(19)
(11)EP 2 755 002 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
16.03.2022 Bulletin 2022/11

(21)Application number: 13151285.7

(22)Date of filing:  15.01.2013
(51)International Patent Classification (IPC): 
G01F 23/00(2022.01)
G01F 23/26(2022.01)
(52)Cooperative Patent Classification (CPC):
G01F 23/243; G01F 23/80

(54)

A level measurement system for conductive liquids

Füllstandsmesssystem für leitfähige Flüssigkeiten

Système de mesure de niveau pour liquides conducteurs


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(43)Date of publication of application:
16.07.2014 Bulletin 2014/29

(73)Proprietor: Electrolux Home Products Corporation N.V.
1130 Brussels (BE)

(72)Inventors:
  • Faraldi, Paolo
    47122 Forli (IT)
  • Martello, Giacomo
    47122 Forli (IT)
  • Foiera, Riccardo
    47122 Forli (IT)
  • Valpiani, Nicola
    47122 Forli (IT)
  • Betti, Edoardo
    47122 Forli (IT)

(74)Representative: Electrolux Group Patents 
AB Electrolux Group Patents S:t Göransgatan 143
105 45 Stockholm
105 45 Stockholm (SE)


(56)References cited: : 
CN-U- 201 497 543
JP-U- S63 122 237
US-A- 5 539 670
US-B1- 6 219 933
CN-Y- 201 285 310
US-A- 5 142 909
US-A1- 2013 073 237
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description


    [0001] The present invention relates to a level measurement system for conductive liquids according to the preamble of claim 1. In particular, the present invention relates to a level measurement system for water in a storage container. Further, the present invention relates to a domestic appliance comprising at least one liquid container for supplying said domestic appliance with liquid.

    [0002] Level measurement of water in storage containers is a substantial feature for any application requiring a feed of water. The information about the level status is relevant for the control of said application, e.g. for launching warning messages or triggering refill or drain actions by specific actuators.

    [0003] Conductivity sensors are well known and used for a discrete level measurement. Two electrodes are arranged inside a liquid container at different levels. If the liquid level is above both electrodes, then an electric circuit is closed and said liquid level above an upper electrode is detected. If the liquid level is below the upper electrode, then the electric circuit is open and said liquid level below the upper electrode is detected. This system allows only the determination, if the liquid level is above or below a defined level.

    [0004] US 5,142,909 discloses a system for indicating levels of material in a vessel. The system comprises a probe with a plurality of electrically discrete probe elements arranged at different levels. Each probe element comprises at least an operational amplifier and resistor elements and/or capacitors. A voltage value is detected for each liquid level.

    [0005] CN 201497543 U discloses a sensor for detecting a number of discrete liquid levels. The sensor comprises an electrode, a resistor element, capacitors and an operational amplifier for each liquid level. A voltage value is detected for each liquid level.

    [0006] CN 201285310 Y discloses a system for detecting discrete levels in a liquid container. The system comprises a network of capacitors and resistor elements, wherein each level corresponds with one capacitor and one resistor element.

    [0007] US 6,219,933 B1 discloses a container for a fluid. The container comprises a carton and a flexible inner bag attached to the inner side of said carton. The inner bag is provided for containing the fluid in it and includes a fluid-discharge port. The inner bag is separated from an inclined inner surface of the carton in a predetermined direction, when the fluid is discharged. A level detecting pattern is printed on the inner surface of the carton. The level detecting pattern includes a plurality of parallel disconnection patterns. Said disconnection patterns are successively separated from the inner surface of the carton, when the fluid is discharged, so that the resistance of the level detecting pattern changes.

    [0008] JP S63 122237 U discloses a level measurement system for conductive liquids. A plurality of vertical electrodes is arranged in a liquid container. The lower ends of said electrodes are arranged at different levels. The upper ends of adjacent electrodes are connected via a resistor element in each case, so that said resistor elements are connected in series. Said series is connected to one terminal of a voltage source via a voltage divider. The other terminal of said voltage source is connected to a reference electrode arranged at the lowest level of the liquid container. The voltage at the voltage divider is detected in order to estimate the liquid level in the container.

    [0009] It is an object of the present invention to provide a level measurement system, which allows a more exact measuring of the liquid level by low complexity.

    [0010] The object of the present invention is achieved by the level measurement system according to claim 1.

    [0011] According to the present invention the network comprises two resistor elements connected in series between the input terminals, wherein at least two electrodes arranged above the lower electrode are connected to the junction of the resistor elements of said series via a further resistor element in each case, and wherein the output terminals are formed by the ground terminal and the junction of the resistor elements of said series.

    [0012] Major aspects of the present invention refer to the at least three electrodes arranged inside the liquid container at different levels and the network of resistor elements connected to said electrodes. One voltage value is sufficient to indicate the at least three different levels of the conductive liquids in the liquid container. The electrodes and the resistor elements allow the level measurement system by low complexity.

    [0013] Optionally, the network comprises further two resistor elements connected in series between the input terminals and arranged parallel to the series of two resistor elements. The resistor elements of said further series allow an increased precision.

    [0014] According to a preferred embodiment of the present invention the level measurement system includes or corresponds with an analogue-digital converter for processing the level of the conductive liquid in the liquid container, wherein the output terminals of the network are connected or connectable to an input of said analogue-digital converter.

    [0015] The output of the analogue-digital converter may be processed by a control unit for further applications.

    [0016] For example, the external voltage is a direct current voltage.

    [0017] Alternatively, the external voltage is an alternating current voltage. This avoids polarization effects on the electrodes and accumulations of substances on said electrodes.

    [0018] Further, the level measurement system may be provided for determining the electric conductivity of the liquid.

    [0019] In particular, the level measurement system may be provided for determining the hardness grade of water or liquids including water.

    [0020] Moreover, predetermined voltage ranges of the voltage between the output terminals are defined, wherein each voltage range corresponds with one discrete level of the conductive liquid in the liquid container.

    [0021] At last, the present invention relates to a domestic appliance comprising at least one liquid container for supplying said domestic appliance with liquid, wherein the domestic appliance comprises at least one level measurement system mentioned above.

    [0022] Novel and inventive features of the present invention are set forth in the appended claims.

    [0023] The present invention will be described in further detail with reference to the drawings, in which
    FIG 1
    illustrates a schematic side view of a liquid container filled at three different liquid levels of a level measurement system according to an embodiment of the present invention,
    FIG 2
    illustrates a schematic equivalent circuitry of an exemplary level measurement system according to an embodiment not being part of the invention and being disclosed for information purposes only,
    FIG 3
    illustrates a schematic equivalent circuitry of the level measurement system according to the present invention, and
    FIG 4
    illustrates three voltage-time diagrams of the level measurement system according to an embodiment of the present invention.


    [0024] FIG 1 illustrates a schematic side view of a liquid container 10 filled at three different liquid levels 12, 14 and 16 of a level measurement system according to an embodiment of the present invention. The liquid container 10 is filled by an electrically conductive liquid, e.g. water.

    [0025] The liquid container 10 is shown triply, wherein said container 10 is filled at an upper level 12, a medium level 14 and a lower level 16, respectively. The level measurement system includes an upper electrode 18, a medium electrode 20 and a lower electrode 22. The upper electrode 18, the medium electrode 20 and the lower electrode 22 are arranged inside the liquid container 10.

    [0026] The upper level 12 is defined as one of the levels above the upper electrode 18. The medium level 14 is defined as one of the levels between the upper electrode 18 and the medium electrode 20. In a similar way, the lower level 16 is defined as one of the levels between the medium electrode 20 and the lower electrode 22.

    [0027] A first terminal A is connected to the upper electrode 18. In a similar way, a second terminal B is connected to the medium electrode 20. At last, a third terminal C is connected to the lower electrode 22.

    [0028] In FIG 1 the electric resistances of the liquid between the electrodes 18, 20 and 22 are represented by symbols RW1, RW2 and RW3. Said symbols RW1, RW2 and RW3 are pictured as the wiring symbols of resistor elements. RW1 represents the resistance between the upper electrode 18 and the medium electrode 20. RW2 represents the resistance between the upper electrode 18 and the lower electrode 22. RW3 represents the resistance between the medium electrode 20 and the lower electrode 22.

    [0029] If the liquid container 10 is filled at the upper level 12, then the electric resistances RW1, RW2 and RW3 of the liquid have measureable values. However, if the liquid container 10 is filled at the medium level 14, then only the electric resistance RW3 of the liquid has a measureable value, while the electric resistances RW1 and RW2 are infinite. Moreover, if the liquid container 10 is filled at the lower level 16, then all three electric resistances RW1, RW2 and RW3 are infinite.

    [0030] FIG 2 illustrates an exemplary schematic equivalent circuitry of a level measurement system according to an embodiment not being part of the invention and being disclosed for information purposes only. The level measurement system relates to the liquid container 10 shown in FIG 1.

    [0031] RW1 represents the resistance of the liquid between the upper electrode 18 and the medium electrode 20. RW2 represents the resistance of the liquid between the upper electrode 18 and the lower electrode 22. RW3 represents the resistance of the liquid between the medium electrode 20 and the lower electrode 22. The upper electrode 18 is connected to the first terminal A. The medium electrode 20 is connected to the second terminal B. The lower electrode 22 is connected to the third terminal C.

    [0032] The level measurement system further includes resistor elements R1, RP1 and RP2. The resistor elements RP1 and RP2 are serially interconnected between a voltage terminal V+ and a ground terminal GND. The resistor elements RP1 and RP2 form a voltage divider. The first terminal A is connected to the voltage terminal V+. The third terminal C is connected to a junction between the resistor elements RP1 and RP2. The resistor element R1 is interconnected between the first terminal A and the second terminal B.

    [0033] The resistor element R1 is dimensioned in such a way that the level measurement system allows a clear distinction between the detected measurements of the upper level 12 and the medium level 14. The voltage across the resistor element RP2 is considered for the measurement. The upper level 12, the medium level 14 and the lower level 16 correspond with a related voltage range across the resistor element RP2 in each case. The related voltage ranges are adapted to different values of the water hardness, if the liquid is water or includes water. The resistance between the electrodes 18, 20 and/or 22 depends on the water hardness.

    [0034] The resistor value R1 can be dimensioned preferably considering typical ranges of water resistivity with different water hardness. Accordingly, it has been found in the present invention that a typical value range of 100 to 300 kOhm is suitable for many cases and is suitable even for a majority of cases. Consequently, dimensioning of the other resistors shall be preferably:



    [0035] The voltage across the resistor element RP2 is connectable to the input terminals of an analogue-digital converter. Thus, a single analogue-digital converter channel is sufficient to detect a plurality of levels 12, 14 and/or 16.

    [0036] FIG 3 illustrates a schematic equivalent circuitry of the level measurement system according to the present invention. The level measurement system relates also to the liquid container 10 shown in FIG 1.

    [0037] RW1 represents the resistance of the liquid between the upper electrode 18 and the medium electrode 20. RW2 represents the resistance of the liquid between the upper electrode 18 and the lower electrode 22. RW3 represents the resistance of the liquid between the medium electrode 20 and the lower electrode 22.

    [0038] The level measurement system includes resistor elements R, R1, R2, R3, RR1 and RR2. The resistor elements R1 and R2 are connected in series between the voltage terminal V+ and the ground terminal GND. In a similar way, the resistor elements R3 and R are connected in series between the voltage terminal V+ and the ground terminal GND.

    [0039] The upper electrode 18 is connected to a resistor element RR2. The other terminal of said resistor element RR2 is connected to the junction between the resistor elements R3 and R. The medium electrode 20 is connected to a resistor element RR1. The other terminal of said resistor element RR1 is also connected to the junction between the resistor elements R3 and R. The lower electrode 22 is connected to the ground terminal GND.

    [0040] The resistor elements R1, R2 are optional and allow an increased precision. The resistor elements R, R1, R2, R3, RR1 and RR2 are dimensioned in order to allow a clear distinction between the detected measurements of the upper level 12 and the medium level 14. The voltage across the resistor element R is considered for the measurement. The upper level 12, the medium level 14 and the lower level 16 correspond with a related voltage range across the resistor element R in each case. The related voltage ranges are adapted to different values of the water hardness, if the liquid is water or includes water. The resistance of the water between the electrodes 18, 20 and/or 22 depends on the water hardness.

    [0041] Preferably, the resistor R1 value can be the same as for the example circuitry previously explained, i.e. in a a value range of 100 to 300 kOhm. Dimensioning of the other resistors shall be preferably:









    [0042] The voltage across the resistor element R is connectable to the input terminals of the analogue-digital converter. Therefore, the single analogue-digital converter channel is sufficient to detect a plurality of levels 12, 14 and/or 16.

    [0043] FIG 4 illustrates three voltage-time diagrams of the level measurement system according to an embodiment of the present invention. The voltage-time diagrams relate to charges of water having a different hardness grade.

    [0044] A first voltage-time diagram 24 relates to water having an hardness of 0.7 °F (French degrees). A second voltage-time diagram 26 relates to water having a hardness of 35°F (French degrees). A third voltage-time diagram 28 relates to a saturated salt solution.

    [0045] If a voltage value upper than 3.5 V occurs, then the liquid in the liquid container 10 is at the lower level 16. If a voltage value between 2.25 V and 3.5 V occurs, then the liquid in the liquid container 10 is at the medium level 14. If a voltage value below 2.25 V occurs, then the liquid in the liquid container 10 is at the upper level 12.

    [0046] FIG 4 clarifies the relationship between the voltage ranges and the different hardness grades. Thus, the level measurement system of the present invention is also suitable for detecting the hardness grade of the liquid, in particular water.

    [0047] In order to prevent polarization effects on the electrodes, the polarity of the applied voltage between the voltage terminal V+ and the ground terminal GND is inverted according to a predetermined scheme. The polarization effects may lead to accumulations of substances on the electrodes. For example, an alternating current may be applied between the voltage terminal V+ and the ground terminal GND.

    [0048] A major advantage of the level measurement system according to the present invention refers to the detection of the plurality of liquid levels via one single analogue-digital converter channel. Additionally, said level measurement system allows the determination of the hardness grade of the liquid, in particular water. Further, the polarity of the applied voltage between the voltage terminal V+ and the ground terminal GND is inverted in order to avoid polarization effects on the electrodes.

    List of reference numerals



    [0049] 
    10
    liquid container
    12
    upper level
    14
    medium level
    16
    lower level
    18
    upper electrode
    20
    medium electrode
    22
    lower electrode
    24
    first voltage-time diagram
    26
    second voltage-time diagram
    28
    third voltage-time diagram
    A
    first terminal
    B
    second terminal
    C
    third terminal
    V+
    voltage terminal
    GND
    ground terminal
    R
    resistor element
    R1
    resistor element
    R2
    resistor element
    R3
    resistor element
    RP1
    resistor element
    RP2
    resistor element
    RR1
    resistor element
    RR2
    resistor element
    RW1
    resistance of the liquid
    RW2
    resistance of the liquid
    RW3
    resistance of the liquid



    Claims

    1. A level measurement system for conductive liquids including a liquid container (10), at least three electrodes (18, 20, 22) arranged inside the liquid container (10) at different levels (12, 14, 16) and a network, wherein

    - the electrodes (18, 20, 22) are connected to the network consisting of a plurality of resistor elements (R, R1, R2, R3, RP1, RP2, RR1, RR2) arranged out of the liquid container (10),

    - the network comprises two input terminals (V+, GND), namely a voltage terminal (V+) and a ground terminal (GND), for applying an external voltage,

    - a lower electrode (22) of the at least three electrodes is connected to the ground terminal (GND), and

    - the network comprises two output terminals providing a voltage depending on the level of the conductive liquid in the liquid container (10),

    - so that the level measurement system is provided for detecting at least three different levels (12, 14, 16) of conductive liquids in the liquid container (10) and indicating said levels (12, 14, 16) by one voltage value at the output terminals,

    characterised in that
    the network comprises two resistor elements (R, R3) connected in series between the input terminals (V+, GND), wherein at least two electrodes (18, 20) of the at least three electrodes arranged above the lower electrode (22) are connected to the junction of the resistor elements (R, R3) of said series via a further resistor element (RR1, RR2) in each case, and wherein the output terminals are formed by the ground terminal (GND) and the junction of the resistor elements (R, R3) of said series.
     
    2. The level measurement system according to claim 1, characterized in that
    the network comprises two further resistor elements (R1, R2) connected in series between the input terminals (V+, GND) and arranged parallel to the series of two resistor elements (R, R3) .
     
    3. The level measurement system according to claim 1 or 2, characterized in that
    the level measurement system includes an analogue-digital converter for processing the level of the conductive liquid in the liquid container (10), wherein the output terminals of the network are connected or connectable to an input of said analogue-digital converter.
     
    4. The level measurement system according to any one of the preceding claims,
    characterized in that
    the external voltage is a direct current voltage.
     
    5. The level measurement system according to any one of the preceding claims,
    characterized in that
    the external voltage is an alternating current voltage.
     
    6. The level measurement system according to any one of the preceding claims,
    characterized in that
    the level measurement system is provided for determining the hardness grade of water or liquids including water, wherein the three different levels (12, 14, 16) each correspond with a related voltage range across the resistor element (R) and wherein the related voltage ranges are adapted to different values of the water hardness of the water or the liquid including water.
     
    7. The level measurement system according to any one of the preceding claims,
    characterized in that
    predetermined voltage ranges of the voltage between the output terminals are defined, wherein each voltage range corresponds with one discrete level of the conductive liquid in the liquid container (10).
     
    8. A domestic appliance comprising at least one liquid container (10) for supplying said domestic appliance with liquid, characterized in that
    the domestic appliance comprises at least one level measurement system according to any one of the claims 1 to 7.
     


    Ansprüche

    1. Füllstandsmesssystem für leitfähige Flüssigkeiten, das einen Flüssigkeitsbehälter (10), mindestens drei Elektroden (18, 20, 22), die innerhalb des Flüssigkeitsbehälters (10) an unterschiedlichen Füllständen (12, 14, 16) angeordnet sind, und ein Netzwerk umfasst, wobei

    - die Elektroden (18, 20, 22) mit dem Netzwerk verbunden sind, das aus einer Vielzahl von Widerstandselementen (R, R1, R2, R3, RP1, RP2, RR1, RR2) besteht, die außerhalb des Flüssigkeitsbehälters (10) angeordnet sind,

    - das Netzwerk zwei Eingangsklemmen (V+, GND) umfasst, nämlich eine Spannungsklemme (V+) und eine Erdungsklemme (GND), um eine externe Spannung anzulegen,

    - wobei eine untere Elektrode (22) der mindestens drei Elektroden mit der Erdungsklemme (GND) verbunden ist, und

    - das Netzwerk zwei Ausgabeklemmen umfasst, die eine Spannung bereitstellen, die von dem Füllstand der leitfähigen Flüssigkeit in dem Flüssigkeitsbehälter (10) abhängt,

    - so dass das Füllstandsmesssystem so ausgestattet ist, dass mindestens drei unterschiedliche Füllstände (12, 14, 16) von leitfähigen Flüssigkeiten in dem Flüssigkeitsbehälter (10) detektiert werden und die Füllstände (12, 14, 16) durch einen Spannungswert an den Ausgabeklemmen angegeben werden, dadurch gekennzeichnet, dass

    das Netzwerk zwei Widerstandselemente (R, R3) umfasst, die in Reihe zwischen den Eingangsklemmen (V+, GND) geschaltet sind, wobei mindestens zwei Elektroden (18, 20) der mindestens drei Elektroden, die oberhalb der unteren Elektrode (22) angeordnet sind, in jedem Fall mit dem Knotenpunkt der Widerstandselemente (R, R3) der Reihe über ein weiteres Widerstandselement (RR1, RR2) verbunden sind, und wobei die Ausgabeklemmen durch die Erdungsklemme (GND) und den Knotenpunkt der Widerstandselemente (R, R3) der Reihe gebildet werden.
     
    2. Füllstandsmesssystem nach Anspruch 1,
    dadurch gekennzeichnet, dass das Netzwerk zwei weitere Widerstandselemente (R1, R2) umfasst, die in Reihe zwischen den Eingangsklemmen (V+, GND) geschaltet sind und parallel zu der Reihe der beiden Widerstandselemente (R, R3) angeordnet sind.
     
    3. Füllstandsmesssystem nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass das Füllstandsmesssystem einen Analog/Digital-Wandler zum Verarbeiten des Füllstands der leitfähigen Flüssigkeit in dem Flüssigkeitsbehälter (10) einschließt, wobei die Ausgabeklemmen des Netzwerks mit einem Eingang des Analog/Digital-Wandlers verbunden oder verbindbar sind.
     
    4. Füllstandsmesssystem nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass die externe Spannung eine Gleichspannung ist.
     
    5. Füllstandsmesssystem nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass die externe Spannung eine Wechselspannung ist.
     
    6. Füllstandsmesssystem nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass das Füllstandsmesssystem zum Ermitteln des Härtegrads von Wasser oder Flüssigkeiten, die Wasser einschließen, bereitgestellt wird, wobei die drei unterschiedlichen Füllstände (12, 14, 16) jeweils einem zugehörigen Spannungsbereich über dem Widerstandselement (R) entsprechen, und wobei die zugehörigen Spannungsbereiche an verschiedene Werte der Wasserhärte des Wassers oder der Flüssigkeit, die Wasser einschließt, angepasst sind.
     
    7. Füllstandsmesssystem nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass vorbestimmte Spannungsbereiche der Spannung zwischen den Ausgabeklemmen definiert sind, wobei jeder Spannungsbereich einem diskreten Füllstand der leitfähigen Flüssigkeit in dem Flüssigkeitsbehälter (10) entspricht.
     
    8. Haushaltsgerät, umfassend mindestens einen Flüssigkeitsbehälter (10) zum Zuführen von Flüssigkeit in das Haushaltsgerät, dadurch gekennzeichnet, dass das Haushaltsgerät mindestens ein Füllstandsmesssystem nach einem der Ansprüche 1 bis 7 umfasst.
     


    Revendications

    1. Système de mesure de niveau pour liquides conducteurs comportant un récipient à liquides (10), au moins trois électrodes (18, 20, 22) disposées à l'intérieur du récipient à liquides (10) à des niveaux différents (12, 14, 16) et un réseau, dans lequel

    - les électrodes (18, 20, 22) sont branchées au réseau consistant en une pluralité d'éléments résistifs (R, R1, R2, R3, RP1, RP2, RR1, RR2) disposés à l'extérieur du récipient à liquides (10),

    - le réseau comprend deux bornes d'entrée (V+, GND), à savoir une borne de tension (V+) et une borne de terre (GND), pour appliquer une tension externe,

    - une électrode inférieure (22) parmi les au moins trois électrodes est branchée à la borne de terre (GND), et

    - le réseau comprend deux bornes de sortie fournissant une tension dépendant du niveau du liquide conducteur dans le récipient à liquides (10),

    - de telle sorte que le système de mesure de niveau est prévu pour détecter au moins trois niveaux différents (12, 14, 16) de liquides conducteurs dans le récipient à liquides (10) et indiquer lesdits niveaux (12, 14, 16) par une valeur de tension aux bornes de sortie,

    caractérisé en ce que
    le réseau comprend deux éléments résistifs (R, R3) branchés en série entre les bornes d'entrée (V+, GND), dans lequel au moins deux électrodes (18, 20) parmi les au moins trois électrodes disposées au-dessus de l'électrode inférieure (22) sont branchées à la jonction des éléments résistifs (R, R3) de ladite série par le biais d'un autre élément résistif (RR1, RR2) dans chaque cas, et dans lequel les bornes de sortie sont formées par la borne de terre (GND) et la jonction des éléments résistifs (R, R3) de ladite série.
     
    2. Système de mesure de niveau selon la revendication 1, caractérisé en ce que
    le réseau comprend deux autres éléments résistifs (R1, R2) branchés en série entre les bornes d'entrée (V+, GND) et disposés en parallèle avec la série de deux éléments résistifs (R, R3).
     
    3. Système de mesure de niveau selon la revendication 1 ou 2,
    caractérisé en ce que
    le système de mesure de niveau comporte un convertisseur analogique-numérique pour traiter le niveau du liquide conducteur dans le récipient à liquides (10), les bornes de sortie du réseau étant branchées ou branchables à une entrée dudit convertisseur analogique-numérique.
     
    4. Système de mesure de niveau selon l'une quelconque des revendications précédentes,
    caractérisé en ce que
    la tension externe est une tension en courant continu.
     
    5. Système de mesure de niveau selon l'une quelconque des revendications précédentes,
    caractérisé en ce que
    la tension externe est une tension en courant alternatif.
     
    6. Système de mesure de niveau selon l'une quelconque des revendications précédentes,
    caractérisé en ce que
    le système de mesure de niveau est prévu pour déterminer le degré de dureté de l'eau ou de liquides comportant de l'eau, les trois niveaux différents (12, 14, 16) correspondant chacun à une gamme associée de tension aux bornes de l'élément résistif (R) et les gammes associées de tension étant adaptées à différentes valeurs de la dureté de l'eau ou du liquide comportant de l'eau.
     
    7. Système de mesure de niveau selon l'une quelconque des revendications précédentes,
    caractérisé en ce que
    des gammes de tension prédéterminées de la tension entre les bornes de sortie sont définies, chaque gamme de tension correspondant à un niveau discret du liquide conducteur dans le récipient à liquides (10).
     
    8. Appareil ménager comprenant au moins un récipient à liquides (10) destiné à fournir un liquide audit appareil ménager,
    caractérisé en ce que
    l'appareil ménager comprend au moins un système de mesure de niveau selon l'une quelconque des revendications 1 à 7.
     




    Drawing

















    Cited references

    REFERENCES CITED IN THE DESCRIPTION



    This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

    Patent documents cited in the description