ELECTROCHEMICAL GAS SENSOR

Description

[0001] The present invention relates to an electrochemical gas sensor.

[0002] Electrochemical gas sensors are well-known. They feature a measuring electrode where a reaction occurs between a target gas contained in a sample gas, i.e., a reaction with the target gas. This reaction produces measurable electrical quantities from which information about the target gas can be derived.

[0003] Providing an electrochemical gas sensor in a compact form is advantageous for many technical applications. For this purpose, it is known to use a stacked arrangement of electrodes and membrane layers, whereby the electrodes are connected via electrolytes enclosed in the membrane layers.

[0004] A disadvantage of such electrochemical gas sensors is that they are sensitive to target gas entering the stack arrangement, as this can lead to distortions in the measurement result.

[0005] DE 10 2014 002 502 A1 discloses an electrochemical gas sensor comprising a housing, an electrolyte reservoir, and several electrodes, wherein the electrodes comprise at least one working electrode and one reference electrode, and wherein the electrolyte reservoir is filled with a liquid electrolyte. All electrodes are arranged on or attached to a common electrode support. The reference electrode is arranged at a lateral distance from the electrodes located in the reaction chamber.

[0006] US 2018 149 614 A1 discloses an electrochemical sensor comprising a housing defining an interior space, a measuring electrode, a counter electrode, and a separator that holds an electrolyte. The electrodes are aligned in a common plane, the separator contacts each of the electrodes, and the separator includes a variety of geometric features, including tabs, thinned sections, cutouts, and rings, as well as variations in compression, density, and surface area. The sensor may include a diffusion barrier around the measuring electrode, while the reference and counter electrodes are located outside the area defined by the diffusion barrier. The diffusion barrier may form a seal and include a shoulder.

[0007] Another electrochemical gas sensor is known from DE 10 2004 059 280 A1.

[0008] The present invention is therefore based on the objective of providing an electrochemical gas sensor whose measurement behavior is improved.

[0009] These and other problems are solved by the subject matter of claim 1.

[0010] Further advantageous features are provided by the dependent claims.

[0011] According to the invention, an electrochemical gas sensor is provided. The electrochemical gas sensor comprises a housing which is divided in the transverse direction into an inner housing area and an outer housing area by a partition extending in a vertical direction of the housing, a measuring electrode, a counter electrode, a reference electrode, and a hydrophilic membrane. The measuring electrode and the hydrophilic membrane are arranged in the inner housing area. The hydrophilic membrane has a membrane arm for receiving the reference electrode. The membrane arm projects from the inner housing area into the outer housing area, so that the reference electrode is located in the outer housing area. The measuring electrode, the hydrophilic membrane, and the counter electrode are arranged in a stacked configuration in the inner housing area.

[0012] The proposed electrochemical gas sensor solves the problem according to the invention by arranging the reference electrode in the outer region of the housing, while the measuring electrode is arranged in the inner region. This spatial separation of the reference and measuring electrodes ensures that the reference electrode does not come into contact with the target gas approaching the measuring electrode, or only to a minimal extent. The reference electrode can thus provide a reference potential that is as constant as possible and therefore function as a particularly reliable reference for measuring the target gas.

[0013] An electrochemical gas sensor is understood to be an electrochemical cell that is designed to detect at least one gaseous substance (in particular a target gas) in a gas or gas mixture (in particular in a sample gas).

[0014] In a preferred case, the electrochemical gas sensor is configured as an oxygen sensor designed to detect oxygen in a gas or gas mixture.

[0015] In the following, the terms "electrochemical gas sensor" and "gas sensor" are used interchangeably.

[0016] The vertical direction of the housing refers to the direction of extension of the housing, i.e., a direction that extends perpendicularly to a base surface of the housing.

[0017] The transverse direction is understood to be a direction perpendicular to the vertical direction of the housing, i.e., a direction that is parallel to a base surface of the housing.

[0018] A membrane arm of the hydrophilic membrane is understood to be a laterally projecting portion (with respect to a normal direction of the hydrophilic membrane) of the hydrophilic membrane, which is configured to receive the reference electrode and project into the outer area of ​​the housing. The hydrophilic membrane, including the membrane arm, preferably extends substantially in one plane, thus providing a substantially planar hydrophilic membrane.

[0019] The hydrophilic membrane is configured to absorb an aqueous electrolyte, for example, an aqueous solution containing sulfuric acid, and to be in contact with the measuring electrode and the reference electrode, so that a connection between the reference electrode and the measuring electrode is established via the hydrophilic membrane and the electrolyte it contains. The measuring electrode is preferably arranged on or attached to the hydrophilic membrane or is connected to the hydrophilic membrane via further membranes, so that the gas sensor is provided in a stacked configuration.

[0020] The partition can be continuous or discontinuous; for example, it can have one or more separate segments. The partition can be ring-shaped in plan view. It can extend from a base surface of the housing and is preferably integral to the housing. It is preferred that the housing and the partition be made of a gas-impermeable material.

[0021] Preferably, the electrochemical gas sensor has a gas inlet on one underside to direct sample gas from the sensor's surroundings towards the measuring electrode. More preferably, the gas inlet is configured to direct sample gas into the interior of the housing. The measuring electrode is preferably arranged between the hydrophilic membrane and the gas inlet to react with the target gas contained in the incoming sample gas.

[0022] The outer housing area can be configured to store the electrolyte. It is known that an electrolyte in an electrochemical gas sensor can absorb and release water due to changes in the ambient humidity of the sensor, thus causing the electrolyte volume within the sensor to change. As a result of this expansion, the electrolyte can migrate into the outer housing area and be stored there. According to the invention, the outer and inner housing areas are connected via the membrane arm to conduct excess electrolyte from the hydrophilic membrane into the outer housing area and vice versa. In other words, the membrane arm acts as a kind of wick. The outer housing area can therefore be shaped like a trough, bounded by the base of the housing, a side wall of the housing, and the partition.

[0023] Preferably, the hydrophilic membrane, and more preferably the membrane arm of the hydrophilic membrane, are in contact with the partition wall in such a way that gas passage from the gas inlet towards the outer housing area, and in particular towards the reference electrode, and vice versa, is prevented. This can be achieved, for example, by arranging the hydrophilic membrane and the membrane arm flush with or against the partition wall, so that there is essentially no gap between the hydrophilic membrane or its membrane arm and the partition wall.

[0024] Furthermore, according to the invention, the partition wall has a recess, wherein the recess is arranged to be in a gas-tight system with the membrane arm.

[0025] This allows the membrane arm to be guided from the inside of the housing through the recess to protrude into the outside of the housing, thereby easily achieving a gas-tight seal between the membrane arm and the recess. This gas-tight seal thus advantageously prevents gas from passing along a contact surface between the membrane arm and the partition.

[0026] Particularly preferably, the recess is designed such that it maintains a predetermined distance from a base surface of the housing's outer area. For this purpose, the recess can, for example, have a contact surface which can maintain the predetermined distance from the base surface of the housing's outer area.

[0027] Providing the predetermined distance ensures that the membrane arm does not lie flush with the base surface when connected to the recess or the contact surface. This minimizes the risk of the membrane arm wrinkling during installation or operation, for example, due to changes in the position of the gas sensor, which could lead to gas leaks. The gas-tight seal is thus advantageously improved compared to a design in which the membrane arm lies flush with a base surface of the housing exterior or the housing itself.

[0028] Furthermore according to the invention, the gas sensor has a hold-down device, wherein the hold-down device is configured to hold the membrane arm in gas-tight contact with the recess, preferably with the contact surface of the recess, if present.

[0029] The retainer restricts the degrees of freedom in the movement of the membrane arm relative to the recess or contact surface, thus improving the gas seal. Furthermore, the retainer can press the membrane arm against the contact surface with a predetermined contact pressure, further enhancing the gas seal.

[0030] In a preferred embodiment, the retainer can further be configured to hold not only the membrane arm but also other parts of the hydrophilic membrane in a gas-tight, for example flush, contact with the partition. In this way, the retainer can press these other parts of the hydrophilic membrane against the contact surface with a predetermined contact pressure, thereby further improving the gas-tight seal.

[0031] The hold-down device can be provided as an independent component of the gas sensor.

[0032] In a preferred embodiment of the invention, the housing is made in two parts and comprises a base element and a lid element, wherein the base element and lid element can be connected to form the housing. For example, the base element and lid element can be connected by means of a snap-fit ​​connection.

[0033] In this preferred embodiment, it is further preferred that the retainer is integrally formed with the cover element. The retainer can, for example, be provided as a projection or as a plurality of projections in the form of one or more retainer elements in the cover element and can be brought into contact with the membrane arm and optionally other parts of the hydrophilic membrane by or during the connection of the cover element to the base element.

[0034] As described, the gas sensor has a counter electrode. The measuring electrode, reference electrode, and counter electrode are connected via the electrolyte.

[0035] Preferably, the gas sensor has a pressure equalization opening in a top surface, wherein the gas sensor further has a protective electrode and wherein the protective electrode is arranged between the pressure equalization opening and the measuring electrode.

[0036] A protective electrode is understood to be an electrode designed to react with an unwanted substance, in particular with the target gas or an unwanted gas (interference gas), so that any target gas or interference gas that might unintentionally enter the gas sensor can be converted before it reaches the measuring electrode. This is particularly relevant if a pressure equalization port is provided, as target gas or interference gas could potentially enter through it.

[0037] By providing the pressure equalization opening, the interior of the gas sensor is set up for pressure equalization with the environment, which can improve the measurement behavior of the gas sensor.

[0038] By positioning the protective electrode between the pressure equalization port and the measuring electrode, the protective electrode can convert any target gas entering through the pressure equalization port before it reaches the reference or measuring electrode and thus distorts the measurement. It is particularly advantageous if the surface area of ​​the protective electrode is larger than that of the measuring electrode. This also offers the advantage that the potential drop across the protective electrode is small compared to a protective electrode with a smaller surface area, thus further improving the measurement performance.

[0039] Preferably, the pressure equalization opening and the gas inlet, if present, are arranged on opposite sides of the housing.

[0040] Preferably, the counter electrode and / or the protective electrode is arranged on a further hydrophilic membrane.

[0041] Particularly preferably, the counter electrode and / or the protective electrode is arranged on a further hydrophilic membrane which has a further membrane arm, wherein the further membrane arm and the membrane arm overlap.

[0042] In this context, overlapping refers to an arrangement of the membrane arm and the further membrane arm in such a way that they at least overlap in a projection along the height direction of the housing (i.e. in a top view), preferably being congruent.

[0043] In this way, the reference electrode is positioned between the membrane arm and the other membrane arm, which advantageously results in redundancy in the gas sensor's design. This means that any damage to either the membrane arm or the other membrane arm that might occur during assembly or operation of the gas sensor can be compensated for. This is achieved by keeping the other membrane arm or membrane arm connected to the reference electrode, so that the reference electrode remains in contact with the measuring electrode, the counter electrode, and the protective electrode (if present) via the electrolyte contained in the hydrophilic membrane or other hydrophilic membranes. Damage during sensor operation can occur, for example, due to shocks or vibrations.

[0044] Furthermore, this ensures that, even in normal operating conditions, the reference electrode is in contact with electrolyte on both sides via the membrane arm and via the other membrane arm.

[0045] By surrounding the reference electrode with the membrane arm and the further membrane arm, the reference electrode is also better protected against mechanical damage.

[0046] Furthermore, preferably in this arrangement the additional hydrophilic membrane is arranged between the protective electrode, if present, and the pressure equalization opening, wherein the measuring electrode is arranged between the hydrophilic membrane and the gas inlet, if present.

[0047] Preferably, the hydrophilic membrane and / or the further hydrophilic membrane comprises a fibrous material, in particular a nonwoven fabric.

[0048] Particularly preferably, the hydrophilic membrane and / or the further hydrophilic membrane consists of a fibrous material, in particular a nonwoven fabric.

[0049] The use of a fiber material advantageously reduces the manufacturing costs of the gas sensor.

[0050] Preferably, the fiber material is a glass fiber material, in particular a glass nonwoven fabric. A glass microfiber nonwoven fabric, especially a borosilicate glass microfiber nonwoven fabric, is preferred as the fiber material. Due to its microporosity, glass nonwoven fabric or glass microfiber nonwoven fabric exhibits sufficiently high hydrophilicity without requiring further treatment such as a surface coating. A further advantage of using fiber materials is that they retain their hydrophilicity throughout the entire service life of the gas sensor. This is not the case with other material classes, particularly hydrophilized PTFE-based membranes. Within the scope of the invention, it was discovered that the latter can lose their hydrophilicity after approximately 1.5 years, rendering the gas sensor unusable.

[0051] Particularly preferably, the hydrophilic membrane and / or the further hydrophilic membrane does not comprise PTFE.

[0052] Another advantage of using fiber material compared to other materials is that the fiber material is more deformable than, for example, sintered materials, so that the fiber material conforms particularly well to the partition wall or recess or to the contact surface.

[0053] Preferably, the hydrophilic membrane has a plurality of membrane arms, each of the plurality of membrane arms projecting from the inside of the housing to the outside of the housing.

[0054] In this way, the orientation independence of the gas sensor can be increased. Each of the plurality of membrane arms acts as a fluid-conducting connection between the outer and inner housings, as described above. Thus, even when the gas sensor is oriented at an angle, it can be ensured that fluid, i.e., electrolyte, can be conducted through at least one of the plurality of membrane arms. Preferably, the hydrophilic membrane has at least three, and particularly preferably at least four, membrane arms.

[0055] Preferably, the reference electrode is integrally formed with the membrane arm.

[0056] This makes it easy to ensure that the reference electrode is stationary relative to the hydrophilic membrane, so that the reference electrode cannot slip during assembly and operation.

[0057] For example, the reference electrode can be printed onto the hydrophilic membrane to provide integral formation.

[0058] Preferably, the gas sensor has a gas inlet in a subside, wherein the gas sensor has an electrolyte-tight, in particular a hydrophobic, membrane which is arranged between the measuring electrode and the gas inlet.

[0059] This advantageously prevents electrolyte from escaping through the gas inlet. The electrolyte-tight membrane is gas-permeable, allowing gas to enter through the gas inlet.

[0060] Preferably, the electrolyte-tight membrane has a thickness of no more than 10 µm.

[0061] It was recognized within the scope of the invention that such a thickness contributes to a sufficiently fast measurement, so that the gas sensor is particularly suitable for use in, for example, ventilation devices such as ventilators and anesthesia machines.

[0062] The electrolyte-tight membrane can, for example, be designed as a PTFE membrane.

[0063] An electrolyte-tight and gas-permeable membrane with comparable advantages can also be arranged between the pressure equalization opening and the counter electrode, if present.

[0064] The gas sensor can have a filter either before or after the pressure equalization opening. Additionally or alternatively, the gas sensor can have a filter either before or after the gas inlet.

[0065] These and other features and advantages of the invention also become apparent from the description of the figures. This shows Fig. 1 a schematic sectional view of an embodiment of a gas sensor according to the invention, Fig. 2 a schematic sectional view of an embodiment of a gas sensor according to the invention, Fig. 3 a schematic sectional view of an embodiment of a gas sensor according to the invention, Fig. 4 a schematic sectional view of an embodiment of a gas sensor according to the invention, Fig. 5a a schematic top view of an embodiment of a further hydrophilic membrane according to the invention, Fig. 5b a schematic top view of an embodiment of a further hydrophilic membrane according to the invention with a protective electrode, Fig. 6a a schematic top view of an embodiment of a hydrophilic membrane according to the invention, Fig. 6b a schematic top view of an embodiment of a hydrophilic membrane according to the invention with reference electrode, Fig. 7 a schematic top view of an embodiment of a base part according to the invention, Fig. 8 a perspective view of an embodiment of a floor part according to the invention.

[0066] According to the invention, an electrochemical gas sensor 100 is provided. Examples of electrochemical gas sensors 100 are in Fig. 1 bis 4 shown.

[0067] The electrochemical gas sensor 100 has a housing 10 which is in Fig. 1 bis 3 The housing 10 is only schematically indicated. In one embodiment, it can be designed in two parts and comprise a base element 15 and a cover element 14, which can be assembled to form the housing 10. Such a two-part housing is shown in Fig. 4 schematically represented.

[0068] As in Fig. 1 - 4 , 7 und 8 As shown, the housing 10 is divided in the transverse direction T by a partition 20 extending in a vertical direction H of the housing 10 into an inner housing region I and an outer housing region A. The partition 20 can, for example, extend from a bottom surface 17 of the housing 10 and is preferably formed integrally with the housing 10.

[0069] The electrochemical gas sensor 100 further indicates, as is shown in Fig. 1 - 4 The electrochemical gas sensor 100 comprises a measuring electrode 30, a reference electrode 40, and a hydrophilic membrane 50. In all embodiments, as also shown, the electrochemical gas sensor 100 further includes a counter electrode 60. As further shown, the measuring electrode 30 and the hydrophilic membrane 50, and preferably also the counter electrode 60, are arranged in the inner housing region I, where they form a stacked arrangement.

[0070] The hydrophilic membrane 50 has a membrane arm 51 for receiving the reference electrode 40, as shown in Fig. 1 - 4 indicated and in Fig. 6a, 6b is shown. Fig. 6a, 6b It has been shown that the hydrophilic membrane 50 can, for example, have a membrane body 52, which in its shape can correspond, for example, to the inner surface of a partition and can, for example, be essentially circular. The membrane arm 51 can extend from the membrane body 52.

[0071] In Fig. 1 - 4 It is evident that the outer housing area A can be shaped like a trough to hold an electrolyte, in Fig. 4 to be included as electrolyte 53. The outer housing area A can be limited on the bottom side, for example, by the base surface 17, partition 20 and an outer side of the base element 15, as shown in Fig. 4 The outer housing area A is thus configured in the illustrated embodiments for storing the electrolyte 53, with the membrane arm 51 forming a kind of wick in the manner described above.

[0072] Preferably and in Fig. 6a, 6b The hydrophilic membrane 50 is shown to have a plurality of membrane arms 51, 51a, 51b, 51c, each of which projects from the inner housing region I into the outer housing region A. One of the membrane arms 51 accommodates the reference electrode 40. The plurality of membrane arms 51, 51a, 51b, 51c can be identical, as in the example shown, or different.

[0073] Preferably, the reference electrode 40 is integrally formed with the membrane arm 51, as shown in Fig. 6b This is evident. For example, the reference electrode 40 can be printed onto the hydrophilic membrane 50 to provide the integral formation.

[0074] The membrane arm 51 projects from the inner housing area I into the outer housing area A, so that the reference electrode 40 is arranged in the outer housing area A, as shown in Fig. 1 - 4 and 7 as is evident.

[0075] In a preferred and in Fig. 4 , 7 und 8 In the illustrated embodiment of the invention, the housing 10 can be made in two parts, comprising a base element 15 and a cover element 14, wherein the base element 15 and the cover element 14 are connectable. The base element 15 preferably provides the base surface 17 from which the partition 20 extends.

[0076] Preferably, the electrochemical gas sensor 100 has a gas inlet 12 in a substructure U to direct sample gas from the environment of the gas sensor 100 towards the measuring electrode 30, as shown in Fig. 4 The diagram is shown schematically. As shown, it is preferred that the gas inlet 12 is configured to direct the sample gas into the inner housing region I. For this purpose, the gas inlet 12 can, for example, be arranged centrally in the underside U. Preferably, the measuring electrode 30 is arranged between the hydrophilic membrane 50 and the gas inlet 12, as shown.

[0077] Preferably and as in Fig. 1 bis 4 As shown, the hydrophilic membrane 50 and the membrane arm 51 are in contact with the partition 20 in such a way that gas passage from the gas inlet 12 towards the outer housing area A and in particular towards the reference electrode 40 and vice versa is prevented.

[0078] According to the invention and in Fig. 1 - 4 indicated as well as in Fig. 7 und 8 The illustration shows that the partition wall 20 has a recess 21, which may, for example, have a contact surface 22, wherein the recess 21, preferably the contact surface 22, is arranged to be in a gas-tight system with the membrane arm 51.

[0079] In the Fig. 8 In the depicted variant, the partition wall 20 has only one recess 21 with a contact surface 22, which corresponds to the membrane arm 51. In the Fig. 7 In the variant shown, the partition wall 20 has a plurality of recesses 21, 21a, 21b, 21c, for example, as shown, four recesses 21, 21a, 21b, 21c, each of which can have a mounting surface 22, 22a, 22b, 22c.

[0080] In the case that the partition 20 has a plurality of recesses 21, 21a, 21b, 21c, these correspond to the plurality of membrane arms 51, 51a, 51b, 51c.

[0081] As in Fig. 8 As can be seen, it is preferred that the recess 21 is designed such that it, for example with respect to its contact surface 22, has a predetermined distance to the base surface 17 of the outer housing area A, so that the membrane arm 51 does not lie flush on the base surface 17.

[0082] The gas sensor 100 can have at least one additional hydrophilic membrane 50'. In the embodiment according to Fig. 3 An additional hydrophilic membrane 50' is arranged between the counter electrode 60 and the hydrophilic membrane 50. This makes it possible to selectively adjust the vertical distance (i.e., a distance in the height direction H) of the counter electrode 60 relative to the hydrophilic membrane 50 and thus relative to the reference electrode 40. This allows the stacked configuration of the gas sensor 100 to be provided with a higher degree of freedom.

[0083] According to the invention, the gas sensor 100, as shown in Fig. 4 The figure shows a retainer 13, wherein the retainer 13 is designed to hold the membrane arm 51 in a gas-tight connection with the contact surface 22.

[0084] It is preferred that the retainer 13 is formed integrally with the cover element 14. The retainer 13 can, for example, be provided as a projection or as a plurality of projections, as shown, for example in the form of a first retainer element 13a and a second retainer element 13b. The retainer 13 can be configured to hold the membrane arm 51 on both sides of the partition 20 by means of the first retainer element 13a and the second retainer element 13b in a gas-tight seal with the recess 21.

[0085] Through the invention according to the invention and in Fig. 4 In the illustrated combination of recess 21 and hold-down device 13, the membrane arm 51 can be clamped in the recess 21, for example via its contact surface 22, thereby improving the gas sealing effect between membrane arm 51 and recess 21.

[0086] Preferably and as in Fig. 2 - 4 As shown, the gas sensor 100 has a pressure equalization opening 11 in a top surface O.

[0087] Furthermore preferably and as in Fig. 4 As shown, the gas sensor 100 has a protective electrode 90, wherein the protective electrode 90 is arranged between the pressure equalization opening 11 and the measuring electrode 30.

[0088] Preferably, the pressure equalization opening 11 and the gas inlet 12 are, as in Fig. 4 shown as being present on opposite sides, i.e. arranged on the top 11 and bottom U of the housing 10.

[0089] Preferably and as in Fig. 4 As shown, the counter electrode 60 and / or the protective electrode 90 is arranged on a further hydrophilic membrane 70, which has a further membrane arm 71, wherein the further membrane arm 71 and the membrane arm 51 are as shown in Fig. 3 und 4 Visible, preferably overlapping.

[0090] The further hydrophilic membrane 70 with the further membrane arm 71 is in Fig. 5a as well as with the counter electrode 60 arranged thereon in Fig. 5b The hydrophilic membrane 70 can correspond to a partition wall interior, for example, having an essentially circular further membrane body 72, from which the further membrane arm 71 extends.

[0091] As in Fig. 4 As can be seen, the reference electrode 40 can be located between membrane arm 51 and the further membrane arm 71.

[0092] As in Fig. 4 As can be seen, the further hydrophilic membrane 70 can be arranged between the counter electrode 60 and the pressure equalization opening 11, with the measuring electrode 30 being arranged between hydrophilic membrane 50 and gas inlet 12.

[0093] As in Fig. 4 As can be seen, the further hydrophilic membrane 70 can be arranged between the protective electrode 90 and the pressure equalization opening 11, with the measuring electrode 30 being arranged between hydrophilic membrane 50 and gas inlet 12.

[0094] In the illustrated embodiments, the hydrophilic membrane 50 and / or the further hydrophilic membrane 70 comprises a fiber material, in particular a nonwoven fabric.

[0095] Preferably, the gas sensor 100 has, as in Fig. 4 shown, in its underside U the gas inlet 12, wherein the gas sensor 100 has an electrolyte-tight membrane 80 which is arranged between the measuring electrode 30 and the gas inlet 12.

[0096] Preferably, the electrolyte-tight membrane 80 in the illustrated example has a thickness of no more than 10 µm.

[0097] The gas sensor 100 can, as described in Fig. 8 As shown, the base part 15 has receiving openings 18 for contact pins 19 in an edge region, so that the gas sensor 100 can be integrated into a measuring system by means of the contact pins 19. The contact pins 19 can be made in contact with the measuring electrode 30, reference electrode 40 and counter electrode 60 as well as protective electrode 90, if present, by means of metal wires (not shown).

[0098] In this case, it is preferred that one or more, preferably all, metal wires for contacting the aforementioned electrodes are not guided through the recess 21 into the housing interior I, but rather through one or more notches in the partition wall located separately from the recess 21. Particularly in the case where the housing is designed in two parts and the partition wall is arranged to be flush with a housing upper part, this method allows the metal wire(s) to be guided through the one or more notches into the housing interior I without reducing the gas seal between the membrane arm 51 and the recess 21.

[0099] The gas sensor 100 can have additional electrodes. For example, the gas sensor 100 can have an additional measuring electrode at which another target gas can be measured.

[0100] All features disclosed herein may be combined in any way, provided that this is not contradictory or does not concern alternatives. Bezugszeichenliste

[0101] 10 Housing 11 Pressure equalization opening 12 Gas inlet 13 Hold-down device 13a, 13b Hold-down element 14 Cover element 15 Base element 16 Additional hold-down device 17 Base surface 18 Receiving opening 19 Contact pin 20Partition 21, 21a, 21b, 21cRecess 22, 22a, 22b, 22cContact surface 30 measuring electrode 40 Reference electrode 50 hydrophilic membrane 50' additional hydrophilic membrane 51, 51a, 51b, 51c membrane arm 52 membrane body 53 electrolyte 60 Counter electrode 70 additional hydrophilic membrane 71 additional membrane arm 72 additional membrane body 80 electrolyte-dense membrane 90 Protective electrode 100 Gas sensor AGehausenausbereich HHenrichtung IGehauseninnenbereich OOberseite TTransversale Richtung UUnterseite

Claims

1. Electrochemical gas sensor (100), comprising: - a housing (10) which is divided into an inner housing region (I) and an outer housing region (A) in the transverse direction (T) by a partition (20) which extends in a vertical direction (H) of the housing (10), - a measuring electrode (30), - a counter electrode (60), - a reference electrode (40), and - a hydrophilic membrane (50), wherein the measuring electrode (30) and the hydrophilic membrane (50) are arranged in the inner housing region (I), wherein the hydrophilic membrane (50) has a membrane arm (51) for receiving the reference electrode (40), and wherein the membrane arm (51) projects from the inner housing region (I) into the outer housing region (A) so that the reference electrode (40) is arranged in the outer housing region (A), wherein the measuring electrode (30), the hydrophilic membrane (50) and the counter electrode (60) are arranged in a stacked arrangement in the inner housing region (I), wherein the partition (20) has a recess (21), wherein the recess (21) is designed to be in gas-tight contact with the membrane arm (51), and further comprising a hold-down device (13), wherein the hold-down device (13) is designed to hold the membrane arm (51) in gas-tight contact with the recess (21).

2. Electrochemical gas sensor (100) according to claim 1, wherein the gas sensor (100) has a pressure equalization opening (11) in a top surface (O), wherein the gas sensor (100) has a protective electrode (90), and wherein the protective electrode (90) is arranged between the pressure equalization opening (11) and the measuring electrode (30).

3. Electrochemical gas sensor (100) according to any of the preceding claims, wherein the counter electrode (60) and / or the protective electrode (90), if present, is arranged on a further hydrophilic membrane (70) which has a further membrane arm (71), wherein the further membrane arm (71) and the membrane arm (51) overlap.

4. Electrochemical gas sensor (100) according to any of the preceding claims, wherein the hydrophilic membrane (50) and / or the further hydrophilic membrane (70) comprises a fibrous material, in particular a nonwoven fabric.

5. Electrochemical gas sensor (100) according to any of the preceding claims, wherein the hydrophilic membrane (50) has a plurality of membrane arms (51a, 51b, 51c), wherein each of the plurality of membrane arms (51a, 51b, 51c) projects from the inner housing region (I) into the outer housing region (A).

6. Electrochemical gas sensor (100) according to any of the preceding claims, wherein the reference electrode (40) is formed integrally with the membrane arm (51).

7. Electrochemical gas sensor (100) according to any of the preceding claims, wherein the gas sensor (100) has a gas inlet (12) in a bottom surface (U), wherein the gas sensor (100) has an electrolyte-impermeable, in particular hydrophobic, membrane (80) which is arranged between the measuring electrode (30) and the gas inlet (12).

8. Electrochemical gas sensor (100) according to claim 7, wherein the electrolyte-impermeable membrane (80) has a thickness of no more than 10 µm.