Method for determining an electrical fault in a conductivity sensor and conductivity sensor
By evaluating the current time distribution characteristic value under the AC voltage applied by the conductivity sensor, the diagnosis electrode short circuit or the power supply line is disconnected, the difficulty of conductivity sensors in the prior art detecting electrical faults is solved, and continuous diagnosis and accurate measurement are achieved.
Patent Information
- Application Number
- CN201980076908.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Priority Date
- 2018-11-21
- Filing Date
- 2019-10-23
- Publication Date
- 2024-12-17
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
Existing conductivity sensors require additional electrical components when detecting electrical faults, and it is difficult to continuously perform fault diagnosis, affecting measurement accuracy.
By applying an AC voltage and evaluating the current amplitude characteristic value of the current time distribution, it is determined whether there is a short circuit in the electrode or the power supply line is disconnected, and the electrical fault diagnosis of the conductivity sensor is achieved without additional electrical components.
Continuous fault diagnosis during conductivity sensor operation is achieved, ensuring the accuracy of measurement and correct measurement of conductivity, avoiding the use of additional electrical components.
Smart Images
Figure CN113015916B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a method for determining an electrical fault of a conductivity sensor and a conductivity sensor, in particular a method for determining an electrical fault of a conductivity sensor and a conductivity sensor for capturing the conductivity of a medium according to the conductivity principle, in particular a liquid medium such as, for example, water. Background Art
[0002] Conductive conductivity sensors are used in a wide range of applications to measure the conductivity of a medium. The best known conductive conductivity sensors are the well-known two-electrode or four-electrode sensors.
[0003] Two-electrode sensors have two electrodes which are immersed in the medium during measuring operation and to which a DC or AC voltage is applied. The measuring electronics connected to the two electrodes measures the electrical impedance of the conductivity measuring cell and from this the specific resistance or specific conductivity of the medium located in the measuring cell is ascertained based on the cell constants which are predetermined by the geometry and properties of the measuring cell.
[0004] Four-electrode sensors have four electrodes immersed in the medium during measuring operation, two of which are operated as so-called current electrodes and two of which are operated as so-called voltage electrodes. During measuring operation, a DC or AC voltage is applied between the two current electrodes and a DC or AC current is thus injected into the medium. The injected current induces a potential difference between the voltage electrodes, which is determined by a preferably currentless measurement. In this case too, the impedance of the conductivity measuring cell resulting from the injected current and the measured potential difference is also determined by the measuring electronics connected to the current and voltage electrodes, and the specific resistance or specific conductivity of the medium located in the measuring cell is then determined based on the cell constants predetermined by the geometry and properties of the measuring cell.
[0005] EP 1 089 072 A2 discloses a conductivity sensor with a cylindrical housing, wherein metal measuring electrodes are arranged in a planar manner on an end wall of the cylindrical housing in the shape of a circular surface. In this case, the metal measuring electrodes form two voltage electrodes and two current electrodes. The voltage electrode is designed as a circular surface and is surrounded by two current electrodes in the form of a circle or ring arranged substantially in a semicircle.
[0006] A measuring cell for measuring and monitoring the electrical conductivity of a liquid is known from US 4227151 A. The measuring cell comprises a plurality of circular electrodes which are arranged alternately at a certain distance from one another and are electrically insulated from one another. Here, at least four concentric circular electrodes are arranged in or on a planar surface and are separated from one another by areas of non-conductive material. Here, the innermost of the four electrodes is of hollow design in order to accommodate a temperature sensitive element.
[0007] Another conductivity measuring transducer is known from EP 0386660 A1. Four concentric metal rings are attached as electrodes for the conductivity measuring transducer at the end face of a cylindrical support made of insulating material. The electrodes are flush with the end face here. The electrodes with the larger cross section are connected here as current electrodes, while the electrodes with the smaller cross section are used as voltage electrodes.
[0008] A conductivity sensor is also known from DE 10 2010 042 637 A1 in which concentrically arranged electrodes have an equal constant area.
[0009] In conductivity sensors known from the prior art, it is known to check the correct function of the circuit of the electrodes by providing an additional circuit. The additional circuit for the voltage electrodes can be provided, for example, in a four-electrode sensor. Here, each voltage electrode is connected to a voltage source via a voltage element. When the electrical connection of the voltage electrodes has correct function, a voltage less than a predetermined voltage threshold is generated. However, in the event of a break in the electrical connection of the voltage electrodes, the voltage rises up to a maximum value of the voltage value of the voltage source and exceeds the predetermined voltage threshold. Summary of the invention
[0010] The invention is based on the object of providing a method for determining an electrical fault in a conductivity sensor, in particular an electrical fault of at least one electrode pair of a conductivity sensor, which method can be performed as continuously as possible during operation of the conductivity sensor and does not require additional electrical components for this purpose.
[0011] This object is achieved by the following method and conductivity sensor.
[0012] The invention is essentially based on the idea of performing a check on the correct functional capability of a conductivity sensor for ascertaining the conductivity of a medium, such as, for example, water for filling in an internal combustion engine of a vehicle, without the need for additional electrical components in the conductivity sensor. The conductivity sensor, which can in particular be a four-electrode sensor, is operated for this purpose in its operating mode for ascertaining the conductivity of the medium, wherein during this operating mode a diagnosis on the correct conductivity can be performed, since it can be checked whether the at least one pair of electrodes is operating correctly. In particular it is checked whether the at least one electrode pair is short-circuited and / or whether there is a line break in the power supply line to the at least one electrode pair. This is ascertained, for example, by evaluating the alternating current generated by the application of an alternating voltage.
[0013] According to a first aspect of the present invention, a method for determining an electrical fault in a conductivity sensor for ascertaining the conductivity of a medium according to the conductivity principle is accordingly disclosed. The conductivity sensor has a first electrode pair, which is designed to be completely placed in the medium. The method according to the present invention comprises applying an alternating voltage at the first electrode pair, ascertaining a time distribution of an alternating current at the first electrode pair generated in response to applying the alternating voltage at the first electrode pair, ascertaining a current amplitude characteristic value of the ascertained time distribution of the alternating current, and determining an electrical fault of the conductivity sensor if the ascertained current amplitude characteristic value is below a first predetermined current threshold value or above a second predetermined current threshold value.
[0014] According to the invention, the application of an alternating voltage to the first electrode pair during operation of the conductivity sensor is carried out while the conductivity of the medium, in particular water for water injection in an internal combustion engine of a vehicle, is captured by means of the conductivity sensor. In particular, the alternating voltage applied to the first electrode pair for operation of the conductivity sensor is simultaneously used for diagnosis of the functional capacity of the conductivity sensor, in particular of the functional capacity of the first electrode pair.
[0015] Determining an electrical fault of the first electrode pair preferably comprises: determining a short circuit between the electrodes of the first electrode pair if the ascertained current amplitude characteristic value is above a first predetermined current threshold value. Additionally or alternatively, according to a preferred embodiment of the method according to the invention, determining an electrical fault of the first electrode pair comprises: determining a break in one of the power supply lines to the electrodes of the first electrode pair if the ascertained current amplitude characteristic value is below a second predetermined current threshold value.
[0016] In particular, the invention is based on the fact that, in the event of a short circuit between the electrodes of the first electrode pair, the alternating current generated by the alternating voltage applied to the first electrode pair is greater than a first predetermined current threshold value and therefore a correct measurement of the conductivity of the medium can no longer be ensured. In contrast, a disconnection of one of the supply lines to the electrodes of the first electrode pair has the consequence that the alternating current is below a second predetermined current threshold value and therefore again a correct measurement of the conductivity of the medium cannot be performed. In an exemplary configuration, when a voltage amplitude of approximately 0.5 V is applied to the first electrode pair, the first predetermined current threshold value is approximately 0.1 mA and the second predetermined current threshold value is approximately 100 mA, depending on the diameter of the rod electrodes and the distance of the rod electrodes from one another. These values for the two current threshold values apply, for example, to rod electrodes with a diameter of approximately 6 mm, a length of approximately 4 mm and a distance between them of approximately 8 mm.
[0017] In a preferred configuration of the method according to the invention, the current amplitude characteristic value corresponds to the amplitude of the time distribution of the alternating current, the root mean square value or the peak-to-peak current value. The peak-to-peak current value here describes the difference between the maximum and minimum values of the time distribution of the sinusoidal shape of the alternating current, i.e., the peak-to-valley value.
[0018] In another preferred configuration of the method according to the invention, the conductivity sensor further comprises a second electrode pair, which is designed to be completely placed in the medium. If it is established that there is no electrical fault of the first electrode pair, which means that the first electrode pair is functioning correctly and can be electrically driven, the method according to the invention further comprises in a preferred configuration ascertaining a time distribution of an alternating voltage at the second electrode pair as a result of the alternating voltage applied at the first electrode pair, ascertaining a voltage amplitude characteristic value of the time distribution of the ascertained alternating voltage at the second electrode pair, and determining an electrical fault of the second electrode pair if the ascertained voltage amplitude characteristic value is below a predetermined voltage threshold.
[0019] In this preferred configuration, it is therefore possible to determine whether the second electrode pair is also functioning correctly and thus the complete conductivity sensor, preferably designed as a four-electrode sensor, can operate correctly. The check of the functional capability of the second electrode pair does not take place until the first electrode pair has been diagnosed as functionally capable, of course. That is, only by applying an alternating voltage to the first electrode pair and thereby generating a correct alternating current at the first electrode pair can a potential difference then be generated at the second electrode pair and therefore only then can it be ascertained whether an electrical fault is present at the second electrode pair.
[0020] In an exemplary configuration, the predetermined voltage threshold with a voltage amplitude of about 0.5 V applied at the first electrode pair can be about 0.1 V, depending on the diameter of the rod electrodes and the distance of the rod electrodes from each other. This value of the voltage threshold applies, for example, to rod electrodes with a diameter of about 6 mm, a length of about 4 mm, and a distance of about 8 mm therebetween. Advantageously, the voltage amplitude characteristic value corresponds to the amplitude, the root mean square value or the peak-to-peak voltage value of the time distribution of the alternating voltage. The peak-to-peak voltage value here describes the difference between the maximum and the minimum value of the sinusoidal-shaped time curve of the alternating voltage generated at the second electrode pair, i.e. the peak-to-valley value.
[0021] In a preferred configuration of the method according to the invention, determining an electrical fault of the second electrode pair comprises ascertaining a phase shift between an alternating voltage applied at the first electrode pair and an alternating voltage generated thereby at the second electrode pair, determining a short circuit between the electrodes of the second electrode pair if the ascertained phase shift is below a predetermined phase threshold, and determining a break in one of the supply lines to the electrodes of the second electrode pair if the ascertained phase shift is above a predetermined phase threshold. Use is made of the fact that, in the presence of a short circuit, there is hardly any phase shift between the temporal voltage profile at the first electrode pair and the temporal voltage profile at the second electrode pair. In contrast, in the case of a line break, this phase shift will increase.
[0022] In addition, according to another aspect of the present invention, a conductivity sensor for capturing the conductivity of a medium according to the conductivity principle is disclosed. The conductivity sensor according to the present invention comprises a first electrode pair designed to be completely placed in the medium, a second electrode pair designed to be completely placed in the medium, and a control unit, which is electrically connected to the first electrode pair and the second electrode pair and is designed to perform a method for determining an electrical fault of the conductivity sensor according to the method according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Further advantages and configurations of the present invention will become apparent to the expert by practicing the teachings described herein and observing the accompanying drawings, in which:
[0024] Figure 1 shows a schematic diagram of a conductivity sensor having a first electrode pair and a second electrode pair according to the present invention,
[0025] Figure 2 shows the time distribution of the alternating current generated at the first electrode pair by the alternating voltage applied to the first electrode pair,
[0026] Figure 3 The method for determining the Figure 1 An exemplary flow chart of a method for detecting an electrical failure of a conductivity sensor, and
[0027] Figure 4 The method for determining the Figure 1 An exemplary flow chart of a preferred configuration of a method for detecting an electrical malfunction of a conductivity sensor. DETAILED DESCRIPTION
[0028] In the context of the present disclosure, the term "electrical fault" refers to a faulty state of the conductivity sensor in its electrical components, in particular its electrodes or the power supply lines to the electrodes. For example, an electrical fault may exist in the form of a short circuit between the electrodes or a break in the power supply lines to the electrodes.
[0029] Figure 1 A schematic diagram of a conductivity sensor 100 according to the present invention is shown. The conductivity sensor 100 according to the present invention is designed to ascertain the conductivity of a medium 10 placed in a container 20. The medium is, for example, water, which can be injected for injection into the combustion chamber of a vehicle internal combustion engine. Alternatively, the medium can also be a urea aqueous solution placed in a urea container and designed to be injected into the exhaust gas duct upstream of an SCR catalytic converter. In addition, the medium can be alcohol, such as, for example, ethanol, which is stored in an alcohol container and is designed to be injected into the combustion chamber of a vehicle internal combustion engine.
[0030] The conductivity sensor 100 according to the present invention includes a first electrode pair 110, a second electrode pair 120 and a control unit ( Figure 1 The control unit is not explicitly shown in the figure), which is electrically connected to the first electrode pair 110 and the second electrode pair 120 and is designed to operate the first electrode pair 110 and the second electrode pair 120 and evaluate the corresponding electrical signals. The control unit is particularly designed to perform the method according to the present invention for determining an electrical fault of the conductivity sensor 100, in particular an electrical fault of the first electrode pair 110 and the second electrode pair 120, which will be referred to below. Figure 3 and 4 Explain in more detail.
[0031] Figure 1 The conductivity sensor 100 is designed as a so-called four-electrode sensor. The first electrode pair 110 includes a first electrode 112 and a second electrode 114, which are arranged at a predetermined distance from each other in the medium 10. The first electrode 112 and the second electrode 114 are each electrically connected to a voltage source 116, in particular an AC voltage source, via power supply lines 118, 119.
[0032] The second electrode pair 120 comprises a third electrode 122 and a fourth electrode 124 which are arranged at a predetermined distance from each other in the medium 10. The third electrode 122 and the fourth electrode 124 are electrically connected to a measuring instrument 126, in particular a voltage measuring instrument, via power supply lines 128, 129, respectively.
[0033] like Figure 1 As shown, the electrodes 122, 124 of the second electrode pair 120 are arranged between the electrodes 112, 114 of the first electrode pair 110. Furthermore, all electrodes 112, 114, 122, 124 are designed as rod electrodes and are suitable for being completely immersed in the medium 10. Alternatively, it is also possible that the electrodes are also designed as cylindrical electrodes arranged concentrically relative to each other, as is known from the prior art of conductivity sensors, in particular four-electrode sensors. In particular, according to the invention, it is contemplated that the shape and arrangement of the electrodes relative to each other are not limited to Figure 1Instead of the configuration shown, the shape and arrangement of the electrodes may be chosen as in conductivity sensors known from the prior art.
[0034] Figure 1 The measuring principle of the conductivity sensor 100 is based on the conductivity principle, as is sufficiently known from the prior art. In particular, an alternating voltage is applied to the electrodes 112, 114 of the first electrode pair 110 by means of an alternating voltage source 160, and the alternating current at the electrodes 112, 114 of the first electrode pair resulting from this is then determined. In order to eliminate boundary and surface effects, the second electrode pair 120 is also used to take these interfering effects into account in order to increase the accuracy of the measurement. For this purpose, the potential difference in the form of an alternating voltage between the electrodes 122, 124 of the second electrode pair 120 is determined by means of a measuring instrument 126. The potential difference between the electrodes 122, 124 of the second electrode pair 120 is generated based on the alternating voltage applied to the electrodes 112, 114 of the first electrode pair 110. The resistance of the medium 10 can then be ascertained from the ascertained potential difference between the electrodes 122, 124 of the second electrode pair and the electrodes 112, 114 of the first electrode pair at the alternating current generated by the alternating voltage applied to them. Taking into account the geometric dimensions of the electrodes, the conductivity can then be ascertained and determined as the inverse of the medium resistance.
[0035] Figure 2 An exemplary time distribution of an alternating current generated at the first electrode pair 110 by an alternating voltage applied to the first electrode pair 110 is shown. Figure 2 The time distribution of the AC current is basically sinusoidal. Figure 2 The arrows in FIG. 2 show the amplitude of the alternating current, and arrow 24 describes the peak-to-peak current value of an oscillating alternating current. The amplitude 22 or the peak-to-peak current value 24 may be referred to later. Figure 3 As explained in more detail for checking the functionality of the conductivity sensor, the rms value of the sinusoidal alternating current can alternatively be used.
[0036] Figure 3 An exemplary flow chart of a method according to the invention for determining an electrical fault of a conductivity sensor 100 according to the invention is shown. The method according to the invention is preferably not performed until it is determined that the electrodes 112, 114, 122, 124 of the conductivity sensor 100 are completely positioned in the medium 10. This can be done, for example, by capturing the level to which the container 20 is filled with the medium 10. If the filling level is above a predetermined filling level threshold, it can be concluded that the electrodes 112, 114, 122, 124 of the conductivity sensor 100 are completely immersed in the medium 10. The same applies to Figure 4 method, which will be further described below.
[0037] Figure 3 Starting from step 300 and then proceeding to step 310, in step 310, an AC voltage is applied to the first electrode pair 110, as is known for proper measurement operation of the conductivity sensor 100. In a subsequent step 320, as is also known for proper measurement operation of the conductivity sensor 100, the temporal distribution of the AC current at the first electrode pair 110 generated in response to the application of the AC voltage at the first electrode pair 110 is ascertained (e.g., see Figure 2 time distribution of the AC current).
[0038] According to the present invention, in the subsequent step 330, the current amplitude characteristic value of the detected alternating current with respect to the time distribution is determined. For example, the amplitude 22 or the peak-to-peak current value 24 of the alternating current with respect to the time distribution can be used (see Figure 2 ). Alternatively, as already described above, its RMS value may be used.
[0039] In a further subsequent step 340 , an electrical fault of the first electrode pair 110 is determined if the ascertained characteristic value of the current amplitude is below a first predetermined current threshold value or above a second predetermined current threshold value.
[0040] In particular, if the ascertained current amplitude characteristic value is above a first predetermined current threshold value, a short circuit between the electrodes 112, 114 of the first electrode pair 110 may be determined. In particular, in the event of a short circuit between the electrodes 112, 114 of the first electrode pair 110, a current value having a higher than average amplitude will be measured, which may then be identified as a short circuit and interpreted as an electrical fault of the conductivity sensor 100.
[0041] However, if the ascertained characteristic value of the current amplitude is below a second predetermined current threshold value, it can be concluded that there is a break in one of the supply lines 118, 119 to the electrodes 112, 114 of the first electrode pair 110. In other words, this break has the effect that no current or only a very low current can flow between the electrodes 112, 114 of the first electrode pair 110 and therefore the AC voltage applied there can no longer be applied correctly.
[0042] According to the invention, it is also provided that after determining the correct functional capability of the first electrode pair 110 of the conductivity sensor 100, the functional capability of the second electrode pair 120 of the conductivity sensor is additionally checked. To this end, Figure 4 An exemplary flow chart of a corresponding method is shown.
[0043] Figure 4 Begins at step 400 and then proceeds to step 410 where the execution of Figure 3In a subsequent step 420, it is queried whether an electrical fault of the first electrode pair 110 of the conductivity sensor 100 has occurred. Figure 3 If an electrical fault of the first electrode pair 110 is determined in step 420, the method proceeds to step 490 and ends. This is because the electrical functional capability of the second electrode pair 120 of the conductivity sensor 100 can be checked only when the first electrode pair 110 of the conductivity sensor 100 functions correctly.
[0044] However, if it is determined in step 420 that there is no electrical fault in the first electrode pair 110 of the conductivity sensor 100, then Figure 4 The method proceeds to step 430 in which the time distribution of the AC voltage at the second electrode pair 120 of the conductivity sensor 100 generated by the AC voltage applied at the first electrode pair 110 is ascertained, which is also done in normal measuring operation of the conductivity sensor 100 .
[0045] Thus, in step 440, the determined time-distributed voltage amplitude characteristic value of the alternating voltage of the second electrode pair 120 of the conductivity sensor 100 is determined. In a subsequent step 450, it is checked whether the determined voltage amplitude characteristic value is below a predetermined voltage threshold. If it is established in step 450 that the determined voltage amplitude characteristic value is greater than the predetermined voltage threshold, the method proceeds to step 460, in which the second electrode pair 120 of the conductivity sensor 100 is determined to be functionally capable, before the method ends at step 490.
[0046] However, if it is established in step 450 that the ascertained voltage amplitude characteristic value is less than the predetermined voltage threshold, the method proceeds to step 470 in which an electrical fault is initially ascertained in the second electrode pair 120 of the conductivity sensor 100. In a subsequent step 480, a phase shift between the alternating voltage applied to the first electrode pair 110 of the conductivity sensor 100 and the alternating voltage found as a result at the second electrode pair 120 of the conductivity sensor 100 is ascertained.
[0047] If it is determined in the subsequent step 482 that the ascertained phase shift is less than a predetermined phase threshold, the method proceeds to step 484, in which a short circuit is established between electrodes 122, 124 of second electrode pair 120 of conductivity sensor 100 before the method ends at step 490. The phase threshold is, for example, approximately 10°.
[0048] However, if it is determined in step 482 that the ascertained phase shift is greater than a predetermined phase threshold, the method proceeds to step 486 in which a break in one of the power supply lines 128 , 129 to the electrodes 122 , 124 of the second electrode pair 120 of the conductivity sensor 100 is established before the method ends at step 490 .
[0049] In particular, the present invention here makes use of the fact that, in the event of a short circuit between the electrodes 122, 124 of the second electrode pair 120 of the conductivity sensor 100, there is hardly any phase shift between the temporal voltage profile at the first electrode pair 110 and the temporal voltage profile at the second electrode pair 110. In contrast, in the event of a line break, this phase shift will increase.
[0050] Using the method according to the invention and the conductivity sensor 100 according to the invention, it is possible to continuously perform diagnostics (such as, for example, OBD diagnostics) regarding the functional capabilities of the conductivity sensor 100 during operation of the conductivity sensor 100, without the need to provide separate electrical components and circuits. Furthermore, the diagnostics can be performed during ongoing operation of the conductivity sensor 100, so that it does not have to be interrupted for diagnostic purposes.
Claims
1. A method for determining an electrical fault in a conductivity sensor (100), the conductivity sensor being used to determine the conductivity of a medium according to the conductivity principle, wherein: The conductivity sensor (100) comprises a first electrode pair (110) designed to be completely placed in the medium and a second electrode pair (120) designed to be completely placed in the medium, wherein the method comprises: - applying an alternating voltage to the first electrode pair (110), - ascertaining the temporal distribution of an alternating current at the first electrode pair (110) generated in response to applying an alternating voltage at the first electrode pair (110), - determining a characteristic value of the current amplitude of the determined alternating current with respect to its time distribution, - if the determined current amplitude characteristic value is below a first current threshold value or above a second current threshold value, an electrical fault of the conductivity sensor (100) is determined, and If there is no electrical fault of the first electrode pair (110): - determining the time distribution of the alternating voltage at the second electrode pair (120) generated by the alternating voltage applied at the first electrode pair (110), - determining a voltage amplitude characteristic value of the determined temporal distribution of the alternating voltage at the second electrode pair (120), and - If the determined voltage amplitude characteristic value is below a voltage threshold value, an electrical fault of the second electrode pair (120) is determined.
2. The method according to claim 1, wherein: Determining an electrical fault of the conductivity sensor (100) comprises: - if the determined current amplitude characteristic value is above the first current threshold value, determining a short circuit between the electrodes (112, 114) of the first electrode pair (110), and / or - if the ascertained characteristic value of the current amplitude is below the first current threshold value, a break in one of the power supply lines to the electrodes (112, 114) of the first electrode pair (110) is determined.
3. The method according to claim 1, wherein: The first current threshold value and / or the second current threshold value are predetermined depending on the applied voltage amplitude value and the geometry of the electrodes (112, 114) of the first electrode pair (110).
4. The method according to any one of claims 1 to 3, wherein: The current amplitude characteristic value corresponds to the amplitude, root mean square value or peak-to-peak current value of the time distribution of the alternating current.
5. The method according to claim 1, wherein: The voltage threshold is predetermined depending on the magnitude of the voltage applied to the first electrode pair (110) and the geometric shapes of the electrodes (122, 124) of the first and second electrode pairs (120).
6. The method according to claim 1, wherein: The voltage amplitude characteristic value corresponds to the amplitude, root mean square value or peak-to-peak voltage value of the time distribution of the AC voltage.
7. The method according to any one of claims 5 to 6, wherein: Determining an electrical fault of the second electrode pair (120) comprises: - determining a phase shift between an alternating voltage applied to the first electrode pair (110) and an alternating voltage generated thereby at the second electrode pair (120), - if the ascertained phase shift is below a predetermined phase threshold, determining a short circuit between the electrodes (122, 124) of the second electrode pair (120), and - If the ascertained phase shift is above a predetermined phase threshold, a break in one of the power supply lines to the electrodes (122, 124) of the second electrode pair (120) is determined.
8. A conductivity sensor (100) for capturing the conductivity of a medium according to the conductivity principle, wherein: The conductivity sensor (100) comprises: - a first electrode pair (110) which is designed to be completely placed in the medium, - a second electrode pair (120) designed to be completely disposed in the medium, and - a control unit electrically connected to the first electrode pair (110) and the second electrode pair (120) and designed to perform the method of determining an electrical fault of the conductivity sensor (100) according to any one of claims 1 to 7.