WO2006005332A2

WO2006005332A2 - Device for determining the characteristics of a gas

Info

Publication number: WO2006005332A2
Application number: PCT/DE2005/001241
Authority: WO
Inventors: Dirk Tuchtenhagen; Gunnar Jung
Original assignee: Aceos Gmbh
Priority date: 2004-07-06
Filing date: 2005-07-04
Publication date: 2006-01-19
Also published as: WO2006005332A3

Abstract

The invention relates to devices for determining the characteristics of a gas with a planar gas sensor that is operated by means of a heating element at a temperature greater than 290 °C and that is located on a carrier substrate for and in a measuring chamber. Said devices are characterised in particular by an extremely simple construction and therefore can be produced extremely economically. The gas sensor consists of a carrier substrate comprising thin layers for at least one heating element, a solid electrolyte and electrodes. The carrier substrate consists of known aluminium oxide, vitroceramic or zirconium oxide-aluminium oxide material. The planar gas sensor is situated on one surface of the carrier substrate and the heating element on another surface of the carrier substrate. The heating element is an electric resistance element comprising at least two feeder lines. At least one conductor is connected to the heating element to act as a potential tap. Said heating element consists of tracks on the carrier substrate.

Description

description

Device for determining the properties of a gas

The invention relates to devices for determining the properties of a gas with a planar at least one heating element with a temperature greater than 290 ° C operated gas sensor on a support substrate for one and thus in a measuring chamber.

Solid electrolyte sensors use the property of certain ionic crystals, already discovered in 1899 by W. NERNST, to transport the electric current in the form of ions at elevated temperature. Two basic arrangements are known as

electroless measurement of the electric potential between a reference electrode and a measuring electrode in the form of solid electrolyte potentiometry and

- Measurement of the ion current of a certain type of ion by the electrolyte when applying an external voltage to the electrodes as amperometry.

Potentiometric (galvanic) solid electrolyte cells, as known inter alia from EP 0 861 419 Bl (method and apparatus for the simultaneous measurement of a volumetric flow and gas partial pressures), known to operate according to the NERNST equation, wherein at a known temperature and known potential at the reference electrode the cell voltage is linearly dependent on the logarithm of the activity or the partial pressure of the component to be measured. Furthermore, the solid electrolyte is a pure ion conductor. The absolute size of the cell voltage depends on the difference between the measuring and reference potential. As possible errors increase with increasing difference of these potentials, the difference between measuring and reference gas pressure should not be too large. The ionic conductivity of the solid electrolyte cell is furthermore temperature-dependent. Cracked or porous electrolyte layers or low electrolyte temperatures lead to high ionic resistances. For exact potential measurements, measuring arrangements with high input resistances are necessary. The invention specified in claim 1 is based on the object, simply 2x1 realizing devices for determining the properties of gases with a hochtem- perierbaren gas sensor with a high resolution to create.

This object is achieved with the features listed in claim 1.

The devices for determination of characteristics of a gas having a planar over wenigs¬ least one heating element having a temperature greater than 290 ⁰ C operated gas sensor on a carrier substrate for a and in a measuring chamber are distinguished in particular by a very simple structure, so that this very are economically produced. The gas sensor consists of a carrier substrate with thin layers for at least one heater, a solid electrolyte and electrodes. The substrate substrate consists of known alumina, glass-ceramic or zirconia-Aluminiumoxyid- materials. The devices are advantageously suitable for gas measurement, which require high operating temperatures. The gas sensors are equipped with a heater that allows an operating temperature of more than 290 ° C.

For this purpose, the planar gas sensor is arranged on one surface of the carrier substrate and the heating element is arranged on another surface of the carrier substrate. The heating element is an electrical resistance element with at least two supply lines. At least one conductor is connected as a potential tap to the heating element. This heating element consists of tracks on the carrier substrate. The planar gas sensor consists of at least one layer of a solid electrolyte and two applied tracks as electrodes for measuring either the applied electrical voltage or the current flowing through the electrodes electrical current, wherein the carrier substrate at least with the electrical resistance element and thus heated solid electrolyte in the measuring chamber of the Housing are located. The heating element can serve by such an implementation for measuring the temperature and / or the temperature distribution and / or the power input. The Temperatur¬ measurement on the device erfogt only the constant temperature range to be maintained, thereby improving the resolution of the temperature measurement at equally accurate measuring devices and errors of the Temperature measurement can be eliminated by heating supply and connection areas. For this purpose, at least one conductor is connected as a potential tap to the electrical resistance element and / or to at least one of the supply lines.

Another advantage is that the heater is used as an electrical resistance element directly for temperature determination. This reduces the inertia of the control process, whereby the measured variable and the manipulated variable are more directly related and control algorithms can be simplified and accelerated. Influencing the properties of heated components or devices with respect to the flow velocity and the temperature of the inflowing medium is reduced or eliminated. For constant properties, it is necessary to keep the temperature distribution of the electrical resistance element as constant as possible and to ensure only the smallest possible deviations from the setpoint temperature even in the event of disturbing influences. Due to the self-adjusting temperature gradient due to the heat conduction through the component, which can not be completely suppressed, to the component fastening, it is necessary to extend the heat input to the entire apparatus. A major problem in this case is that the electrical resistance of the leads falsifies the precise determination of the electrical resistance of the electrical resistance element and thus its temperature to be kept constant. Ideally, the ratio of the electrical resistance of the electrical resistance element to the electrical resistances of the supply lines must be as large as possible, so that even very small changes in either a cooling or heating can be detected. A reduction in the electrical resistances of the supply lines is known to minimize their falsifying influences. The electrical resistance of the leads can not be reduced arbitrarily. Borders are given by the space and the warmth of the entire facility. By connecting at least one conductor as potential tap to the electrical resistance element and / or to at least one of the supply lines, this heater is divided into a plurality of separately measurable sections. Advantageously, the sensitive area and the supply area can thus be detected separately by measurement. With an advantageous placement of conductors as Potentialabgriffe the electrical resistance of the electrical resistance element and thus the average temperature can be determined accurately. The influence of the supply lines is completely eliminated and the manipulated variable of the control process can be calculated so that the electrical resistance of the electrical Resistance element and not the electrical resistance of the electrical Widerstands¬ element including the leads is kept constant.

The heating element is further characterized by a reduced dependence of the flow rate, since the supplied heating power is a direct measure of the flow parameters to be determined. There may be a measurement of both magnitude and direction by determining the temperature distribution on the device. Depending on the flow conditions, a characteristic temperature or resistance distribution is formed. The higher the flow velocity, the greater the temperature differences of the individual regions of the device compared to the state without flow. At a fluid temperature that is lower than the temperature of the device, areas that are more heavily flowed will cool more strongly than areas that are less affected. These effects can be used to determine the magnitude and the one- and multi-dimensional direction of a flow with the aid of a single electrical resistance element. A subdivision into additional areas enables the detection of further directional components of the flow.

Advantageous embodiments of the invention are specified in the claims 2 to 19.

The resistance element according to the embodiment of claim 2 has the shape of a meander, a polygon, a conic or at least a combination of two of these forms and a web-shaped conductor as potential tap is centrally located on the sheet-shaped resistor element and connected thereto. This makes it possible to determine the electrical resistance of both the one half and the other half of the device. Temperature differences between the halves can be demonstrated by the specific electrical resistance of the webs. Several web-shaped conductors as potential taps advantageously lead to an increase in the resolution of the temperature distribution over the electrical resistance element.

By the development according to claim 3, wherein the resistance element of two spaced apart and externally connected together in series geschal- Teten forms of a meander, a polygonal, a conic or at least a combination of two of these forms, a web-shaped potential tap centered on a meandering shape and at least one further web-shaped potential tap arranged at the junctions of the meandering forms and connected to this, the temperature distribution can be determine via the device so that a two-dimensional direction detection of a flow is possible.

According to the embodiment of patent claim 4, successive layers of the solid electrolyte, electrodes with connection tracks and an diffusion barrier covering an electrode up to its connection track are arranged as an oxygen sensor on a region of the carrier substrate. The solid-state electrolyte consists of a doped and ion-conducting zirconium oxide, the chemical interaction between the gas component as oxygen and the solid electrolyte in conjunction with the electrodes causing an electrical charge transport. The diffusion barrier is a printed layer of a glass, aluminum oxide or a combination thereof.

The oxygen measurement is based on an amperometric circuit based on the principle of the diffusion limit current probe. With the aid of a direct voltage applied to the two electrodes, an electric current flows through the solid electrolyte as a functional ceramic with the transported oxygen ions as a circuit. In this case, molecular oxygen is converted into ionic oxygen at the cathode, transported to the anode by the applied voltage and converted there back into molecular oxygen. If the solid electrolyte is a pure ion conductor, Faraday's laws apply. The first Faraday's law is used in the form of coulometric measurement methods, the mass of the electrochemically reacted substance being proportional to the amount of electricity flowed. The electrical conductivity of a solid is determined primarily by its atomic lattice structure. The charge transport in a ceramic solid electrolyte takes place above all through defects. The cause of these defects may be thermal or contaminant-induced disordering of the lattice structure, as well as macroscopic lattice disturbances, for example, as dislocations or grain boundaries. The charge transport can occur by changing the location of the atomic lattice defects (ion transport) or by the migration of electrons or holes between the charged lattice defects walk.

Every ceramic is basically a mixed conductor. If the density of the defects is low, such as in an undisturbed crystal, then there is an insulator. Ionically conductive ceramics are formed by increasing the number of ionic defect sites through the targeted introduction of impurities (dopants). An increase in the concentration of any kind of defects can be achieved by increasing the temperature. The base material for the electrolyte is zirconium dioxide. This material has good mechanical and thermal properties. Pure zirconia is present at ambient temperature in a monoclinic lattice structure. From about 1150 ° C, this transforms into a tetragonal and from 2370 ° C in a cubic lattice structure. In order to avoid these phase transformations, which are also associated with changes in shape and volume and to increase the number of defect sites which conduct oxygen ions, pure zirconium dioxide is doped with diyttrium trioxide. By a sintering process at temperatures above 1300 ⁰ C, a stabilization of the highly conductive cubic phase is achieved, which is then also at room temperatures. The ionic conductivity of this ceramic is comparable to liquid electrolytes at temperatures above 600 ° C.

Solid-state gas sensors convert the chemical interaction between gas component and sensor material (ion conduction) into an electrical signal.

The interaction between the gas component and the solid can only be converted into an electrical signal through the exchange and transport of electrons. This presupposes the presence of metallically conductive or semi-conductive surface areas and electrodes in the area of the gas-solid interaction, since the solid electrolyte itself has no or only a negligible electron conduction. On the other hand, the noble metals used as electron conductors have no transport properties for oxygen or for ions. Therefore, in the gas-solid-state reaction toward electric charge transport, a chain of physicochemical phenomena at the gas / electrode / solid electrolyte interface, also known as the three-phase boundary, proceeds. The reaction at the Festkörperober¬ surface is preceded by the arrival and Abdiffusion the gaseous components in the gas space. The primary step in the interaction between the solid surface and the gas component is adsorption / desorption. The inflow of oxygen to the cathode is limited by a diffusion barrier, wherein Due to the physical properties of the diffusion, the measurable sensor current in the range of 0-100% oxygen is linearly dependent on the oxygen concentration. With the linear characteristic curve, the two-point calibration customary with potentiometric sensors is dispensed with and thus the use of reference gas (reference chamber) for calibrating the sensor becomes superfluous. A simple one-point calibration, for example, with ambient air is sufficient, since the second point of the linear characteristic is always known. No oxygen flows when there is no oxygen.

The materials of the electrodes perform two functions. On the one hand, these are the electrical conductors for the closure of the measuring circuit and on the other hand, in combination with the solid electrolyte, they influence the gas exchange with the environment.

The increased compared to the ambient temperature operating temperature of the gas sensors ermög¬ the simultaneous measurement of flow rates or flow velocities according to the principle of temperature-constant thin-film geometry. By keeping the sensor temperature constant, the volume flow can be determined on the basis of the required heating power to ensure these temperatures. Thus, as a result of a flow, the gas sensor is cooled and it is a larger heat output for a constant temperature necessary. The volume flow is dependent on the difference between the heating power in the streamed state and the heating power in the non-streamed state.

The solid electrolyte is advantageously according to the embodiment of claim 5, a layer of a zirconium oxide doped with Diyttriumtrioxid with a layer thickness of the doped zirconia greater than or equal to 1 micron and less than or equal to 500 microns as Festkörper¬ electrolyte.

The layers as a solid electrolyte, electrodes with connection tracks, diffusion barrier and heating element with connection tracks are advantageously applied according to the embodiment of claim 6 by means of the known screen printing technique. In this case, the layer is pressed by a stencil which is on a sieve-like fabric or part of the sieve-like fabric of a printing frame by doctor blade on the plate-shaped support. With this method, certain layer thicknesses can be economically printed. With a wiring of the sensor according to the embodiment of claim 7, both the oxygen and the volume or the flow of a gas can be measured with a sensor.

On one area of the carrier substrate, layers of the solid-state electrolyte and electrodes as a measuring electrode and a reference electrode, each with a connecting path according to the embodiment of claim 8, are arranged successively as a carbon monoxide sensor. The reference electrode consists of either platinum or a platinum-YSZ mixture and the measuring electrode is a metal or a metal mixture. The solid electrolyte consists of an yttrium-stabilized zirconium oxide, wherein between the measuring electrode and the reference electrode, a voltage potential in dependence of the carbon monoxide partial pressure is applied.

Layers of the solid-state electrolyte, electrodes as a measuring electrode and a reference electrode, each with an attachment path and metal carbonate on the measuring electrode according to the embodiment of patent claim 9, are successively arranged as a carbon dioxide sensor on a region of the carrier substrate. The reference electrode and the measuring electrode are made of either gold or a gold-sodium ion conductor mixture. The solid electrolyte consists of a sodium ion conductor, wherein a voltage potential is applied between the measuring electrode and the reference electrode as a function of the carbon dioxide partial pressure.

The development of claim 10 leads to sensors, which are characterized in particular by a thermal insulation between the sensor element and the sensor holder / sensor attachment with simultaneous alignment and positioning relative to an easily fixable base plate. The base plate is advantageously at the same time the Sensorbe¬ consolidation. The base plate has an opening for receiving the end region with the gas sensor and the heating element opposite end region of the carrier substrate, so that the heated gas sensor is arranged at a distance from the base plate. The opening is advantageously at the same time the fixation of the carrier substrate, so that predetermined positions of the gas sensors, for example, in the measuring space of the housing can be easily realized. The dimensions can be chosen so that a clamping connection between Träger¬ substrate and base plate is given, so that a fixed position of the carrier substrate gegen¬ on the base plate is already present during the joining. Thus, a very accurate alignment of the gas sensors and heating elements is easily possible, so that easily, for example, different angle of attack can be adjusted. The opening is also an assembly aid. With the base plate easy handling and mounting option is available. The same applies to an exchange with the same measuring chambers, so that measuring chambers for a variety of tasks are easily feasible.

Thus, a low-cost gas sensor can also be made available as Secker. The handling and mounting of the base plate is easily possible and automated, so that cost and therefore economical gas sensors are available. The base plate can also be designed as a component carrier, resulting in the most diverse applications. This is

a thermal insulation of the heated sensor element from the overall structure,

electrical connections for the electrical supply of the sensor and transmission of the sensor signals to an evaluation unit,

a mechanical connection to the environment of the sensor,

a seal of a gas measuring chamber with respect to the housing or the environment,

- Alignment and positioning of the sensor elements in the medium to be measured and

- The protection of the sensor element against external mechanical or strömungsmecha¬ African influences given.

The connections of the tracks of the base plate with those of the carrier substrate are metallic wire, ribbon or solder bridges. The conductor tracks of the base plate can also be used as contacts or as electrical connections to component connections, so that the base plate is at the same time a component carrier. As a result, the measurement signals of the sensor elements can be processed via components as evaluation or conversion devices. Components can also be connecting elements, so that electrical contacting is easily possible. The carrier substrate and the base plate are connected according to the embodiment of claim 11 via a compound of a temperature-resistant and a poor thermal conductivity auf¬ facing adhesive, so that a large heat input into the base plate can be prevented. For this purpose, an adhesive with a low heat conductance is advantageously used. At the same time this is a temperature-resistant and advantageously a gas-tight adhesive, so that a mechanical impairment of the adhesive layer is largely avoided. In particular, a ceramic adhesive or an epoxy resin adhesive is used.

The further developments of claim 12 enable an automated production of the metallic solder bridges between the conductor tracks of the carrier substrate and those of the base plate. The bulges between adjacent tracks of the base plate advantageously prevent bridging between adjacent tracks.

A housing for a device for determining the property of a gas with oxygen with a gas sensor on a plate-shaped carrier according to the embodiment of the patent claim 13 is characterized in particular by a simple structure. At the same time, there is little heating of both the environment and the gas to be analyzed. For this purpose, a first tube is arranged at a distance in a second tube, the gas sensor is located in the first tube, there is a spatial connection between both the intermediate space and the space in the first tube and the tubes in the housing are connected and disconnected ¬ tions provided for the gas to be analyzed and bushings of the electrical lines for the gas sensor, wherein between the wall of the second tube and the corresonding thereto arranged housing a distance and thus an interior is present.

With such a realization is further ensured that a gas sensor several hundred degrees Celsius is placed in a small space. This results in a low power consumption of the sensor and a fast gas exchange is given. The two tubes and the housing advantageously function as a heat exchanger, wherein supplied cold gas to be analyzed is heated by the hot gas to be analyzed at the sensor. At the same time, the gas to be analyzed at the sensor is cooled by the inflowing gas to be analyzed. This simultaneously reduces the required Heating power, a reduction in the outside temperature of the housing and a reduction in the temperature of the discharged gas to be analyzed. As a result, a compact construction of the housing is available.

In another housing, the gas sensor is located in the space of a tubular body as a housing. An opening and thus an end is the gas inlet, so that with the gas sensor both for oxygen measurement and for volume flow and / or flow measurement can be used.

Advantageously, according to the embodiment of claim 14 in the base plate of the housing in the direction of the gap and the space of the second tube leading bores are introduced, which are simultaneously flow channels for the gas to be analyzed. This gives a simple and compact design. At the same time, a passive cooling can take place with a mounting on a heat sink.

The outwardly facing openings of the holes have connection fittings for the supply and discharge of the gas to be analyzed, so that this housing can be easily integrated with the gas sensor in measuring systems. For this purpose, for example, hose lines can be connected, so that connections to suction devices can be easily established.

The development of claim 15, wherein the base plate and a housing wall each having at least one continuous and pointing in the direction of the interior opening and on the base plate of the housing, a fan for generating an air flow in the interior is arranged, leads to the possibility of additional cooling of the interior Thus, an active cooling is present, which does not affect the flow of the gas to be analyzed. The air flow produced by the fan causes the housing to be handled during operation. At the same time, gas sensors can be used which require very high operating temperatures for sufficient ion conductivity of the solid electrolyte.

The end region of the tubes are fixed according to the embodiment of claim 16 at least in the base plate of the housing. This results in a simple realization of the housing. This is available for gas sensors.

The development of claim 17, wherein at least on the wall of the second tube and / or a wall of the housing and in the interior at least one temperature sensor is arranged and are in the housing Durchfuhrungen the electrical wires for the temperature sensor, causes over the flow of the fan flow, the temperature can be controlled or regulated on the housing.

The second tube is according to the embodiment of claim 18 advantageously a bushing with a Öfϊhung for receiving a portion of the first tube, so that there is a simple structure and a simple fixation of the tubes to each other.

The development of claim 19, wherein the second tube has a pointing in the direction of the interior opening for the gas to be analyzed and both the base plate and the housing each have at least one opening to the interior of the housing and on the base plate of the housing, a fan for generating an air flow is arranged in the interior, advantageously leads to an air flow in the housing. This air flow causes a negative pressure at the opening of the second tube, so that the gas to be analyzed from the first tube is sucked through the gap and passes with the air flow through the opening in the housing to the outside.

Embodiments of the invention are illustrated in principle in the drawings and will be described in more detail below.

Show it:

1 shows a gas sensor both for oxygen measurement and for volume flow and / or

Fig. 2 shows a gas sensor both for oxygen measurement and for volume flow and / or

FIG. 3 shows a measuring circuit with a sensor for both oxygen measurement and for the purpose of measuring oxygen in an exploded view

Volume flow and / or flow measurement, 4 shows a device with web-shaped supply lines respectively applied on a support, resistance element in a meandering form and conductor as potential tap, FIG.

5 shows a device with web-shaped supply lines respectively applied on a support, resistance element in a meandering form and two conductors as potential tap, FIG.

6 shows a wiring of a device,

FIG. 7 shows a device with web-shaped supply lines respectively applied on a carrier, resistive element in a meandering form, and twelve conductors as potential tap, FIG.

8 shows a device with a resistance element of two interconnected meandering forms and three conductors as potential taps,

9 is a carbon monoxide sensor in a sectional view,

10 shows a side of the carrier substrate with the sensor element with plate-shaped electrodes,

11 shows a side of the carrier substrate with the sensor element with electrodes in a meandering shape,

12 shows a wiring of the carbon monoxide sensor,

13 is a carbon dioxide sensor in a sectional view,

14 shows a plate-shaped carrier with a base plate,

15 is a connection of conductor tracks of the plate-shaped carrier and the base plate via solder bridges in a sectional view,

16 shows the connection of the illustration in FIG. 15 in a plan view, FIG.

17 shows a device as a sensor plug,

Fig. 18 shows a first housing with a gas sensor and

19 shows a second housing with the gas sensor in two views.

1st exemplary embodiment

A sensor for oxygen measurement as well as for volumetric flow and / or Anströmmes¬ solution consists essentially of a support substrate in the form of a plate-shaped support 1 with a sensor and a heating element 6, each arranged on opposing Ober¬ surfaces of the plate-shaped support 1 are. 1 shows in principle a sensor for both the oxygen measurement and the volume flow and / or flow measurement in a sectional view. The plate-shaped carrier 1 is an electrical insulator made of aluminum oxide. The sensor element consists of successively applied layers of a solid electrolyte 2, of electrodes 3, 4 with connection tracks and a layer 3 covering an electrode 3 up to its connecting track as diffusion barrier 5. The solid electrolyte 2 is a Diyttriumtrioxide-doped and ion-conducting zirconium oxide with a layer thickness greater / equal to 1 micron and less / equal to 500 microns applied. This causes the chemical interaction between the gas component as oxygen and the solid electrolyte 2 in conjunction with the electrodes 3, 4 and an electric charge transport. The elec trodes 3, 4 including their connection tracks are made of platinum and are applied as comb-like structures, wherein the teeth of the comb-like structures are each arranged alternately spaced parallel to each other (representation in FIG. 2). The layer as a diffusion barrier 5 made of glass and / or aluminum oxide completely covers a cathode 3 representing the cathode except for the connecting track.

On a region of the second surface of the plate-shaped carrier 1 opposite the sensor element, a layer of an electrical conductor made of platinum is arranged as at least one heating element 6. A conductor track 7 as potential tap is connected at a distance from the connecting tracks to the heating element 6 (illustration in FIG. 2).

The components of the sensor are successively applied as a layer on the plate-shaped carrier 1 by means of screen printing.

For oxygen measurement, the plate-shaped support 1 is located with the sensor element and the heating element in the measuring chamber with the gas to be measured. A reference chamber with a reference gas is not necessary. For this purpose, the electrode 3 covered by the diffusion barrier 5 is connected to the cathode of a first electrical energy source 8 and the other electrode 4 is connected to the anode of the first electrical energy source 8 via an ammeter and the connections of the electrical heating element 6 to a second electrical energy source 9 , For simultaneously possible volume or flow measurement are a connection of the electric heating element 6 and the conductor 7 with a first voltmeter and the other terminal of the electric heating element 6 and the conductor 7 with a Connected second voltmeter. The voltage drop of the regions of the electrical heating element 6 is thereby measured via the voltmeter. FIG. 3 shows a measuring circuit with a sensor for oxygen measurement as well as for volume flow and / or flow measurement.

2nd exemplary embodiment

In the following exemplary embodiment, further arrangements of conductor structures on the second surface of the plate-shaped carrier 1 as carrier substrate are described, each with at least one conductor track 7 connected to at least the electric heating element 6 as a potential tap. Such an arrangement is used to measure the temperature, the temperature distribution and / or the power input and consists essentially of the plate-shaped carrier 1 with applied layers as a sensor element on the first surface corresponding to those of the first embodiment and in the form of conductor tracks as a sheet-shaped electrical resistance element 10, web-shaped supply lines IIa, Ib and at least one web-shaped conductor 7 as potential tap, wherein the at least one sheet-shaped resistance element 10 to the web-shaped leads IIa, IIb and the sheet-shaped resistance element 10 and / or at least one of the web-shaped leads I Ia, 1 Ib the web-shaped conductor 7 are connected as Potential¬ tap on the second surface of the plate-shaped carrier 1. The plate-shaped carrier 1 is preferably a plate in particular of an Al ₂ θ3 ceramic, a glass or quartz. The layers as resistive and / or conductive track pastes are applied using known thin-film or thick-film technology. In the thick-film technique as an additive technique, for example, the screen, stencil or pad printing method is used. As is known, the resistive and conductive track pastes consist of hardened pasty mixtures of an organic and / or inorganic binder with pulverulent metals and metal oxides. Of course, also known subtractive techniques can be used, wherein a layer is removed in regions.

In a first embodiment of the second embodiment, the sheet-shaped resistance element 10 is applied in a meandering shape and a sheet-shaped conductor 7 as Potential tap is centered on the sheet-shaped resistance element 10 and connected thereto (shown in FIG. 4).

In a second embodiment of the second exemplary embodiment, a plurality of sheet-shaped conductors 7a, 7b,... 7n are connected as potential taps to the sheet-like resistance element 10 applied in a meandering form (illustrations in FIGS. 5 and 7). There are three or more individual and separately measurable subareas. Analogous to the second embodiment of the first exemplary embodiment, the leads are the resistors Rl and R3, the resistors of the strip-shaped leads I Ia, Ib and the resistance R2 is the resistance of the sheet-shaped resistive element 10. These are determined by the flowing electric current I and the differential voltages Ul, U2 and U3 according to the Ohm's law Rl = Ul / I, R2 = U2 / I and R3 = U3 / I (representation in FIG. 6). The current I flows through only the web-shaped leads I Ia, Ib and the resistance element 10. The web-shaped conductors 7 can be regarded as currentless, so that their electrical resistance is also not relevant. In this way, arbitrarily thin conductor arrangements can be used.

The influence of the web-shaped supply lines IIa, 11b is thus completely eliminated and the manipulated variable of the control process is calculated so that the electrical resistance of the sheet-shaped resistance element 10 and not the electrical resistance of the entire device is kept constant.

The exact determination of the introduced electrical power is the basis, for example, for use as a temperature-constant anemometer, since the power supplied is a direct measure of the flow parameters to be determined. The power input into the sheet-shaped resistance element 10 can be determined very accurately according to P2 = I × U2 or P2N = I × U2N with N = 2, 3,... (In the case of three and more conductors as potential taps). Due to the temperature constancy, the power input is a much more accurate measure of the flow parameters to be determined than the measurement of the power over the entire device. Depending on the flow conditions, a characteristic temperature and consequential resistance distribution develops. The higher the inflow velocity, the greater the temperature differences of the individual resistors R1, R2, R3, (... RN for three or more conductors as potential taps) in comparison to the state without incident flow. At a temperature of the flowing medium that is lower than the temperature of the device, For example, areas of the device that are more heavily flowed will cool more strongly than areas that are less affected. These effects can be used to determine the magnitude and one- and multi-dimensional direction of a flow using a single device.

In a third Ausftihrungsform of the second exemplary embodiment, the sheet-shaped resistance element 10 of two spaced apart and connected together in series connected sheet resistance elements I Ia, Ib in Mäan¬ derformen, wherein a web-shaped conductor 7c as a potential tap center of a meandering shape and in each case a further web-shaped conductor 7a, 7b are arranged as a potential tap at the connection points of the meandering forms and connected thereto (representation in FIG. 8). If this device is flown, the temperature distribution over the device can be determined so that a two-dimensional directional detection of a flow is possible.

In addition to the meandering shape for the sheet-shaped resistance element, other geometric shapes as polygonal or conic or a combination of at least two of these forms as an electrical resistance element on the plate-shaped support 1 are realizable and for measuring the temperature, the temperature distribution and / or the Leistungs¬ entry can be used.

3. Exemplary embodiment

In a third exemplary embodiment as a carbon monoxide sensor, layers of the solid electrolyte 2 and electrodes 3, 4 as a measuring electrode and a reference electrode, each with a connecting track, are successively arranged on a region of the carrier substrate as a plate-shaped carrier 1. FIG. 9 shows a carbon monoxide sensor in a sectional view. The electrode 4 as a reference electrode consists of either platinum or a platinum-YSZ mixture and the electrode 3 as a measuring electrode is a metal or a metal mixture. The layer of the solid electrolyte 2 consists of an yttrium-stabilized zirconium oxide, wherein between the measuring electrode and the reference electrode a Spannungs¬ potential as a function of the Kohlenmonoxidpartialdruckes at an operating temperature between 35O ⁰ C and 800 ° C is applied. This voltage potential is connected to the voltmeter Electrodes 3, 4 measured (shown in Fig. 12). The reference electrode acts oxidizing on the gas mixture, while the measuring electrode acts less or not oxidizing. The electrodes 3, 4 can be applied both in a plate form (illustration in FIG. 10) and in a meandering form (illustration in FIG. 11). The realization of the heating element corresponds to those of the second exemplary embodiment. A circuit of a carbon monoxide sensor with a heating element 6 corresponding to that shown in Fig. 5 shows in principle the Fig. 12. The temperature is determined by the electrical resistance R2 of the electrical resistance element 10 without resistors of the web-shaped leads 11, which also partially Heizwendelwiderstände can affect the measurement result.

During the measurement, the plate-shaped carrier 1 is located with the layer of Festkör¬ perelektrolyten 2, the measuring electrode and the reference electrode on one side and the heating element 6 on the other side in the measuring chamber, so that a reference chamber with a reference gas is not necessary.

4. Exemplary embodiment

In a fourth exemplary embodiment as a carbon dioxide sensor, layers of a solid electrolyte 2, electrodes 3, 4 as a measuring electrode and a reference electrode, each with a connecting track and a layer of a metal carbonate 12 on the measuring electrode, are arranged successively on a region of a carrier substrate as a plate-shaped carrier 1 ( Representation in FIG. 13 as a sectional view). The reference electrode and the measuring electrode are made of either gold or a gold-sodium ion conductor mixture. The layer of the solid electrolyte 2 is a sodium ion conductor, wherein between the measuring electrode and the reference electrode, a voltage potential depending on the carbon dioxide partial pressure at an operating temperature between 350 ⁰ C and 800 ⁰ C is applied. The design of the electrodes 3, 4 correspond to those of the third exemplary embodiment. The Ausfüh¬ tion of the heating element 6 and its wiring correspond to those of the second Ausführungs¬ example.

During the measurement, the plate-shaped carrier 1 is located with the layer of Festkör¬ perelektrolyten 2, the measuring electrode, the reference electrode and the layer of a metal carbonate 12 on one side and the heating element 6 on the other side in the Measuring chamber, so that a reference chamber with a reference gas is not necessary.

5th exemplary embodiment

An attachment for a gas sensor according to the first, third or fourth embodiment on a plate-shaped support 1 essentially consists of this plate-shaped support 1 and a base plate 13 with at least one opening 16 for receiving the end region with the sensor element and heating element 6 opposite end region (illustration in FIG. 14). The dimensions of the opening 16 are greater than at least the dimensions of the cross section of the end region with the sensor element and heating element 6 opposite end portion of the plate-shaped support 1, so that the opening 16 in addition to the positive reception of the end portion and the positioning tion of the plate-shaped support 1 serves. The opening 16 determines the orientation and position of the plate-shaped carrier 1 and thus of the sensor element and the heating element 6 in the measuring chamber and thus in the medium to be measured. The base plate 13 is made of aluminum oxide, a glass ceramic, a polymer or be¬ known printed circuit board material of a glass fiber reinforced epoxy resin, so that certain properties such as heat conduction, strength, temperature resistance and thermal Aus¬ expansion coefficient are application specific. The opening 16 is introduced by the known methods such as erosion, laser cutting, water jet cutting, drilling or milling, so that a very accurate and close tolerance opening 16 can be achieved. The accuracy of the orientation of the plate-shaped carrier 1 is thus dependent on the shape of the opening 16 and the tolerances that arise during insertion of the opening 16. The plate-shaped carrier 1 and the base plate 13 have strip conductors 15, 17. The printed conductors 17 of the plate-shaped carrier 1 are the supply lines of the electrodes 3, 4 and of the electrical heating element 6. The printed conductors 15, 17 are applied, for example, by the known technologies of thick-film technology using screen or stencil printing and then hardened. The contacting of the conductor tracks 15, 17 via solder bridges 18 (representations in FIGS. 15 and 16). In a first variant, the conductor tracks 15 of the base plate 13 terminate at the opening 16 or, in a second variant, are also continued on wall regions of the opening 16. As a result, the solder bridges 18 are easy to implement. In the second variant, solder also advantageously flows through capillary In order to improve the handling and simplification are located between adjacent tracks 15 of the base plate 13 bulges in the base plate 13. This prevents that Lot also accumulates between the tracks 15 and shorting bridges arise. On the base plate 13 is still in accordance with introduced recordings a connector 19 (shown in Fig. 17), so that a slight contact of the existing sensor plug is given. For easy and secure mounting, the base plate 13 has a plurality of openings 14 for fastening elements, for example, as screws.

In a further embodiment of the fifth exemplary embodiment, electronic components can also be fastened to the base plate 13, contacted and connected via the printed conductors 15 in addition to the plug connector 19. As a result, the base plate simultaneously represents a component carrier.

6th embodiment

A first housing with a measuring chamber for gas sensors on a plate-shaped support 1 according to the first, third or fourth embodiment consists essentially of a first tube 21 and a second tube 22 in a cuboid housing with inlets and outlets for the gas to be analyzed (illustration in Fig. 18). The housing is a cuboid with a base plate 25, a cover plate 26 and four side walls 23. In this housing are the first tube 21 and the second tube 22, which are each thin-walled tubes. The end regions of the tubes 21, 22 are secured in blind bores of the base plate 26. The outer diameter of the first tube 21 is smaller than the inner diameter of the second tube 22. The first tube 21 is spaced apart in the second tube 22, so that a gap between the outer wall of the first tube 21 and inner wall of the second tube 22 is present. The second tube 22 terminates at the cover plate 26 and the first tube 21 ends spaced from the cover plate 26, so that a gap is provided as a spatial connection between the gap and the interior of the first tube 21 with the gas sensor on the plate-shaped support 1. The plate-shaped support 1 is located in the first tube 21 and its attachment 20 is part of the cover plate 26 or connected thereto. The embodiment may advantageously correspond to that of the fifth exemplary embodiment.

In the base plate 25 bores as inlets and outlets of the gas to be analyzed in the direction of both the interspace of the two tubes 21, 22 and the first tube 21 are introduced. The tubes 21, 22 are thus arranged in the housing with inlets and outlets for the gas to be analyzed and bushings of the electrical lines for the gas sensor with the sensor elements and the heating elements 6, that between the outer wall of the second tube 22 and inner wall of the side walls 23 of the housing a distance and thus an interior is present. As a result, the hole connected to the intermediate space, the gap, the gap, the space as a measuring chamber with the plate-shaped carrier 1 in the first tube 21 and the associated at least one bore Strömungs¬ channels for the gas to be analyzed.

The outwardly facing end portions of the holes are used to connect pipes or hoses for conducting the gas to be analyzed.

7th embodiment

A second housing with a measuring chamber for gas sensors according to the first, third or fourth embodiment consists essentially of a first tube 21 and a second tube 22 in a cuboid housing with inlets and outlets for the gas to be analyzed.

FIG. 19 shows a housing with a gas sensor on a plate-shaped carrier 1 in two views.

The housing is a cuboid with a base plate 25, a cover plate 26 and four Seiten¬ walls 23. In this housing are the first tube 21 and the second tube 22, which are each thin-walled tubes. The first tube 21 with a plurality of apertures in the wall thereof is arranged at a distance in the second tube 22, so that a gap is present vor¬. For this purpose, the outer diameter of the first tube 21 is smaller than the Innendurch¬ diameter of the second tube 22. The openings are spatial connections of Zwischen¬ space and the space of the first tube 21 with the gas sensor on the plate-shaped support 1. The second tube 22 provides a Socket with an opening for receiving and fixing a portion of the first tube 21. The plate-shaped carrier 1 is located at its attachment 20 in the first tube 21. The first tube 21 is connected to the base plate 25 and the cover plate 26 and the second tube 22 is connected to the base plate 25 of the housing. In the base plate 25 bores as inlets and outlets of the gas to be analyzed in the direction of the intermediate space of the two tubes 21, 22 and the first tube 21 are introduced. The tubes 21, 22 are so arranged in the housing with inlets and outlets for the gas to be analyzed and Durchfuhrungen the electrical lines for the gas sensor that between the outer wall of the second tube 22 and inner walls of the side walls 23 of the housing a distance and thus an interior is present. Thereby, the bore connected to the interspace of the tubes 21, 22, the gap, the openings, the space with the plate-shaped carrier 1 in the first tube 21 and the at least one bore connected to the space as a measuring chamber with the gas sensor in the first tube 21 are flow channels for the gas to be analyzed.

The outwardly facing openings of the bores have connection fittings 24 for fastening hoses for the gas to be analyzed.

In embodiments of the embodiments six and seven, the Grund¬ plate 25 and at least one side wall 23 of the housing may each have at least one durchgeh¬ end and pointing in the direction of the interior of each opening. Furthermore, a fan may be arranged on the base plate 25 of the housing such that an air flow for cooling the housing in the interior can be generated.

In further embodiments of the exemplary embodiments six and seven, the second tube 22 can each have a breakthrough in the direction of the interior for the gas to be analyzed. The base plate 25 and a wall of the housing have at least one opening to the interior and on the base plate 25, a fan for generating an air flow in the interior is arranged. By this air flow creates a negative pressure in the opening and / or the nozzle, so that the gas to be analyzed through the bore to the space of the first tube 21, the gap and the opening and / or the nozzle of the second tube 22 is sucked. With the air flow, the gas to be analyzed passes through an opening in the housing to the outside. In further embodiments of the exemplary embodiments six and seven, at least one temperature sensor can be arranged at least either on the outer wall of the second tube 22 and / or on an inner wall of the housing and thus in the inner space, whereby passages of the electrical lines for the temperature sensor are located in the housing.

The housing with the measuring chamber of the embodiments six and seven may also have other geometric body shapes. Thus, the base plate 25 and the cover plate 26 may have a circular shape or a further polygonal shape.

Claims

claims

1. Device for determining the properties of a gas with a planar at least one heating element with a temperature greater than 290 ° C operated gas sensor on a carrier substrate in a measuring chamber, characterized in that on a surface of the carrier substrate of an electrical insulator of the planar gas sensor as a sensor element and on another surface of the carrier substrate, the heating element (6) are arranged, that the heating element (6) is an electrical resistance element (10) with at least two leads (11), that at least one conductor (7) as potential tap to the heating element (6) in that the electrical resistance element (10), the leads (11) and the conductor (7) are potential traces on the carrier substrate and that the planar gas sensor comprises at least one layer of a solid electrolyte (2) and two applied tracks as electrodes ( 3, 4) for measuring either the applied voltage o that of the electric current flowing through the electrodes (3, 4), wherein the carrier substrate is located in the measuring chamber at least with the electrical resistance element (10) and the solid electrolyte heated thereby.

2. Device according to claim 1, characterized in that the electrical heating element as a sheet-shaped resistance element (10) has a shape of a meander, a polygon, a conic or a combination thereof and either that the sheet-shaped conductor (7) as a potential tap center on the web Resistance element (10) is arranged and connected thereto or that the electrical heating element as a sheet-shaped resistance element (10) has a shape of a meander, a polygon, a conic or a combination thereof and that a plurality of web-shaped conductors (7) spaced as potential taps on the web Resistance element (10) are arranged and connected thereto.

3. A device according to claim 1, characterized in that the sheet-shaped resistance element (10) consists of two mutually spaced and externally connected in series forms of a meander, a polygon, a conic or a combination thereof that at least one sheet-shaped conductor ( 7c) as a potential tap centered on the sheet-shaped resistance element (10) and that at least one further sheet-shaped conductor (7a, 7b) are arranged as a potential tap at the connection points of the sheet-shaped resistance elements (10) and connected thereto.

4. Device according to claim 1, characterized in that successively layers of the solid electrolyte (2), electrodes (3, 4) with connection tracks and an electrode covering the connection track covering the diffusion barrier (5) are arranged as an oxygen sensor on a region of the carrier substrate, in that the layer of the solid electrolyte (2) consists of a doped and ion-conducting zirconium oxide, the chemical interaction between the gas component as oxygen and the layer of the solid electrolyte (2) in conjunction with the electrodes (3, 4) causing an electric charge transport and the Diffusion barrier (5) is a printed layer of a glass, alumina or a combination thereof.

5. Device according to claim 4, characterized in that the solid electrolyte (2) is a layer of a zirconium oxide doped with Diyttriumtrioxid and that the layer thickness of the doped zirconia is greater than or equal to 1 micron and less than or equal 500 microns as a solid electrolyte (2).

6. Device according to claims 1 and 4, characterized in that the successively screen-printed layers of the solid electrolyte (2), the electrodes (3, 4) with connection tracks and the one electrode up to the connection track covering the diffusion barrier (5) on a surface the carrier substrate (1) and that the one Screen printed layer of the heating element (6) with their connection tracks and the at least one web-shaped conductor (7) on the other surface of the carrier substrate (1).

7. Device according to claim 1, characterized in that for oxygen measurement with the DifBαsionsbarriere (5) covered electrode (3) with the cathode of a first electrical energy source (8) and the other electrode (4) via an ammeter with the anode of the first electrical power source (8) and the terminals of the electric heating element (6) with a second electrical energy source (9) are interconnected and that for volume or Anstruchteessung at least one connecting track as a connection of the electric heating element (6) and the conductor track (7) with a first voltmeter and the other connecting track as a connection of the electric heating element (6) and the conductor track (7) are connected to a second voltmeter.

8. Device according to claim 1, characterized in that successively layers of the solid electrolyte (2) and electrodes (3, 4) are arranged as a measuring electrode and a reference electrode each having a connecting track as a carbon monoxide sensor on a region of the carrier substrate, wherein the reference electrode from either Platinum or a platinum-YSZ mixture and the measuring electrode made of a metal or a metal mixture, and that the layer of the solid electrolyte (2) consists of a yttrium-stabilized zirconia, wherein between the measuring electrode and the reference electrode, a voltage potential depending on the carbon monoxide partial pressure.

9. Device according to claim 1, characterized in that successively layers of the solid electrolyte (2), electrodes (3, 4) as a measuring electrode and a reference electrode each having a connecting track and a layer of a metal carbonate (12) on the one Measuring electrode are arranged as a carbon dioxide sensor, wherein the reference electrode and the measuring electrode made of either gold or a gold-sodium ion conductor mixture, and that the layer of the solid electrolyte (2) of a sodium ion conductor, wherein between the measuring electrode and the reference electrode, a voltage potential in dependence of the carbon dioxide partial pressure is applied.

10. Device according to claims 1, 4, 8 and 9, characterized in that in a base plate (13) for placement in a space of the measuring chamber at least one opening (16) for receiving the end region with the gas sensor and the heating element ( 6) opposite end portion of the carrier substrate is that the dimensions of the opening (16) are equal to or greater than at least the dimensions of the cross section of the end region with the gas sensor and heating element (6) opposite end portion of the carrier substrate that the end region with the gas sensor and the heating element (6) opposite end portion of the carrier substrate in the opening (16) of the base plate (13) is fixed, so that the base plate (13) and the sensor plate are arranged at an angle to each other, that on the base plate (13) as a printed circuit conductor tracks ( 15) are located and that in each case a conductor track (15) of the base plate (13) with a supply line, the conductor and the connecting tracks of the carrier substrate via at least one with the conductor tracks (15, 17) connected to metallic wire, ribbon or solder bridge (18) are electrically connected.

11. Device according to claim 10, characterized in that the carrier substrate and the base plate (13) are connected via a connection of a temperature-resistant and a poor thermal conductivity having adhesive.

12. Device according to claim 10, characterized in that either at a wall region of the opening (16) of the base plate (13) a conductor track (15) ends or that at least one wall portion of the opening (16) of the base plate (13) with conductor tracks, wherein in each case one conductor track of the wall is connected to a supply line, the conductor and a connecting track are connected to the surface of the baseplate (13), and that the opening between adjacent interconnects at least partially a bulge is and that in each case a conductor track (15) of the base plate (13) are electrically conductively connected to the leads, the conductor and the connection tracks of the carrier substrate via at least one metallic solder bridge.

13. Device according to claim 1, characterized in that the gas sensor is in the space of a tubular body as a measuring chamber, wherein an opening of the tubular body is the gas inlet, or that a first tube (21) as a measuring chamber spaced in a second tube ( 22) is arranged such that the gas sensor is located in the first tube (21) that at least the space both between the first tube (21) and the second tube (22) as an intermediate space and the space with the gas sensor as a measuring chamber in the first tube (21) and a spatial connection of the space and the space with the gas sensor flow channels for the gas to be analyzed and that the tubes (21, 22) in the housing with inlets and outlets for the gas to be analyzed and passages of the electrical lines for the gas sensor are arranged so that between the wall of the second tube (22) and the housing wall arranged corresponding thereto, a distance and thus an interior is present.

14. Device according to claim 13, characterized in that in the base plate (25) of the housing in the direction of the gap and the space in the first tube (21) leading holes are introduced, that bores are flow channels for the gas to be analyzed and that the end portions the bores are at the same time connection elements or that the outwardly facing openings of the bores have connection fittings (24).

15. Device according to claim 13, characterized in that the base plate (25) and a housing wall each have at least one continuous and pointing in the direction of the interior opening and that arranged on the base plate (25) of the housing, a fan for generating an air flow in the interior is.

16. Device according to claim 13, characterized in that end portions of the tubes (21, 22) are fixed at least in the base plate (25) of the housing.

17. Device according to claim 13, characterized in that at least either on the wall of the second tube (22) and / or on a wall of the housing in the interior at least one temperature sensor is arranged and that in the housing passages of the electrical lines for the temperature sensor are located.

18. Device according to claim 13, characterized in that the second tube (22) is a bushing with an opening for receiving a portion of the first tube (21).

19. The device according to claim 13, characterized in that the second tube (22) has a pointing in the direction of the interior opening and / or nozzle for the gas to be analyzed, that the base plate (25) and the housing each have at least one opening to the interior have and that on the base plate (25) of the housing, a fan for generating an air flow in the interior is arranged.