Sensor device

Abstract

A sensor device (100) measures an electric conductivity and / or impedance of a fluid in a measurement chamber (160) made of a non-conducting material. Measurement electrode pairs (110, 120) are arranged in the measurement chamber (160) to make electrical contact with the fluid in the measurement chamber (160). A processing unit supplies a probing signal to the measurement electrode pairs (110, 120) and determines the conductivity and / or impedance of the fluid in the measurement chamber (160) based on at least one resulting signal obtained via the measurement electrode pairs (110, 120). A printed circuit board (150) has respective conductive traces that connect each electrode in the measurement electrode pairs (110, 120) electrically with the proces-sing unit. Specifically, a respective deformable element (231) is arranged to connect each of the electrodes electrically with the respective conductive trace. The respective deformable element (231) is configured to be compressed by a respective connector member of the respective electrode (111) when assembled in a housing of the sensor device (100).

Description

[0001] Sensor Device

[0002] TECHNICAL FIELD

[0003] The present invention relates generally to the measurement of the electric conductivity and / or impedance of fluids. Such measurements, may for example be useful to determine the presence of liquid, study milk flow patterns and / or to establish a milk flow rate. Especially, the invention relates to a sensor device according to the preamble of claim 1 .

[0004] BACKGROUND

[0005] There are many areas of use for fluid sensor devices, which are based on conductivity and / or impedance measurements. For instance, such sensor devices may be employed in milking installations to perform various kinds of measurements. Due to fluctuations in a milk-to-air ratio in a fluid containing both milk and air, it is typically challenging to determine an accurate milk flow rate of such a fluid. Inter alia, to tackle this problem, different types of sensor equipment have been developed.

[0006] US 11 ,903,362 discloses a milk measuring cell that has an inlet channel and an outlet, a cavity, a barrier which protrudes from a bottom of the cavity and divides the cavity into a measurement trough on the side of the inlet channel and an outlet channel on the side of the outlet. A peak of the barrier is positioned below an elevation of the inlet channel.

[0007] EP 733 884 shows a quantity meter for determining the quantity of liquid flowing through a line. The quantity meter is provided with at least two electrically conducting elements arranged in the line at some distance from each other, and in communication with an electronic circuit. In this electronic circuit, on the basis of the electric conductivity of the liquid measured by the electronic circuit, the length of the interval of time during which this conduc- tivity is measured, the distance between the electrically conducting elements in the line, the rate of flow of the liquid and the specific electric resistance, there is determined the quantity of liquid flowed through.

[0008] US 10,598,528 reveals electrodes, a reference device, and a processor. The processor determines a speed of a fluid traveling between the first and second pairs of electrodes and determines a reference conductance of the fluid using the reference device. The processor also determines a measured conductance of the fluid using at least one of the first and second pairs of electrodes and determines, based on the reference conductance and the measured conductance, a cross-sectional area of the fluid at an electrode. The processor further adds a correction factor to the determined speed to produce a bulk speed of the fluid. The processor further determines a volumetric flow rate of the fluid based on the bulk speed and the determined area and determines a volume of the fluid based on the determined volumetric flow rate.

[0009] US 9,470,565 describes a device for determining a mass flow rate of a fluid in a conduit, for instance a milk flow through a tube. The device includes a measuring member for determining an electrical conductivity of the fluid; an additional measuring member for determining the electrical conductivity of the fluid at an additional position; and a processing unit for determining the mass flow rate of the fluid in the conduit on the basis of the determinations, wherein the specific resistance can be determined per cross-sectional area in the flow.

[0010] Although the known sensor devices may be capable of determining relatively accurate fluid flow rates, their designs leave room for improvement. For example, the sensor devices must be capable of withstanding harsh conditions in terms of humidity and temperature variations. This, in turn, translates into high material and / or production costs. SUMMARY

[0011] The object of the present invention is to offer a solution that mitigates the above problems and enables cost-effective production of accurate and sturdy fluid sensor devices.

[0012] According to the invention, the object is achieved by a sensor device for measuring an electric conductivity and / or impedance of a fluid in a measurement chamber of a non-conducting material. The sensor device contains at least one measurement electrode pair, a processing unit and a printed circuit board (PCB). The at least one measurement electrode pair is arranged in the measurement chamber. Each of at least one measurement electrode pair includes respective first and second electrodes, which each is positioned to make electrical contact with the fluid in the measurement chamber. The processing unit is configured to: supply a probing signal to the at least one measurement electrode pair, obtain at least one resulting signal from the at least one measurement electrode pair, and based thereon, determine the conductivity and / or impedance of the fluid in the measurement chamber. The PCB has respective conductive traces that connect each of the first and second electrodes electrically with the processing unit. In particular, a respective deformable element connects each of said first and second electrodes electrically with the respective conductive trace. Here, the respective deformable element is configured to be deformed by a respective connector member of the respective electrode when assembled in a housing of the sensor device. For example, the respective deformable element may be configured to be deformed elastically and / or plastically in at least one direction relative to a plane represented by the PCB.

[0013] This sensor device is advantageous because the deformable elements make it straightforward to install the electrodes and attain a reliable electric contact between the electrodes and the conductive traces of the PCB without soldering. Further, the deformable elements are capable of accommodating for dimensional variations in the measurement chamber and / or the electrodes resulting from temperature variations in the fluid being passed through the measurement chamber and / or in the environment surrounding the sensor device. Actually, according to the invention, such relative movements between the electrodes and the PCB are welcome, since these movements reduce the risk for the build-up of corrosion on the contact surfaces between the electrodes and the PCB that may be caused by humidity.

[0014] According to one embodiment of the invention, the first and second electrodes in each of the at least one measurement electrode pair are separated from one another along an extension of the measurement chamber by a first distance, and each of the first and second electrodes is positioned to enable electrical contact with the fluid in the measurement chamber along an entire circumference of an inner surface of the measurement chamber. The fact that the electrodes are able to pass electric current through the fluid at all levels of filling in the measurement chamber make it is possible to measure the electric conductivity and / or impedance of the fluid also if the fluid shows very large variations in the relative proportions of the components included in the fluid.

[0015] Preferably, each of the first and second electrodes in each of the at least one measurement electrode pair is arranged in the measurement chamber such that the electrode surrounds a cross section of the measurement chamber, and each electrode of the first and second electrodes in each of the at least one measurement electrode pair is arranged such that the electrode and an internal surface of the measurement chamber constitute together one body with an uninterrupted and smooth surface. Namely, this causes no disturbance of the fluid flow while ensuring electrical contact with the fluid regardless of how the different components in the fluid are distributed in the measurement chamber.

[0016] According to one embodiment of the invention, the cross section of the measurement chamber has an annular shape. Consequent- ly, the respective inner surfaces of the first and second electrodes likewise have annular shapes. Typically, this is advantageous for hydrodynamic reasons, for example with respect to the flow resistance experienced by the fluid when passing through the measurement chamber.

[0017] According to another embodiment of the invention, the sensor device contains a reference electrode pair, which is arranged in the measurement chamber. The reference electrode pair includes a first reference electrode and a second reference electrode. Each of the first and second reference electrodes is positioned in the measurement chamber to make electrical contact with the fluid in the measurement chamber.

[0018] According to one embodiment of the invention, each of the first and second reference electrodes contains a respective contact surface that is arranged to make the electrical contact with the fluid in the measurement chamber, where each respective contact surface extends along less than an entire circumference of an inner surface of the measurement chamber. Namely, it is normally sufficient if the first and second reference electrodes make electrical contact with the fluid at respective points in the measurement chamber, which respective points are located along a line therein that is covered by the fluid at any degree of filling of the measurement chamber, e.g. a respective lowest point of the cross-section where each of the first and second reference electrodes respectively is arranged.

[0019] According to yet another embodiment of the invention, the PCB further contains respective conductive traces that connect each of the first and second reference electrodes electrically with the processing unit. Further, analogous to the above, a respective deformable element connects each of the first and second reference electrodes electrically with said respective conductive trace, where the respective deformable element is configured to be compressed by a respective connector member of the respective electrode when assembled in the housing of the sensor device. Thus, it is straightforward also to install the reference electrodes and attain a reliable electric contact between the reference electrodes and the conductive traces of the PCB without soldering.

[0020] Further, the deformable elements are capable of accommodating for any temperature-related dimensional variations in the measurement chamber and / or the reference electrodes.

[0021] According to still another embodiment of the invention, the respective contact surface coincides with an inner surface of the measurement chamber without protruding from said inner surface at any point of the respective contact surface. For the same reasons as above, this is advantageous for hydrodynamic reasons.

[0022] According to a further embodiment of the invention, the sensor device includes a shielding member that is arranged between the measurement chamber and the PCB. The shielding member surrounds a contact interface comprising the connector member of at least one of the first and second electrodes and the respective deformable element that connects said connector member electrically with the conductive trace of the PCB. The shielding member provides a tight sealed space around the contact interface, which tight sealed space is delimited by the shielding member and the PCB. This protects the contact interface both mechanically and chemically.

[0023] According to one embodiment of the invention, the tight sealed space contains a non-conductive fluid that covers the connector member and the respective deformable element. Thereby, the contact interface is further protected, such that for example the shortcut risk is substantially reduced. Preferably, the non-con- ductive fluid is hydrophobic, and it may have a viscosity in the range 4 to 10 mm2 / s.

[0024] According to another embodiment of the invention, the sensor device contains first and second measurement electrode pairs that each comprises respective first and second electrodes. The second measurement electrode pair is here separated from the first measurement electrode pair along an extension of the measurement chamber by a second distance. Thereby, it is possible to establish accurate flow-rate values of a fluid that is transported through the measurement chamber also if the fluid shows large and rapid variations in the relative proportions of the components included in the fluid. In short, the processing unit may be configured to determine the flow rate of the fluid passing through the measurement chamber by correlating a first filling-degree value at the first measurement electrode pair with a second filling-degree value at the second measurement electrode pair. The filling degree values, in turn, are derived based on electric conductivity and / or impedance measurements for which the reference electrodes provide a basis. As a result, for example the flow rate of a fluid containing a mixture of milk and air may be determined at high accuracy.

[0025] Preferably, the above contact interface includes the connector members of the respective first and second electrodes of the first and second measurement electrode pairs and the respective deformable elements that connect each of said electrodes electrically with the respective conductive trace of the printed circuit board. This namely reduces the overall material and manufacturing costs.

[0026] According to yet another embodiment of the invention, the shielding member includes a flexible skirt that makes contact with the PCB along an unbroken boundary line around the shielding member. Consequently, the risk is minimized that any undesired objects enter the contact interface.

[0027] According to still another embodiment of the invention, a noncon- ductive potting is arranged in at least one space between the measurement chamber and the PCB. This provides general mechanical and moisture protection for the components of the sensor device. Preferably, therefore, the non-conductive potting fills an entire interior of the housing. According to a further embodiment of the invention, the PCB has a component side that is opposite to a side thereof on which the respective deformable element is arranged. The component side contains at least one electrically controllable light source, e.g. in the form of a light emitting diode (LED) that indicates an operating status of the sensor device. In addition, a transparent or translucent non-conductive potting covers an area of the component side, which area contains said at least one light source. As a result, the at least one light source may be read with a quick glance at the sensor device.

[0028] Further advantages, beneficial features and applications of the present invention will be apparent from the following description and the dependent claims.

[0029] BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The invention is now to be explained more closely by means of preferred embodiments, which are disclosed as examples, and with reference to the attached drawings.

[0031] Figure 1 shows a cross-section side view of a measurement chamber and a sensor device according to one embodiment of the invention;

[0032] Figure 2 shows a cross-section view of the measurement chamber and sensor device in Figure 1 , which cross-section view is shifted 90 degrees relative to the one of Figure 1 ;

[0033] Figures 3a-c show perspective views of a shielding member according to one embodiment of the invention, which shielding member is arranged between the measurement chamber and the PCB;

[0034] Figure 4 shows a measurement electrode according to one embodiment of the invention;

[0035] Figure 5 shows a reference electrode according to one embodiment of the invention; Figure 6 shows a deformable element according to a first embodiment of the invention;

[0036] Figure 7 shows a deformable element according to a second embodiment of the invention; and

[0037] Figures 8a-b show a deformable element according to a third embodiment of the invention.

[0038] DETAILED DESCRIPTION

[0039] Figure 1 shows a cross-section side view of a measurement chamber 160 and a sensor device 100 according to one embodiment of the invention. Figure 2 shows a cross-section view of the measurement chamber 160 and sensor device 100 in Figure 1 , which is shifted 90 degrees relative to the cross-section view shown in Figure 1 .

[0040] The sensor device 100 is adapted for measuring an electric conductivity and / or impedance of a fluid in a measurement chamber 160 of a non-conducting material. The measured electric conductivity and / or impedance of the fluid may, in turn, serve as a basis for determining various parameters of the fluid, e.g. the mere fact that liquid is present in the measurement chamber 160, a flow pattern of the fluid passing through the measurement chamber 160 and / or to establish flow rate of the fluid passing through the measurement chamber 160.

[0041] The sensor device 100 contains at least one measurement electrode pair, exemplified by 110 and 120 respectively in Figure 1 , a PCB 150 and a processing unit 250.

[0042] The measurement electrode pairs 110 and 120 are arranged in the measurement chamber 160. Each of the measurement electrode pairs 110 and 120 includes respective first and second electrodes 111 , 112 and 121 , 122 respectively, which each is positioned to make electrical contact with the fluid in the measurement chamber 160. The processing unit 250 is configured to supply a probing signal to the measurement electrode pairs 110 and 120, obtain a respective resulting signal from each of the measurement electrode pairs 110 and 120, and based thereon, determine the conductivity and / or impedance of the fluid in the measurement chamber 160.

[0043] In short, a single measurement electrode pair is sufficient to determine the conductivity and / or impedance of the fluid in the measurement chamber 160, while at least two measurement electrode pairs are required to draw conclusions about fluid movements through the measurement chamber 160, for instance to establish a flow pattern and / or a flow rate of the fluid.

[0044] The PCB 150 has conductive traces, where a respective conductive trace connects each of the first and second electrodes 111 , 112 and 121 , 122 respectively electrically with the processing unit 250. Figure 4 schematically illustrates one these conductive traces by the reference numeral 451 . Figures 1 and 4 further show a deformable element 231 , e.g. represented by a resilient element as shown in Figures 2 and 6, which deformable element 231 connects a first measurement electrode 111 electrically with the conductive trace 451 . According to the invention, each of the measurement electrodes 112 and 121 , 122 are likewise connected to the processing unit 250 via respective corresponding deformable elements and conductive traces. Each of the deformable elements, such as 231 , is con-figured to be compressed by a respective connector member 211 of the respective electrode 111 when assembled in a housing 200 of the sensor device 100.

[0045] This renders it straightforward to install the reference electrodes and attain a reliable electric contact between the reference electrodes and the conductive traces of the PCB 150 without soldering. Further, the deformable element 231 is capable of accommodating for any temperature-related dimensional variations in the measurement chamber 160 and / or the reference electrodes 111.

[0046] According to one embodiment of the invention, the first and se- cond electrodes 111 , 112 and 121 , 122 respectively in each of the measurement electrode pairs 110 and 120 are separated from one another along an extension of the measurement chamber 160 by a first distance d1. The specific length of the first distance d1 is uncritical. However, preferably, the first distance d1 is approximately in the same order of magnitude as an internal width D the measurement chamber 160, say 0,2D < d1 < 2D. Moreover, each of the first and second electrodes is preferably positioned to enable electrical contact with the fluid in the measurement chamber 160 along an entire circumference of an inner surface of the measurement chamber 160. Figure 4 schematically illustrates this as a contact surface 411 . Thereby, regardless of how a mixture of for example gas and liquid in the fluid is distributed, the contact surface 411 will always be able to make electrical contact with the liquid component of the fluid, so that the processing unit 250 may pass an electric current from a first electrode, say 111 , in one of the measurement electrode pairs, say 110, to a second electrode, say 112, in the same electrode pair 110, and thus measure the electric conductivity and / or impedance of the fluid.

[0047] According to embodiments of the invention, the sensor device 100 contains first and second measurement electrode pairs 110 and 120 respectively that each includes respective first and second electrodes 111 , 112 and 121 , 122 respectively wherein the second measurement electrode pair 120 is separated from the first measurement electrode pair 110 along an extension of the measurement chamber 160 by a second distance d2. The specific length of the second distance d2 is relatively uncritical. However, second distance d2 should have a length that is suitable for an expected range of flow rates of the fluid to be passed through the measurement chamber 160. Namely, as mentioned above, the processing unit 250 may be configured to determine the flow rate of the fluid by correlating a first filling-degree value at the first measurement electrode pair 110 with a second filling-degree value at the second measurement electrode pair 120. For accuracy reasons, the second distance d2 should not be too long, such that the spe- cific distribution of the fluid in the measurement chamber 160 may change significantly when the fluid travels between the first and second measurement electrode pairs 110 and 120. However, the second distance d2 must be sufficient long to allow a first fillingdegree value to be distinguished from a second ditto. The processing unit 250 is further configured to derive the filling-degree values based on electric conductivity and / or impedance measurements. Specifically, to derive the filling-degree values, a reference measurement may be carried out, for example by using a reference electrode pair 171 and 172 as described below. The reference measurement involves measuring the electric conductivity and / or impedance of the liquid component only in the fluid that passes through the measurement chamber 160. The measured value of the electric conductivity and / or impedance of the liquid component alone is equivalent to a value that will be measured by the first and second measurement electrode pairs 110 and 120 respectively if the measurement chamber 160 was completely filled with liquid, i.e. without any air / gas component present at the cross-section in question where the respective electrode pair is located. The filling-degree value may attain a number between 0 and 1 , where 0 reflects that no liquid is present and 1 reflects that the measurement chamber 160 is completely filled with liquid at the crosssection where the measurement electrode pair 110 or 120 respectively is located.

[0048] According to one embodiment of the invention, each of the first and second electrodes 111 , 112 and 121 , 122 respectively in each of the measurement electrode pairs 110 and 120 is arranged in the measurement chamber 160 such that the electrode surrounds a cross section of the measurement chamber 160, for example as illustrated by the electrode 111 in Figure 4. Further, to minimize the electrodes’ influence on the fluid flow through the measurement chamber 160, each electrode of the first and second electrodes 111 , 112 and 121 , 122 respectively in each of the measurement electrode pairs 110 and 120 is preferably arranged such that the electrode and an internal surface of the measurement chamber 160 constitute together one body with an uninterrupted and smooth surface.

[0049] Additionally, for hydrodynamic reasons, the cross section of the measurement chamber 160 preferably has an annular shape. Of course, in order to make the internal surface of the measurement chamber 160 and the electrode form an uninterrupted and smooth surface this also means that the contact surface 411 must have an annular shape and that the dimension thereof must coincide with that of the internal surface of the measurement chamber 160.

[0050] According to one embodiment of the invention, the sensor device 100 contains a reference electrode pair 171 and 172, which is arranged in the measurement chamber 160. For example, the reference electrode pair 171 and 172 may be arranged between the measurement electrode pairs 110 and 120 (as shown in Figure 1 ). However, the reference electrode pair 171 and 172 may equally well be arranged upstream or downstream of both of the measurement electrode pairs 110 and 120, or upstream or downstream of one of them if the sensor device 100 only includes a single measurement electrode pair.

[0051] The reference electrode pair includes a first reference electrode 171 and a second reference electrode 172. Each of the first and second reference electrodes 171 and 172 is positioned in the measurement chamber 160 to make electrical contact with the fluid in the measurement chamber 160.

[0052] Analogous to the above, the PCB 150 has a respective conductive trace that connects each of the first and second reference electrodes 171 and 172 respectively electrically with the processing unit 250. Figure 5 schematically exemplifies one such trace by the reference numeral 452. In further analogy to the above, a respective deformable element, illustrated by reference numeral 182 in Figures 1 and 5, connects each of the first and second reference electrodes 171 and 172 respectively electrically with the respective conductive trace 452. The respective deformable element 182 is configured to be compressed by a respective connector member 272 of the respective electrode 172 when assembled in the housing 200 of the sensor device 100.

[0053] As discussed above, in contrast to the first and second electrodes 111 , 112 and 121 , 122 respectively it is typically sufficient if the first and second reference electrodes 171 and 172 respectively only make electrical contact with the fluid at a respective lowest point of the cross-section of the measurement chamber 160 where the reference electrodes 171 and 172 are located. Namely, at any ratio of liquid and gas in the fluid, it can be expected that said lowest point always makes contact with the liquid component of the fluid such that an electrical current may be passed there through. Therefore, according to one embodiment of the invention, each respective contact surface 572 of the first and second reference electrodes 171 and 172 respectively extends along less than an entire circumference of an inner surface of the measurement chamber 160.

[0054] In any case, for hydrodynamic reasons, the respective contact surface 572 preferably coincides with the inner surface of the measurement chamber 160 without protruding from said inner surface at any point of the respective contact surface 572.

[0055] To provide mechanical protection, reduce the shortcut risk and prevent the ingress of moisture, according to one embodiment of the invention, a non-conductive potting 190 is arranged in at least one space between the measurement chamber 160 and the PCB 150. Preferably, the non-conductive potting 190 fills an entire interior of the housing 200, possibly where a portion of the non- conductive potting 190 is transparent / translucent as described below.

[0056] According to one embodiment of the invention, the PCB 150 has a component side that is opposed to a side thereof on which the respective deformable element 231 is arranged. The component side here contains at least one electrically controllable light sour- ce 155, e.g. in the form of an LED. Furthermore, a transparent or translucent non-conductive potting 191 covers an area of the component side, which area comprises said at least one light source 155. Consequently, light emitted from the electrically controllable light source 155 may be readily observed from outside the housing 200. An operator and / or an external light sensor may thus for example register an operational status of the sensor device 100 based on said emitted light.

[0057] Figure 3a shows a first perspective view of a shielding member 300 according to one embodiment of the invention, which shielding member 300 is arranged between the measurement chamber and the PCB. The shielding member 300 is made of a non-conductive synthetic material, for example an organic polymer such as polyethylene (PVC).

[0058] Figure 3b shows a cross-section perspective view of the shielding member 300 along a section BB in Figure 3a, and Figure 3c shows a cross-section perspective view of the shielding member 300 along a section CC in Figure 3a. Each of Figures 1 , 2, 4 and 5 also shows cross-section views of the shielding member 300.

[0059] According to one embodiment of the invention, the sensor device 100 includes the shielding member 300 that is arranged between the measurement chamber 160 and the PCB 150. The shielding member 300 surrounds a contact interface, which contains the connector member 211 of at least one of the first and second electrodes 111 , 112 and 121 , 122, preferably all of them, and the respective deformable element 231 that connects said connector member 211 electrically with the conductive trace 451 of the PCB 150.

[0060] Figure 3a illustrates one embodiment of the invention, where the shielding member 300 has a set of openings 311 , 312, 321 and 322, which are adapted to pass through a respective connector member 211 of each of the first and second electrodes 111 , 112, 121 and 122 to the respective deformable element 231 on the PCB 150. Additionally, Figure 3a shows openings 371 and 372, which are adapted to pass through a respective connector member 272 of each of the reference electrodes 171 and 172 to the respective deformable element 182 on the PCB 150. The shielding member 300 provides a tight sealed space 400 around the contact interface, which tight sealed space 400 is delimited by the shielding member 300 and the PCB 150.

[0061] To improve the protective capability, the tight sealed space 400 may contain a non-conductive fluid that covers said connector member 211 and the respective deformable element 231. Preferably, the non-conductive fluid fills an entire volume between the shielding member 300 and the PCB 150. It is generally preferable if the non-conductive fluid has a kinematic viscosity in the range 4 to 10 mm2 / s (or cSt). Preferably, the kinematic viscosity of the non-conductive fluid is around 6 mm2 / s. Namely, since this allows for convenient application and retention of the non-conductive fluid in the tight sealed space 400. Additionally, or alternatively, the non-conductive fluid may be hydrophobic, thereby improving the moisture repellence.

[0062] To enhance the mechanical efficiency, the shielding member 300 is preferably provided with a flexible skirt 360 that makes contact with the PCB 150 along an unbroken boundary line around the shielding member 300. An opposite portion 360 of the shielding member 300 that faces the measurement chamber 160 is, however, preferably rigid to provide stability when assembling the electrodes, say 111 , in the housing 200 such that the respective connector member 211 compresses the deformable element 231 on the PCB 150. The opposite portion 360 may contain an edge, or frame 380, which surrounds the shielding member 300. To allow the escape of moisture, the edge / frame 380 may contain one or more openings 381 , preferably directed parallel to the PCB 150.

[0063] Figure 6 shows a deformable element 231 according to a first embodiment of the invention. Here, the deformable element 231 is resilient. This means that the deformable element 231 is configu- red to be deformed elastically in a direction DFo being essentially orthogonal to a plane represented by the PCB 150. The deformable element 231 may thus for example include at least one electrically conductive metal piece being elastically movable in the direction DFo in response to the connector member 211 being pushed towards the PCB 150

[0064] Figure 7 shows a deformable element 731 according to a second embodiment of the invention. Here, the deformable element 731 is configured to be elastically deformed in a direction DFP being essentially parallel to the plane represented by the PCB 150. The deformable element 731 may thus for example include first and second electrically conductive metal pieces each of which is elastically movable in the direction DFo in response to the connector member 211 being inserted between them.

[0065] Figures 8a and 8b show a deformable element 831 according to a third embodiment of the invention. Here, the deformable element 831 is configured to be plastically deformed in at least one direction, for example both the above directions DFo and DFP in relation to the plane represented by the PCB 150. The deformable element 831 may thus for example include a piece of electrically conductive metal, e.g. a rectangular block of bronze, which is softer than the connector member 211 , such that the deformable element 831 collapses / alters its shape in such a manner that it makes contact with at least one side of the connector member 211 when the connector member 211 is pushed P against the deformable element 831 .

[0066] Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

[0067] The term “comprises / comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or components. The term does not preclude the presence or ad- dition of one or more additional elements, features, integers, steps or components or groups thereof. The indefinite article "a" or "an" does not exclude a plurality. In the claims, the word “or” is not to be interpreted as an exclusive or (sometimes referred to as “XOR”). On the contrary, expressions such as “A or B” covers all the cases “A and not B”, “B and not A” and “A and B”, unless otherwise indicated. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advanta- ge. Any reference signs in the claims should not be construed as limiting the scope.

[0068] It is also to be noted that features from the various embodiments described herein may freely be combined, unless it is explicitly stated that such a combination would be unsuitable. The invention is not restricted to the described embodiments in the figures, but may be varied freely within the scope of the claims.

Claims

Claims1 . A sensor device (100) for measuring an electric conductivity and / or impedance of a fluid in a measurement chamber (160) of a non-conducting material, the sensor device (100) comprising: at least one measurement electrode pair (110, 120) arranged in the measurement chamber (160), which at least one measurement electrode pair (110, 120) each comprises respective first and second electrodes (111 , 112; 121 , 122) which each is positioned to make electrical contact with the fluid in the measurement chamber (160), and a processing unit (250) configured to: supply a probing signal to the at least one measurement electrode pair (110, 120), obtain at least one resulting signal from the at least one measurement electrode pair (110, 120), and based thereon determine the conductivity and / or impedance of the fluid in the measurement chamber (160), characterized in that the sensor device (100) comprises a printed circuit board (150) with respective conductive traces (451 ) connecting each of said first and second electrodes (111 , 112; 121 , 122) electrically with the processing unit (250), wherein a respective deformable element (231 , 731 , 831 ) connects each of said first and second electrodes electrically with said respective conductive trace (451 ), which respective deformable element (231 , 731 , 831 ) is configured to be deformed by a respective connector member (211 ) of the respective electrode (111 ) when assembled in a housing (200) of the sensor device (100).

2. The sensor device (100) according to claim 1 , wherein the respective deformable element (231 , 731 , 831 ) is configured to be deformed elastically and / or plastically in at least one direction (DFo, DFP) relative to a plane represented by the printed circuit board (150).

3. The sensor device (100) according to any one of claims 1 or2, wherein: the first and second electrodes (111 , 112; 121 , 122) in each of the at least one measurement electrode pair (110, 120) are separated from one another along an extension of the measurement chamber (160) by a first distance (d 1 ), and each of the first and second electrodes is positioned to enable electrical contact with the fluid in the measurement chamber (160) along an entire circumference (411 ) of an inner surface of the measurement chamber (160).

4. The sensor device (100) according to any one of the preceding claims, wherein: each of the first and second electrodes (111 , 112; 121 , 122) in each of the at least one measurement electrode pair (110, 120) is arranged in the measurement chamber (160) such that the electrode surrounds a cross section of the measurement chamber (160), and each electrode of the first and second electrodes (111 , 112; 121 , 122) in each of the at least one measurement electrode pair (110, 120) is arranged such that the electrode and an internal surface of the measurement chamber (160) constitute together one body with an uninterrupted and smooth surface.

5. The sensor device (100) according to claim 4, wherein the cross-section of the measurement chamber (160) has an annular shape.

6. The sensor device (100) according to any one of the preceding claims, comprising: a reference electrode pair (171 , 172) arranged in the measurement chamber (160), which reference electrode pair comprises a first reference electrode (171 ) and a second reference electrode (172), wherein each of the first and second reference electrodes (171 ; 172) is positioned in the measurement chamber (160) to make electrical contact with the fluid in the measurement chamber (160).

7. The sensor device (100) according to claim 6, wherein the printed circuit board (150) comprises respective conductive traces (452) connecting each of the first and second reference electrodes (171 ; 172) electrically with the processing unit (250), wherein a respective deformable element (182) connects each of the first and second reference electrodes (171 ; 172) electrically with said respective conductive trace (452), which respective deformable element (182) is configured to be compressed by a respective connector member (272) of the respective electrode (172) when assembled in the housing (200) of the sensor device (100).

8. The sensor device (100) according to claim 7, wherein: each of the first and second reference electrodes (171 ; 172) comprises a respective contact surface (572) arranged to make the electrical contact with the fluid in the measurement chamber (160), which each respective contact surface (572) extends along less than an entire circumference of an inner surface of the measurement chamber (160).

9. The sensor device (100) according to claim 8, wherein the respective contact surface (572) coincides with an inner surface of the measurement chamber (160) without protruding from said inner surface at any point of the respective contact surface (572).

10. The sensor device (100) according to any one of the preceding claims, comprising: a shielding member (300) arranged between the measurement chamber (160) and the printed circuit board (150), which shielding member (300) surrounds a contact interface comprising the connector member (211 ) of at least one of the first and second electrodes (111 , 112; 121 , 122) and the respective deformable element (231 , 731 , 831 ) that connects said connector member (211 ) electrically with the conductive trace (451 ) of the printed circuit board (150), which shielding member (300) provides a tight sealed space (400) around the contact interface, which tight sealed space (400) is delimited by the shielding member (300) andthe printed circuit board (150).11 . The sensor device (100) according to claim 10, wherein the tight sealed space (400) comprises a non-conductive fluid that covers said connector member (211 ) and the respective deformable element (231 , 731 , 831 ).

12. The sensor device (100) according to any one of claims 10 or 11 , comprising first and second measurement electrode pairs (110, 120) that each comprises respective first and second electrodes (111 , 112; 121 , 122), wherein the second measurement electrode pair (120) is separated from the first measurement electrode pair (110) along an extension of the measurement chamber (160) by a second distance (d2).

13. The sensor device (100) according to claim 12, wherein the contact interface comprises the connector members (211 ) of the respective first and second electrodes (111 , 112; 121 , 122) of the first and second measurement electrode pairs (110, 120) and the respective deformable elements (231 , 731 , 831 ) that connect each of said electrodes electrically with the respective conductive trace (451 ) of the printed circuit board (150).

14. The sensor device (100) according to any one of claims 10 to 13, wherein the shielding member (300) comprises a flexible skirt (360) that makes contact with the printed circuit board (150) along an unbroken boundary line around the shielding member (300).15 The sensor device (100) according to any one of claims 11 to 14, wherein the non-conductive fluid has a kinematic viscosity in the range 4 mm2 / s to 10 mm2 / s.

16. The sensor device (100) according to any one of claims 11 to 15, wherein the non-conductive fluid is hydrophobic.

17. The sensor device (100) according to any one of the preceding claims, wherein a non-conductive potting is arranged in at least one space between the measurement chamber (160) and the printed circuit board (150).

18. The sensor device (100) according to claim 17, wherein the non-conductive potting fills an entire interior of the housing (200).

19. The sensor device (100) according to any one of the preceding claims, wherein: the printed circuit board (150) has a component side that is opposed to a side thereof on which the respective deformable element (231 , 731 , 831 ) is arranged, which component side comprises at least one electrically controllable light source (155), and a transparent or translucent non-conductive potting (191 ) covers an area of the component side, which area comprises said at least one light source (155).

20. The sensor device (100) according to any one of the preceding claims, wherein the respective connector member (211 ) forms an integral part of the respective electrode (111 ).

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