Device for measuring electrical conductivity in liquid medium

Abstract

An apparatus for measuring electrical conductivity, comprising: an electrode (700a, 700b); a current source (100) configured to inject a current into the medium (600); a switching block (200) configured to generate a current flow through the medium (600) from the first electrode (700a) to the second electrode (700b) or from the second electrode (700b) to the first electrode (700a); a sensor block (300) connected to the first electrode (700a) and / or the second electrode (700b), configured to amplify an electrical amplitude of the medium (600) generated in response to a current flow in the medium (600); and a feedback block (400) configured to connect the sensor block (300) to the current source (100).

Description

Technical Field

[0001] The subject of the invention is a device for measuring electrical conductivity, in particular a device suitable for measuring the electrical conductivity of a liquid medium.

[0002] The device for measuring the electrical conductivity which is the subject of the present invention allows measuring and detecting changes in the electrical conductivity of a liquid medium with high resolution for a very wide range of conductivity values, minimizing or avoiding problems associated with degradation of the measuring electrodes.

[0003] The device for measuring electrical conductivity that is the subject of the present invention is applicable in the industry dedicated to the design and manufacture of electronic measuring devices, and more particularly, devices for measuring the electrical conductivity of liquid media. Background Art

[0004] In the field of devices for measuring electrical conductivity, the most common technique consists of inserting or immersing two electrodes in a medium (solid or liquid) and circulating a direct current (DC) of a certain strength between the electrodes and subsequently measuring the voltage drop between the electrodes in order to infer the conductivity of the medium.

[0005] A problem associated with the technique mentioned in the previous paragraph is that when a direct current intensity is applied between electrodes, when they are immersed in a liquid medium, an electrochemical reaction frequently occurs between the electrodes and the liquid medium, resulting in rapid degradation of the electrodes.

[0006] One solution to the problem of electrode degradation is to use alternating current (AC) instead of direct current. Document ES2684611A1 describes a device for detecting water in a diesel filter. The device includes two electrodes configured to be immersed in a liquid medium. The device includes a direct current source designed using current mirror technology. The device also includes two switches, which are configured to be opened and closed alternately so that always one of the two switches is open (preventing current from passing) and the other of the switches is closed (allowing current to pass), so that at any given time, depending on which of the switches is open and which of the switches is closed, a current flow is generated between the electrodes in one direction or the other (AC current).

[0007] Although the flow of alternating current between the electrodes enables the problem of electrode degradation to be solved, there are further disadvantages associated with measuring conductivity in a medium, especially in a liquid medium.

[0008] In fact, when the intention is to infer the conductivity of a medium by injecting direct current into the medium and measuring the voltage drop that occurs between the electrodes, there is a non-linear response similar to an exponential curve, so that for decreasing values ​​of conductivity, the voltage drop between the electrodes responds very strongly to changes in conductivity.

[0009] By digitizing this voltage drop signal using an analog-to-digital converter (ADC), a very good resolution is obtained, since the ADC converter perfectly distinguishes between the two voltage drop values ​​(and therefore the two conductivity values) when the two voltage drop values ​​are far enough from each other (if the ADC converter has a sensitivity value that is larger than the difference of the voltage drop values).

[0010] However, due to the fact that this response resembles an exponential curve, for high values ​​of the conductivity of the medium, the voltage drop between the electrodes responds very little to changes in conductivity. In general, the greater the conductivity of the medium, the smaller the change in the voltage drop between the electrodes.

[0011] It may therefore be the case that the difference in voltage drop between the electrodes due to conductivity changes of the medium is below the sensitivity of the ADC converter, resulting in the sensor device no longer being usable (it does not have sufficient resolution) to measure conductivity changes of the medium. Summary of the invention

[0012] In order to solve the above disadvantages, the present invention is directed to a device for measuring electrical conductivity.

[0013] The device for measuring electrical conductivity, which is the subject of the present invention, comprises:

[0014] o a first electrode and a second electrode, both electrodes being configured to be introduced into a medium, preferably a liquid medium, for measuring the conductivity of said medium;

[0015] o a current source configured to inject current into the medium, and;

[0016] o a switching block configured to generate a flow of electric current through the medium from the first electrode to the second electrode or from the second electrode to the first electrode.

[0017] In a novel manner, the device for measuring electrical conductivity which is the subject of the present invention also comprises:

[0018] o a sensor block connected to the first electrode and / or the second electrode, configured to amplify an electrical amplitude of the medium generated in response to a current flowing in the medium, and;

[0019] oA feedback block configured to connect the sensor block to a current source.

[0020] Thus, the device for measuring conductivity provides a native response (before digitization and processing) that varies linearly with conductivity, that is, for the same change in conductivity, the change induced in the output voltage of the system will be the same regardless of the conductivity range of the medium. By digitizing this signal using an ADC converter, the resolution in terms of conductivity will be the same over any conductivity range.

[0021] The current source may include a first operational amplifier (U1) or a current mirror.

[0022] The device is configured to inject an electric current into the medium via feedback to a current source of amplified electric amplitude, the current intensity of which value depends on the conductivity of the medium.

[0023] With the device described, a reference signal is introduced into the sensor block, that is to say it is subtracted from the internal response of the system. The difference is amplified by the sensor block (which comprises a second operational amplifier (U2)) and fed back to the adjustable current source, which is automatically regulated to keep the voltage between the electrodes of the medium constant and to ensure that for any value of conductivity that the medium has, the difference between the signal and the set point becomes zero. Since, in order to achieve this, the output voltage generated by the sensor block will have to be different as the conductivity varies, said output voltage of the sensor block is used as the output of the system, which is linear, thereby converting the nonlinearity into the evolution of the electrode current depending on the conductivity being measured. By varying the output voltage linearly with the conductivity, the problem of lack of resolution in the high conductivity range encountered by those embodiments in which the medium is polarized with a constant current is solved.

[0024] The current source may be an AC source, thereby avoiding degradation of the electrodes.

[0025] However, according to the invention, the current source is preferably a direct current source.

[0026] The current source may be configured to inject current into the medium through the first electrode, and wherein the second electrode is connected to ground through the decoupling capacitor (C1). In this way, alternating current is achieved between the electrodes via the switch block and the decoupling capacitor (C1).

[0027] Preferably, the switch block comprises a switch (S) (which may be a transistor) configured to be controlled by the microcontroller, and wherein the switch (S) is connected to ground.

[0028] The switch (S) may be connected to ground via a discharge resistor (Rdisch).

[0029] According to a first embodiment of the device for measuring conductivity, which is the subject of the present invention, the switches (S) of the switching block are configured:

[0030] - adopting a first configuration, wherein a switch (S) establishes a connection between a current source and a first electrode, and;

[0031] - A second configuration is adopted, wherein the switch disconnects the first electrode from the current source and establishes a connection between the first electrode and ground.

[0032] Alternatively, according to a second embodiment of the device for measuring conductivity that is the subject of the invention, the switch (S) is connected to ground in parallel with the medium and in series with a discharge resistor (Rdisch) of lower value than the equivalent resistor (Rmedium) of the medium.

[0033] In this second embodiment, the switch (S) may be made using a MOSFET type transistor.

[0034] Preferably, in this second embodiment of the invention, the sensor block has a resistive voltage divider connected to its input, formed by two resistors (Rdiv1, Rdiv2) so that a resistance proportional to the supply voltage (VDC) of the current source is applied at the input of the sensor block.

[0035] Also preferably, in this second embodiment of the invention, the means for measuring conductivity comprises a filter block connected between the sensor block and the feedback block. The filter block is configured to stabilize the voltage at the output of the sensor block.

[0036] Preferably, the filter block comprises an RC filter.

[0037] Furthermore, the filter block may include at least a first RC branch connected in parallel with the RC filter.

[0038] Also according to the second embodiment of the device for measuring electrical conductivity, the sensor block may include a non-inverting amplifier stage formed by an operational amplifier (second operational amplifier (U2)) connected in parallel with a compensation capacitor.

[0039] In a second embodiment of the device for measuring conductivity, which is the subject of the present invention, different types of current sources can be implemented.

[0040] For example, the current source may include a first operational amplifier (U1) connected to a first transistor (Q1) through a polarization resistor (Rbase), wherein a non-inverting input of the first operational amplifier (U1) is connected to the feedback block.

[0041] Alternatively, the current source may comprise a current mirror.

[0042] In a second embodiment of the device for measuring electrical conductivity, which is the subject of the present invention, the switching block may comprise a parallel resistor (Rpar) connected in parallel with the switch (S).

[0043] Using such a parallel resistor (Rpar) it is possible to increase the range of conductivity values ​​that the device is able to measure.

[0044] As an alternative to the parallel resistor (Rpar), a current source including a second current range switch module can be used. With the help of the second current range switch, it is also possible to expand the range of conductivity values ​​that the device of the present invention can measure. The two elements (parallel resistor (Rpar) and second range switch) can be used alternately or simultaneously. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The following drawings have been included as part of the explanation of at least one embodiment of the present invention.

[0046] Figure 1 A schematic diagram showing a circuit for measuring electrical conductivity according to a first embodiment of a device for measuring electrical conductivity which is the subject of the present invention.

[0047] Figure 2 A simplified diagram showing sampling of the conductivity of a medium during a period of current injection into the medium.

[0048] Figure 3 A schematic diagram of a circuit for measuring the electrical conductivity of a medium shows a first variant of a second embodiment of the device according to the invention.

[0049] Figure 4 Detail of a circuit for measuring the electrical conductivity of a medium is shown for a second variant of a second embodiment of the device according to the invention.

[0050] Figure 5 A detailed view of a circuit for measuring the electrical conductivity of a medium is shown for a third variant of the second embodiment of the device according to the invention.

[0051] Figure 6 A detailed view of a circuit for measuring the electrical conductivity of a medium is shown for a fourth variant of the second embodiment of the device according to the invention.

[0052] Figure 7a A first source type usable in a device for measuring electrical conductivity according to a second embodiment thereof is shown.

[0053] Figure 7b A second source type usable in the device for measuring electrical conductivity according to a second embodiment thereof is shown.

[0054] Figure 7c A third source type usable in the device for measuring electrical conductivity according to a second embodiment thereof is shown.

[0055] Figure 7dA fourth source type usable in the device for measuring electrical conductivity according to a second embodiment thereof is shown.

[0056] Figure 8 A schematic diagram of a circuit for measuring the electrical conductivity of a medium shows a fifth variant of the second embodiment of the device according to the invention.

[0057] Fig. 9 A schematic diagram of a circuit for measuring the electrical conductivity of a medium shows a sixth variant of the second embodiment of the device according to the invention.

[0058] Fig.10 Graph showing the variation of the digitized output voltage as a function of the variation of the conductivity of the medium for a first variant of the second embodiment of the device according to the invention. DETAILED DESCRIPTION

[0059] As described above, the present invention relates to an apparatus for measuring electrical conductivity.

[0060] The device comprises an electric circuit for measuring the electrical conductivity of a medium (600), wherein the electric circuit varies in some of its features and elements according to different embodiments of the device according to the invention.

[0061] The medium (600) in which the electrical conductivity is measured via the device of the present invention is typically a liquid medium.

[0062] In the circuit of the attached figure, the medium (600) is represented by its equivalent resistor (Rmedium). The value of the conductivity of the medium (600) to be measured via the device that is the subject of the invention is the inverse of the equivalent resistor of the medium (1 / Rmedium).

[0063] The device comprises a current source (100) configured to inject current into a medium (600) in which the conductivity is to be measured.

[0064] The device also includes a switch block (200) configured to connect and disconnect the current source (100) to and from the medium (600).

[0065] The apparatus includes a conductivity sensor block (300) configured to receive and amplify the electrical amplitude of a medium (600) in response to current being injected into the medium (600) by a current source (100).

[0066] The sensor block (300) is configured to be connected to an analog-to-digital converter (ADC) (not shown in the figure) for digitizing the amplified electrical amplitude of the medium (600).

[0067] The apparatus includes a feedback block (400) including a feedback loop (or line) connecting the output of the sensor block (300) to a current source (100).

[0068] The device may further comprise a filter block (500) and / or a stabilisation of the electrical amplitude of the medium (600), which is configured to stabilise the measurement of the electrical amplitude of the medium (600) measured by the sensor block (300).

[0069] According to the present invention, the device comprises two electrodes (700a, 700b) which are arranged to be immersed in a medium (600). The device is configured to inject current into the medium (600) through the first electrode (700a) via a current source (100). The second electrode (700b) is grounded via a decoupling capacitor (C1).

[0070] The switch block (200) comprises a switch (S) (or transistor) configured to be controlled by a microcontroller (not shown in the figure), which allows control of the opening and closing pulses and the opening time of the switch (S). The switch (S) has one of its poles connected to ground (e.g., through a discharge resistor (Rdisch)).

[0071] Figure 1 A schematic diagram of a circuit for measuring the electrical conductivity of a medium (600) is shown in a first exemplary embodiment of a device according to the invention.

[0072] In this first embodiment of the device, the current source (100) is based on a first operational amplifier (U1) connected to a first transistor (Q1) (for example, a transistor of BJT type) via a polarization resistor (Rbase). A control signal is connected to the non-inverting input of the first operational amplifier (U1) which is proportional to the output voltage Vout of the device.

[0073] Due to the fact that the sensor block (300) comprises a second operational amplifier (U2) which generates at its output an output voltage Vout of the device which is a result of the electrical amplitude of the amplified medium (600) , this output voltage Vout is proportional to the voltage drop between the measuring electrodes (700a, 700b) which, given the configuration of the circuit, causes the output voltage Vout to decrease for increasing conductivity values.

[0074] Therefore, via the feedback block (400), a control signal is connected to the current source (100), which control signal is proportional to the voltage drop between the electrodes (700a, 700b), taking advantage of this and taking into account the operation of the power supply (100), so that the current is increased to increase the conductivity value.

[0075] In this first embodiment of the conductivity measuring device, the switch (S) of the switch block (200) can: adopt a first configuration, in which the switch (S) establishes a connection between the current source (100) and the first electrode (700a), so that the current source (100) injects current into the medium (600); and adopt a second configuration, in which the switch disconnects the first electrode (700a) from the current source (100) and connects the first electrode (700a) to ground (for example, through the aforementioned discharge resistor (Rdisch)).

[0076] Therefore, when the switch (S) of the switching block (200) is in the second configuration, the current source (100) no longer injects current into the medium (600), and a discharge current is generated from the medium (600) to ground through the switch (S) (and through the discharge resistor (Rdisch), if present).

[0077] In this way, by alternating the switch (S) controlled by the microprocessor between its two configurations at regular intervals, an alternating current is generated in the medium (600) thanks to the decoupling capacitor (C1).

[0078] exist Figure 2 Schematic diagram of time intervals (shown as intervals with a duration of 2 ms as an example) is shown in , wherein current is injected into the medium ( 600 ) via the current source ( 100 ) of the device.

[0079] As an example, Figure 2 The simplified diagram in shows that 5 samples (p1, p2, p3, p4, p5) are taken from the measurement of the electrical amplitude performed by the device of the present invention (taken at intervals of 0.5 ms). These samples can be taken using a device with installed conductivity measurement software, wherein the device is connected to the device of the present invention (usually through an ADC converter).

[0080] In this way, an operation sequence easily implemented by a microcontroller can consist, for example, of the following: the switch (S) is piloted by means of a 0-1 logic signal established according to a square wave pattern, wherein each current injection interval is followed by another discharge interval of similar duration, the current injection-sampling-discharge cycle is repeated uninterruptedly, and thus changes in the conductivity of the medium (600) are reflected very directly in the output signal.

[0081] Figure 3 A schematic diagram of a circuit for measuring the electrical conductivity of a medium (600) is shown in a first variant of a second embodiment of the device according to the invention.

[0082] In this second embodiment of the device for measuring conductivity, the switch (S) of the switching block (200) is a MOSFET type transistor connected in parallel to the medium (600) and to ground through a branch comprising a discharge resistor (Rdisch) having a very low value compared to the equivalent resistor (Rmedium) of the medium (600).

[0083] Therefore, in this second embodiment, when the switch (S) of the switching block (200) is in the first configuration, the current generated by the current source (100) is directed to the medium (600) through the first electrode (700a), and when the switch (S) of the switching block (200) is in the second configuration, the switch (S) conducts the current generated by the current source (100) and also allows a discharge current to be directed from the medium (600) to the switch (S), thereby discharging the decoupling capacitor (C1).

[0084] In this way, an alternating current is generated in the medium (600) due to the switching switch (S) and the decoupling capacitor (C1) controlled by the microcontroller.

[0085] In this second embodiment, a resistive voltage divider formed by two resistors (Rdiv1, Rdiv2) has been included at the input of the sensor block (300). In this way, a reference voltage proportional to the supply voltage (VDC) of the current source (100) is applied at the input of the sensor block (300).

[0086] Due to the fact that the first electrode (700a) is connected to the non-inverting input of the second operational amplifier (U2) of the sensor block (300), and due to the gain of the second operational amplifier (U2) of the sensor block (300), the reference voltage is transferred to the non-inverting input of the second operational amplifier (U2), or, equivalently, to the node to which the electrodes (700a, 700b) are connected. This node will remain at that constant voltage within the defined conductivity range for which the system has been dimensioned, since the control voltage will simultaneously and automatically be applied to the current source (100), which will result in an output current inversely proportional to the conductivity of the medium (600), which is necessary at each moment to maintain the two inputs of the second operational amplifier (U2) at the reference voltage.

[0087] In this second embodiment, there is a filter block (500) connected between the sensor block (300) and the feedback block (400).

[0088] The second form of embodiment of the device for measuring conductivity allows different variants, each of which relates to various aspects of each of the blocks of the measurement circuit. These different variants can be combined with the measurement circuit previously described for this second embodiment of the device for measuring conductivity.

[0089] Therefore, according to the first modification of the second embodiment (in Figure 3 ), the filter block (500) consists of an RC filter configured to stabilize the voltage at the output of the sensor block (300) to avoid oscillation.

[0090] In a first variant of the second embodiment of the device, the current source (100) is based on a first operational amplifier (U1) connected to a first transistor (Q1), for example a transistor of MOSFET type, via a polarization resistor (Rbase). A control signal is connected to the non-inverting input of the first operational amplifier (U1) and is proportional to the output voltage Vout of the device, which in turn is proportional to the voltage drop between the measuring electrodes (700a, 700b).

[0091] Figure 4 A schematic diagram of a circuit for measuring the electrical conductivity of a medium (600) is shown in a second variant of a second embodiment of the device according to the invention.

[0092] exist Figure 4 In the circuit for measuring conductivity shown in , the representation of the current source (100) and the feedback block (400) have been omitted.

[0093] As can be seen, in this second variant of the second embodiment of the device for measuring conductivity, the filter block (500) comprises an additional first RC branch connected in parallel with the RC filter of the first variant.

[0094] Figure 5 A schematic diagram of a circuit for measuring the electrical conductivity of a medium (600) is shown according to a third variant of the second embodiment of the device according to the invention.

[0095] exist Figure 5 In the circuit for measuring conductivity shown in , only the sensor block (300) and the filter block (500) are shown in detail.

[0096] As can be seen, in this third variant of the second embodiment of the device for measuring conductivity, the filter block (500) comprises an additional first RC branch and an additional second RC branch, both connected in parallel with the filter RC of the first variant.

[0097] Likewise, as can be seen, in this third variant of the second embodiment of the device for measuring conductivity, the sensor block (300) comprises a non-inverting amplification step due to the arrangement of the compensation capacitor in parallel with the second operational amplifier (U2).

[0098] Figure 6A schematic diagram of a circuit for measuring the electrical conductivity of a medium (600) shows a fourth variant of the second embodiment of the device according to the invention.

[0099] exist Figure 6 In the circuit for measuring conductivity shown in , only the switch block (200) is shown in detail.

[0100] As can be seen, in this fourth variant of the second embodiment of the device for measuring conductivity, the switch block (200) comprises a parallel resistor (Rpar) connected in parallel to the switch (S).

[0101] The parallel resistor (Rpar) increases the range of conductivity values ​​of the medium (600) that can be measured by the measuring device.

[0102] The second embodiment of the device for measuring conductivity allows the use of various different current sources (100).

[0103] Figure 7a , Figure 7b , Figure 7c and Figure 7d Different types of current sources (100) that can be used in a device for measuring conductivity according to a second embodiment thereof are shown.

[0104] Figure 7a A first type (100a1) of current source (100) based on using a first operational amplifier (U1) is shown.

[0105] In a first variant of this second embodiment of the device for measuring conductivity (in Figure 3 As shown in Figure 7a The first embodiment (100a1) shown in FIG. 1 shows a current source (100).

[0106] Figure 7b A second type (100a2) is shown which is also based on a current source (100) using a first operational amplifier (U1). In this case, and due to the specific operating mode of this source (100), the output voltage Vout of the system will increase for increasing conductivity values.

[0107] Figure 7c A third type (100a3) is shown which is also based on a current source (100) using a first operational amplifier (U1). As in case 7b, the output voltage Vout of the system will increase for increasing conductivity values.

[0108] Figure 7d A fourth type (100b) of current source (100) based on the use of a current mirror is shown.

[0109] Figure 8A schematic diagram of a circuit for measuring the electrical conductivity of a medium (600) shows a fifth variant of the second embodiment of the device according to the invention.

[0110] exist Figure 8 In the circuit for measuring conductivity shown in , only the current source (100) is shown in detail.

[0111] As can be seen, in this fifth variant of the second embodiment of the device for measuring conductivity, the current source (100) comprises a module according to the first type (100a1) of current source (100), and a second current range switch module (100').

[0112] Fig. 9 A schematic diagram of a circuit for measuring the electrical conductivity of a medium (600) is shown according to a sixth variant of the second embodiment of the device according to the invention.

[0113] exist Fig. 9 In the circuit for measuring conductivity shown in , only the current source (100) is shown in detail.

[0114] As can be seen, in this sixth variant of the second embodiment of the device for measuring conductivity, the current source (100) comprises a module according to the fourth type (100b) of the current source (100), and a second current range switch module (100').

[0115] Using the second current range switch module (100') of the fifth and sixth variations of the second embodiment of the device for measuring conductivity according to the present invention in a current source (100) increases the range of conductivity values ​​of the medium (600) that can be measured by the measuring device.

[0116] at last, Fig.10 Shown according to Figure 7d Graph showing the variation of the digitized output voltage Vout as a function of the variation of the conductivity of the medium ( 600 ) of the second embodiment of the device of the invention shown in .

[0117] In this graph, it can be seen how linearity appears in the output signal Vout, so that the relationship between the change in conductivity of the medium (600) and the change in output voltage is linear. With this, it can be seen that for high values ​​of conductivity of the medium (600), the change in voltage can still be measured by avoiding the generation of a non-linear curve.

[0118] The different lines in the graph correspond to lines obtained according to the time interval between switching and sampling, that is, by modifying the time at which the voltage Vout is measured at the output node after injecting current into the medium (600), as Figure 2 as shown in .

Claims

1. A device for measuring electrical conductivity, comprising: o a first electrode (700a) and a second electrode (700b), both electrodes (700a, 700b) being configured to be introduced into a medium (600) for measuring the conductivity of the medium (600); o a current source (100) configured to inject current into the medium (600), and; o a switching block (200) configured to generate a flow of electric current through the medium (600) from the first electrode (700a) to the second electrode (700b) or from the second electrode (700b) to the first electrode (700a); The device is characterized in that it also includes: o a sensor block (300) connected to the first electrode (700a) and / or the second electrode (700b), configured to amplify an electrical amplitude of the medium (600) generated in response to the current flowing in the medium (600), and; o a feedback block (400) configured to connect the sensor block (300) to the current source (100); The device is configured to inject current into the medium (600) via voltage feedback from the output of the sensor block (300) to the current source (100), the current intensity value of the current being inversely proportional to the conductivity of the medium (600), so that the output voltage of the sensor block (300) changes linearly with the conductivity.

2. The device for measuring conductivity according to claim 1, wherein: The current source (100) is configured to inject current into the medium (600) through the first electrode (700a), and wherein the second electrode (700b) is connected to ground through a decoupling capacitor (C1).

3. The device for measuring conductivity according to claim 1 or 2, wherein: The switch block (200) comprises a switch (S) configured to be controlled by a microcontroller and wherein one of the poles of the switch (S) is connected to ground.

4. The device for measuring conductivity according to claim 3, wherein: One of the poles of the switch (S) is connected to ground via a discharge resistor (Rdisch).

5. The device for measuring conductivity according to claim 3 or 4, wherein: The switch (S) of the switch block (200) is configured as follows: o adopting a first configuration, wherein the switch (S) establishes a connection between the current source (100) and the first electrode (700a), and; o A second configuration is adopted, wherein the switch (S) disconnects the first electrode (700a) from the current source (100) and establishes a connection between the first electrode (700a) and ground.

6. The device for measuring conductivity according to claim 3, wherein the switch (S) is connected in parallel with the medium (600) and is connected to the ground in series with a discharge resistor (Rdisch), and the value of the discharge resistor (Rdisch) is lower than the equivalent resistor (Rmedium) of the medium (600).

7. The device for measuring conductivity according to claim 6, wherein: The sensor block (300) has a resistive voltage divider connected to its input, the resistive voltage divider being formed by two resistors (Rdiv1, Rdiv2) so that a supply voltage (V DC ) is proportional to the reference voltage.

8. The device for measuring conductivity according to any of the preceding claims, comprising a filter block (500) connected between the sensor block (300) and the feedback block (400), wherein the filter block (500) is configured to stabilize the voltage at the output of the sensor block (300).

9. The device for measuring conductivity according to claim 8, wherein: The filter block (500) includes an RC filter.

10. The device for measuring conductivity according to claim 9, wherein: The filter block (500) comprises at least one first RC branch connected in parallel with the RC filter.

11. The device for measuring conductivity according to claim 10, wherein: The sensor block (300) includes a non-inverting amplification step formed by an operational amplifier connected in parallel with a compensation capacitor.

12. A device for measuring electrical conductivity according to any one of the preceding claims, wherein: The current source (100) comprises a first operational amplifier (U1) connected to a first transistor (Q1) through a polarization resistor (Rbase), wherein a non-inverting input of the first operational amplifier (U1) is connected to the feedback block (400).

13. The device for measuring electrical conductivity according to any one of claims 1 to 10, wherein: The current source (100) comprises a current mirror.

14. A device for measuring electrical conductivity according to any one of the preceding claims, wherein: The switch block (200) includes a parallel resistor (Rpar) connected in parallel with the switch (S).

15. The device for measuring electrical conductivity according to any one of claims 1 to 14, wherein: The current source (100) comprises a second current range switch module (100').

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