Sensor device and method for detecting properties of a medium

Abstract

Sensor device for detecting properties of a medium with - an interior space (52) delimited by a wall (50), - an open measuring capacitor (10a, 10b) arranged in the interior (52) and - at least one coupling capacitor (40a, 40b) having two coupling capacitor surfaces (46a, 46b, 48a, 48b), wherein at least a part of the wall (50a) is arranged between an inner coupling capacitor surface (46a, 46b) and an outer coupling capacitor surface (48a, 48b), wherein the inner coupling capacitor surface (46a, 46b) is connected to the measuring capacitor (10a, 10b), characterized in that - the measuring capacitor (10a, 10b) comprises a capacitor comb (20a, 20b), wherein the capacitor comb (20a, 20b) has a rear wall (22a, 22b) and at least two capacitor comb surfaces (24a, 24b) attached at an angle to the rear wall (22a, 22b) and parallel to one another, wherein the rear wall (22a, 22b) of the capacitor comb (20a, 20b) is the inner coupling capacitor surface (46a, 46b).

Description

[0001] The invention relates to a sensor device and a method for detecting properties of a medium.

[0002] Sensor devices and methods for detecting media properties are used in various technical fields to investigate the composition of the medium. Of particular interest is the measurement of contaminants such as unwanted particles or liquids in the medium. For example, it is known to measure capacitance changes in a capacitor resulting from a change in the dielectric properties of the medium caused by contaminants. Particularly when measuring low-viscosity media, special attention must be paid to the sealing of the test chamber of the sensor device. This can lead to sealing problems in the case of wired connections.

[0003] US 4,344,293 A describes a device containing a measuring capacitor mounted in a refrigerant channel, the capacitance of which changes depending on a change in the dielectric properties of the refrigerant. The measuring capacitor is connected to electrodes inserted through two holes in the refrigerant channel.

[0004] US 10 433 666 B1 teaches a smart beverage container for monitoring a user's fluid intake. The container has at least one sensor for detecting the amount of fluid in the container.

[0005] US 2016 / 0 298 996 A1 discloses a system and method for measuring the flow head and velocity and other properties of water, drilling mud, or other fluids flowing through a pipe. The system comprises at least one, and preferably a plurality of, capacitive pads connected to a data acquisition system capable of measuring the capacitance of each pad. These capacitive pads can be arranged radially around the inner diameter of a pipe or on a probe inserted vertically into the pipe. Pads submerged below the fluid level in the pipe have a greater capacitance due to their proximity to a highly dielectric fluid such as water or drilling mud.

[0006] It can be considered an object of the invention to provide a sensor device and a method that enables a good sealing of the test space in the measurement area and enables a simple transmission of signals from a closed test area.

[0007] The object is achieved by a sensor device according to claim 1 and a method according to claim 12. Dependent claims relate to advantageous embodiments of the invention.

[0008] The sensor device according to the invention for detecting properties of a medium has an interior space, a measuring capacitor and at least one coupling capacitor.

[0009] According to the invention, the interior space is defined by a wall. The wall can ensure that the interior space is sealed. Thus, the medium located in the interior space can be hermetically sealed off by the wall. Depending on the application, the wall can, for example, define the interior space in the shape of a cylinder or cuboid. The wall can, for example, be made of an electrically insulating material such as plastic or ceramic. Particularly preferably, the wall can make the interior pressure-resistant.

[0010] According to the invention, the measuring capacitor is arranged in the interior space. It is advantageous to adapt the measuring capacitor to the size of the interior space in order to capture the largest possible proportion of the medium present in the interior space with the measuring capacitor. The measuring capacitor can preferably be arranged in the interior space such that the measuring capacitor extends over the majority of the cross-section of the interior space. In this case, multiple measuring capacitors can also be arranged in the interior space.

[0011] According to the invention, the measuring capacitor is open. This means that the measuring capacitor can have an open connection to the interior. The measuring capacitor can be designed to be open in such a way that the medium can penetrate from the interior into the measuring capacitor and is thus at least partially located within the measuring capacitor. Particularly preferably, the measuring capacitor can be completely filled with the medium. Consequently, the medium can be considered a dielectric in the measuring capacitor. The medium can be stationary in the measuring capacitor or flow through the measuring capacitor.

[0012] According to the invention, the coupling capacitor has at least two coupling capacitor surfaces, comprising an inner and an outer coupling capacitor surface. The inner capacitor surface can be arranged on the wall in the interior space, while the outer coupling capacitor surface can be arranged on the side opposite the inner capacitor surface, outside the interior space, on or in the wall.

[0013] Depending on the wall geometry, the coupling capacitor can be adapted to the wall. If the wall is cuboid-shaped, it may be advantageous to arrange planar, congruent outer and inner coupling capacitor surfaces opposite one another on the wall. In the case of curved walls, such as a cylindrical interior, the outer coupling capacitor surface and the inner coupling capacitor surface can be curved. Particularly preferably, the coupling capacitor surfaces can extend over as large a surface area of ​​the wall as possible in order to maximize the capacitance of the coupling capacitor.

[0014] Furthermore, according to the invention, at least part of the wall is arranged between the inner coupling capacitor surface and the outer coupling capacitor surface. Sealing can thus also be ensured in the area of ​​the coupling capacitor by means of a continuous, uninterrupted wall. It may be advantageous to keep the thickness of the wall at the location of the coupling capacitor surfaces, and consequently the distance between the coupling capacitor surfaces, small in order to keep the capacitance as high as possible and the impedance as low as possible. Particularly preferably, the thickness of the wall can be formed such that the wall at the location of the coupling capacitor is pressure-resistant and has sufficient mechanical stability.

[0015] According to the invention, the inner coupling capacitor surface is electrically connected to the measuring capacitor. The measuring capacitor can be connected to the inner coupling capacitor surface, for example, with a conductor. Thus, the measuring capacitor and the coupling capacitor can form a series circuit.

[0016] A second conductor can also be connected to the measuring capacitor to close the circuit and thus measure the change in capacitance. For example, the second conductor can be routed through the wall. Particularly preferably, the second conductor can be connected to a second coupling capacitor to maintain the hermetic seal of the wall.

[0017] The capacitance of the measuring capacitor can therefore be measured from outside the interior. According to the invention, at least one connection from the interior to the outer coupling capacitor surface is wireless.

[0018] The sensor device according to the invention thus enables both a good seal of the interior space by the wall and a simple, wireless coupling of the measuring capacitor from the interior space via the coupling capacitor. Within the scope of this invention, properties of the medium can be measured without any sealing problems.

[0019] Furthermore, the invention relates to a method for detecting properties of a medium using the sensor device according to claim 1, wherein the medium is located in the interior space defined by the wall with the open measuring capacitor, and a capacitance is detected on the coupling capacitor having two coupling capacitor surfaces, wherein at least a portion of the wall is arranged between the inner coupling capacitor surface and the outer coupling capacitor surface, and the inner coupling capacitor surface is connected to the measuring capacitor. The detected capacitance can allow conclusions to be drawn about properties of the medium. With the aid of the sensor device, even small amounts of contaminants in the medium can be measured. In particular, when detecting a liquid in another liquid, such as water in oil, even small amounts of contamination can be measured.

[0020] According to a preferred embodiment of the invention, at least one coupling capacitor surface can be at least partially embedded in the wall. Embedding at least one coupling capacitor surface can be understood to mean that at least one coupling capacitor surface is partially located in the wall. Particularly preferably, the coupling capacitor surfaces can be aligned parallel to the wall such that a large portion of the coupling capacitor surface is located in the wall. This structure can be achieved by overmolding the coupling capacitor surface. During overmolding, liquid plastic, for example, can be used to create a mechanical connection between the wall and the coupling capacitor surface. Consequently, the fastening of the coupling capacitor surface in the wall and the stability of the wall can be ensured.Furthermore, reducing the distance between the coupling capacitor surfaces may be useful to increase the capacitance of the coupling capacitor.

[0021] According to an advantageous embodiment of the invention, at least one coupling capacitor surface can be completely embedded in the wall to minimize the distance between the coupling capacitor surfaces. This can be understood as meaning that the wall completely encloses the coupling capacitor surface. This embodiment of the invention can also be achieved by overmolding the coupling capacitor surface. In this embodiment, the highest capacitance of the coupling capacitor can be achieved.

[0022] According to the invention, the measuring capacitor comprises a capacitor comb, wherein the capacitor comb has a rear wall and at least two capacitor comb surfaces arranged parallel to each other at an angle to the rear wall. By forming capacitor comb surfaces, the area of ​​the measuring capacitor can be enlarged to further increase the capacitance of the measuring capacitor.

[0023] The backplane can serve as both an electrical and a mechanical connection between the capacitor comb surfaces. The capacitor comb can, for example, be formed in one piece from a bent sheet metal part or a continuous casting.

[0024] Particularly preferably, the rear wall can have the same length as the capacitor comb surfaces. "Same length" here means that the dimensions in the area of ​​the contact surfaces are the same. The capacitor comb surfaces can be arranged on one or more sides of the rear wall. The capacitor comb surfaces are attached to the rear wall at an angle and parallel to one another. Particularly preferably, the capacitor comb surfaces can be arranged at a right angle to the rear wall. This configuration can also enable a simple, parallel alignment of the capacitor comb surfaces to one another.

[0025] According to the invention, the rear wall of the capacitor comb forms the inner coupling capacitor surface. This allows for the most compact design possible, as additional components are eliminated.

[0026] In a further preferred embodiment of the invention, the rear wall can be partially embedded in the wall to secure the capacitor comb and / or minimize the distance to the outer coupling capacitor surface. Simple attachment can be achieved by overmolding the rear wall into the wall.

[0027] According to an advantageous development of the invention, the measuring capacitor can comprise at least one capacitor comb and at least one counter-capacitor comb, wherein the counter-capacitor comb engages with the capacitor comb. The counter-capacitor comb has at least two capacitor comb surfaces and a rear wall. In this context, engagement can be understood as the at least partial insertion of the counter-capacitor comb into the capacitor comb. In this case, each capacitor comb surface of the counter-capacitor comb can be arranged between two capacitor comb surfaces of the capacitor comb. Alternatively, each capacitor comb surface of the capacitor comb can be inserted between two capacitor comb surfaces of the counter-capacitor comb. Within the meaning of this embodiment of the invention, the counter-capacitor comb can have capacitor comb surfaces that have the same size and / or shape as the capacitor comb.In a preferred embodiment of the invention, the capacitor comb can be arranged closer to the wall in the interior than the counter-capacitor comb.

[0028] According to a preferred embodiment of the invention, two capacitor combs can engage with the counter-capacitor comb. The counter-capacitor comb can couple the two capacitor combs in such a way that a series connection of two partial measuring capacitances is created. In this embodiment of the invention, the counter-capacitor comb preferably has a higher number of capacitor comb surfaces than each of the capacitor combs.

[0029] In a further preferred embodiment of the invention, the two capacitor combs can be arranged side by side. Thus, signals can be coupled in and out on one side of the interior space.

[0030] According to a particularly preferred embodiment of the invention, a measuring device can be arranged on an outer side of the wall, wherein the outer coupling capacitor surface has an electrical connection to the measuring device. The wall can have an outer side facing away from the interior. In this case, it can be advantageous to arrange the measuring device directly on the outer side in order to make the sensor device as compact as possible. In the context of this embodiment of the invention, the measuring device can be an electrical circuit. The measuring device can be designed to perform, process, and evaluate capacitance measurements of the measuring capacitor and / or the coupling capacitor.

[0031] In principle, the outer coupling capacitor surface and the measuring device can be connected, for example, with a conductor of any desired shape. According to a preferred embodiment of the invention, the outer coupling capacitor surface and the connection to the measuring device can be formed as a single piece. In this case, the outer coupling capacitor surface and connection can be stamped, for example, from a single piece of sheet metal. Particularly preferably, the integrally formed coupling capacitor surface and connection can be at least partially embedded in the wall, both to minimize the distance to the inner coupling capacitor surface and to ensure protection against external influences. In this case, the measuring device can be incorporated into the wall by overmolding.

[0032] According to a further development of the invention, the measuring device can additionally include the outer coupling capacitor surface. For example, the measuring device can be formed as an electrical circuit on a circuit carrier, e.g., a printed circuit board. The coupling capacitor surface can then be formed, for example, as a conductor surface on the circuit carrier. This allows the sensor device to be designed particularly compactly, since components are formed multifunctionally.

[0033] In a further preferred embodiment of the invention, the interior space can have two openings, with two measuring capacitors arranged one behind the other in the direction from the first opening to the second opening. The openings can particularly preferably be formed on opposite sides to ensure a flow of the medium through the interior space. To enable the sensor device to represent a safety-relevant system, the measuring capacitors can be designed redundantly. Consequently, two measuring capacitors can be arranged in the interior space such that the medium can flow through both measuring capacitors arranged one behind the other in the flow direction, and the signals from the two measuring capacitors can be balanced.

[0034] According to a preferred embodiment of the invention, at least one coupling capacitor surface can have at least one hole. This embodiment can optimize the flow of a material for overmolding, e.g., plastic, between the coupling capacitor surfaces. This can prevent air bubbles from forming between the coupling capacitor surfaces during overmolding, and can also cause the material to cool through the coupling capacitor surfaces, causing it to harden prematurely. This can consequently lead to sealing problems. Therefore, it can be particularly advantageous to design multiple holes in at least one coupling capacitor surface, as the holes allow the material to be optimally distributed. This embodiment also optimizes mechanical strength.

[0035] Embodiments of the invention are described in more detail below with reference to the drawings. In the drawings: Fig. 1 shows a perspective view of a sensor device, with a housing partially cut away; Fig. 2 the sensor device Fig. 1 in perspective exploded view; Fig. 3 a cross section of the sensor device along a section line AA according to Fig. 1; Fig. 4 shows a schematic circuit diagram of the sensor device.

[0036] Fig. 1 shows, by way of example, a perspective view of a sensor device 1 with a wall 50 spanning and delimiting an interior space 52, two measuring capacitors 10a, 10b each with two coupling capacitors 40a, 40b, and a measuring device 44.

[0037] The interior space 52 is provided for receiving a medium that flows in through a first opening 54 in the wall 50, flows through the interior space 52, and flows out through a second opening 56 in the wall 50. The first opening 54 and the second opening 56 are formed opposite one another in the flow direction FR. The wall 50 is formed in a cuboid shape from plastic.

[0038] In the interior space 52, two measuring capacitors 10a, 10b, wherein the measuring capacitors 10a, 10b are identical in construction, are arranged one behind the other in the flow direction FR and are open to the interior space 52, so that as much of the medium as possible flows through the two measuring capacitors 10a, 10b. Each of the measuring capacitors 10a, 10b consists of two capacitor combs 20a, 20b, which are coupled by a counter-capacitor comb 30. The measuring capacitors 10a, 10b comprise two partial measuring capacitors.

[0039] Due to the open design of the measuring capacitors 10a, 10b, the medium located in the interior 52 flows into the interior of the measuring capacitors 10a, 10b and thereby forms the dielectric of the measuring capacitors 10a, 10b. The capacitance values ​​of the measuring capacitors 10a, 10b depend on the properties of the medium, in particular on impurities in the medium. The medium can be, for example, oil, which may contain unknown amounts of water in the form of individual droplets as a contaminant. The sensor device 1 serves to measure any water content. Since the permittivity of oil is considerably lower than the permittivity of water, water contamination leads to an increase in the capacitance value of the measuring capacitors 10. Likewise, other components in the medium that have dielectric properties that differ from the pure medium can lead to a detectable change.

[0040] The exploded view in Fig. 2 provides a detailed view of the interior 52 of the sensor device 1. The capacitor combs 20a, 20b of each measuring capacitor 10a, 10b are arranged next to one another on the wall 50. Each capacitor comb 20a, 20b has a rear wall 22a, 22b and four capacitor comb surfaces 24a, 24b arranged at a right angle to the rear wall 22a, 22b. The rear walls 22a, 22b of the capacitor combs 20a, 20b form both a mechanical and an electrical connection between the capacitor comb surfaces 24a, 24b. The rear walls 22a, 22b and capacitor comb surfaces 24a, 24b have the same length in the region of the contact surfaces. The condenser comb surfaces 24a, 24b are also formed congruently and arranged parallel and equidistant. The distance between the condenser comb surfaces 24a, 24b is selected such that the medium can flow through as unhindered as possible.

[0041] In Fig. Figure 3 shows the interior in the assembled state based on a cross-section of the sensor device 1. The counter-capacitor comb 30 engages with the two capacitor combs 20a, 20b. The counter-capacitor comb 30 also has a rear wall 32 and seven capacitor comb surfaces 34. The rear wall 32 of the counter-capacitor comb 30 serves as both a mechanical and electrical connection for the capacitor comb surfaces 34. Of the seven capacitor comb surfaces 34, three capacitor comb surfaces 34 each engage with the capacitor comb surfaces 24a, 24b of the capacitor combs 20a, 20b. Here, one partial measuring capacitor comprises the capacitor comb 20a and the lower half of the counter capacitor comb 30 and the second partial measuring capacitor comprises the capacitor comb 20b and the upper half of the counter capacitor comb 30. The counter capacitor comb 30 is fastened in the interior 52 (not shown here).

[0042] Here, the coupling capacitors 40a, 40b are arranged on the wall 50 such that a continuous portion of the wall 50a is arranged between the rear walls 22a, 22b and the outer coupling capacitor surfaces 48a, 48b. The rear walls 22a, 22b and the outer coupling capacitor surfaces 48a, 48b are arranged congruently and opposite one another on the wall 50. The outer coupling capacitor surfaces 48a, 48b are completely inserted into the wall 50 and each have a hole 49 for optimal overmolding (see FIG. Fig. 1 and Fig. 2). Using the coupling capacitors 40a, 40b, wireless coupling through the wall 50 is possible. The tightness of the wall 50 remains intact, as holes for cables, for example, are eliminated. Furthermore, the outer coupling capacitor surface 48 is formed integrally with a connection 42, which connects the outer coupling capacitor surface 48 to the measuring device 44 (see FIG. Fig. 2). The measuring device 44 is arranged on an outer side of the wall 50. The outer side here refers to the side of the wall 50 opposite the interior space 52.

[0043] In Fig.Figure 4 shows a schematic representation of a circuit diagram of the sensor device 1, which explains the basic electrical structure. The coupling capacitors 40a, 40b, together with the measuring capacitor 10a, form a series circuit, wherein the measuring capacitors 10a, 10b are in turn formed by a series connection of the partial measuring capacitors. The capacitance of the coupling capacitors 40a, 40b is constant. Since the medium is designed as the dielectric of the measuring capacitors 10a, 10b, the capacitance of the measuring capacitors 10a, 10b changes due to impurities depending on the dielectric properties of the medium. Thus, the capacitance of the series circuit is measured using the measuring device 44, and contamination of the medium is determined based on the measured values. The redundant design of the measuring capacitors 10a, 10b enables redundant measurements to design a safety-relevant system.

[0044] It should also be noted that the capacitance values ​​of the measuring capacitor 10 are temperature-dependent. Therefore, a temperature sensor (not shown here) is preferably arranged in the interior space 52, the measurement signal of which is also fed to the measuring device 44. The measuring device 44 is designed to correct the measurement signal by a previously calculated or experimentally determined compensation curve depending on the temperature signal.

[0045] It should also be noted that the invention is not limited to the described embodiments and variants; further embodiments are possible. For example, instead of two measuring capacitors, only one measuring capacitor or a different number of capacitor combs with a different number of capacitor comb surfaces can be provided. For example, the coupling can be provided on opposite sides. In this case, the coupling capacitor surfaces can be arranged on the wall without being embedded. In general, the features of the embodiments and the claims can be combined as desired.

Claims

[1] Sensor device for detecting properties of a medium with - an interior space (52) delimited by a wall (50), - an open measuring capacitor (10a, 10b) arranged in the interior (52) and - at least one coupling capacitor (40a, 40b) having two coupling capacitor surfaces (46a, 46b, 48a, 48b), wherein at least a part of the wall (50a) is arranged between an inner coupling capacitor surface (46a, 46b) and an outer coupling capacitor surface (48a, 48b), wherein the inner coupling capacitor surface (46a, 46b) is connected to the measuring capacitor (10a, 10b), characterized by , that - the measuring capacitor (10a, 10b) comprises a capacitor comb (20a, 20b), wherein the capacitor comb (20a, 20b) has a rear wall (22a, 22b) and at least two capacitor comb surfaces (24a, 24b) attached at an angle to the rear wall (22a, 22b) and parallel to one another, wherein the rear wall (22a, 22b) of the capacitor comb (20a, 20b) is the inner coupling capacitor surface (46a, 46b). [2] Sensor device according to claim 1, characterized by that at least one coupling capacitor surface (46a, 46b, 48a, 48b) is at least partially embedded in the wall (50). [3] Sensor device according to claim 1 or 2, characterized by that at least one coupling capacitor surface (46a, 46b, 48a, 48b) is completely embedded in the wall (50). [4] Sensor device according to one of the preceding claims, characterized by that the rear wall (22a, 22b) is partially embedded in the wall (50). [5] Sensor device according to one of the preceding claims, characterized by that the measuring capacitor (10a, 10b) comprises at least one capacitor comb (20a, 20b) and at least one counter-capacitor comb (30a, 30b), wherein the counter-capacitor comb (30a, 30b) engages in the capacitor comb (20a, 20b). [6] Sensor device according to claim 5, characterized by that two capacitor combs (20a, 20b) are in engagement with the counter capacitor comb (30a, 30b). [7] Sensor device according to claim 6, characterized by that the two capacitor combs (20a, 20b) are arranged next to each other. [8] Sensor device according to one of the preceding claims, characterized by that a measuring device (44) is arranged on an outer side of the wall (50), wherein the outer coupling capacitor surface (48a, 48b) has an electrical connection (42) to the measuring device (44). [9] Sensor device according to claim 8, characterized bythat the outer coupling capacitor surface (48a, 48b) and the connection (42) to the measuring device (44) are formed in one piece. [10] Sensor device according to one of the preceding claims, characterized by that the interior (52) has two openings (54, 56), wherein two measuring capacitors (10a, 10b) are arranged one behind the other in the direction from the first opening (54) to the second opening (56). [11] Sensor device according to one of the preceding claims, characterized by that at least one coupling capacitor surface (48a, 48b) has at least one hole (49). [12] Method for detecting properties of a medium with the sensor device according to claim 1, in which - the medium is located in the interior space (52) delimited by the wall (50) with the open measuring capacitor (10a, 10b) and - a capacitance is detected on the coupling capacitor (40a, 40b) having two coupling capacitor surfaces (46a, 46b, 48a, 48b), wherein at least a part of the wall (50a) is arranged between the inner coupling capacitor surface (46a, 46b) and the outer coupling capacitor surface (48a, 48b) and the inner coupling capacitor surface (46a, 46b) is connected to the measuring capacitor (10a, 10b).

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