Method for producing inductive conductivity sensor and inductive conductivity sensor

Abstract

The invention relates to a method for manufacturing an inductive conductivity sensor and an inductive conductivity sensor, the sensor comprising:-an electronics unit (10) comprising a printed circuit board extending along a first axis and having a first axial end and a second axial end, a transmitter coil, a receiver coil and a temperature sensor, the printed circuit board has a first board side and a second board side, a first through-hole and a second through-hole, the first through-hole being arranged between a first axial end and a second axial end of the printed circuit board, and the second through-hole being arranged between the first axial end and the first through-hole such that a bracket is formed between the first axial end and the second through-hole, the temperature sensor is arranged on the support, the transmitter coil is arranged on the first plate side around the first through-hole, and the receiver coil is arranged on the second plate side around the first through-hole, and a housing which encloses the electronic unit in a fluid-tight manner such that the first through-hole and the second through-hole each allow a fluid to at least partially pass therethrough.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an inductive conductivity sensor and an inductive conductivity sensor. Background Art

[0002] Inductive conductivity sensors are used in various applications in laboratory and process measurement technologies to measure the conductivity of liquid measurement media. They are preferably used where large measurement ranges and high chemical or thermal loads occur. This is the case, for example, in various industrial chemical processes, but also in thermal steam sterilization processes, which are commonly used in the food technology field due to high hygiene requirements.

[0003] An inductive conductivity sensor includes a transmitter coil and a receiver coil, which are typically designed as toroidal coils, also known as toroidal coils. Such a conductivity sensor functions as a dual transformer, where the transmitter coil and the receiver coil are introduced far enough into the measurement medium such that a closed current path can be created through the measurement medium and involving the transmitter coil and the receiver coil. When the transmitter coil is excited with an alternating voltage signal, it generates a magnetic field, which induces a current in the closed medium path involving the above coils, the intensity of which depends on the conductivity of the measurement medium. Since this alternating current in the medium in turn generates a changing magnetic field around the medium, an alternating current is induced in the receiver coil. The alternating current and the corresponding alternating voltage sent out by the receiver coil as the output signal are respectively a measure of the conductivity of the measurement medium.

[0004] Since the conductivity of the measurement medium depends on the temperature of the measurement medium, it is crucial to measure the temperature simultaneously and, if possible, at the same location where the conductivity measurement takes place with the highest accuracy. Summary of the Invention

[0005] Therefore, an object of the present invention is to provide an inductive conductivity sensor having a temperature sensor with a reliable, stable and simple design and a manufacturing method thereof.

[0006] According to the present invention, this object is achieved by an inductive conductivity sensor according to claim 1 and a manufacturing method according to claim 6.

[0007] The inductive conductivity sensor according to the present invention includes: - an electronic unit, the electronic unit including a printed circuit board, a transmitter coil, a receiver coil and a temperature sensor, wherein the printed circuit board extends along a first axis and has a first axial end and a second axial end, wherein the printed circuit board has a first board side and a second board side, a first through hole and a second through hole, Wherein, the first through-hole is arranged between the first axial end and the second axial end of the printed circuit board, and the second through-hole is arranged between the first axial end and the first through-hole, such that a bracket is formed between the first axial end and the second through-hole. Wherein, the temperature sensor is arranged on the bracket. Wherein, the transmitter coil is arranged on the first board side around the first through-hole, and the receiver coil is arranged on the second board side around the first through-hole. - A housing that fluid-tightly encloses the electronic unit such that each of the first through-hole and the second through-hole allows fluid to pass through at least partially.

[0008] The inductive conductivity sensor according to the present invention allows its temperature sensor to be optimally exposed to the fluid to be measured, which results in optimal temperature sensitivity. In addition, the shape of the bracket ensures maximum stability and maximum robustness against external mechanical influences. Furthermore, due to the combined design of the housing and the electronic unit, a minimum housing thickness for optimal sensitivity for both conductivity measurement and temperature measurement can be achieved. In addition, the symmetrical arrangement of the temperature sensor ensures that the electromagnetic fields of the transmitter coil and the receiver coil are minimally affected.

[0009] According to an embodiment of the present invention, the housing is integrally connected to the electronic unit by an injection molding process.

[0010] According to an embodiment of the present invention, the housing has a housing thickness, and the housing thickness is less than 2 mm, preferably less than 1 mm, at least above the temperature sensor.

[0011] According to an embodiment of the present invention, the transmitter coil has a transmitter coil inner diameter, the receiver coil has a receiver coil inner diameter, and the first through-hole has a first through-hole inner diameter, wherein the transmitter coil inner diameter and the receiver coil inner diameter are greater than the first through-hole inner diameter.

[0012] According to an embodiment of the present invention, the first through-hole has a first through-hole inner diameter, and the second through-hole has a second through-hole inner diameter, wherein the second through-hole inner diameter is equal to or greater than the first through-hole inner diameter.

[0013] The above object is also achieved by a method for manufacturing an inductive conductivity sensor according to claim 6.

[0014] The method according to the present invention includes: - Providing an electronic unit and an injection mold, Wherein, the electronic unit has a printed circuit board, a transmitter coil, a receiver coil, and a temperature sensor. Wherein, the printed circuit board extends along a first axis and has a first axial end and a second axial end, Wherein, the printed circuit board has a first board side and a second board side, a first through hole and a second through hole, Wherein, the first through hole is arranged between the first axial end and the second axial end of the printed circuit board, and the second through hole is arranged between the first axial end and the first through hole, such that a bracket is formed between the first axial end and the second through hole, Wherein, the temperature sensor is arranged on the bracket, Wherein, the transmitter coil is arranged on the first board side, and the receiver coil is arranged on the second board side, and the transmitter coil and the receiver coil each surround the first through hole; - Fixing the electronic unit relative to the injection mold using a clamping unit, wherein the clamping unit clamps the printed circuit board at a clamping point; - Injecting a plastic material to form a housing of the inductive conductivity sensor; - Removing the clamping unit; - Closing the housing at the clamping point.

[0015] According to an embodiment of the present invention, the clamping unit clamps the printed circuit board at the first through hole.

[0016] According to an embodiment of the present invention, the transmitter coil has a transmitter coil inner diameter, the receiver coil has a receiver coil inner diameter, and the first through hole has a first through hole inner diameter, wherein the transmitter coil inner diameter and the receiver coil inner diameter are greater than the first through hole inner diameter, such that a first annular surface is formed on the first board side and a second annular surface is formed on the second board side, wherein the clamping unit clamps the printed circuit board on the first annular surface and the second annular surface.

[0017] According to an embodiment of the present invention, the electronic unit has a first half shell and a second half shell, and the first half shell and the second half shell are arranged such that the transmitter coil and the receiver coil are protected, and the clamping unit clamps the printed circuit board, the first half shell and the second half shell when fixing the electronic unit.

[0018] According to an embodiment of the present invention, when closing the housing at the clamping point, a welding mandrel and a welding cap are used, wherein the welding mandrel and the welding cap are welded to the housing by an ultrasonic process. Description of the Drawings

[0019] The present invention will be explained in more detail based on the following drawings. In the drawings:

[0020] - Figure 1 shows an exemplary representation of an inductive conductivity sensor according to the present invention,

[0021] - Figure 2 shows Figure 1 a cross-sectional representation of the inductive conductivity sensor shown,

[0022] - Figure 3 shows Figure 1 an exemplary representation of the manufacturing of the inductive conductivity sensor shown,

[0023] Figure 4 shows Figure 2 an enlarged cross-sectional view of the inductive conductivity sensor shown in Detailed Description of the Embodiment

[0024] Figures 1 to 4 The inductive conductivity sensor 100 according to the present invention shown includes an electronic unit 10 and a housing 60.

[0025] The electronic unit 10 includes a printed circuit board 20, a transmitter coil 30, a receiver coil 40, and a temperature sensor 50 (see Figure 2 ). Preferably, the electronic unit 10 further includes a first half-shell H1 and a second half-shell H2, which particularly surround temperature-sensitive components and / or pressure-sensitive components (see Figure 4 ). When placed on top of each other, the first half-shell H1 and the second half-shell H2 preferably have a substantially annular shape. This ensures that the transmitter coil 30 and the receiver coil 40 are ideally protected by the two half-shells H1, H2.

[0026] The printed circuit board 20 extends along a first axis Z (see Figure 3 ), and has a first axial end 21 and a second axial end 22.

[0027] The printed circuit board 20 has a first board side 23 and a second board side 24, a first through-hole 25, and a second through-hole 26.

[0028] The first through-hole 25 is arranged between the first axial end 21 and the second axial end 22 of the printed circuit board, and the second through-hole 26 is arranged between the first axial end 21 and the first through-hole 25, such that a bracket 27 is formed between the first axial end 21 and the second through-hole 26. Preferably, the bracket 27 is designed to be symmetric about the first axis Z. Preferably, the bracket 27 has the same outer radius as the transmitter coil 30 and the receiver coil 40 (see Figure 1 ).

[0029] The temperature sensor 50 is arranged on the support 27. The temperature sensor 50 is preferably arranged centrally on the support 27, i.e., arranged along the first axis Z. This achieves a symmetric arrangement of the temperature sensor 50 on the inductive conductivity sensor 100. In Figure 1 , the temperature sensor 50 is covered by the housing 60, which is why the temperature sensor 50 is shown in dashed lines.

[0030] The transmitter coil 30 is arranged on the first plate side 23 around the first through-hole 25, and the receiver coil 40 is arranged on the second plate side 24 around the first through-hole 25.

[0031] The housing 60 encloses the electronic unit 10 in a fluid-tight manner such that each of the first through-hole 25 and the second through-hole 26 allows fluid to pass through at least partially. The housing 60 is integrally connected to the electronic unit 10 by an injection molding process. Preferably, the electronic unit 10 at least partially has a shielding element (not shown) to prevent electromagnetic interference fields. The housing 60 has a housing thickness GD, and the housing thickness GD is less than 2 mm, preferably less than 1 mm, at least above the temperature sensor 50.

[0032] The transmitter coil 30 has a transmitter coil inner diameter SI, the receiver coil 40 has a receiver coil inner diameter EI, and the first through-hole 25 has a first through-hole inner diameter DI1. According to an embodiment of the present invention, the transmitter coil inner diameter SI and the receiver coil inner diameter EI are preferably greater than the first through-hole inner diameter DI1. This means that a first annular surface RF1 is formed on the first plate side 23, and a second annular surface RF2 is formed on the second plate side 24.

[0033] The first through-hole 25 has a first through-hole inner diameter DI1, and the second through-hole 26 has a second through-hole inner diameter DI2.

[0034] According to Figure 1 the illustrated embodiment, the second through-hole inner diameter DI2 is equal to the first through-hole inner diameter DI1 or greater than the first through-hole inner diameter DI1.

[0035] Next, a method for manufacturing the above-described inductive conductivity sensor 100 according to the present invention will be discussed.

[0036] First, the above-described electronic unit 10 and an injection mold (not shown) are provided. According to an advantageous step, the first half-shell H1 and the second half-shell H2 are then welded together by ultrasound. This enables, in particular, the fixing of the printed circuit board 20 and protects the transmitter coil 30 and the receiver coil 40 from the injection pressure. Of course, the injection mold has a mold surface that corresponds to the shape of the housing 60 of the inductive conductivity sensor 100 and allows the accommodation of the electronic unit 10. In the region of the first through-hole 25, the injection mold has a recess complementary to the clamping unit 200.

[0037] Then, the clamping unit 200 is used to fix the electronic unit 10 relative to the injection mold (see Figure 3 ). The clamping unit 200 includes, for example, a first tool core 201 and a second tool core 202. The clamping unit 200 clamps the printed circuit board 20 at the clamping point and / or preferably clamps two half-shells H1, H2. The clamping unit 200 preferably clamps the printed circuit board 20 at the first through hole 25.

[0038] In the case where the inner diameter SI of the transmitter coil and the inner diameter EI of the receiver coil are greater than the inner diameter DI1 of the first through hole, such that a first annular surface RF1 is formed on the first plate side 23 and a second annular surface RF2 is formed on the second plate side 24, the clamping unit 200 preferably clamps the printed circuit board 20 on the first annular surface RF1 and the second annular surface RF2 (see Figure 4 ).

[0039] Next, a plastic material is injected to form the housing 60 of the inductive conductivity sensor. The plastic material is preferably PEEK. Preferably, the injection into the injection mold is performed in the region of the flange of the housing 60. The clamping unit 200 seals the injection mold tightly in the region of the recess of the injection mold.

[0040] Then, the clamping unit 200 is removed. Here, the first tool core 201 and the second tool core 202 are preferably removed from the printed circuit board 20 transversely to the first axis Z. After removing the clamping unit 200, the printed circuit board 20 and / or preferably the first half-shell H1 and the second half-shell H2 are exposed at the clamping point.

[0041] Then, the housing 60 is closed at the clamping point. This means that the region that cannot be overmolded to hold the printed circuit board 20 is now also closed. The clamping point is preferably closed by a welding mandrel 61 and a welding cap 62 (see Figure 4 ). An ultrasonic welding process is preferably used to close the housing 60 by means of the welding mandrel 61 and the welding cap 62. Of course, other joining methods known to those skilled in the art, such as gluing, can also be used as long as they are compatible with the applicable hygiene regulations.

[0042] List of reference numerals

[0043] 10 Electronic unit

[0044] 20 Printed circuit board

[0045] 21 First axial end

[0046] 22 Second axial end

[0047] 23 First plate side

[0048] 24 Second plate side

[0049] 25 First through-hole

[0050] 26 Second through-hole

[0051] 27 Bracket

[0052] 30 Transmitter coil

[0053] 40 Receiver coil

[0054] 50 Temperature sensor

[0055] 60 Housing

[0056] 61 Welding mandrel

[0057] 62 Welding cover

[0058] 100 Inductive conductivity sensor

[0059] 200 Clamping unit

[0060] 201 First tool core

[0061] 202 Second tool core

[0062] DI1 Inner diameter of the first through-hole

[0063] DI2 Inner diameter of the second through-hole

[0064] EI Inner diameter of the receiver coil

[0065] GD Housing thickness

[0066] RF1 First annular surface

[0067] RF2 Second annular surface

[0068] SI Inner diameter of the transmitter coil

[0069] Z First axis

[0070] H1 First half-shell

[0071] H2 Second half-shell

Claims

1. An inductive conductivity sensor (100), comprising: - an electronic unit (10), said electronic unit (10) comprising a printed circuit board (20), a transmitter coil (30), a receiver coil (40) and a temperature sensor (50), The printed circuit board (20) extends along a first axis (Z) and has a first axial end (21) and a second axial end (22). The printed circuit board (20) has a first board side (23) and a second board side (24), a first through hole (25) and a second through hole (26). The first through hole (25) is arranged between the first axial end (21) and the second axial end (22) of the printed circuit board (20), and the second through hole (26) is arranged between the first axial end (21) and the first through hole (25), so that a bracket (27) is formed between the first axial end (21) and the second through hole (26). The temperature sensor (50) is arranged on the bracket (27). wherein the transmitter coil (30) is arranged on the first board side (23) around the first through hole (25), and the receiver coil (40) is arranged on the second board side (24) around the first through hole (25), A housing (60) enclosing the electronic unit (10) in a fluid-tight manner, such that the first through hole (25) and the second through hole (26) each allow a fluid to at least partially pass through.

2. The inductive conductivity sensor (100) according to claim 1, wherein: The housing (60) is integrally connected to the electronic unit (10) through an injection molding process.

3. The inductive conductivity sensor (100) according to claim 1 or 2, wherein: The housing (60) has a housing thickness (GD), and the housing thickness (GD) is less than 2 mm, preferably less than 1 mm, at least above the temperature sensor (50).

4. The inductive conductivity sensor (100) according to one of the preceding claims, wherein The transmitter coil (30) has a transmitter coil inner diameter (SI), the receiver coil (40) has a receiver coil inner diameter (EI), and the first through hole (25) has a first through hole inner diameter (DI1), wherein the transmitter coil inner diameter (SI) and the receiver coil inner diameter (EI) are larger than the first through hole inner diameter (DI1).

5. The inductive conductivity sensor (100) according to one of the preceding claims, wherein The first through hole (25) has a first through hole inner diameter (DI1), and the second through hole (26) has a second through hole inner diameter (DI2), wherein the second through hole inner diameter (DI2) is equal to the first through hole inner diameter (DI1) or greater than the first through hole inner diameter (DI1).

6. A method for manufacturing an inductive conductivity sensor (100), comprising: - providing an electronic unit (10) and an injection mold, The electronic unit (10) comprises a printed circuit board (20), a transmitter coil (30), a receiver coil (40) and a temperature sensor (50). The printed circuit board (20) extends along a first axis (Z) and has a first axial end (21) and a second axial end (22). The printed circuit board (20) has a first board side (23) and a second board side (24), a first through hole (25) and a second through hole (26). The first through hole (25) is arranged between the first axial end (21) and the second axial end (22) of the printed circuit board, and the second through hole (26) is arranged between the first axial end (21) and the first through hole (25), so that a bracket (27) is formed between the first axial end (21) and the second through hole (26). The temperature sensor (50) is arranged on the bracket (27). wherein the transmitter coil (30) is arranged on the first board side (23), and the receiver coil (40) is arranged on the second board side (24), and the transmitter coil (30) and the receiver coil (40) each surround the first through hole (25); - fixing the electronic unit (10) relative to the injection mold using a clamping unit (200), wherein the clamping unit (200) clamps the printed circuit board (20) at a clamping point; - injecting plastic material to form the housing (60) of the inductive conductivity sensor (100); - removing the clamping unit (200); - Closing the housing (60) at the clamping point.

7. The method for manufacturing an inductive conductivity sensor (100) according to claim 6, wherein: The clamping unit (200) clamps the printed circuit board (20) at the first through hole (25).

8. Method for producing an inductive conductivity sensor (100) according to one of claims 6 or 7, wherein: The transmitter coil (30) has a transmitter coil inner diameter (SI), the receiver coil (40) has a receiver coil inner diameter (EI), and the first through hole (25) has a first through hole inner diameter (DI1), wherein the transmitter coil inner diameter (SI) and the receiver coil inner diameter (EI) are larger than the first through hole inner diameter (DI1), so that a first annular surface (RF1) is formed on the first board side (23) and a second annular surface (RF2) is formed on the second board side (24), wherein the clamping unit (200) clamps the printed circuit board (20) on the first annular surface (RF1) and the second annular surface (RF2).

9. Method for manufacturing an inductive conductivity sensor (100) according to one of claims 6 to 8, wherein: The electronic unit (10) comprises a first half shell (H1) and a second half shell (H2), the first half shell (H1) and the second half shell (H2) being arranged so that the transmitter coil (30) and the receiver coil (40) are protected, and the clamping unit (200) clamps the printed circuit board (20), the first half shell (H1) and the second half shell (H2) when fixing the electronic unit (10).

10. The method for manufacturing an inductive conductivity sensor (100) according to claim 9, wherein: When the shell (60) is closed at the clamping point, a welding mandrel (61) and a welding cover (62) are used, wherein the welding mandrel (61) and the welding cover (62) are welded to the shell (60) by an ultrasonic process.

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