METHOD AND DEVICE FOR PRODUCING A REFERENCE ELECTRODE

Abstract

The present disclosure relates to a method for producing a reference electrode, wherein an internal space of the reference electrode is delimited by an outer wall and wherein the internal space contains a reference electrolyte up to a specified height, wherein the reference electrode is introduced into a pressurization chamber, wherein a defined overpressure is applied to the pressurization chamber and, via an opening that is located above the specified height in the outer wall of the reference electrode to the internal space of the reference electrode, and wherein the opening in the outer wall of the reference electrode is closed at the defined overpressure . The present disclosure further relates to a device for carrying out the method.

Claims

1. A method for producing a reference electrode, comprising: introducing a reference electrode into a pressurization chamber, the reference electrode including an outer wall at least partially defining an internal space, wherein the internal space contains a reference electrolyte to a specified height within the internal space; applying a defined overpressure to the pressurization chamber and to the internal space of the reference electrode via an opening in the outer wall of the reference electrode, the opening disposed above the specified height and in communication with the internal space; and closing the opening when the internal space is at the defined overpressure.

2. The method according to claim 1, the method further comprising generating the opening in the outer wall of the reference electrode by supplying energy selectively.

3. The method according to claim 2, wherein the opening in the outer wall of the reference electrode is generated or closed by thermal fusion or melt-sealing by means of laser radiation or a flame.

4. The method according to claim 1, wherein the opening in the outer wall of the reference electrode is closed by supplying energy selectively.

5. The method according to claim 1, the method further comprising, after closing the opening, venting or reducing the applied to the pressurization chamber to a pressure prevailing in the surroundings of the pressurization chamber.

6. A sensor assembly, comprising a reference electrode, wherein the reference electrode is manufactured by: introducing the reference electrode into a pressurization chamber, the reference electrode including an outer wall at least partially defining an internal space, wherein the internal space contains a reference electrolyte to a specified height within the internal space; applying a defined overpressure to the pressurization chamber and to the internal space of the reference electrode via an opening in the outer wall of the reference electrode, the opening disposed above the specified height and in communication with the internal space; and closing the opening when the internal space is at the defined overpressure.

7. The sensor assembly according to claim 6, wherein the reference electrode is further manufactured by generating the opening in the outer wall of the reference electrode by supplying energy selectively.

8. The sensor assembly according to claim 7, wherein the opening in the outer wall of the reference electrode is generated or closed by thermal fusion or melt-sealing by means of laser radiation or a flame.

9. The sensor assembly according to claim 6, wherein the opening in the outer wall of the reference electrode is closed by supplying energy selectively.

10. The sensor assembly according to claim 6, wherein the reference electrode is further manufactured by, after closing the opening, venting or reducing the pressure applied to the pressurization chamber to a pressure prevailing in the surroundings of the pressurization chamber.

11. The sensor assembly according to claim 6, wherein the reference electrode is made of glass or plastic.

12. The sensor assembly according to claim 6, wherein the sensor assembly is a potentiometric single-rod measuring chain.

13. A device for manufacturing a reference electrode having an opening site, the device comprising: a pressurization chamber having a housing structured to accept the reference electrode; a pressure supply configured to apply and adjusted a defined overpressure in the pressurization chamber; and a laser disposed and focused such that an opening is produced and/or closed at the opening site of the reference electrode by means of laser radiation, wherein the reference electrode is disposed within the pressurization chamber.

14. The device according to claim 13, wherein the laser is arranged outside the housing of the pressurization chamber, and wherein at least one section of the housing of the pressurization chamber is made of a material that is transparent to the laser radiation produced by the laser.

15. The device according to claim 13, wherein the laser is arranged inside the housing of the pressurization chamber.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present disclosure is explained in more detail with reference to the following figures. Illustrated are:

[0023] FIG. 1 shows a cross-sectional view of a potentiometric pH sensor designed as a single-rod measuring chain;

[0024] FIG. 2 shows a schematic representation of a pH electrode designed as a single-rod measuring chain with an opening in the outer wall of the reference electrode;

[0025] FIG. 3 shows a cross-sectional view of a pressurization chamber; and

[0026] FIG. 4 shows a schematic representation of an embodiment of a device according to the present disclosure for producing a pressurized reference electrode.

DETAILED DESCRIPTION

[0027] FIG. 1 shows a schematic representation of a potentiometric sensor for pH measurement, which sensor comprises a potentiometric measuring chain, designed as a single-rod measuring chain 7, with a reference half-cell or reference electrode 1 and a measuring half-cell or measuring electrode 12. The pipe-shaped housing wall 17 of the measuring electrode 12 is closed at its end region facing the measuring medium 16 by a pH-sensitive diaphragm 14. The end regions of the measuring electrode 12 facing away from the measuring medium 16 and the reference electrode 1 are closed in a gas-tight manner by means of a sensor head 21, which can also comprise parts of an electronic measuring/evaluation unit 20.

[0028] The internal space 13 of the measuring electrode 12 contains an inner electrolyte 15 that comprises a pH buffer system. A deflecting element 19 is immersed in the inner electrolyte 15. The deflecting element 19 is, for example, a chlorinated silver wire. The deflecting element 19 is connected to the electronic measuring/evaluation unit 20, which is either fully or partially located in the sensor head 21 or in a remotely arranged transmitter.

[0029] The reference electrode 1 is designed as a silver/silver chloride reference electrode. The internal space 2 of the reference electrode 1 is formed by the housing wall 17 of the measuring electrode 12 and the outer wall 3 of the reference electrode 1. The reference electrode 1 is arranged annularly around the measuring electrode 12. In the end regions facing the pH-sensitive diaphragm 14, the measuring electrode 12 and the reference electrode 1 are connected to one another. The internal space 2 of the reference electrode 1 contains the reference electrolyte 4. The reference electrolyte 4 can comprise a highly concentrated KCl solution with a molar concentration of, for example, 3 M. The reference electrolyte 4 can be thickened by adding a polymer, such as, for example, a polyacrylamide or a slightly cross-linked DADMAC-based gel.

[0030] In the reference electrolyte 4, a deflecting element 22 is immersed that can be designed as a chlorinated silver wire, just like the deflecting element 19 of the measuring electrode 12. In the outer wall 3 of the reference electrode 1, a bridge is provided that is designed as, for example, a through-opening or as a porous diaphragm 23. Via the diaphragm 23, the reference electrolyte 4 is in electrolytic contact with the measuring medium 16 in the region of the pH-sensitive diaphragm 14.

[0031] The electronic measuring/evaluation unit 20 generates a measurement signal, which represents the pH value of the measuring medium 16, based upon the potential difference picked up between the deflecting element 19 of the measuring electrode 12 and the deflecting element 22 of the reference electrode 1. This measurement signal is forwarded wired or wirelessly via an appropriate connection to a superordinate unit (not shown in FIG. 1). The superordinate unit can be a data processing unit, e.g., a transmitter, a traditional personal computer, or a process control unit, such as a programmable logic controller (PLC).

[0032] FIG. 2 shows a schematic representation of a pH sensor, designed as a single-rod measuring chain 7, with an opening 5 in the outer wall 3 of the reference electrode 1. A corresponding single-rod measuring chain 7 is illustrated in FIG. 1. Nonetheless, all types of reference electrodes or sensors in which a reference electrode is provided can be pressurized by the method according to the present disclosure and using the device according to the present disclosure.

[0033] The pressurization takes place according to the present disclosure via the opening 5 that is provided in the outer wall 3 of the reference electrode 1. This opening 5 is preferably arranged in a region that is not in contact with the reference electrolyte 4 when the single-rod measuring chain 7 is positioned appropriately, for example, upright. In FIG. 1, the filling height of the reference electrolyte 4 is marked h. The opening 5 is thus, preferably, above the filling height h.

[0034] The outer wall 3 of the reference electrode 1 preferably consists of plastic or glass. The opening 5 is introduced into the outer wall 3 of the reference electrode 1 by means of one of the known methods. If the outer wall 3 consists of glass, the opening 5 is preferably produced by thermal fusion in the flame or by means of laser.

[0035] FIG. 3 shows a schematic representation of a pressurization chamber 6 that can be used in connection with the present disclosure. The appropriately prepared reference electrode 1 (as a component of a single-rod measuring chain 7 in the case shown) is introduced into the pressurization chamber 6 for purposes of pressurization.

[0036] FIG. 4 shows a schematic representation of an embodiment of the device according to the present disclosure for producing a pressurized reference electrode 1.

[0037] As previously mentioned, the opening 5 can also be produced by thermal fusion, after the single-rod measuring chain 7 has been positioned in the pressurization chamber 6. The fusion takes place, in the case shown, using the laser radiation LS of the laser 10 via a section 11.

[0038] As shown in FIGS. 3 and 4, the pressurization chamber 6 consists of a pressure-resistant housing 9 with a removable opening 18 for introducing and removing the sensors. The opening 18 can be mounted to the housing 9 in a pressure-tight manner. Furthermore, a pressure supply 8 or a gas connection for a gas pressure regulator, not shown separately in FIG. 3, is provided on the pressurization chamber 6. The section 11 of the wall of the housing 9 can be designed as an optical window 11. Via the section 11 that is transparent to the laser radiation LS, the laser radiation LS produced by the laser 10 is radiated into the pressurization chamber 8. The laser radiation LS is focused onto the outer wall 3 of the reference electrode 1 in the region of the opening 5.

[0039] As soon as the pH sensor is in the pressurization chamber 6 and has the opening 5, the desired overpressure is adjusted in the pressurization chamber 6 via the pressure supply 8. Since the gas-filled space region 24 remaining above the reference electrolyte 4 communicates with the internal space of the pressurization chamber 6 via the opening 5, the adjusted overpressure P.sub.O also prevails in the reference electrode 1 after a short dwell time. The opening 5 is then sealed, and thus closed, by means of the focused laser radiation LS. The pressurization chamber 6 is subsequently vented; the pressure is reduced, for example, to atmospheric pressure P.sub.N. The pressure previously adjusted via the pressurization chamber 6 continues to prevail in the reference electrode 1. Finally, the pH sensor with the pressurized reference electrode 1, or even the pressurized reference electrode 1 as such, is removed from the pressurization chamber 6.

[0040] In summary, the advantages of the method according to the present disclosure or the device according to the present disclosure are as follows:

[0041] the pressure in a reference electrode 1 can be adjusted with high precision;

[0042] reference electrodes 1 can be produced in a reproducible manner within a very short period of time; and

[0043] the production method according to the present disclosure can be automated easily by means of a robot. The accordingly produced reference electrodes 1 are, therefore, cost-effective.