Method for manufacturing a measurement chamber of a fluid flow sensor device

Abstract

A measurement chamber (100) of a fluid-flow sensor device (140) is manufactured by: arranging measurement electrodes (111, 112, 121, 122) and reference electrodes (171, 172) in a first outer mold piece by inser- ting a respective first outward projecting tab of each electrode into a respective first opening in the first outer mold piece, each measu- rement electrode having a respective annular shape with inner ope- nings of a first diameter, and each reference electrode comprising an active contact member positioned such that when the respective first outward projecting tabs of all of electrodes are inserted in the respective first openings the active contact members are located in line (L) with one another and in line (L) with at least one point on a respective inner surface of each measurement electrode; arranging a cylindrically shaped mold core (210) in the inner openings of the measurement electrodes (111, 112, 121, 122), the mold core (210) having a diameter that matches the first diameter, and the mold core (210) being arranged such that an outer surface thereof contacts the active contact members; arranging a second outer mold piece in connection with the first outer mold piece such that the first and second outer mold pie- ces surround all of said electrodes and the mold core (210) and the first and second outer mold pieces form an enclosed volume toge- ther with the mold core (210); and injecting a non-conductive casting compound (150) in the en- closed volume formed between the mold core (210) and the first and second outer mold pieces.

Description

[0001] Method for Manufacturing a Measurement Chamber of a Fluid Flow Sensor Device

[0002] TECHNICAL FIELD

[0003] The present invention relates generally to the measurement of fluid flows, for example milk flow rates. Especially, the invention relates to a manufacturing method according to the preamble of claim 1 .

[0004] BACKGROUND

[0005] Typically, the process of automatically extracting milk from a dairy animal involves transporting a mixture of milk and air from at least one teatcup through a conduit. The specific ratio of milk and air in the mixture varies in a highly irregular manner during a milking session. It is therefore challenging to measure the milk flow rate in the conduit with adequate accuracy. Further, since an overall milk yield during the milking session is normally calculated by integrating the milk-flow-rate values over time, the milk yield value also becomes unreliable if the milk flow rate is inaccurate. The prior art includes various examples of fluid flow sensor devices that tackle this problem.

[0006] US 10,598,528 reveals an apparatus including a tube, first and second pairs of 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 de- termined area and determines a volume of the fluid based on the determined volumetric flow rate.

[0007] US 9,470,565 describes 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.

[0008] CN 107006377 B discloses a cow milking capacity detection device and a method based on a neural network. The device includes a square pipe, a constant current source module, an infrared light emitting module, a triode switch module, a temperature sensor, a single chip microcomputer, a signal filtering and amplification module, a wireless communication module, a radio frequency card module, an infrared receiving module and a host computer system. The infrared light emitting module, the triode switch module and the temperature sensor are located on the top of the square pipe. The single chip microcomputer, the signal filtering and amplification module, the wireless communication module, the radio frequency card module and the infrared receiving module is located on the bottom of the square pipe. In the design of the system, near infrared light is used for non-contact measurement, the neural network algorithm is added in the designed system, so that the detection is more accurate and faster, and the problem that nonlinear variation of unknown interference factors affect the calculation result in the cow milking capacity calculation process is solved. By means of the device and the method, liquid, solid, semiconductor, colloid and other samples can be directly measured.

[0009] Thus, technical solutions exist for measuring the milk-flow rate in a conduit that contains a mixture of milk and air, where the relationship between milk and air varies over time. However, the design of the known milk-flow meters is such that the process of manufacturing the measurement chamber of these devices becomes either complicated, expensive, or both.

[0010] SUMMARY

[0011] The object of the present invention is to offer a solution that mitigates the above problem, and thus allows for a cost-effective production of a top-class fluid-flow sensor device that for example is suitable for measuring milk-flow-rate.

[0012] According to the invention, the object is achieved by a method for manufacturing a measurement chamber of a fluid-flow sensor device. The method involves arranging at least three measurement electrodes and first and second reference electrodes in a first outer mold piece by inserting a respective first outward projecting tab of each of said electrodes into a respective first opening in the first outer mold piece. Each of the measurement electrodes has a respective inner opening. Each of the first and second reference electrodes contains a respective active contact member that is positioned relative to the respective first outward projecting tab of the first and second reference electrodes and the respective first openings such that when the respective first outward projecting tabs of all of said electrodes are inserted in the respective first openings the active contact members are located in line with one another and in line with at least one point on a respective inner surface of the inner openings of each of the measurement electrodes. Additionally, the method involves arranging a mold core in the respective inner openings of the at least three measurement electrodes. The mold core has a cross-section shape that matches the respective inner openings. The mold core is arranged such that an outer surface thereof contacts each of the respective active contact members. The method further involves arranging a second outer mold piece in connection with the first outer mold piece, such that the first and second outer mold pieces surround all of said electrodes and the mold core and the first and second outer mold pieces form an enclosed volume together with the mold core. In addition, the method involves injecting a non-conductive casting compound in the enclosed volume formed between the mold core and the first and second outer mold pieces.

[0013] This manufacturing method is advantageous because, while being straightforward to implement, it ensures that the active contact members and the contact surfaces of the measurement electrodes all align perfectly with one another and also align with an inner surface of the measurement chamber. As a result, highly accurate measurements may be performed without disturbing the fluid flow inside the measurement chamber. Moreover, since the inner surface of the measurement chamber can be made perfectly smooth, the risk is minimized that any fluid constituents stick to this surface.

[0014] According to one embodiment of the invention, each of the respective inner openings of each of the measurement electrodes has a respective annular shape with a respective a first diameter. Further, the mold core is cylindrically shaped and has a diameter that matches the first diameter. Here, the method involves arranging the cylindrically shaped mold core in the respective inner openings of the at least three measurement electrodes. A circular cross-section shape of the measurement chamber is generally preferable both for hydrodynamic reasons and because it is straightforward to handle a cylindrically the cylindrically shaped mold core in the manufacturing process.

[0015] According to another embodiment of the invention, the mold core has a tapered tip and the arranging of the mold core in the respective inner openings of the at least three measurement electrodes involves inserting the mold core with the tip first through the respective inner openings of the four measurement electrodes in a sequential order. Thereby, arranging the mold core in the respective inner openings of the at least three measurement electrodes is facilitated, and is comparatively easy to place the mold core in position without disturbing how the electrodes are arranged. According to another embodiment of the invention, the non-con- ductive casting compound is injected via at least one injection point, e.g. a so called tunnel gate in at least one of the first and second outer mold pieces. By for example using two or more injection points it is less difficult to reach all volumes to be filled with the casting compound.

[0016] According to yet another embodiment of the invention, the method further involves allowing the non-conductive casting compound to set, and after that the non-conductive casting compound has set, thus forming the measurement chamber; separating the first and second outer mold pieces from one another; separating each of the first and second outer mold pieces from the measurement chamber; and withdrawing the mold core from inside the measurement chamber. Consequently, a measurement chamber is obtained, which is ready to be mounted in a fluid-sensor device.

[0017] According to still another embodiment of the invention, each of the first and second reference electrodes has a respective annular shape with a respective second inner diameter that exceeds each of the first inner diameter and the diameter of the mold core. Each of the respective active contact member protrudes towards a center of the respective reference electrode and extends along a fraction of an inner perimeter of the respective reference electrode. The annular shape of the reference electrodes is advantageous since it facilitates aligning the reference electrodes with one another as well as with the measurement electrodes.

[0018] Preferably, each of the respective active contact members only extends along a fraction of the of the inner perimeter of the respective first and second reference electrode, say less than one tenth, and preferably around 1 / 30th, thereof. Namely, it is normally sufficient if each reference electrodes makes 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 whe- re each of the first and second reference electrodes respectively is arranged.

[0019] Additionally, according to one embodiment of the invention, each of the measurement electrodes includes at least one respective second outward projecting tab, and the method further involves inserting the at least one respective second outward projecting tab into a respective at least one second opening in at least one of the first and second outer mold pieces. This namely further stabilizes the measurement electrodes and assists in aligning them on the mold core.

[0020] According to a further embodiment of the invention, each of the first and second reference electrodes includes at least one respective third outward projecting tab, and the method involves inserting the at least one respective third outward projecting tab into a respective at least one third opening in at least one of the first and second outer mold pieces. Thereby, the measurement electrodes may be aligned on the mold core in an even more stable manner.

[0021] According to yet another embodiment of the invention, the at least three comprises four measurement electrodes, and the method involves arranging two of the four measurement electrodes in a first pair of measurement electrodes; and arranging two other of the four measurement electrodes in a second pair of measurement electrodes. In each of the first and second pairs of measurement electrodes, the electrodes are separated from one another by a first distance along the mold core. The first pair of measurement electrodes is separated from the second pair of measurement electrodes by a second distance along the mold core. Such an arrangement of the measurement electrodes is advantageous because 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. Namely, based on conductance / impedance measurements using the measurement electrodes it is possible to determine a 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.

[0022] According to still another embodiment of the invention, prior to arranging the at least three measurement electrodes in the first outer mold piece, the method involves punching out each of the four measurement electrodes from a sheet material of conductive metal. Additionally, or alternatively, prior to arranging the first second reference electrodes in the first outer mold piece, the method may involve punching out each of the first second reference electrodes from a sheet material of conductive metal. Such a manufacturing process is advantageous because it enables a cost-efficient means to obtain electrodes with measures of high- precision.

[0023] Further advantages, beneficial features and applications of the present invention will be apparent from the following description and the dependent claims.

[0024] BRIEF DESCRIPTION OF THE DRAWINGS

[0025] 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.

[0026] Figure 1 shows a perspective cross-section view of a mold core around which measurement and reference electrodes are mounted during the manufacturing method according to one embodiment of the invention; Figure 2 shows a perspective view of a mold core according to one embodiment of the invention;

[0027] Figures 3a-e exemplify designs of the measurement and reference electrodes according to embodiments of the invention;

[0028] Figure 4 shows a cross-section side view of a fluid-flow sensor device with a measurement chamber according to one embodiment of the invention; and

[0029] Figure 5 illustrates, by means of a flow diagram, the general method according to the invention for manufacturing a measurement chamber.

[0030] DETAILED DESCRIPTION

[0031] Figure 1 shows a perspective cross-section view of a cylindrically shaped mold core 210 of an inner mold 200, which mold core 210 is used in a manufacturing method according to one embodiment of the invention to produce a measurement chamber 100 of a fluidflow sensor device 140 (see Figure 4) that for example may be used to determine a milk-flow rate of a mixture of milk and gas that passes through a conduit. Figure 2 shows a perspective view of the mold core 210 according to one embodiment of the invention.

[0032] The manufacturing method of the invention involves arranging at least three measurement electrodes and first and second reference electrodes in a first outer mold piece (not shown). Technically three measurement electrodes are sufficient because two pairs of measurement electrodes may be defined by having one measurement electrode in common between the two pairs. The embodiment shown in Figure 1 includes four measurement electrodes 111 , 112, 121 and 122 respectively, and first and second reference electrodes are represented by 171 and 172 respectively. All of said electrodes are arranged in the first outer mold piece by inserting a respective first outward projecting tab 331 and 332 respectively of each of said electrodes 1 1 1 , 1 12, 121 , 122, 171 and 172 into a respective first opening in the first outer mold piece.

[0033] In this embodiment, each of the measurement electrodes 1 1 1 , 1 12, 121 and 122 has a respective annular shape with a respective inner opening of a first diameter Di. The mold core 210 has a diameter Dmthat matches the first diameter Di. This means that the diameter Dmis essentially equal to the first diameter Di, however Dm< Di. The method namely involves arranging the mold core 210 in the respective inner openings of the four measurement electrodes 1 1 1 , 1 12, 121 and 122 respectively.

[0034] According to other embodiments of the invention, the measurement electrodes 1 1 1 , 1 12, 121 and 122 may have other shapes, for example a rectilinear outline as shown in Figure 3e. Analogously, the measurement electrodes 1 1 1 , 1 12, 121 and 122 may have a respective inner opening OPN that is non-circular, e.g. square shaped. In the general case, the mold core 210 thus has a cross-section shape that is configured to match the respective inner openings OPN of the measurement electrodes 1 1 1 , 1 12, 121 and 122; and the method involves arranging a mold core 210 in the respective inner openings of the at least three measurement electrodes 1 1 1 , 1 12, 121 and 122 respectively.

[0035] According to one embodiment of the invention, the mold core 210 has a tapered tip 215, i.e. where a diameter Dmt of the tip is smaller than the diameter Dm, and the arranging of the mold core 210 in the respective inner openings of the at least three measurement electrodes 1 1 1 , 1 12, 121 and 122 involves inserting the mold core 210 with the tip 215 first through the respective inner openings of the four measurement electrodes 1 1 1 , 1 12, 121 and 122 in a sequential order. Moreover, the inner mold 200 may have an end section 220 with a diameter larger than the diameter Dm, such that the mold core 210 cannot be inserted further than intended.

[0036] The mold core 210 is arranged such that an outer surface thereof contacts each of the respective active contact members 371 and 372. Each of the first and second reference electrodes 371 and 372 has a respective active contact member 371 and 372 respectively that is positioned relative to the respective first outward projecting tab 332 of the first and second reference electrodes 171 and 172 and the respective first openings in the first outer mold piece, such that when the respective first outward projecting tabs 331 and 332 of all of said electrodes are inserted in the respective first openings the active contact members 371 and 372 are located in line L both with one another and with at least one point on a respective inner surface of the inner openings OPN of each of the measurement electrodes 111 , 112, 121 and 122 as illustrated in Figure 1 .

[0037] After arranging the electrodes 111 , 112, 121 , 122, 171 and 172 respectively in the first outer mold piece, the method involves arranging a second outer mold piece (not shown) in connection with the first outer mold piece, such that the first and second outer mold pieces surround all of said electrodes 111 , 112, 121 , 122, 171 and 172 and the mold core 210 so that the first and second outer mold pieces form an enclosed volume together with the mold core 210.

[0038] Subsequently, the method involves injecting a non-conductive casting compound 150 in the enclosed volume formed between the mold core 210 and the first and second outer mold pieces. After having set, the non-conductive casting compound 150 will form the measurement chamber 100.

[0039] According to one embodiment of the invention, the non-conductive casting compound 150 is injected via at least one injection point in at least one of the first and second outer mold pieces. For example, the at least one injection point may be so-called tunnel gates. Injecting the non-conductive casting compound 150 via two or more injection points is advantageous because this facilitates reaching all parts of the above-mentioned enclosed volume with the non-conductive casting compound 150. According to one embodiment of the invention, the method involves allowing the non-conductive casting compound 150 to set, and after that the non-conductive casting compound 150 has set, the method further involves: separating the first and second outer mold pieces from one another; separating each of the first and second outer mold pieces from the measurement chamber 100; and withdrawing the mold core 210 from inside the measurement chamber 100. At this point, the measurement chamber 100 is ready to be mounted in the fluid-flow sensor device 140.

[0040] Figure 3b illustrates how the reference electrodes 171 and 172 may be designed according to one embodiment of the invention. Here, analogous the measurement electrodes 111 , 112, 121 and 122, each of the first and second reference electrodes 171 and 152 has a respective annular shape. Each reference electrode

[0041] 171 and 172 has a respective second inner diameter Drthat exceeds each of the first inner diameter Di and the diameter Dmof the mold core 210. Specifically, the difference between the second inner diameter Drand the diameter Dmis equivalent to the material thickness of the measurement chamber 100. Each of the respective active contact member 371 and 372 protrudes towards a center of the respective reference electrode 171 and 172, and each of the respective active contact member 371 and 372 extends along a fraction of an inner perimeter of the respective reference electrode 171 and 172. In the completed measurement chamber 100 said extension of the respective reference electrode 171 and

[0042] 172 along the fraction of the inner perimeter constitutes a part of the respective reference electrode 171 and 172 that is configured to make direct electrical contact with the fluid inside the measurement chamber 100, whereas all other parts of the respective reference electrode 171 and 172 are located outside the measurement chamber 100.

[0043] Since it is normally sufficient if each reference electrodes 171 and 172 makes electrical contact with the fluid at respective points in the measurement chamber 100, which respective points are located along a line therein that is covered by the fluid at any de- gree of filling of the measurement chamber - a respective lowest point of the cross-section where each of the first and second reference electrodes respectively is arranged, the active contact member 371 and 372 only needs to occupy a relatively small part of the inner circumference of the measurement chamber 100. Preferably, each of the respective active contact members 371 and 372 extends along less than one tenth, and more preferably around 1 / 30th, of the inner perimeter of the respective first and second reference electrode 171 and 172.

[0044] Figure 3c illustrates how the reference electrodes 171 and 172 may be designed according to one embodiment of the invention. Here, each of the first and second reference electrodes 171 and 172 form a respective semicircular shape, or more precisely a respective half annular shape of the second inner diameter Dr.

[0045] In the embodiments of Figures 3b and 3c, each of the first and second reference electrodes 171 and 172 has a respective first outward projecting tab 332. Moreover, each of the first and second reference electrodes 171 and 172 has a respective second outward projecting tab 3322 and 333 respectively. According to one embodiment of the invention, the second outward projecting tab 3322 and 333 respectively is configured to be received in at least one respective second opening in the second outer mold piece.

[0046] According to one embodiment of the invention, each of the measurement electrodes 111 , 112, 121 and 122 respectively also includes at least one respective second outward projecting tab. Figure 3a shows two such tabs in the form of 3312 and 3313 respectively, which are arranged at orthogonal angles relative to one another on an outer perimeter of the respective measurement electrode 111 , 112, 121 and 122. Furthermore, the method according to this embodiment of the invention involves inserting the at least one respective second outward projecting tab 3312 and / or 3313 into a respective second opening in the first mold piece and / or the second outer mold piece. Analogously, according to one embodiment of the invention, each of the first and second reference electrodes 171 and 172 respectively includes at least one respective third outward projecting tab, exemplified by 3322, 3323 and 333 in Figures 3b and 3c. Here, the method further involves inserting the at least one respective third outward projecting tab 3322, 3323 and 333 into a respective at least one third opening in the first outer mold piece and / or the second outer mold piece.

[0047] Figure 3d illustrates how the reference electrodes 171 and 172 may be designed according to one embodiment of the invention. Here, each of the first and second reference electrodes 171 and 172 form a respective quarter annular shape with an inner curved shape having a radius equal to the second inner diameter Dr / 2. Further, each of the reference electrodes 171 and 172 has a respective first outward projecting tab 332 as described above, which during manufacture of the measurement chamber 100 may be inserted into a respective first opening in the first outer mold piece.

[0048] Figure 4 shows a cross-section side view of a fluid-flow sensor device 140 with a measurement chamber 100 according to one embodiment of the invention. The fluid-flow sensor device 140 also contains a measurement unit 130 configured to produce a stream of data RD that reflects at least one electrical characteristic of a fluid, e.g. comprising a mixture of milk and gas that passes through the measurement chamber 100. The stream of data RD may reflect current and / or voltage values measured via the measurement electrodes 111 , 112, 121 and 122 and the reference electrodes 171 and 172. The fluid-flow sensor device 140 may also include a processing device 150, which is configured to obtain the stream of data RD and based thereon derive conductivity values and / or impedance values of the mixture that passes through the measurement chamber 100. The conductivity values and / or impedance values, in turn, may serve as a basis for deriving milk-flow rate values and / or a milk yield during a milking session.

[0049] In the embodiment of Figure 4, two of the at least three measure- ment electrodes, say 111 and 1 12, are arranged in a first pair of measurement electrodes 110; and two other of the at least three measurement electrodes, say 121 and 122, are arranged in a second pair of measurement electrodes 120. In each of the first and second pairs of measurement electrodes 110 and 120 respectively, the electrodes are separated from one another by a first distance d1 along the mold core 210. The first pair of measurement electrodes 110, in turn, is separated from the second pair of measurement electrodes 120 by a second distance d2 along the mold core 210, where preferably d2 > d1. Such an arrangement of the measurement electrodes namely renders it is possible to establish accurate flow-rate values of a fluid that is transported in said fluid through the measurement chamber 100 based on the at least one electrical characteristic also if the fluid shows large and rapid variations in the relative proportions of the components included in the fluid. Namely, based on conductance / impedance measurements using the measurement electrodes it is possible to determine a 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 the electric conductivity and / or impedance measurements for which the reference electrodes provide reference values. Based on the electric conductivity and / or impedance measurements, for example the flow-rate values may be determined at high accuracy.

[0050] For cost-efficiency and to attain a high degree of smoothness of the surface of the interior of the measurement chamber 100, it is generally preferable if, prior to arranging the at least three electrodes 111 , 112, 121 and 122 in the first outer mold piece, the method involves punching out each of the four measurement electrodes 111 , 112, 121 and 122 from a sheet material of conductive metal.

[0051] Analogously, it is likewise advantageous if prior to arranging the first second reference electrodes 171 and 172 in the first outer mold piece, the method involves punching out each of the first second reference electrodes 171 and 172 from a sheet material of conductive metal.

[0052] As an alternative to punching, the measurement electrodes 111 , 112, 121 and 122 and / or the first second reference electrodes 171 and 172 may be cut out from a sheet material of conductive metal by means of laser cutting, plasma cutting, waterjet cutting, flame cutting, oxy-fuel gas cutting or mechanical cutting.

[0053] Additionally, it is beneficial if each of the measurement electrodes 111 , 112, 121 and 122 and each of the reference electrodes 171 and 172 has a respective outward projecting tab configured to connect the electrode in question to a particular conductive trace on a printed circuit board (PCB) 310 in the fluid-flow sensor device 140. Figures 1 and 3a to 3d further show resilient elements r1 , r2, r3, r4, 181 and 182 configured to connect the respective outward projecting tab of each of the electrodes 111 , 112, 121 , 122, 171 and 172 respectively mechanically and electrically to said dedicated conductive trace on the PCB 310. Each of the resilient elements r1 , r2, r3, r4, 181 and 182 is configured to be compressed by a respective outward projecting tab of the respective electrode when the measurement chamber 100 is assembled in the housing of the fluid-flow sensor device 140. 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 310 without soldering. Further, the resilient elements r1 , r2, r3, r4, 181 and 182 are capable of accommodating for any temperature-related dimensional variations in the measurement chamber 100 and / or said electrodes 111 , 112, 121 , 122, 171 and 172.

[0054] To sum up, and with reference to the flow diagram in Figure 5, we will now describe the general method according to the invention for manufacturing a measurement chamber 100, which may be included in the fluid-flow sensor device 140. In a first step 510, at least three measurement electrodes and first and second reference electrodes are arranged in a first outer mold piece by inserting a respective first outward projecting tab of each of said electrodes into a respective first opening in the first outer mold piece. Each of the measurement electrodes has a respective inner opening, and each of the first and second reference electrodes includes a respective active contact member that is positioned relative to the respective first outward projecting tab of the first and second reference electrodes and the respective first openings such that when the respective first outward projecting tabs of all of said electrodes are inserted in the respective first openings the active contact members are located in line with one another and in line with at least one point on a respective inner surface of each of the measurement electrodes.

[0055] In a step 520 thereafter, a mold core is arranged in the respective inner openings of the at least three measurement electrodes. The mold core has a shape that matches the respective inner openings. The mold core is arranged such that an outer surface thereof contacts each of the respective active contact members.

[0056] Subsequently, in a step 530, a second outer mold piece is arranged in connection with the first outer mold piece, such that the first and second outer mold pieces surround all of the electrodes and the mold core, and the first and second outer mold pieces form an enclosed volume together with the mold core.

[0057] Thereafter, in a step 540, a non-conductive casting compound is injected in the enclosed volume formed between the mold core and the first and second outer mold pieces. After that, the procedure ends.

[0058] 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.

[0059] 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 addition 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 reci- ted in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

[0060] 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.

[0061] 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 method for manufacturing a measurement chamber (100) of a fluid-flow sensor device (140), the method comprising: arranging at least three measurement electrodes (111 , 112, 121 , 122) and first and second reference electrodes (171 , 172) in a first outer mold piece by inserting a respective first outward projecting tab (331 , 332) of each of said electrodes (111 , 112, 121 , 122, 171 , 172) into a respective first opening in the first outer mold piece, each of the measurement electrodes having a respective inner opening (OPN), and each of the first and second reference electrodes comprising a respective active contact member (371 ; 372) that is positioned relative to the respective first outward projecting tab (332) of the first and second reference electrodes (171 , 172) and the respective first openings such that when the respective first outward projecting tabs (331 , 332) of all of said electrodes are inserted in the respective first openings the active contact members (371 ; 372) are located in line (L) with one another and in line (L) with at least one point on a respective inner surface of the inner openings (OPN) each of the measurement electrodes, arranging a mold core (210) in the respective inner openings (OPN) of the at least three measurement electrodes (111 , 112, 121 , 122), the mold core (210) having a cross-section shape configured to match the respective inner openings (OPN) of the measurement electrodes, and the mold core (210) being arranged such that an outer surface thereof contacts each of the respective active contact members (371 ; 372) arranging a second outer mold piece in connection with the first outer mold piece such that the first and second outer mold pieces surround all of said electrodes and the mold core (210) and the first and second outer mold pieces form an enclosed volume together with the mold core (210), and injecting a non-conductive casting compound (150) in the enclosed volume formed between the mold core (210) and the first and second outer mold pieces.

2. A method according to claim 1 , wherein the respective inner openings (OPN) of each of the measurement electrodes has a respective annular shape with a first diameter (Di), and the mold core (210) is cylindrically shaped and has a diameter (Dm) that matches the first diameter (Di), and the method comprises: arranging the cylindrically shaped mold core (210) in the respective inner openings of the at least three measurement electrodes (111 , 112, 121 , 122).

3. The method according to any of claims 1 or 2, wherein the mold core (210) has a tapered tip (215) and the arranging of the mold core (210) in the respective inner openings of the at least three measurement electrodes (111 , 112, 121 , 122) comprises inserting the mold core (210) with the tip (215) first through the respective inner openings of the at least three measurement electrodes (111 , 112, 121 , 122) in a sequential order.

4. The method according to any of the preceding claims, wherein the non-conductive casting compound (150) is injected via at least one injection point in at least one of the first and second outer mold pieces.

5. The method according to any of the preceding claims, further comprising: allowing the non-conductive casting compound (150) to set, and after that the non-conductive casting compound (150) has set, thus forming the measurement chamber (100), separating the first and second outer mold pieces from one another, separating each of the first and second outer mold pieces from the measurement chamber (100), and withdrawing the mold core (210) from inside the measurement chamber (100).

6. The method according to any of claims 2 to 5, wherein each of the first and second reference electrodes has a respectiveannular shape with a respective second inner diameter (Dr) that exceeds each of the first inner diameter (Di) and the diameter (Dm) of the mold core (210), and each of the respective active contact member (371 ; 372) protrudes towards a center of the respective reference electrode (171 ; 172) and extends along a fraction of an inner perimeter of the respective reference electrode (171 ; 172).

7. The method according to claim 6, wherein each of the respective active contact members (371 ; 372) extends along less than one tenth, and preferably around 1 / 30th, of the inner perimeter of the respective first and second reference electrode (171 ; 172).

8. The method according to any one of the preceding claims, wherein each of the measurement electrodes (111 , 112, 121 , 122) comprises at least one respective second outward projecting tab (3312, 3313), and the method further comprising: inserting the at least one respective second outward projecting tab (3312, 3313) into a respective at least one second opening in at least one of the first and second outer mold pieces.

9. The method according to any one of the preceding claims, wherein each of the first and second reference electrodes (171 , 172) comprises at least one respective third outward projecting tab (3322, 3323, 333), and the method further comprising: inserting the at least one respective third outward projecting tab (3322, 3323, 333) into a respective at least one third opening in at least one of the first and second outer mold pieces.

10. The method according to any one of the preceding claims, wherein the at least three comprises four measurement electrodes (111 , 112, 121 , 122), and the method comprises: arranging two of the four measurement electrodes (111 , 112, 121 , 122) in a first pair of measurement electrodes (110); and arranging two other of the four measurement electrodes (111 , 112, 121 , 122) are arranged in a second pair of measu-rement electrodes (120), and wherein in each of the first and second pairs of measurement electrodes (110; 120) the electrodes are separated from one another by a first distance (d1 ) along the mold core (210), and the first pair of measurement electrodes (110) is separated from the second pair of measurement electrodes (120) by a second distance (d2) along the mold core (210).

11. The method according to any one of the preceding claims, wherein prior to arranging the at least three electrodes in the first outer mold piece, the method comprising: punching out each of the four measurement electrodes (111 , 112, 121 , 122) from a sheet material of conductive metal.

12. The method according to any one of the preceding claims, wherein prior to arranging the first second reference electrodes (171 ; 172) in the first outer mold piece, the method comprising: punching out each of the first second reference electrodes (171 ; 172) from a sheet material of conductive metal.

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