Sensor cap for a sensor and manufacturing method of the sensor cap

Abstract

The invention relates to a sensor cap (100) for an electrochemical sensor (10) for determining the concentration of an analyte (2) in a measuring medium (1), comprising: - a base body (110) extending along a first axis (X) and having a first end (111) with a first opening (113) and a second end (112) opposite the first end (111) with a second opening (114), wherein an electrolyte chamber (117) extends between the first opening (113) and the second opening (114) and a connecting unit (119) is formed at the second end (112) in order to connect the sensor cap (100) to a sensor body (11) of the electrochemical sensor (10), - a membrane unit (130) having a first membrane element (140) and a second membrane element (150), wherein the first membrane element (140) is permeable to the analyte (2) and the second membrane element (150) comprises a material which is impermeable to the analyte (2), wherein the second membrane element (150) has a through-hole (151).

Description

[0001] The invention relates to a sensor cap for an electrochemical sensor, a sensor cap for an optochemical sensor, an electrochemical sensor, an optochemical sensor, a manufacturing method of the sensor cap for the electrochemical sensor and a manufacturing method of the sensor cap for the optochemical sensor.

[0002] In analytical measurement technology, particularly in water management, environmental analysis, industrial applications such as food technology, biotechnology, and pharmaceuticals, as well as for a wide variety of laboratory applications, measured variables such as pH, conductivity, or the concentration of analytes, such as ions or dissolved gases in a gaseous or liquid medium, are of great importance. These measured variables can be recorded and / or monitored using electrochemical sensors, such as potentiometric, amperometric, voltammetric, coulometric, or optochemical sensors.

[0003] Electrochemical and optochemical sensors often comprise a membrane which, in a continuous measuring principle, is brought into contact with a measuring medium, for example a measuring gas or a measuring liquid, in order to record measured values. Depending on whether the sensor is electrochemical or optochemical, the membrane serves a different function and is specifically designed for its use. In the case of electrochemical sensors, the membrane is often a porous layer, in particular one having pores or openings, which is at least partially permeable to the measuring medium or at least an analyte contained therein. In the case of optochemical sensors, for example, the membrane is often a thin film which is used as a carrier material.

[0004] A characteristic of these membranes is that mass transport through the membrane can occur in both directions, i.e., from the measuring medium to the interior of the sensor and vice versa. This makes it possible, for example, for the analyte to be detected by the sensor to migrate into the interior of the sensor, which is also desirable. However, in electrochemical sensors, for example, which have an internal electrolyte, components of the electrolyte can also migrate from the measuring chamber of the sensor through the membrane into the surrounding medium. This leads to a reduction in the service life of the electrolyte. Consequently, the sensor's electrolyte must be changed regularly, which increases the sensor's maintenance effort.

[0005] It is therefore an object of the invention to provide a sensor which is durable, reliable and accurate.

[0006] This object is achieved according to the invention by a sensor cap for an electrochemical sensor for determining the concentration of an analyte in a measuring medium according to claim 1.

[0007] The sensor cap according to the invention comprises: - a base body extending along a first axis and having a first end with a first opening and a second end opposite the first end with a second opening, wherein an electrolyte chamber extends between the first opening and the second opening and a connecting unit is formed at the second end to connect the sensor cap to a sensor body of the electrochemical sensor, - a membrane unit comprising a first membrane element and a second membrane element, wherein the first membrane element is permeable to the analyte and the second membrane element comprises a material which is impermeable to the analyte, wherein the second membrane element has a through hole, wherein the membrane unit is connected to the base body in such a way that the first opening is closed by the membrane unit, wherein the first membrane element and the second membrane element are welded to the base body.

[0008] The sensor cap according to the invention makes it possible to reduce leaching of the electrolyte arranged in the electrolyte chamber of the sensor head, which increases the service life of the sensor.

[0009] According to one embodiment of the invention, the first membrane element comprises a hydrophilic material, in particular PET, and the second membrane element comprises a gas-tight material, in particular PVDF.

[0010] According to a further embodiment of the invention, the base body has a positioning aid in the electrolyte chamber, and a spacer element is arranged between the membrane unit and the positioning aid, wherein the positioning aid holds the spacer element at a predetermined axial position.

[0011] According to one embodiment of the invention, the base body has a pressure equalization opening which opens into the electrolyte chamber and is closed by a valve unit.

[0012] According to one embodiment of the invention, the base body comprises a plastic material and the membrane unit is ultrasonically welded to the base body.

[0013] The above-mentioned object is also achieved by an electrochemical sensor according to claim 6.

[0014] The electrochemical sensor according to the invention comprises a sensor cap according to the invention and a sensor body with an electrode unit, wherein the electrode unit has an electrode and wherein the sensor cap is connected to the sensor body via a connecting unit and an electrolyte is arranged in the electrolyte chamber.

[0015] According to one embodiment of the invention, the through-hole of the second membrane element has a predetermined first diameter and the electrode has a predetermined second diameter, wherein the first diameter and the second diameter are substantially identical.

[0016] The above-mentioned object is also achieved by a method for producing a sensor cap according to claim 8.

[0017] The method according to the invention comprises: - Providing a base body and a membrane unit, wherein the base body extends along a first axis and has a first end with a first opening and a second end opposite the first end with a second opening, wherein an electrolyte chamber extends between the first opening and the second opening and a connecting unit is formed at the second end to connect the sensor cap to a sensor body of the electrochemical sensor, - Connecting the membrane unit and the base body so that the first membrane element and the second membrane element are connected to the base body and close the first opening, wherein the first membrane element and the second membrane element are simultaneously ultrasonically welded to the base body.

[0018] According to one embodiment of the invention, the base body has a positioning aid in the electrolyte chamber and, before connecting the membrane unit and the base body, a spacer element is inserted into the electrolyte chamber so that the spacer element is held by the positioning aid.

[0019] The above-mentioned object is also achieved by a sensor cap for an optochemical sensor for determining the concentration of an analyte in a measuring medium according to claim 10.

[0020] The sensor cap according to the invention comprises: - a base body extending along a first axis and having a first end and a second end opposite the first end, wherein a window is formed at the first end and a connecting unit is formed at the second end to connect the sensor cap to a sensor body of the electrochemical sensor, - a membrane unit comprising a first membrane element and a second membrane element, wherein the first membrane element is permeable to the analyte and the second membrane element comprises a material comprising a luminescent substance, wherein the membrane unit is connected to the base body in such a way that the window is covered by the membrane unit, wherein the first membrane element and the second membrane element are welded to the base body.

[0021] The above-mentioned object is also achieved by a method for producing a sensor cap according to claim 11.

[0022] The method according to the invention comprises: - Providing a base body and a membrane unit, wherein the base body extends along a first axis and has a first end and a second end opposite the first end, wherein a window is formed at the first end, - Connecting the membrane unit and the base body so that the first membrane element and the second membrane element are welded to the base body and the window is covered by the membrane unit.

[0023] The above-mentioned object is also achieved by an optochemical sensor according to claim 12.

[0024] The optochemical sensor according to the invention comprises a sensor cap according to the invention and a sensor body, wherein the sensor cap is connected to the sensor body.

[0025] The invention is explained in more detail with reference to the following description of the figures. They show: - Fig. 1: an electrochemical sensor according to the invention, - Fig. 2: an inventive sensor cap of the electrochemical sensor from Fig. 1, - Fig. 3: an optochemical sensor according to the invention, - Fig. 4: an inventive sensor cap of the optochemical sensor from Fig. 3.

[0026] Fig. 1 shows an electrochemical sensor 10 according to the invention with a sensor cap 100 and a sensor body 11. The sensor body 11 has an electrode unit 12 with an electrode 13. The electrode unit 12 comprises a counter electrode 14. The counter electrode 14 is designed, for example, as a sleeve. The electrode 13 is preferably a cathode and the counter electrode 14 an anode. The sensor cap 100 is detachably connected to the sensor body 11. The electrochemical sensor 10 is suitable for detecting an analyte 2 in a measuring medium 1, i.e., for example, for determining the concentration of the analyte 2 in the measuring medium 1. The analyte 2 is, for example, free chlorine or bound chlorine.

[0027] Fig. Figure 2 shows the sensor cap 100 in detail in an exploded view. The sensor cap 100 comprises a base body 110, an electrode 120, and a membrane unit 130.

[0028] The base body 110 extends along a first axis X and has a first end 111 and a second end 112 opposite the first end 111. A first opening 113 is formed at the first end 111. A second opening 114 is formed at the second end 112. An electrolyte chamber 117 extends between the first opening 113 and the second opening 114. The electrolyte chamber 117 is formed, for example, by the entire interior of the base body 110. The electrolyte chamber 117 can be filled with electrolyte from the second opening 114.

[0029] The base body 110 comprises plastic, for example, PVDF, enabling ultrasonic welding with the membrane unit 130. A positioning aid 115 is preferably formed in the electrolyte chamber 117 to position a spacer element 160 relative to an electrode head 121 of the electrode 120 in the electrolyte chamber 117. The base body 110 preferably has several, for example, three, positioning aids 115. The positioning aids 115 are preferably arranged around the first axis X in the base body 110.

[0030] An electrolyte is stored in the electrolyte chamber 117.

[0031] The base body 110 preferably has a pressure equalization opening 116, which opens into the electrolyte chamber 117 and is closed by a valve unit 120. The valve unit 120 is, for example, an elastic ring or an elastic band, which is stretched around the base body 110 via the pressure equalization opening 116 (see Fig. 2). To prevent the elastic band from slipping axially, the base body 110 preferably has an axially circumferential recess complementary to the elastic band.

[0032] At the first end 111, the base body 110 preferably has one or more, in particular three, supports 118, which preferably extend parallel to the first axis X, so that the electrochemical sensor 10 can be placed on a flat surface using the three supports 118 without the membrane unit 130 touching the flat surface. This enables, in particular, simple and safe filling of the electrolyte chamber 117 through the second opening 114 when the sensor cap 100 is separated from the sensor body 11. The support 118 thus allows the sensor cap 100 to be placed stably on a surface.

[0033] At the second end 112, a connecting unit 119 is formed to connect the sensor cap 100 to the sensor body 11 of the electrochemical sensor 10. The connecting unit 119 is configured, for example, as a thread that is complementary to a thread on the sensor body (not shown).

[0034] The membrane unit 130 is attached to the base body 110 such that the membrane unit 130 closes the first opening 113. The membrane unit 130 has a first membrane element 140 and a second membrane element 150. The membrane unit 130 is welded to the base body 110.

[0035] The first membrane element 140 is permeable to the analyte 2, and the second membrane element 150 comprises a material that is impermeable to the analyte 2. The first membrane element 140 is, for example, a sensory hydrophilic membrane. According to an alternative embodiment, it is also possible for the first membrane element 140 to have hydrophobic properties, which leads to lower mass transport through the first membrane element 140. The first membrane element 140 comprises a hydrophilic material, in particular PET, and the second membrane element 150 comprises a gas-tight material, in particular PVDF. The first membrane element 140 and the second membrane element 150 preferably have the same diameter. The first membrane element 140 and the second membrane element 150 are connected to the base body 110 by means of ultrasonic welding.

[0036] The second membrane element 150 has a through-hole 151. The through-hole 151 is preferably arranged centrally in the second membrane element 150. The through-hole 151 has a predetermined first diameter D1, and the electrode 13 has a predetermined second diameter D2. The first diameter D1 and the second diameter D2 are preferably substantially identical. The electrode 13 is preferably arranged axially aligned with the through-hole 151, i.e., on the first axis X.

[0037] According to an embodiment not shown, it is also possible to arrange a third membrane element in the membrane unit 130. The third membrane element is, for example, a support grid or a carrier material with a mediator for an intermediate chemical reaction with the analyte 2.

[0038] A positioning aid 115 is preferably formed in the electrolyte chamber 117. A spacer element 160 is preferably arranged in the electrolyte chamber 117 between the membrane unit 130 and the positioning aid 115. The positioning aid 115 enables the spacer element 160 to be held at a predetermined axial position. The spacer element 160 is, for example, a grid or a porous element. The grid is made of polyester, for example. The spacer element 160 has a predetermined thickness and is in contact, on the one hand, with the membrane unit 130, preferably with the second membrane element 150, and, on the other hand, with the electrode 13 when the sensor cap 100 is connected to the sensor body 11, so that the predetermined thickness of the spacer element 160 defines the distance between the electrode 13 and the membrane unit 130.This ensures a predetermined diffusion path between the electrode 13, which is preferably used as a cathode, and the membrane unit 130. This, in turn, guarantees maximum accuracy for the measurements performed with the electrochemical sensor 10, in particular the so-called slope of the electrochemical sensor 10.

[0039] The membrane unit 130 is connected to the base body 110 such that the electrolyte chamber 117 is closed by the membrane unit 130. The second membrane element 150 is arranged between the first membrane element 140 and the base body 110 such that the electrode 13 is arranged at the through-hole 151. The first membrane element 140 and the second membrane element 150 are jointly connected to the base body 110 by ultrasonic welding. The membrane unit 130 is preferably welded circumferentially to the base body 110 at its edge region. The base body 110 preferably has a so-called concentrator (not shown) formed at the first end 111 and circumferentially extending around the first axis X.

[0040] The following describes a method for manufacturing the sensor cap 100 described above.

[0041] First, the base body 110 and the membrane unit 130 are provided.

[0042] Next, the membrane unit 130 and the base body 110 are connected so that the first membrane element 140 and the second membrane element 150 are simultaneously connected to the base body 110 and close the first opening 113. The connection is achieved by ultrasonic welding. When welding the membrane unit 130, the first membrane element 140 and the second membrane element 150 are simultaneously welded to the base body 110. For this purpose, the first membrane element 140 and the second membrane element 150 are placed on top of one another and welded together to the base body 110. It is advantageous if the first membrane element 140 and the second membrane element 150 have the same diameter.

[0043] Preferably, the membrane unit 130 is welded all around its edge area.

[0044] Before connecting the membrane unit 130 and the base body 110, the spacer element 160 is preferably inserted onto the positioning aid 115 in the electrolyte chamber 117.

[0045] An alternative embodiment of the sensor cap in the application case of an optochemical sensor 20 is described below.

[0046] In Fig. Figure 3 shows an optochemical sensor 20 with a sensor cap 200 and a sensor body 21 for detecting an analyte 3, such as oxygen. The sensor cap 200 is detachably connected to the sensor body 21.

[0047] Fig. Figure 4 shows the sensor cap 200 in an enlarged view. The sensor cap 200 comprises a base body 210 and a membrane unit 230.

[0048] The base body 210 extends along the first axis X and has a first end 211 and a second end 212 opposite the first end 211. A window 219 is formed at the first end 211, and a connecting unit 214 is formed at the second end 212 to connect the sensor cap 200 to a sensor body 21 of the optochemical sensor 20. As shown in Fig. 4, the connecting unit 214 is designed, for example, as an internal thread which is complementary to an external thread (not shown) on the sensor body.

[0049] The membrane unit 230 comprises a first membrane element 240 and a second membrane element 250. The first membrane element 240 is permeable to the analyte 3 and at the same time, for example, hydrophilic. The second membrane element 250 comprises a material that includes a luminescent substance. The second membrane element 250 is also referred to as a functional layer.

[0050] The membrane unit 230 is connected to the base body 210 such that the window is covered by the membrane unit 230. The second membrane element 250 is arranged between the first membrane element 240 and the base body 210.

[0051] The manufacturing process of the sensor cap 200 is discussed below.

[0052] First, the base body 210 and the membrane unit 230 are provided.

[0053] Then, the membrane unit 230 and the base body 210 are joined together, so that the first membrane element 240 and the second membrane element 250 are joined together to the base body 210, and the window 219 is covered by the membrane unit 230. The joining is carried out by an ultrasonic welding process, as in the first embodiment described above. List of reference symbols 1 measuring medium 2 Analyte (free chlorine, combined chlorine) 3 Analyte (Oxygen) 10 electrochemical sensor 11 Sensor body 12 Electrode unit 13 Electrode 14 Counter electrode 20 optochemical sensor 21 Sensor body 100 sensor caps 110 basic bodies 111 first end 112 second end 113 first opening 114 second opening 115 Positioning aid 116 Pressure equalization opening 117 Electrolyte chamber 118 Support 119 Connection unit 120 valve unit 130 membrane unit 140 first membrane element 150 second membrane element 151 through hole 160 spacer element 200 sensor cap 210 basic body 211 first end 212 second end 230 membrane unit 240 first membrane element 250 second membrane element D1 first diameter D2 second diameter X first axis

Claims

[1] Sensor cap (100) for an electrochemical sensor (10) for determining the concentration of an analyte (2) in a measuring medium (1), comprising: - a base body (110) extending along a first axis (X) and having a first end (111) with a first opening (113) and a second end (112) opposite the first end (111) with a second opening (114), wherein an electrolyte chamber (117) extends between the first opening (113) and the second opening (114) and a connecting unit (119) is formed at the second end (112) in order to connect the sensor cap (100) to a sensor body (11) of the electrochemical sensor (10), - a membrane unit (130) with a first membrane element (140) and a second membrane element (150), wherein the first membrane element (140) is permeable to the analyte (2) and the second membrane element (150) comprises a material which is impermeable to the analyte (2), wherein the second membrane element (150) has a through-hole (151), wherein the membrane unit (130) is connected to the base body (110) such that the first opening (113) is closed by the membrane unit (130), wherein the first membrane element (140) and the second membrane element (150) are welded to the base body (110). [2] Sensor cap (100) according to claim 1, wherein the first membrane element (140) comprises a hydrophilic material, in particular PET, and the second membrane element (150) comprises a gas-tight material, in particular PVDF. [3] Sensor cap (100) according to claim 1 or 2, wherein the base body (110) has a positioning aid (115) in the electrolyte chamber (117), and a spacer element (160) is arranged between the membrane unit (130) and the positioning aid (115), wherein the positioning aid (115) holds the spacer element (160) at a predetermined axial position. [4] Sensor cap (100) according to one of the preceding claims, wherein the base body (110) has a pressure equalization opening (116) which opens into the electrolyte chamber (117) and is closed by a valve unit (120). [5] Sensor cap (100) according to one of the preceding claims, wherein the base body (110) comprises a plastic material and the membrane unit (130) is ultrasonically welded to the base body (110). [6] Electrochemical sensor (10) with a sensor cap (100) according to one of the preceding claims and a sensor body (11) with an electrode unit (12), wherein the electrode unit (12) has an electrode (13) and wherein the sensor cap (100) is connected to the sensor body (11) via a connecting unit (119) and an electrolyte is arranged in the electrolyte chamber (117). [7] The electrochemical sensor (10) according to claim 6, wherein the through-hole (151) of the second membrane element (150) has a predetermined first diameter (D1) and the electrode (13) has a predetermined second diameter (D2), the first diameter (D1) and the second diameter (D2) being substantially identical. [8] A method for manufacturing a sensor cap (100) according to claims 1 to 5, comprising: - Providing a base body (110) and a membrane unit (130), wherein the base body (110) extends along a first axis (X) and has a first end (111) with a first opening (113) and a second end (112) opposite the first end (111) with a second opening (114), wherein an electrolyte chamber (117) extends between the first opening (113) and the second opening (114) and a connecting unit (119) is formed at the second end (112) in order to connect the sensor cap (100) to a sensor body (11) of the electrochemical sensor (10), - connecting the membrane unit (130) and the base body (110) so that the first membrane element (140) and the second membrane element (150) are connected to the base body (110) and close the first opening (113), wherein the first membrane element (140) and the second membrane element (150) are simultaneously ultrasonically welded to the base body (110). [9] Method according to claim 8, wherein the base body (110) has a positioning aid (115) in the electrolyte chamber (117) and before connecting the membrane unit (130) and the base body (110), a spacer element (160) is inserted into the electrolyte chamber (117) so that the spacer element (160) is held by the positioning aid (115). [10] Sensor cap (200) for an optochemical sensor (20) for determining the concentration of an analyte (3) in a measuring medium (1), comprising: - a base body (210) extending along a first axis (X) and having a first end (211) and a second end (212) opposite the first end (211), wherein a window (219) is formed at the first end (211) and a connecting unit (214) is formed at the second end (212) in order to connect the sensor cap (200) to a sensor body (21) of the electrochemical sensor (20), - a membrane unit (230) with a first membrane element (240) and a second membrane element (250), wherein the first membrane element (240) is permeable to the analyte (3) and the second membrane element (250) comprises a material which comprises a luminescent substance, wherein the membrane unit (230) is connected to the base body (210) in such a way that the window (219) is covered by the membrane unit (230), wherein the first membrane element (240) and the second membrane element (250) are welded to the base body (210). [11] A method of manufacturing a sensor cap (200) according to claim 10, comprising: - Providing a base body (210) and a membrane unit (230), wherein the base body (210) extends along a first axis (X) and has a first end (211) and a second end (212) opposite the first end (211), wherein a window (219) is formed at the first end (211), - connecting the membrane unit (230) and the base body (210) so that the first membrane element (240) and the second membrane element (250) are welded to the base body (210) and the window (219) is covered by the membrane unit (230). [12] Optochemical sensor (20) comprising a sensor cap (200) according to claim 10 and a sensor body (21), wherein the sensor cap (200) is connected to the sensor body (21).

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