature level as the basis for a third data set is achieved, for example, using the approach according to the following formula 4: CO2=R1*a2 / b2+R2*(a2 / b2)2+R3*a2+R4*a22+R5*R1+R6*b22+R7*c2+… .

[0069] Considering a further temperature level as the basis for a fifth data set is done, for example, using the approach according to the following formula 5: CO2=S1*a3 / b3+S2*(a3 / b3)2+S3*a3+S4*a32+S5*S1+S6*b32+S7*c3+… .

[0070] In this way, the calculation and control unit is able to incorporate the relationship between the decrease in air pressure and temperature with altitude. Formula 6 below, with two examples, serves as an explanation. Formula 6 describes the general relationship between air pressure, altitude, and temperature: p(h1)=p(h0)(1−0.0065⋅ΔhT(h0))5.255

[0071] Based on a reference altitude h0 (0.00 m, sea level, NN) with a pressure level p(h0) of 1013 mbar (corresponding to 1013 hPa) and an assumed reference temperature T(h0) of 288.15 K (corresponding to 15°C), a pressure level p(h1) of approximately 617 hPa results at an altitude h1 of approximately 4000 meters above sea level. At the same altitude of approximately 4000 meters, a pressure level p(h1) of approximately 605 hPa results at a temperature of 5°C.

[0072] This enables the calculation and control unit to take into account not only the pressure-dependent effect resulting from the altitude when using thermoelectric voltage signals to determine the current oxygen concentration during operation of the measuring system, but also the dependence of the pressure-dependent effect on the temperature level prevailing during operation.

[0073] In a further preferred embodiment, the calculation and control unit can be configured to incorporate into the determination of the oxygen concentration a measured value from a humidity sensor, which indicates a humidity level in the breathing gas mixture in the measuring chamber, and / or provided information regarding the current moisture content in the breathing gas mixture. The current moisture content in the breathing gas mixture can, for example, be included in the data sets based on formulas 1 to 5, or directly or indirectly in formulas 1 to 5, which contain the measured quantities of thermal conductivity a1, a2, a3, b1, b2, b3, c1, c2, c3 as parameters or information on vapor pressures, dew points of the gases in the gas mixture, or their water content in the gas mixture.

[0074] In a further preferred embodiment, a temperature sensor can be arranged in or on the measuring chamber.

[0075] In a further preferred embodiment, a humidity sensor can be arranged in or on the measuring chamber.

[0076] In a further preferred embodiment, the calculation and control unit can be configured, in conjunction with a measuring chamber heater, to temperature-control the measuring chamber to a level with a predetermined temperature difference above the ambient temperature, for example, above the temperature in the aircraft cockpit. In this way, condensation in the measuring chamber can be prevented with minimal heating energy expenditure. To implement this further preferred embodiment in practice, it is necessary to provide the calculation and control unit with a temperature value at an interface, indicating the ambient temperature and / or the cockpit temperature.

[0077] In a further preferred embodiment, the calculation and control unit can be configured to initiate, after predetermined time intervals, the heating of the measuring chamber to a temperature level significantly above the typical body temperature of the pilot and the current ambient temperature for a predetermined period. In this way, condensation in the measuring chamber can be reliably prevented with minimal heating energy expenditure during the predetermined period. Furthermore, the influence of the temperature dependencies of the thermal conductivities of the gases oxygen, nitrogen, and carbon dioxide present in the breathing gas mixture, as well as the influence of humidity, on the determination of the current oxygen concentration in the breathing gas mixture can be reduced for the predetermined period.In this way, an up-to-date oxygen concentration value of the breathing gas mixture can be determined from time to time, which is characterized by improved accuracy compared to the oxygen concentration value determined by switching, interpolation or extrapolation based on the first and second data set.

[0078] In a preferred embodiment, the calculation and control unit can be configured, in conjunction with a measuring chamber heater, to maintain the temperature of the measuring chamber at a selected level for a predetermined period. The calculation and control unit can select the temperature level for the predetermined period based on the current temperature value and at least one of the data records stored in the data memory. This advantageously and energy-efficiently enables the temperature of the measuring chamber to be maintained at a temperature level that was also present when the first, second, or subsequent data records were generated.

[0079] For example: The current temperature in the measuring chamber is 33 °C. The third data set comprises a characteristic curve, a family of characteristic curves, or a characteristic map with a reference temperature of 25 °C. The fourth data set comprises a characteristic curve, a family of characteristic curves, or a characteristic map with a reference temperature of 40 °C. The first and second data sets comprise characteristic curves based on a first and second pressure level, respectively.

[0080] If the measuring chamber is now kept at a stable temperature of 40°C, the fourth data set can be used directly, i.e., without the application of interpolations or extrapolations.

[0081] The calculation and control unit can then determine a current oxygen concentration in the breathing gas mixture from the thermoelectric voltage signals with AC and DC signal components, taking into account the stable temperature of 40°C in the measuring chamber created by temperature control, and exclusively using the first, second, and fourth data sets. In this way, a current oxygen concentration value of the breathing gas mixture can be determined continuously or intermittently during measurement operation. This value is characterized by improved accuracy compared to oxygen concentration values ​​determined by switching, interpolation, or extrapolation, while requiring only minimal energy expenditure for temporary temperature control.

[0082] The invention is explained in more detail below with reference to the figures. Identical elements in the Fig. 1 and Fig. 2 are in the Fig. 1, Fig. 2 with identical reference numbers.

[0083] They show: the Fig. 1: A representation of a monitoring system, the Fig. 2: A measuring system for determining concentration.

[0084] The Fig. Figure 1 shows a schematic representation of a monitoring system 100 according to the state of the art as defined in US 2021 / 0405008A1. The monitoring system 100 is connected to a person 99 via a measuring gas line 10 and a breathing mask 20. The person 99 represents an aircraft operator (pilot, co-pilot), boat operator, or diver. The breathing mask 20 has a gas connection 21, a connection element 23, and hoses 24 and 25. The hoses 24 and 25 serve to supply and deliver breathing gases to the person 99. The monitoring system 100 includes operating elements 40, display elements 44, a gas delivery module 50, and a measuring system 60 with a measuring device 66. The measuring device 66 has a sensor, in particular a sensor for gas analysis, but may also have other sensors, for example a sensor which is designed to measure temperatures, pressures or humidity.The gas delivery module 50 is preferably configured as a pump P. M trained.

[0085] Furthermore, the monitoring system 100 includes a control and evaluation unit 70. The operating elements 40, the display elements 44, the sensors, and the gas delivery module 50 are connected to the control and evaluation unit 70 via – in this Fig. 1. Not shown - signal and data lines or control lines are connected. These control lines or signal and data lines can, for example, be configured as a bus system (CAN) or network.

[0086] The control and evaluation unit 70 is designed and intended to control and / or actuate the gas delivery module 50 in such a way that breathing gases are delivered from the breathing mask 20 through the measuring gas line 10 and a gas inlet 51 to the measuring system 60. Thus, a quantity or partial quantity of breathing gas is then available to the measuring device 66 for metrological analysis and for the control and evaluation unit 70 to receive the measured values.

[0087] The control and evaluation unit 70 makes it possible to evaluate, process and display the measured values ​​on display elements 44.

[0088] The monitoring system 100 can optionally include further measuring arrangements for temperature and / or pressure measurements in the breathing mask 20 or in the cockpit. The monitoring system 100 can also optionally include further sensors, such as an inertial measurement system, a gyrometer, an electronic compass, or a 2-axis or 3-axis accelerometer.

[0089] The Fig. Figure 2 shows the measuring system 60 with the measuring device 66 and the control and evaluation unit 70 according to the Fig. 1 in detail, as well as with an additional data storage device 77, which is designed and suitable to store a first data record 78 and at least one further data record 79 and to provide it to the control and evaluation unit 70.

[0090] Quantities of breathing gas mixture 15 can be conveyed by means of a feed through module 50 ( Fig. 1) The gas is transported via a gas inlet 51 to and into a measuring chamber 30 and out again via a gas outlet 52 – for example, into an environment 5. The control and evaluation unit 70 is designed and configured to carry out a process for determining the concentration in the breathing gas mixture 15.

[0091] The measuring system 60 has a measuring device 66 with a circuit arrangement 68, which is designed to determine a concentration of oxygen (O2) in the breathing gas mixture 15 based on paramagnetic effects of thermal conductivity.

[0092] The circuit arrangement 68 comprises a magnet arrangement 683 with an electromagnet and a coil, as well as electronic components for operating the coil and magnetic field, and for performing signal processing and filtering. The measuring device 66 comprises a measuring element 681 with heating elements, thermocouples, or thermopiles arranged on a membrane. During operation, a cyclic application of a magnetic field to the measuring element 681 is generated by the interaction of the control and evaluation unit 70, the circuit arrangement 68, and the magnet arrangement 683.

[0093] The magnet arrangement 683 exhibits, in addition to the features described in this document, the following characteristics: Fig. The diagram shows two schematically indicated elements for guiding a magnetic field, an electromagnet with coils in a coil arrangement, which – like the magnetic field itself – is shown in this diagram for the sake of clarity. Fig. 2 are only hinted at.

[0094] Thermoelectric voltage signals 682 are generated at thermocouples or thermopiles, with and without the influence of a magnetic field, as signals with a DC voltage component U. TH= and with an alternating voltage component U TH∼ determined. The thermoelectric voltage signals 682 U determined at the thermocouples or thermopiles TH=, U TH∼ indicate a thermal conductivity of the breathing gas mixture 15 upon contact with the measuring element 681.

[0095] The thermoelectric voltage signals 682 U TH= , U TH∼ are provided to the control and evaluation unit 70.

[0096] The measuring device 66 includes a pressure measuring arrangement 59 with a pressure sensor 591 arranged on the measuring chamber 30 for determining a pressure level in the breathing gas mixture 15 as well as its changes in the breathing gas supply of the person 99 ( Fig. 1) on. The control and evaluation unit 70 is designed to receive signals from the pressure sensor 591 as a current pressure measurement value P. x 599 continuously to record, which represents a current pressure level in the breathing gas mixture 15.

[0097] An optional measuring chamber heating system 33 is arranged on the measuring chamber 30, which is designed to effect, in conjunction with the calculation and control unit 70, at least temporary heating of the measuring chamber 30 in order to at least temporarily reduce condensation of moisture in the measuring chamber 30.

[0098] In the first data set 78, a characteristic curve for various typical proportions of moisture and the gases nitrogen, oxygen, carbon dioxide in the breathing gas mixture 15 is stored with reference to a first pressure level.

[0099] The second data set 79 contains a characteristic curve for typical proportions of moisture and the gases nitrogen, oxygen, carbon dioxide in the breathing gas mixture 15 with reference to another pressure level.

[0100] The control and evaluation unit 70 is designed based on the data of the first data set 78 and the data of the further data set 79, taking into account the current pressure level P. x 599 the thermoelectric voltage signals 682 U TH =, U TH to evaluate, i.e., a ratio of DC voltage component U TH = and AC component U TH∼ to form in order to determine a current concentration value of oxygen (O2) in the breathing gas mixture 15 and to provide it as an output signal 908, which indicates the current concentration value of oxygen in the breathing gas mixture 15, and an output unit 44 ( Fig. 1) or to provide it via an optional interface.

[0101] The measuring system 60 can optionally include further measuring arrangements for temperature and / or pressure measurements and / or humidity measurements. REFERENCE MARK LIST 5 Environment 10 Measuring gas line for breathing gas mixture 15 Breathing gas mixture 20 breathing masks 21 Gas connection to breathing mask 23 Connection element 24, 25 hose lines 30 measuring chamber 33 Heating the measuring chamber 40 input elements 44 display elements 50 Module for gas conveyance, pump P M 51 Gas inlet 52 Gas outlet 59 Pressure measuring arrangement 591 Pressure sensor 599 Pressure reading 60 measuring system 66 Measuring device, sensors 68 Circuit arrangement 681 Measuring element with heating and thermocouple arrangement 682 Thermoelectric voltage signals U TH 683 Magnet arrangement 70 Control and evaluation unit 77 Data storage 78, 79 record, records 99 people, pilot, parachutist, boat captain, diver 100 monitoring systems 908 Output signal

Claims

[1] Measuring system (100) for determining gas concentrations in a breathing gas mixture (15) for a monitoring system for monitoring a breathing gas supply of an aircraft or a submersible vehicle with a gas transport module (50), a measuring gas line (10), a measuring device (66) with a measuring element (681) in a measuring chamber (30), with a pressure sensor (591), a magnetic arrangement (683) comprising an electromagnet and a coil, a calculation and control unit (70) with an associated data storage (77) and a circuit arrangement (68), • wherein the module for gas transport (50) is designed to supply a quantity of a breathing gas mixture (15) to the measuring element (681) in the measuring chamber (30), • wherein the measuring device (66) is configured with the circuit arrangement (68) to operate a heating structure on a membrane of the measuring element (681) in order to transfer defined quantities of heat into the breathing gas mixture (15) or to subsets of the breathing gas mixture (15) in the measuring chamber (30), • wherein the measuring device (66) is configured with the pressure sensor (591) to determine a pressure measurement value (599) which indicates a pressure inside the measuring chamber (30), • wherein an acceleration sensor is arranged in or on the measuring system (100), which is configured to determine measurement data on accelerations, on a current spatial orientation of the measuring system (100) or changes in spatial orientation and to provide this data to the calculation and control unit (70), • wherein the measuring device (66) is designed with the electromagnet, the coil and the circuit arrangement (68) to generate a magnetic field acting on the measuring element (681), • wherein the circuit arrangement (68) is configured to measure the measured values ​​of the measuring element (681) with an alternating voltage signal component U X∼ and with a DC signal component U X =to provide to the calculation and control unit (70), • wherein the data storage (77) contains a first data record (78) with initial data and at least one second data record (79) with further data, • where the first data set (78) indicates a first situation in the breathing gas mixture (15) at a first pressure level, • where the second data set (79) indicates a second situation of gases or breathing gas mixture (15) at a second pressure level, • wherein the calculation and control unit (70) is based on the AC signal components and DC signal components ◯ including the pressure reading (599), which indicates a current pressure level inside the measuring chamber (30), ◯ including the first data set (78) and ◯ including the second data set (79) to determine a current oxygen concentration in the breathing gas mixture (15), • wherein the calculation and control unit (70) is designed to perform a predictive inclusion of the current pressure measurement value (599) and the first and second data set (78, 79) in the determination of the current oxygen concentration based on the measurement data of the accelerometer, • wherein the calculation and control unit (70) is configured to provide an output signal (908) indicating the current oxygen concentration in the breathing gas mixture (15). [2] Measuring system (100) according to claim 1, wherein at least one further or third data set with further values ​​for a third or further pressure levels is stored in the data storage (77), which indicates a third or further situation in the breathing gas mixture (15) at a further pressure level. [3] Measuring system (100) according to claim 1 or claim 2, wherein the calculation and control unit (70) incorporates the current pressure measurement value (599), the first data set (78) and the second data set (79) or the third or further data sets by means of a switching between the data sets (78, 79) to determine the current oxygen concentration. [4] Measuring system (100) according to claim 1 or claim 2, wherein the calculation and control unit (70) is configured to include the first data set (78) and the second data set (79) or the third or further data sets by means of an interpolation based on the values ​​of the data sets (78, 79) for the current pressure measurement value to determine the current oxygen concentration. [5] Measuring system (100) according to claim 1 or claim 2, wherein the calculation and control unit (70) is configured to include the first data set (78) and the second data set (79) or the third or further data sets by means of an extrapolation based on the values ​​of the data sets (78, 79) for the current pressure measurement value to determine the current oxygen concentration. [6] Measuring system (100) according to claim 4 or claim 5, where the calculation and control unit (70) to perform the interpolation or extrapolation as a linear interpolation or extrapolation or a piecewise linear interpolation or extrapolation or to perform the interpolation or extrapolation as a nonlinear interpolation or nonlinear extrapolation, in particular as a quadratic or cubic interpolation or extrapolation. [7] Measuring system (100) according to any one of the preceding claims, wherein the calculation and control unit (70) is formed, to include in the determination of the oxygen concentration a measured value from a temperature sensor which indicates a temperature level in the measuring chamber (30), and / or provided information regarding a temperature level in the breathing gas mixture (15) and / or wherein the calculation and control unit (70) is formed, to include in the determination of the oxygen concentration a measured value from a humidity sensor which indicates a humidity situation in the breathing gas mixture (15) in the measuring chamber (30), and / or provided information regarding a current humidity content in the breathing gas mixture (15). [8] Measuring system (100) according to claim 7, wherein the temperature sensor is arranged in or on the measuring chamber (30), which indicates a temperature level in the measuring chamber (30) and / or wherein the humidity sensor is arranged in or on the measuring chamber (30), which indicates a humidity level in the measuring chamber (30). [9] Measuring system (100) according to one of claims 7 to 8, wherein the calculation and control unit (70) is designed in conjunction with the temperature sensor and with a measuring chamber heating system (33), temperature control of the measuring chamber (30) a. to be carried out at a temperature level with a predetermined temperature difference above an ambient temperature (5); b. to perform at a temperature level above the body temperature of the pilot (99) for a specified period of time; c. to perform at a selected temperature level for a specified time period, wherein the calculation and control unit (70) is configured to select the temperature level selected for the specified time period based on the current temperature level in the measuring chamber (30) and based on at least one of the data sets stored in the data storage (77).

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