Contactless filling level measurement of liquids

1. A device for the noninvasive capacitive filling level measurement of a filling medium, said device comprising:

a liquid container having a bottom and a sidewall and configured to receive and hold the filling medium,

at least two measurement electrodes which are arranged in different horizontal planes and define a measurement surface with a vertical extent;

at least one reference electrode which defines a reference surface with a vertical extent, each reference electrode being formed by a region of the container sidewall, each measurement electrode arranged with respect to the at least one reference electrode to define a capacitor having a respective electric field, wherein the vertical extent of the reference surface corresponds to the vertical extent of the measurement surface; and

an evaluation instrument configured to:

receive capacitance signals detected by the at least two measurement electrodes,

determine changes in the measured capacitance for respective measurement electrodes,

compare the measured capacitance of different measurement electrodes to one another,

determine an adjustment or correction based on the comparison of the measured capacitance of different measurement electrodes to one another, and

calculate a filling level of the filing medium held in the container based on (a) the determined changes in the measured capacitance for the respective measurement electrodes and (b) the adjustment or correction determined based on the comparison of the measured capacitance of different measurement electrodes to one another.

2. The device as claimed in claim 1 , wherein at least two reference electrodes define the reference surface and wherein the reference electrodes are arranged in different horizontal planes, a measurement electrode on a horizontal plane respectively forming a capacitor with a reference electrode on the same horizontal plane.

3. The device as claimed in claim 1 wherein the device has exactly as many reference electrodes as measurement electrodes, each measurement electrode being assigned exactly one reference electrode on the same horizontal plane.

4. The device as claimed in claim 1 wherein the measurement electrodes have a different size.

5. The device as claimed in claim 1 comprising at least 3 measurement electrodes.

6. A method for the noninvasive capacitive measurement of the filling level of a filling medium in a container using a device having at least two measurement electrodes arranged in different horizontal planes and define a measurement surface with a vertical extent and at least one reference electrode which defines a reference surface with a vertical extent, each measurement electrode respectively forming a capacitor together with the at least one reference electrode so that an electric field can respectively be formed, the method comprising the following steps:

arranging the device on or in the immediate vicinity of an outer wall of the container, so that the horizontal planes on which the at least two measurement electrodes are arranged extend parallel to the surface of the filling medium;

measuring the capacitances of the at least two capacitors;

determining changes in the measured capacitances detected by respective capacitors,

comparing the measured capacitances detected by different capacitors with one another, including calculating a ratio of measured capacitances detected by at least two different capacitors:

determining an adjustment or correction based on the comparison of the measured capacitances detected by different capacitors to one another; and

calculating the filling level of the filing medium in the container based on (a) the determined changes in the measured capacitances detected by the respective capacitors and (b) the adjustment or correction determined based on the comparison of the measured capacitances from different capacitors.

7. The method as claimed in claim 6 , wherein the measured capacitances are correlated with one another by a plausibility check.

8. The method as claimed in claim 6 , wherein the capacitances are measured continuously.

9. The device as claimed in claim 6 , wherein determining an adjustment or correction based on the comparison of the measured capacitance values from different measurement electrodes to one another comprises:

determining that the capacitance detected by one or more particular capacitors is erroneous based on the comparison of the measured capacitances values detected by different capacitors to one another; and

determining to ignore the measured capacitances detected by one or more particular capacitors.

10. The device as claimed in claim 6 , wherein determining an adjustment or correction based on the comparison of the measured capacitance values from different measurement electrodes to one another comprises:

determining a correction factor for the capacitances detected by each capacitor based on the comparison of the measured capacitances values detected by different capacitors to one another; and

applying the correction factor to the capacitances detected by each capacitor.

11. A method for the noninvasive capacitive measurement of the tilling level of a filling medium in a container using a device having at least two measurement electrodes arranged in different horizontal planes and define a measurement surface with a vertical extent and at least one reference electrode which defines a reference surface with a vertical extent, each measurement electrode respectively forming a capacitor together with the at least one reference electrode so that an electric field can respectively be formed, the method comprising the following steps:

arranging the device on or in the immediate vicinity of an outer wall of the container, so that the horizontal planes on which the at least two measurement electrodes are arranged extend parallel to the surface of the filling medium;

measuring the capacitances of the at least two capacitors;

determining changes in the measured capacitances detected by respective capacitors,

performing a plausibility check by comparing the measured capacitances detected by different capacitors with one another;

determining an adjustment or correction based on the results of the plausibility check; and

calculating the filling level of the filing medium in the container based on (a) the determined changes in the measured capacitances detected by the respective capacitors and (b) the adjustment or correction determined based on the results of the plausibility check.

12. A method for the noninvasive capacitive measurement of the filling level of a filling medium in a container using a device having at least two measurement electrodes arranged in different horizontal planes and define a measurement surface with a vertical extent and at least one reference electrode which defines a reference surface with a vertical extent, each measurement electrode respectively forming a capacitor together with the at least one reference electrode so that an electric field can respectively be formed, the method comprising the following steps:

arranging the device on or in the immediate vicinity of an outer wall of the container, so that the horizontal planes on which the at least two measurement electrodes are arranged extend parallel to the surface of the tilling medium;

measuring the capacitances of the at least two capacitors;

determining changes in the measured capacitances detected by respective capacitors,

comparing the measured capacitances detected by different capacitors with one another;

determining an adjustment or correction based on the comparison of the measured capacitances detected by different capacitors to one another, including:

determining that the capacitance detected by one or more particular capacitors is erroneous based on the comparison of the measured capacitances values detected by different capacitors to one another; and

determining to ignore the measured capacitances detected by one or more particular capacitors; and

calculating the filling level of the filing medium in the container based on (a) the determined changes in the measured capacitances detected by the respective capacitors and (b) the adjustment or correction determined based on the comparison of the measured capacitances from different capacitors.